[PATCH] Fix avoid_constant_pool_reference (PR middle-end/77377)

[PATCH] Fix avoid_constant_pool_reference (PR middle-end/77377)

[Jakub Jelinek]

Hi!

Returning c from avoid_constant_pool_reference for constant pool references
is only fine if the modes match and offset is zero, otherwise if the offset
is sane, we can try to simplify it as subreg.  But, returning c for out of
bounds offsets is always wrong, and especially if the mode doesn't match, it
can results in all kinds of ICEs.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2016-08-29  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/77377
	* simplify-rtx.c (avoid_constant_pool_reference): For out of bounds
	constant pool reference return x instead of c.

	* gcc.target/i386/pr77377.c: New test.

--- gcc/simplify-rtx.c.jj	2016-08-12 17:33:46.000000000 +0200
+++ gcc/simplify-rtx.c	2016-08-29 13:32:38.126859949 +0200
@@ -251,15 +251,14 @@ avoid_constant_pool_reference (rtx x)
       /* If we're accessing the constant in a different mode than it was
          originally stored, attempt to fix that up via subreg simplifications.
          If that fails we have no choice but to return the original memory.  */
-      if ((offset != 0 || cmode != GET_MODE (x))
-	  && offset >= 0 && offset < GET_MODE_SIZE (cmode))
+      if (offset == 0 && cmode == GET_MODE (x))
+	return c;
+      else if (offset >= 0 && offset < GET_MODE_SIZE (cmode))
         {
           rtx tem = simplify_subreg (GET_MODE (x), c, cmode, offset);
           if (tem && CONSTANT_P (tem))
             return tem;
         }
-      else
-        return c;
     }
 
   return x;
--- gcc/testsuite/gcc.target/i386/pr77377.c.jj	2016-08-29 13:39:01.707328239 +0200
+++ gcc/testsuite/gcc.target/i386/pr77377.c	2016-08-29 13:38:55.901396832 +0200
@@ -0,0 +1,6 @@
+/* PR middle-end/77377 */
+/* { dg-do compile } */
+/* { dg-options "-O3 -msse" } */
+/* { dg-additional-options "-fpic" { target fpic } } */
+
+#include "../../c-c++-common/pr59037.c"

	Jakub

Re: [PATCH] Fix avoid_constant_pool_reference (PR middle-end/77377)

[Richard Biener]

On August 29, 2016 9:43:50 PM GMT+02:00, Jakub Jelinek <jakub@redhat.com> wrote:
>Hi!
>
>Returning c from avoid_constant_pool_reference for constant pool
>references
>is only fine if the modes match and offset is zero, otherwise if the
>offset
>is sane, we can try to simplify it as subreg.  But, returning c for out
>of
>bounds offsets is always wrong, and especially if the mode doesn't
>match, it
>can results in all kinds of ICEs.
>
>Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

OK.

Thanks,
Richard.

>2016-08-29  Jakub Jelinek  <jakub@redhat.com>
>
>	PR middle-end/77377
>	* simplify-rtx.c (avoid_constant_pool_reference): For out of bounds
>	constant pool reference return x instead of c.
>
>	* gcc.target/i386/pr77377.c: New test.
>
>--- gcc/simplify-rtx.c.jj	2016-08-12 17:33:46.000000000 +0200
>+++ gcc/simplify-rtx.c	2016-08-29 13:32:38.126859949 +0200
>@@ -251,15 +251,14 @@ avoid_constant_pool_reference (rtx x)
>     /* If we're accessing the constant in a different mode than it was
>  originally stored, attempt to fix that up via subreg simplifications.
> If that fails we have no choice but to return the original memory.  */
>-      if ((offset != 0 || cmode != GET_MODE (x))
>-	  && offset >= 0 && offset < GET_MODE_SIZE (cmode))
>+      if (offset == 0 && cmode == GET_MODE (x))
>+	return c;
>+      else if (offset >= 0 && offset < GET_MODE_SIZE (cmode))
>         {
>           rtx tem = simplify_subreg (GET_MODE (x), c, cmode, offset);
>           if (tem && CONSTANT_P (tem))
>             return tem;
>         }
>-      else
>-        return c;
>     }
> 
>   return x;
>--- gcc/testsuite/gcc.target/i386/pr77377.c.jj	2016-08-29
>13:39:01.707328239 +0200
>+++ gcc/testsuite/gcc.target/i386/pr77377.c	2016-08-29
>13:38:55.901396832 +0200
>@@ -0,0 +1,6 @@
>+/* PR middle-end/77377 */
>+/* { dg-do compile } */
>+/* { dg-options "-O3 -msse" } */
>+/* { dg-additional-options "-fpic" { target fpic } } */
>+
>+#include "../../c-c++-common/pr59037.c"
>
>	Jakub