Re: [C/C++ PATCH] Implement -Wshift-overflow (PR c++/55095) (take 3)

Re: [C/C++ PATCH] Implement -Wshift-overflow (PR c++/55095) (take 3)

[David Edelsohn]

This seems to have caused a number of new failures in the PPC
testsuite for vmx/unpack.

- David

Re: [C/C++ PATCH] Implement -Wshift-overflow (PR c++/55095) (take 3)

[Marek Polacek]

On Mon, Jul 20, 2015 at 04:23:08PM -0400, David Edelsohn wrote:
> This seems to have caused a number of new failures in the PPC
> testsuite for vmx/unpack.

Sorry about that.  Should be fixed with this patch I'm about to commit.

2015-07-21  Marek Polacek  <polacek@redhat.com>

	* gcc.dg/vmx/unpack-be-order.c: Use -Wno-shift-overflow.
	* gcc.dg/vmx/unpack.c: Likewise.
	* gcc.target/powerpc/quad-atomic.c: Likewise.

diff --git gcc/testsuite/gcc.dg/vmx/unpack-be-order.c gcc/testsuite/gcc.dg/vmx/unpack-be-order.c
index e174433..6eb98f4 100644
--- gcc/testsuite/gcc.dg/vmx/unpack-be-order.c
+++ gcc/testsuite/gcc.dg/vmx/unpack-be-order.c
@@ -1,4 +1,4 @@
-/* { dg-options "-maltivec=be -mabi=altivec -std=gnu99 -mno-vsx" } */
+/* { dg-options "-maltivec=be -mabi=altivec -std=gnu99 -mno-vsx -Wno-shift-overflow" } */
 
 #include "harness.h"
 
diff --git gcc/testsuite/gcc.dg/vmx/unpack.c gcc/testsuite/gcc.dg/vmx/unpack.c
index 3c13163..e71a5a6 100644
--- gcc/testsuite/gcc.dg/vmx/unpack.c
+++ gcc/testsuite/gcc.dg/vmx/unpack.c
@@ -1,3 +1,5 @@
+/* { dg-options "-Wno-shift-overflow" } */
+
 #include "harness.h"
 
 #define BIG 4294967295
diff --git gcc/testsuite/gcc.target/powerpc/quad-atomic.c gcc/testsuite/gcc.target/powerpc/quad-atomic.c
index 0d7089b..dc0e3a8 100644
--- gcc/testsuite/gcc.target/powerpc/quad-atomic.c
+++ gcc/testsuite/gcc.target/powerpc/quad-atomic.c
@@ -3,7 +3,7 @@
 /* { dg-skip-if "" { powerpc*-*-*spe* } { "*" } { "" } } */
 /* { dg-require-effective-target p8vector_hw } */
 /* { dg-skip-if "do not override -mcpu" { powerpc*-*-* } { "-mcpu=*" } { "-mcpu=power8" } } */
-/* { dg-options "-mcpu=power8 -O2" } */
+/* { dg-options "-mcpu=power8 -O2 -Wno-shift-overflow" } */
 
 /* Test whether we get the right bits for quad word atomic instructions.  */
 #include <stdlib.h>

	Marek

Re: [C/C++ PATCH] Implement -Wshift-overflow (PR c++/55095) (take 3)

[David Edelsohn]

On Tue, Jul 21, 2015 at 5:59 AM, Marek Polacek <polacek@redhat.com> wrote:
> On Mon, Jul 20, 2015 at 04:23:08PM -0400, David Edelsohn wrote:
>> This seems to have caused a number of new failures in the PPC
>> testsuite for vmx/unpack.
>
> Sorry about that.  Should be fixed with this patch I'm about to commit.
>
> 2015-07-21  Marek Polacek  <polacek@redhat.com>
>
>         * gcc.dg/vmx/unpack-be-order.c: Use -Wno-shift-overflow.
>         * gcc.dg/vmx/unpack.c: Likewise.

This doesn't fully fix the failures.

>         * gcc.target/powerpc/quad-atomic.c: Likewise.

> diff --git gcc/testsuite/gcc.dg/vmx/unpack.c gcc/testsuite/gcc.dg/vmx/unpack.c
> index 3c13163..e71a5a6 100644
> --- gcc/testsuite/gcc.dg/vmx/unpack.c
> +++ gcc/testsuite/gcc.dg/vmx/unpack.c
> @@ -1,3 +1,5 @@
> +/* { dg-options "-Wno-shift-overflow" } */
> +

Should this be dg-additional-options ?

>  #include "harness.h"
>
>  #define BIG 4294967295

Re: [C/C++ PATCH] Implement -Wshift-overflow (PR c++/55095) (take 3)

[Marek Polacek]

On Wed, Jul 22, 2015 at 08:35:12AM -0400, David Edelsohn wrote:
> On Tue, Jul 21, 2015 at 5:59 AM, Marek Polacek <polacek@redhat.com> wrote:
> > On Mon, Jul 20, 2015 at 04:23:08PM -0400, David Edelsohn wrote:
> >> This seems to have caused a number of new failures in the PPC
> >> testsuite for vmx/unpack.
> >
> > Sorry about that.  Should be fixed with this patch I'm about to commit.
> >
> > 2015-07-21  Marek Polacek  <polacek@redhat.com>
> >
> >         * gcc.dg/vmx/unpack-be-order.c: Use -Wno-shift-overflow.
> >         * gcc.dg/vmx/unpack.c: Likewise.
> 
> This doesn't fully fix the failures.
 
Ouch.  What other failures do you see?  I've tried the patch on ppc64-linux
and didn't see any others.

It'd be very weird to see -Wshift-overflow warnings when -Wno-shift-overflow
is in effect.

> > --- gcc/testsuite/gcc.dg/vmx/unpack.c
> > +++ gcc/testsuite/gcc.dg/vmx/unpack.c
> > @@ -1,3 +1,5 @@
> > +/* { dg-options "-Wno-shift-overflow" } */
> > +
> 
> Should this be dg-additional-options ?

I did what was in gcc.dg/vmx/unpack-be-order.c, i.e. dg-options.  Or does
using dg-additional-options help?

	Marek

Re: [C/C++ PATCH] Implement -Wshift-overflow (PR c++/55095) (take 3)

[Segher Boessenkool]

On Wed, Jul 22, 2015 at 02:39:14PM +0200, Marek Polacek wrote:
> On Wed, Jul 22, 2015 at 08:35:12AM -0400, David Edelsohn wrote:
> > On Tue, Jul 21, 2015 at 5:59 AM, Marek Polacek <polacek@redhat.com> wrote:
> > > On Mon, Jul 20, 2015 at 04:23:08PM -0400, David Edelsohn wrote:
> > >> This seems to have caused a number of new failures in the PPC
> > >> testsuite for vmx/unpack.
> > >
> > > Sorry about that.  Should be fixed with this patch I'm about to commit.
> > >
> > > 2015-07-21  Marek Polacek  <polacek@redhat.com>
> > >
> > >         * gcc.dg/vmx/unpack-be-order.c: Use -Wno-shift-overflow.
> > >         * gcc.dg/vmx/unpack.c: Likewise.
> > 
> > This doesn't fully fix the failures.
>  
> Ouch.  What other failures do you see?  I've tried the patch on ppc64-linux
> and didn't see any others.

vmx.exp sets a bunch of options and the test overrides that now.  Options
like -maltivec are pretty important for this test to work -- it #includes
altivec.h, which does #error unless -maltivec is set, and things go downhill
from that.  unpack-be-order.c works, unpack.c blows up.

Does your compiler maybe default to -maltivec?


Segher

Re: [C/C++ PATCH] Implement -Wshift-overflow (PR c++/55095) (take 3)

[Marek Polacek]

On Wed, Jul 22, 2015 at 07:48:47AM -0500, Segher Boessenkool wrote:
> vmx.exp sets a bunch of options and the test overrides that now.  Options
> like -maltivec are pretty important for this test to work -- it #includes
> altivec.h, which does #error unless -maltivec is set, and things go downhill
> from that.  unpack-be-order.c works, unpack.c blows up.

Ah, right.
 
> Does your compiler maybe default to -maltivec?

I suppose -- I didn't see any failures on cfarm 112, but I was able to
reproduce the unpack.c fail on cfarm 110.  Turned out I should've used
dg-additional-options.  Thanks.

Tested vmx.exp on powerpc64-unknown-linux-gnu, applying to trunk.

2015-07-22  Marek Polacek  <polacek@redhat.com>

	* gcc.dg/vmx/unpack.c: Use dg-additional-options rather than
	dg-options.

diff --git gcc/testsuite/gcc.dg/vmx/unpack.c gcc/testsuite/gcc.dg/vmx/unpack.c
index e71a5a6..b3ec93a 100644
--- gcc/testsuite/gcc.dg/vmx/unpack.c
+++ gcc/testsuite/gcc.dg/vmx/unpack.c
@@ -1,4 +1,4 @@
-/* { dg-options "-Wno-shift-overflow" } */
+/* { dg-additional-options "-Wno-shift-overflow" } */
 
 #include "harness.h"
 

	Marek

Re: [C/C++ PATCH] Implement -Wshift-overflow (PR c++/55095) (take 3)

[Marek Polacek]

On Fri, Jul 17, 2015 at 03:51:33PM -0600, Jeff Law wrote:
> I'll approve the C++ parts given how simple they are :-)

Thanks, I've committed the patch now after another regtest/bootstrap.

	Marek

Re: [C/C++ PATCH] Implement -Wshift-overflow (PR c++/55095) (take 3)

[Jeff Law]

On 07/17/2015 02:09 AM, Marek Polacek wrote:
> Ping^6.
>
> On Fri, Jul 10, 2015 at 03:23:43PM +0200, Marek Polacek wrote:
>> Ping^5.
>>
>> On Fri, Jul 03, 2015 at 09:42:39AM +0200, Marek Polacek wrote:
>>> Ping^4.
>>>
>>> On Fri, Jun 26, 2015 at 10:08:51AM +0200, Marek Polacek wrote:
>>>> I'm pinging the C++ parts.
>>>>
>>>> On Fri, Jun 19, 2015 at 12:44:36PM +0200, Marek Polacek wrote:
>>>>> Ping.
>>>>>
>>>>> On Fri, Jun 12, 2015 at 11:07:29AM +0200, Marek Polacek wrote:
>>>>>> Ping.
>>>>>>
>>>>>> On Fri, Jun 05, 2015 at 10:55:08AM +0200, Marek Polacek wrote:
>>>>>>> On Thu, Jun 04, 2015 at 09:04:19PM +0000, Joseph Myers wrote:
>>>>>>>> The C changes are OK.
>>>>>>>
>>>>>>> Jason, do you want to approve the C++ parts?
I'll approve the C++ parts given how simple they are :-)

jeff

Re: [C/C++ PATCH] Implement -Wshift-overflow (PR c++/55095) (take 3)

[Marek Polacek]

Ping^6.

On Fri, Jul 10, 2015 at 03:23:43PM +0200, Marek Polacek wrote:
> Ping^5.
> 
> On Fri, Jul 03, 2015 at 09:42:39AM +0200, Marek Polacek wrote:
> > Ping^4.
> > 
> > On Fri, Jun 26, 2015 at 10:08:51AM +0200, Marek Polacek wrote:
> > > I'm pinging the C++ parts.
> > > 
> > > On Fri, Jun 19, 2015 at 12:44:36PM +0200, Marek Polacek wrote:
> > > > Ping.
> > > > 
> > > > On Fri, Jun 12, 2015 at 11:07:29AM +0200, Marek Polacek wrote:
> > > > > Ping.
> > > > > 
> > > > > On Fri, Jun 05, 2015 at 10:55:08AM +0200, Marek Polacek wrote:
> > > > > > On Thu, Jun 04, 2015 at 09:04:19PM +0000, Joseph Myers wrote:
> > > > > > > The C changes are OK.
> > > > > > 
> > > > > > Jason, do you want to approve the C++ parts?

	Marek

Re: [C/C++ PATCH] Implement -Wshift-overflow (PR c++/55095) (take 3)

[Marek Polacek]

Ping^5.

On Fri, Jul 03, 2015 at 09:42:39AM +0200, Marek Polacek wrote:
> Ping^4.
> 
> On Fri, Jun 26, 2015 at 10:08:51AM +0200, Marek Polacek wrote:
> > I'm pinging the C++ parts.
> > 
> > On Fri, Jun 19, 2015 at 12:44:36PM +0200, Marek Polacek wrote:
> > > Ping.
> > > 
> > > On Fri, Jun 12, 2015 at 11:07:29AM +0200, Marek Polacek wrote:
> > > > Ping.
> > > > 
> > > > On Fri, Jun 05, 2015 at 10:55:08AM +0200, Marek Polacek wrote:
> > > > > On Thu, Jun 04, 2015 at 09:04:19PM +0000, Joseph Myers wrote:
> > > > > > The C changes are OK.
> > > > > 
> > > > > Jason, do you want to approve the C++ parts?

	Marek

Re: [C/C++ PATCH] Implement -Wshift-overflow (PR c++/55095) (take 3)

[Marek Polacek]

Ping^4.

On Fri, Jun 26, 2015 at 10:08:51AM +0200, Marek Polacek wrote:
> I'm pinging the C++ parts.
> 
> On Fri, Jun 19, 2015 at 12:44:36PM +0200, Marek Polacek wrote:
> > Ping.
> > 
> > On Fri, Jun 12, 2015 at 11:07:29AM +0200, Marek Polacek wrote:
> > > Ping.
> > > 
> > > On Fri, Jun 05, 2015 at 10:55:08AM +0200, Marek Polacek wrote:
> > > > On Thu, Jun 04, 2015 at 09:04:19PM +0000, Joseph Myers wrote:
> > > > > The C changes are OK.
> > > > 
> > > > Jason, do you want to approve the C++ parts?

	Marek

Re: [C/C++ PATCH] Implement -Wshift-overflow (PR c++/55095) (take 3)

[Marek Polacek]

I'm pinging the C++ parts.

On Fri, Jun 19, 2015 at 12:44:36PM +0200, Marek Polacek wrote:
> Ping.
> 
> On Fri, Jun 12, 2015 at 11:07:29AM +0200, Marek Polacek wrote:
> > Ping.
> > 
> > On Fri, Jun 05, 2015 at 10:55:08AM +0200, Marek Polacek wrote:
> > > On Thu, Jun 04, 2015 at 09:04:19PM +0000, Joseph Myers wrote:
> > > > The C changes are OK.
> > > 
> > > Jason, do you want to approve the C++ parts?

	Marek

Re: [C/C++ PATCH] Implement -Wshift-overflow (PR c++/55095) (take 3)

[Marek Polacek]

Ping.

On Fri, Jun 12, 2015 at 11:07:29AM +0200, Marek Polacek wrote:
> Ping.
> 
> On Fri, Jun 05, 2015 at 10:55:08AM +0200, Marek Polacek wrote:
> > On Thu, Jun 04, 2015 at 09:04:19PM +0000, Joseph Myers wrote:
> > > The C changes are OK.
> > 
> > Jason, do you want to approve the C++ parts?

	Marek

Re: [C/C++ PATCH] Implement -Wshift-overflow (PR c++/55095) (take 3)

[Marek Polacek]

Ping.

On Fri, Jun 05, 2015 at 10:55:08AM +0200, Marek Polacek wrote:
> On Thu, Jun 04, 2015 at 09:04:19PM +0000, Joseph Myers wrote:
> > The C changes are OK.
> 
> Jason, do you want to approve the C++ parts?
> 
> Thanks,

	Marek

Re: [C/C++ PATCH] Implement -Wshift-overflow (PR c++/55095) (take 3)

[Marek Polacek]

On Thu, Jun 04, 2015 at 09:04:19PM +0000, Joseph Myers wrote:
> The C changes are OK.

Jason, do you want to approve the C++ parts?

Thanks,

	Marek

Re: [C/C++ PATCH] Implement -Wshift-overflow (PR c++/55095) (take 3)

[Joseph Myers]

On Wed, 3 Jun 2015, Marek Polacek wrote:

> > Well, ok then.  This new version incorporates Richard S.'s suggestion,
> > and warns even for 1 << 31 in C99/C11 (also in C90 when -Wshift-overflow
> > is explicitely specified).  For C++, it warns about 1 << 31 by default
> > only in C++11 mode, in C++14 never, otherwise only if -Wshift-overflow
> > is specified.
> > 
> > But the fallout seems to be nonnegligible.  So I think the default should
> > be -Wshift-overflow=1 that doesn't warn about 1 << 31, but still rejects
> > e.g. enum { A = 1 << 31 };.  And -Wshift-overflow=2 would warn even about
> > 1 << 31.  (Perhaps this is exactly what you had in mind, but I'm not sure.)
> 
> Done in the following.  I think this is the best approach.  The documentation
> hopefully makes it clear what's the intended behavior.
> 
> Bootstrapped/regtested on x86_64-linux, ok for trunk?

The C changes are OK.

-- 
Joseph S. Myers
joseph@codesourcery.com

Re: [C/C++ PATCH] Implement -Wshift-overflow (PR c++/55095) (take 3)

[Marek Polacek]

On Tue, Jun 02, 2015 at 09:25:32PM +0200, Marek Polacek wrote:
> On Fri, May 29, 2015 at 08:49:58PM +0000, Joseph Myers wrote:
> > On Mon, 25 May 2015, Marek Polacek wrote:
> > 
> > > +/* Warn if signed left shift overflows.  Note that we don't warn
> > > +   about left-shifting 1 into the sign bit; cf.
> > > +   <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3367.html#1457>
> > > +   for C++ and <http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1817.htm>
> > > +   for C.  LOC is a location of the shift; OP0 and OP1 are the operands.
> > > +   Return true if an overflow is detected, false otherwise.  */
> > 
> > But for C that was declared not a defect.  See 
> > <http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1931.htm#dr_463>.  So 
> > for C99 and later we *should* consider this an overflow (for the purposes 
> > of pedwarns-if-pedantic in contexts where an integer constant expression 
> > is required; maybe -Wshift-overflow=2 for other warnings?).  If then a 
> > future C standard changes things here (in the list of issues to be 
> > considered for a future C standard in Standing Document 3, 
> > <http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1917.htm>), then, as a 
> > non-defect change, it should be considered a non-overflow in GCC only for 
> > future C standard versions as well as C90.
> > 
> > (Although treating something as not an integer constant expression does 
> > have consequences beyond pedwarns-if-pedantic - a zero derived from that 
> > expression is not a null pointer constant and that can affect the types of 
> > conditional expressions - I don't expect any significant breakage of real 
> > code from that.)
> 
> Well, ok then.  This new version incorporates Richard S.'s suggestion,
> and warns even for 1 << 31 in C99/C11 (also in C90 when -Wshift-overflow
> is explicitely specified).  For C++, it warns about 1 << 31 by default
> only in C++11 mode, in C++14 never, otherwise only if -Wshift-overflow
> is specified.
> 
> But the fallout seems to be nonnegligible.  So I think the default should
> be -Wshift-overflow=1 that doesn't warn about 1 << 31, but still rejects
> e.g. enum { A = 1 << 31 };.  And -Wshift-overflow=2 would warn even about
> 1 << 31.  (Perhaps this is exactly what you had in mind, but I'm not sure.)

Done in the following.  I think this is the best approach.  The documentation
hopefully makes it clear what's the intended behavior.

Bootstrapped/regtested on x86_64-linux, ok for trunk?

2015-06-03  Marek Polacek  <polacek@redhat.com>
	    Richard Sandiford  <richard.sandiford@arm.com>

	PR c++/55095
	* c-common.c (c_fully_fold_internal): Warn about left shift overflows.
	Use EXPR_LOC_OR_LOC.
	(maybe_warn_shift_overflow): New function.
	* c-common.h (maybe_warn_shift_overflow): Declare.
	* c-opts.c (c_common_post_options): Set warn_shift_overflow.
	* c.opt (Wshift-overflow): New option.

	* c-typeck.c (digest_init): Pass OPT_Wpedantic to pedwarn_init.
	(build_binary_op): Warn about left shift overflows.

	* typeck.c (cp_build_binary_op): Warn about left shift overflows.

	* doc/invoke.texi: Document -Wshift-overflow and -Wshift-overflow=.

	* c-c++-common/Wshift-overflow-1.c: New test.
	* c-c++-common/Wshift-overflow-2.c: New test.
	* c-c++-common/Wshift-overflow-3.c: New test.
	* c-c++-common/Wshift-overflow-4.c: New test.
	* c-c++-common/Wshift-overflow-5.c: New test.
	* g++.dg/cpp1y/left-shift-1.C: New test.
	* gcc.dg/c90-left-shift-2.c: New test.
	* gcc.dg/c90-left-shift-3.c: New test.
	* gcc.dg/c99-left-shift-2.c: New test.
	* gcc.dg/c99-left-shift-3.c: New test.
	* gcc.dg/pr40501.c: Use -Wno-shift-overflow.
	* gcc.c-torture/execute/pr40386.c: Likewise.
	* gcc.dg/vect/pr33373.c: Likewise.
	* gcc.dg/vect/vect-shift-2-big-array.c: Likewise.
	* gcc.dg/vect/vect-shift-2.c: Likewise.

diff --git gcc/c-family/c-common.c gcc/c-family/c-common.c
index 36c984c..dc31fad 100644
--- gcc/c-family/c-common.c
+++ gcc/c-family/c-common.c
@@ -1371,7 +1371,7 @@ c_fully_fold_internal (tree expr, bool in_init, bool *maybe_const_operands,
       if (TREE_OVERFLOW_P (ret)
 	  && !TREE_OVERFLOW_P (op0)
 	  && !TREE_OVERFLOW_P (op1))
-	overflow_warning (EXPR_LOCATION (expr), ret);
+	overflow_warning (EXPR_LOC_OR_LOC (expr, input_location), ret);
       if (code == LSHIFT_EXPR
 	  && TREE_CODE (orig_op0) != INTEGER_CST
 	  && TREE_CODE (TREE_TYPE (orig_op0)) == INTEGER_TYPE
@@ -1401,6 +1401,18 @@ c_fully_fold_internal (tree expr, bool in_init, bool *maybe_const_operands,
 			 ? G_("left shift count >= width of type")
 			 : G_("right shift count >= width of type")));
 	}
+      if (code == LSHIFT_EXPR
+	  /* If either OP0 has been folded to INTEGER_CST...  */
+	  && ((TREE_CODE (orig_op0) != INTEGER_CST
+	       && TREE_CODE (TREE_TYPE (orig_op0)) == INTEGER_TYPE
+	       && TREE_CODE (op0) == INTEGER_CST)
+	      /* ...or if OP1 has been folded to INTEGER_CST...  */
+	      || (TREE_CODE (orig_op1) != INTEGER_CST
+		  && TREE_CODE (TREE_TYPE (orig_op1)) == INTEGER_TYPE
+		  && TREE_CODE (op1) == INTEGER_CST))
+	  && c_inhibit_evaluation_warnings == 0)
+	/* ...then maybe we can detect an overflow.  */
+	maybe_warn_shift_overflow (loc, op0, op1);
       if ((code == TRUNC_DIV_EXPR
 	   || code == CEIL_DIV_EXPR
 	   || code == FLOOR_DIV_EXPR
@@ -12226,6 +12238,53 @@ maybe_warn_bool_compare (location_t loc, enum tree_code code, tree op0,
     }
 }
 
+/* Warn if signed left shift overflows.  We don't warn
+   about left-shifting 1 into the sign bit in C++14; cf.
+   <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3367.html#1457>
+   LOC is a location of the shift; OP0 and OP1 are the operands.
+   Return true if an overflow is detected, false otherwise.  */
+
+bool
+maybe_warn_shift_overflow (location_t loc, tree op0, tree op1)
+{
+  if (TREE_CODE (op0) != INTEGER_CST
+      || TREE_CODE (op1) != INTEGER_CST)
+    return false;
+
+  tree type0 = TREE_TYPE (op0);
+  unsigned int prec0 = TYPE_PRECISION (type0);
+
+  /* Left-hand operand must be signed.  */
+  if (TYPE_UNSIGNED (type0))
+    return false;
+
+  /* Handle the left-shifting 1 into the sign bit case.  */
+  if (integer_onep (op0)
+      && compare_tree_int (op1, prec0 - 1) == 0)
+    {
+      /* Never warn for C++14 onwards.  */
+      if (cxx_dialect >= cxx14)
+	return false;
+      /* Otherwise only if -Wshift-overflow=2.  But return
+	 true to signal an overflow for the sake of integer
+	 constant expressions.  */
+      if (warn_shift_overflow < 2)
+	return true;
+    }
+
+  unsigned int min_prec = (wi::min_precision (op0, SIGNED)
+			   + TREE_INT_CST_LOW (op1));
+  bool overflowed = min_prec > prec0;
+  if (overflowed && c_inhibit_evaluation_warnings == 0)
+    warning_at (loc, OPT_Wshift_overflow_,
+		"result of %qE requires %u bits to represent, "
+		"but %qT only has %u bits",
+		build2_loc (loc, LSHIFT_EXPR, type0, op0, op1),
+		min_prec, type0, prec0);
+
+  return overflowed;
+}
+
 /* The C and C++ parsers both use vectors to hold function arguments.
    For efficiency, we keep a cache of unused vectors.  This is the
    cache.  */
diff --git gcc/c-family/c-common.h gcc/c-family/c-common.h
index 61900db..c067f42 100644
--- gcc/c-family/c-common.h
+++ gcc/c-family/c-common.h
@@ -1061,6 +1061,7 @@ extern void record_locally_defined_typedef (tree);
 extern void maybe_record_typedef_use (tree);
 extern void maybe_warn_unused_local_typedefs (void);
 extern void maybe_warn_bool_compare (location_t, enum tree_code, tree, tree);
+extern bool maybe_warn_shift_overflow (location_t, tree, tree);
 extern vec<tree, va_gc> *make_tree_vector (void);
 extern void release_tree_vector (vec<tree, va_gc> *);
 extern vec<tree, va_gc> *make_tree_vector_single (tree);
diff --git gcc/c-family/c-opts.c gcc/c-family/c-opts.c
index 8996fe3..2e9f785 100644
--- gcc/c-family/c-opts.c
+++ gcc/c-family/c-opts.c
@@ -866,6 +866,10 @@ c_common_post_options (const char **pfilename)
   if (warn_implicit_int == -1)
     warn_implicit_int = flag_isoc99;
 
+  /* -Wshift-overflow is enabled by default in C99 and C++11 modes.  */
+  if (warn_shift_overflow == -1)
+    warn_shift_overflow = cxx_dialect >= cxx11 || flag_isoc99;
+
   /* -Wshift-negative-value is enabled by -Wextra in C99 and C++11 modes.  */
   if (warn_shift_negative_value == -1)
     warn_shift_negative_value = (extra_warnings
diff --git gcc/c-family/c.opt gcc/c-family/c.opt
index 285952e..dc760d7 100644
--- gcc/c-family/c.opt
+++ gcc/c-family/c.opt
@@ -780,6 +780,14 @@ Wshadow-ivar
 ObjC ObjC++ Var(warn_shadow_ivar) EnabledBy(Wshadow) Init(1) Warning
 Warn if a local declaration hides an instance variable
 
+Wshift-overflow
+C ObjC C++ ObjC++ Warning Alias(Wshift-overflow=, 1, 0)
+Warn if left shift of a signed value overflows
+
+Wshift-overflow=
+C ObjC C++ ObjC++ Joined RejectNegative UInteger Var(warn_shift_overflow) Init(-1) Warning
+Warn if left shift of a signed value overflows
+
 Wshift-count-negative
 C ObjC C++ ObjC++ Var(warn_shift_count_negative) Init(1) Warning
 Warn if shift count is negative
diff --git gcc/c/c-typeck.c gcc/c/c-typeck.c
index f55d4c6..0d2a7fe 100644
--- gcc/c/c-typeck.c
+++ gcc/c/c-typeck.c
@@ -6909,7 +6909,7 @@ digest_init (location_t init_loc, tree type, tree init, tree origtype,
 	  inside_init = error_mark_node;
 	}
       else if (require_constant && !maybe_const)
-	pedwarn_init (init_loc, 0,
+	pedwarn_init (init_loc, OPT_Wpedantic,
 		      "initializer element is not a constant expression");
 
       return inside_init;
@@ -10630,15 +10630,15 @@ build_binary_op (location_t location, enum tree_code code,
           converted = 1;
         }
       else if (code0 == VECTOR_TYPE && code1 == VECTOR_TYPE
-	  && TREE_CODE (TREE_TYPE (type0)) == INTEGER_TYPE
-          && TREE_CODE (TREE_TYPE (type1)) == INTEGER_TYPE
-          && TYPE_VECTOR_SUBPARTS (type0) == TYPE_VECTOR_SUBPARTS (type1))
+	       && TREE_CODE (TREE_TYPE (type0)) == INTEGER_TYPE
+	       && TREE_CODE (TREE_TYPE (type1)) == INTEGER_TYPE
+	       && TYPE_VECTOR_SUBPARTS (type0) == TYPE_VECTOR_SUBPARTS (type1))
 	{
 	  result_type = type0;
 	  converted = 1;
 	}
       else if ((code0 == INTEGER_TYPE || code0 == FIXED_POINT_TYPE)
-	  && code1 == INTEGER_TYPE)
+	       && code1 == INTEGER_TYPE)
 	{
 	  doing_shift = true;
 	  if (TREE_CODE (op1) == INTEGER_CST)
@@ -10680,15 +10680,15 @@ build_binary_op (location_t location, enum tree_code code,
           converted = 1;
         }
       else if (code0 == VECTOR_TYPE && code1 == VECTOR_TYPE
-	  && TREE_CODE (TREE_TYPE (type0)) == INTEGER_TYPE
-          && TREE_CODE (TREE_TYPE (type1)) == INTEGER_TYPE
-          && TYPE_VECTOR_SUBPARTS (type0) == TYPE_VECTOR_SUBPARTS (type1))
+	       && TREE_CODE (TREE_TYPE (type0)) == INTEGER_TYPE
+	       && TREE_CODE (TREE_TYPE (type1)) == INTEGER_TYPE
+	       && TYPE_VECTOR_SUBPARTS (type0) == TYPE_VECTOR_SUBPARTS (type1))
 	{
 	  result_type = type0;
 	  converted = 1;
 	}
       else if ((code0 == INTEGER_TYPE || code0 == FIXED_POINT_TYPE)
-	  && code1 == INTEGER_TYPE)
+	       && code1 == INTEGER_TYPE)
 	{
 	  doing_shift = true;
 	  if (TREE_CODE (op0) == INTEGER_CST
@@ -10711,7 +10711,6 @@ build_binary_op (location_t location, enum tree_code code,
 		    warning_at (location, OPT_Wshift_count_negative,
 				"left shift count is negative");
 		}
-
 	      else if (compare_tree_int (op1, TYPE_PRECISION (type0)) >= 0)
 		{
 		  int_const = false;
@@ -10719,6 +10718,10 @@ build_binary_op (location_t location, enum tree_code code,
 		    warning_at (location, OPT_Wshift_count_overflow,
 				"left shift count >= width of type");
 		}
+	      else if (TREE_CODE (op0) == INTEGER_CST
+		       && maybe_warn_shift_overflow (location, op0, op1)
+		       && flag_isoc99)
+		int_const = false;
 	    }
 
 	  /* Use the type of the value to be shifted.  */
diff --git gcc/cp/typeck.c gcc/cp/typeck.c
index fef4f4f..5e2ab11 100644
--- gcc/cp/typeck.c
+++ gcc/cp/typeck.c
@@ -4360,6 +4360,9 @@ cp_build_binary_op (location_t location,
 		    warning (OPT_Wshift_count_overflow,
 			     "left shift count >= width of type");
 		}
+	      else if (TREE_CODE (const_op0) == INTEGER_CST
+		       && (complain & tf_warning))
+		maybe_warn_shift_overflow (location, const_op0, const_op1);
 	    }
 	  /* Avoid converting op1 to result_type later.  */
 	  converted = 1;
diff --git gcc/doc/invoke.texi gcc/doc/invoke.texi
index e25bd62..2d83cfd 100644
--- gcc/doc/invoke.texi
+++ gcc/doc/invoke.texi
@@ -273,6 +273,7 @@ Objective-C and Objective-C++ Dialects}.
 -Wpointer-arith  -Wno-pointer-to-int-cast @gol
 -Wredundant-decls  -Wno-return-local-addr @gol
 -Wreturn-type  -Wsequence-point  -Wshadow  -Wno-shadow-ivar @gol
+-Wshift-overflow -Wshift-overflow=@var{n} @gol
 -Wshift-count-negative -Wshift-count-overflow -Wshift-negative-value @gol
 -Wsign-compare  -Wsign-conversion -Wfloat-conversion @gol
 -Wsizeof-pointer-memaccess  -Wsizeof-array-argument @gol
@@ -3981,6 +3982,26 @@ Warn if shift count >= width of type. This warning is enabled by default.
 Warn if left shifting a negative value.  This warning is enabled by
 @option{-Wextra} in C99 and C++11 modes (and newer).
 
+@item -Wshift-overflow
+@itemx -Wshift-overflow=@var{n}
+@opindex Wshift-overflow
+@opindex Wno-shift-overflow
+Warn about left shift overflows.  This warning is enabled by
+default in C99 and C++11 modes (and newer).
+
+@table @gcctabopt
+@item -Wshift-overflow=1
+This is the warning level of @option{-Wshift-overflow} and is enabled
+by default in C99 and C++11 modes (and newer).  This warning level does
+not warn about left-shifting 1 into the sign bit.  (However, in C, such
+an overflow is still rejected in contexts where an integer constant expression
+is required.)
+
+@item -Wshift-overflow=2
+This warning level also warns about left-shifting 1 into the sign bit,
+unless C++14 mode is active.
+@end table
+
 @item -Wswitch
 @opindex Wswitch
 @opindex Wno-switch
diff --git gcc/testsuite/c-c++-common/Wshift-overflow-1.c gcc/testsuite/c-c++-common/Wshift-overflow-1.c
index e69de29..9969629 100644
--- gcc/testsuite/c-c++-common/Wshift-overflow-1.c
+++ gcc/testsuite/c-c++-common/Wshift-overflow-1.c
@@ -0,0 +1,58 @@
+/* PR c++/55095 */
+/* { dg-do compile { target int32 } } */
+/* { dg-options "-O" } */
+/* { dg-additional-options "-std=c++11" { target c++ } } */
+
+#define INTM1 (sizeof (int) * __CHAR_BIT__ - 1)
+#define INTM2 (sizeof (int) * __CHAR_BIT__ - 2)
+#define LLONGM1 (sizeof (long long) * __CHAR_BIT__ - 1)
+#define LLONGM2 (sizeof (long long) * __CHAR_BIT__ - 2)
+
+int i1 = 1 << INTM1;
+int i2 = 9 << INTM1; /* { dg-warning "requires 36 bits to represent" } */
+int i3 = 10 << INTM2; /* { dg-warning "requires 35 bits to represent" } */
+int i4 = __INT_MAX__ << 2; /* { dg-warning "requires 34 bits to represent" } */
+int i5 = __INT_MAX__ << INTM1; /* { dg-warning "requires 63 bits to represent" } */
+int i6 = -1 << INTM1;
+int i7 = -9 << INTM1; /* { dg-warning "requires 36 bits to represent" } */
+int i8 = -10 << INTM2; /* { dg-warning "requires 35 bits to represent" } */
+int i9 = -__INT_MAX__ << 2; /* { dg-warning "requires 34 bits to represent" } */
+int i10 = -__INT_MAX__ << INTM1; /* { dg-warning "requires 63 bits to represent" } */
+
+int r1 = 1 >> INTM1;
+int r2 = 9 >> INTM1;
+int r3 = 10 >> INTM2;
+int r4 = __INT_MAX__ >> 2;
+int r5 = __INT_MAX__ >> INTM1;
+int r6 = -1 >> INTM1;
+int r7 = -9 >> INTM1;
+int r8 = -10 >> INTM2;
+int r9 = -__INT_MAX__ >> 2;
+int r10 = -__INT_MAX__ >> INTM1;
+
+unsigned u1 = 1 << INTM1;
+unsigned u2 = 9 << INTM1; /* { dg-warning "requires 36 bits to represent" } */
+unsigned u3 = 2U << INTM1;
+unsigned u4 = 9U << INTM1;
+unsigned u5 = 10U << INTM2;
+
+long long int l1 = 1LL << LLONGM1;
+long long int l2 = 9LL << LLONGM1; /* { dg-warning "requires 68 bits to represent" } */
+long long int l3 = 10LL << LLONGM2; /* { dg-warning "requires 67 bits to represent" } */
+long long int l4 = __LONG_LONG_MAX__ << 2; /* { dg-warning "requires 66 bits to represent" } */
+long long int l5 = __LONG_LONG_MAX__ << LLONGM1; /* { dg-warning "requires 127 bits to represent" } */
+long long int l6 = -1LL << LLONGM1;
+long long int l7 = -9LL << LLONGM1; /* { dg-warning "requires 68 bits to represent" } */
+long long int l8 = -10LL << LLONGM2; /* { dg-warning "requires 67 bits to represent" } */
+long long int l9 = -__LONG_LONG_MAX__ << 2; /* { dg-warning "requires 66 bits to represent" } */
+long long int l10 = -__LONG_LONG_MAX__ << LLONGM1; /* { dg-warning "requires 127 bits to represent" } */
+
+void
+fn (void)
+{
+  const int a = 10;
+  const __SIZE_TYPE__ b = INTM1;
+  int k1 = a << b; /* { dg-warning "requires 36 bits to represent" } */
+  int k2 = 10 << b; /* { dg-warning "requires 36 bits to represent" } */
+  int k3 = a << INTM1; /* { dg-warning "requires 36 bits to represent" } */
+}
diff --git gcc/testsuite/c-c++-common/Wshift-overflow-2.c gcc/testsuite/c-c++-common/Wshift-overflow-2.c
index e69de29..d5115d0 100644
--- gcc/testsuite/c-c++-common/Wshift-overflow-2.c
+++ gcc/testsuite/c-c++-common/Wshift-overflow-2.c
@@ -0,0 +1,58 @@
+/* PR c++/55095 */
+/* { dg-do compile { target int32 } } */
+/* { dg-options "-O -Wno-shift-overflow" } */
+/* { dg-additional-options "-std=c++11" { target c++ } } */
+
+#define INTM1 (sizeof (int) * __CHAR_BIT__ - 1)
+#define INTM2 (sizeof (int) * __CHAR_BIT__ - 2)
+#define LLONGM1 (sizeof (long long) * __CHAR_BIT__ - 1)
+#define LLONGM2 (sizeof (long long) * __CHAR_BIT__ - 2)
+
+int i1 = 1 << INTM1;
+int i2 = 9 << INTM1;
+int i3 = 10 << INTM2;
+int i4 = __INT_MAX__ << 2;
+int i5 = __INT_MAX__ << INTM1;
+int i6 = -1 << INTM1;
+int i7 = -9 << INTM1;
+int i8 = -10 << INTM2;
+int i9 = -__INT_MAX__ << 2;
+int i10 = -__INT_MAX__ << INTM1;
+
+int r1 = 1 >> INTM1;
+int r2 = 9 >> INTM1;
+int r3 = 10 >> INTM2;
+int r4 = __INT_MAX__ >> 2;
+int r5 = __INT_MAX__ >> INTM1;
+int r6 = -1 >> INTM1;
+int r7 = -9 >> INTM1;
+int r8 = -10 >> INTM2;
+int r9 = -__INT_MAX__ >> 2;
+int r10 = -__INT_MAX__ >> INTM1;
+
+unsigned u1 = 1 << INTM1;
+unsigned u2 = 9 << INTM1;
+unsigned u3 = 2U << INTM1;
+unsigned u4 = 9U << INTM1;
+unsigned u5 = 10U << INTM2;
+
+long long int l1 = 1LL << LLONGM1;
+long long int l2 = 9LL << LLONGM1;
+long long int l3 = 10LL << LLONGM2;
+long long int l4 = __LONG_LONG_MAX__ << 2;
+long long int l5 = __LONG_LONG_MAX__ << LLONGM1;
+long long int l6 = -1LL << LLONGM1;
+long long int l7 = -9LL << LLONGM1;
+long long int l8 = -10LL << LLONGM2;
+long long int l9 = -__LONG_LONG_MAX__ << 2;
+long long int l10 = -__LONG_LONG_MAX__ << LLONGM1;
+
+void
+fn (void)
+{
+  const int a = 10;
+  const __SIZE_TYPE__ b = INTM1;
+  int k1 = a << b;
+  int k2 = 10 << b;
+  int k3 = a << INTM1;
+}
diff --git gcc/testsuite/c-c++-common/Wshift-overflow-3.c gcc/testsuite/c-c++-common/Wshift-overflow-3.c
index e69de29..ed57d5d 100644
--- gcc/testsuite/c-c++-common/Wshift-overflow-3.c
+++ gcc/testsuite/c-c++-common/Wshift-overflow-3.c
@@ -0,0 +1,59 @@
+/* PR c++/55095 */
+/* { dg-do compile { target int32 } } */
+/* { dg-options "-O -Wshift-overflow" } */
+/* { dg-additional-options "-std=gnu90" { target c } } */
+/* { dg-additional-options "-std=c++03" { target c++ } } */
+
+#define INTM1 (sizeof (int) * __CHAR_BIT__ - 1)
+#define INTM2 (sizeof (int) * __CHAR_BIT__ - 2)
+#define LLONGM1 (sizeof (long long) * __CHAR_BIT__ - 1)
+#define LLONGM2 (sizeof (long long) * __CHAR_BIT__ - 2)
+
+int i1 = 1 << INTM1;
+int i2 = 9 << INTM1; /* { dg-warning "requires 36 bits to represent" } */
+int i3 = 10 << INTM2; /* { dg-warning "requires 35 bits to represent" } */
+int i4 = __INT_MAX__ << 2; /* { dg-warning "requires 34 bits to represent" } */
+int i5 = __INT_MAX__ << INTM1; /* { dg-warning "requires 63 bits to represent" } */
+int i6 = -1 << INTM1;
+int i7 = -9 << INTM1; /* { dg-warning "requires 36 bits to represent" } */
+int i8 = -10 << INTM2; /* { dg-warning "requires 35 bits to represent" } */
+int i9 = -__INT_MAX__ << 2; /* { dg-warning "requires 34 bits to represent" } */
+int i10 = -__INT_MAX__ << INTM1; /* { dg-warning "requires 63 bits to represent" } */
+
+int r1 = 1 >> INTM1;
+int r2 = 9 >> INTM1;
+int r3 = 10 >> INTM2;
+int r4 = __INT_MAX__ >> 2;
+int r5 = __INT_MAX__ >> INTM1;
+int r6 = -1 >> INTM1;
+int r7 = -9 >> INTM1;
+int r8 = -10 >> INTM2;
+int r9 = -__INT_MAX__ >> 2;
+int r10 = -__INT_MAX__ >> INTM1;
+
+unsigned u1 = 1 << INTM1;
+unsigned u2 = 9 << INTM1; /* { dg-warning "requires 36 bits to represent" } */
+unsigned u3 = 2U << INTM1;
+unsigned u4 = 9U << INTM1;
+unsigned u5 = 10U << INTM2;
+
+long long int l1 = 1LL << LLONGM1;
+long long int l2 = 9LL << LLONGM1; /* { dg-warning "requires 68 bits to represent" } */
+long long int l3 = 10LL << LLONGM2; /* { dg-warning "requires 67 bits to represent" } */
+long long int l4 = __LONG_LONG_MAX__ << 2; /* { dg-warning "requires 66 bits to represent" } */
+long long int l5 = __LONG_LONG_MAX__ << LLONGM1; /* { dg-warning "requires 127 bits to represent" } */
+long long int l6 = -1LL << LLONGM1;
+long long int l7 = -9LL << LLONGM1; /* { dg-warning "requires 68 bits to represent" } */
+long long int l8 = -10LL << LLONGM2; /* { dg-warning "requires 67 bits to represent" } */
+long long int l9 = -__LONG_LONG_MAX__ << 2; /* { dg-warning "requires 66 bits to represent" } */
+long long int l10 = -__LONG_LONG_MAX__ << LLONGM1; /* { dg-warning "requires 127 bits to represent" } */
+
+void
+fn (void)
+{
+  const int a = 10;
+  const __SIZE_TYPE__ b = INTM1;
+  int k1 = a << b; /* { dg-warning "requires 36 bits to represent" } */
+  int k2 = 10 << b; /* { dg-warning "requires 36 bits to represent" } */
+  int k3 = a << INTM1; /* { dg-warning "requires 36 bits to represent" } */
+}
diff --git gcc/testsuite/c-c++-common/Wshift-overflow-4.c gcc/testsuite/c-c++-common/Wshift-overflow-4.c
index e69de29..92f8cf8 100644
--- gcc/testsuite/c-c++-common/Wshift-overflow-4.c
+++ gcc/testsuite/c-c++-common/Wshift-overflow-4.c
@@ -0,0 +1,59 @@
+/* PR c++/55095 */
+/* { dg-do compile { target int32 } } */
+/* { dg-options "-O" } */
+/* { dg-additional-options "-std=gnu90" { target c } } */
+/* { dg-additional-options "-std=c++03" { target c++ } } */
+
+#define INTM1 (sizeof (int) * __CHAR_BIT__ - 1)
+#define INTM2 (sizeof (int) * __CHAR_BIT__ - 2)
+#define LLONGM1 (sizeof (long long) * __CHAR_BIT__ - 1)
+#define LLONGM2 (sizeof (long long) * __CHAR_BIT__ - 2)
+
+int i1 = 1 << INTM1;
+int i2 = 9 << INTM1;
+int i3 = 10 << INTM2;
+int i4 = __INT_MAX__ << 2;
+int i5 = __INT_MAX__ << INTM1;
+int i6 = -1 << INTM1;
+int i7 = -9 << INTM1;
+int i8 = -10 << INTM2;
+int i9 = -__INT_MAX__ << 2;
+int i10 = -__INT_MAX__ << INTM1;
+
+int r1 = 1 >> INTM1;
+int r2 = 9 >> INTM1;
+int r3 = 10 >> INTM2;
+int r4 = __INT_MAX__ >> 2;
+int r5 = __INT_MAX__ >> INTM1;
+int r6 = -1 >> INTM1;
+int r7 = -9 >> INTM1;
+int r8 = -10 >> INTM2;
+int r9 = -__INT_MAX__ >> 2;
+int r10 = -__INT_MAX__ >> INTM1;
+
+unsigned u1 = 1 << INTM1;
+unsigned u2 = 9 << INTM1;
+unsigned u3 = 2U << INTM1;
+unsigned u4 = 9U << INTM1;
+unsigned u5 = 10U << INTM2;
+
+long long int l1 = 1LL << LLONGM1;
+long long int l2 = 9LL << LLONGM1;
+long long int l3 = 10LL << LLONGM2;
+long long int l4 = __LONG_LONG_MAX__ << 2;
+long long int l5 = __LONG_LONG_MAX__ << LLONGM1;
+long long int l6 = -1LL << LLONGM1;
+long long int l7 = -9LL << LLONGM1;
+long long int l8 = -10LL << LLONGM2;
+long long int l9 = -__LONG_LONG_MAX__ << 2;
+long long int l10 = -__LONG_LONG_MAX__ << LLONGM1;
+
+void
+fn (void)
+{
+  const int a = 10;
+  const __SIZE_TYPE__ b = INTM1;
+  int k1 = a << b;
+  int k2 = 10 << b;
+  int k3 = a << INTM1;
+}
diff --git gcc/testsuite/c-c++-common/Wshift-overflow-5.c gcc/testsuite/c-c++-common/Wshift-overflow-5.c
index e69de29..c9f4643 100644
--- gcc/testsuite/c-c++-common/Wshift-overflow-5.c
+++ gcc/testsuite/c-c++-common/Wshift-overflow-5.c
@@ -0,0 +1,11 @@
+/* PR c++/55095 */
+/* { dg-do compile { target int32 } } */
+/* { dg-options "-O -Wshift-overflow=2" } */
+/* { dg-additional-options "-std=c++11" { target c++ } } */
+
+#define INTM1 (sizeof (int) * __CHAR_BIT__ - 1)
+#define LLONGM1 (sizeof (long long) * __CHAR_BIT__ - 1)
+
+int i1 = 1 << INTM1; /* { dg-warning "requires 33 bits to represent" } */
+unsigned u1 = 1 << INTM1; /* { dg-warning "requires 33 bits to represent" } */
+long long int l1 = 1LL << LLONGM1; /* { dg-warning "requires 65 bits to represent" } */
diff --git gcc/testsuite/g++.dg/cpp1y/left-shift-1.C gcc/testsuite/g++.dg/cpp1y/left-shift-1.C
index e69de29..a24caae 100644
--- gcc/testsuite/g++.dg/cpp1y/left-shift-1.C
+++ gcc/testsuite/g++.dg/cpp1y/left-shift-1.C
@@ -0,0 +1,11 @@
+// PR c++/55095
+// { dg-do compile { target c++14 } }
+// { dg-options "-Wshift-overflow=2" }
+// { dg-require-effective-target int32plus }
+
+#define INTM1 (sizeof (int) * __CHAR_BIT__ - 1)
+#define LLONGM1 (sizeof (long long) * __CHAR_BIT__ - 1)
+
+int i1 = 1 << INTM1;
+unsigned u1 = 1 << INTM1;
+long long int l1 = 1LL << LLONGM1;
diff --git gcc/testsuite/gcc.c-torture/execute/pr40386.c gcc/testsuite/gcc.c-torture/execute/pr40386.c
index f39f1de..c701304 100644
--- gcc/testsuite/gcc.c-torture/execute/pr40386.c
+++ gcc/testsuite/gcc.c-torture/execute/pr40386.c
@@ -1,4 +1,4 @@
-/* { dg-options "-fno-ira-share-spill-slots" } */
+/* { dg-options "-fno-ira-share-spill-slots -Wno-shift-overflow" } */
 
 extern void abort (void);
 extern void exit (int);
diff --git gcc/testsuite/gcc.dg/c90-left-shift-2.c gcc/testsuite/gcc.dg/c90-left-shift-2.c
index e69de29..f79ab8b 100644
--- gcc/testsuite/gcc.dg/c90-left-shift-2.c
+++ gcc/testsuite/gcc.dg/c90-left-shift-2.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-std=iso9899:1990 -pedantic-errors" } */
+
+#define INTM2 (sizeof (int) * __CHAR_BIT__ - 2)
+
+enum { A = 10 << INTM2 };
+int k = 10 << INTM2;
+
+void
+fn (int i)
+{
+  switch (i)
+  case 10 << INTM2: break;
+}
diff --git gcc/testsuite/gcc.dg/c90-left-shift-3.c gcc/testsuite/gcc.dg/c90-left-shift-3.c
index e69de29..43942dd 100644
--- gcc/testsuite/gcc.dg/c90-left-shift-3.c
+++ gcc/testsuite/gcc.dg/c90-left-shift-3.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-std=iso9899:1990 -pedantic-errors" } */
+
+#define INTM1 (sizeof (int) * __CHAR_BIT__ - 1)
+
+enum { A = 1 << INTM1 };
+int k = 1 << INTM1;
+
+void
+fn (int i)
+{
+  switch (i)
+  case 1 << INTM1: break;
+}
diff --git gcc/testsuite/gcc.dg/c99-left-shift-2.c gcc/testsuite/gcc.dg/c99-left-shift-2.c
index e69de29..e35786e 100644
--- gcc/testsuite/gcc.dg/c99-left-shift-2.c
+++ gcc/testsuite/gcc.dg/c99-left-shift-2.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-std=iso9899:1999 -pedantic-errors -Wno-shift-overflow" } */
+
+#define INTM2 (sizeof (int) * __CHAR_BIT__ - 2)
+
+enum { A = 10 << INTM2 }; /* { dg-error "constant expression" } */
+int k = 10 << INTM2; /* { dg-error "constant expression" } */
+
+void
+fn (int i)
+{
+  switch (i)
+  case 10 << INTM2: break; /* { dg-error "constant expression" } */
+}
diff --git gcc/testsuite/gcc.dg/c99-left-shift-3.c gcc/testsuite/gcc.dg/c99-left-shift-3.c
index e69de29..59d0f24 100644
--- gcc/testsuite/gcc.dg/c99-left-shift-3.c
+++ gcc/testsuite/gcc.dg/c99-left-shift-3.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-std=iso9899:1999 -pedantic-errors -Wno-shift-overflow" } */
+
+#define INTM1 (sizeof (int) * __CHAR_BIT__ - 1)
+
+enum { A = 1 << INTM1 }; /* { dg-error "constant expression" } */
+int k = 1 << INTM1; /* { dg-error "constant expression" } */
+
+void
+fn (int i)
+{
+  switch (i)
+  case 1 << INTM1: break; /* { dg-error "constant expression" } */
+}
diff --git gcc/testsuite/gcc.dg/pr40501.c gcc/testsuite/gcc.dg/pr40501.c
index e6ce217..7610a20 100644
--- gcc/testsuite/gcc.dg/pr40501.c
+++ gcc/testsuite/gcc.dg/pr40501.c
@@ -1,5 +1,5 @@
 /* { dg-do compile { target alpha*-*-* ia64*-*-* i?86-*-* x86_64-*-* s390x-*-* } } */
-/* { dg-options "-O2" } */
+/* { dg-options "-O2 -Wno-shift-overflow" } */
 /* { dg-require-effective-target lp64 } */
 
 /* PR middle-end/40501 */
diff --git gcc/testsuite/gcc.dg/vect/pr33373.c gcc/testsuite/gcc.dg/vect/pr33373.c
index 8da4371..efba2ab 100644
--- gcc/testsuite/gcc.dg/vect/pr33373.c
+++ gcc/testsuite/gcc.dg/vect/pr33373.c
@@ -1,3 +1,4 @@
+/* { dg-options "-Wno-shift-overflow" } */
 /* { dg-do compile } */
 void DOSMEM_FillIsrTable(int*isr) {
     int i;
diff --git gcc/testsuite/gcc.dg/vect/vect-shift-2-big-array.c gcc/testsuite/gcc.dg/vect/vect-shift-2-big-array.c
index 46909ca..85ff0e0 100644
--- gcc/testsuite/gcc.dg/vect/vect-shift-2-big-array.c
+++ gcc/testsuite/gcc.dg/vect/vect-shift-2-big-array.c
@@ -1,3 +1,4 @@
+/* { dg-options "-Wno-shift-overflow" } */
 /* { dg-require-effective-target vect_shift } */
 /* { dg-require-effective-target vect_int } */
 /* Check the standard integer types for left and right shifts to see if the
diff --git gcc/testsuite/gcc.dg/vect/vect-shift-2.c gcc/testsuite/gcc.dg/vect/vect-shift-2.c
index 68186db..6199cd6 100644
--- gcc/testsuite/gcc.dg/vect/vect-shift-2.c
+++ gcc/testsuite/gcc.dg/vect/vect-shift-2.c
@@ -1,3 +1,4 @@
+/* { dg-options "-Wno-shift-overflow" } */
 /* { dg-require-effective-target vect_shift } */
 /* { dg-require-effective-target vect_int } */
 /* Check the standard integer types for left and right shifts to see if the

	Marek