Re: [PATCH] Fixes to must-tail-call tests

[David Malcolm <dmalcolm@redhat.com>]

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On Fri, 2016-05-27 at 13:29 +0100, Thomas Preudhomme wrote:
> Hi Rainer,
> 
> On Wednesday 25 May 2016 11:31:12 Rainer Orth wrote:
> > David Malcolm <dmalcolm@redhat.com> writes:
> > > The following fixes the known failures of the must-tail-call
> > > tests.
> > > 
> > > Tested with --target=
> > > * aarch64-unknown-linux-gnu
> > > * ia64-unknown-linux-gnu
> > > * m68k-unknown-linux-gnu
> > > * x86_64-pc-linux-gnu
> > 
> > Even with this patch, there are still failures on sparc-sun
> > -solaris2.12:
> > 
> > FAIL: gcc.dg/plugin/must-tail-call-1.c 
> > -fplugin=./must_tail_call_plugin.so
> > (test for excess errors)
> > 
> > Excess errors:
> > /vol/gcc/src/hg/trunk/local/gcc/testsuite/gcc.dg/plugin/must-tail
> > -call-1.c:1
> > 2:10: error: cannot tail-call: target is not able to optimize the
> > call into
> > a sibling call
> > 
> > FAIL: gcc.dg/plugin/must-tail-call-2.c 
> > -fplugin=./must_tail_call_plugin.so
> > (test for excess errors)
> > 
> > Excess errors:
> > /vol/gcc/src/hg/trunk/local/gcc/testsuite/gcc.dg/plugin/must-tail
> > -call-2.c:3
> > 2:10: error: cannot tail-call: target is not able to optimize the
> > call into
> > a sibling call


My aim with these tests was to try to cover the various ways in which
mandatory tail-call optimization can fail.

However, this is very target-dependent, and, as written, the test over
-specifies the output.

Sorry about this.

I've run the test on all of the configurations in contrib/config
-list.mk (using the patch kit in
  https://gcc.gnu.org/ml/gcc-patches/2016-05/msg02100.html )

Collated output can be seen here:
  https://dmalcolm.fedorapeople.org/gcc/2016-05-27/must-tail-call-logs.txt
showing all the different error messages across every configuration.

It's not clear to me what the best way forward here is.
We could simply check for
   error: cannot tail-call:
and leave the precise messages we're checking for unspecified.

If we care about checking for the precise messages, one of more
duplicate copy(s) of the test could be provided, filtering by target to
specify precise targets, giving more precise output, where this is
known.

I'm attaching a patch (sans ChangeLog) which strips the precise
messages in the manner described above.  Retesting on all targets with
this patch, the only remaining failures are of the form:
  must-tail-call-1.c:12:10: error: cannot tail-call: machine
description does not have a sibcall_epilogue instruction pattern
on targets lacking the pattern.

Thoughts?

Sorry again about the breakage

Dave


> Now that the logic is in place, you probably want to add sparc-sun
> -solaris in 
> plugin.exp to the the list of architecture where tail call plugin
> tests should 
> be skipped, alongside Thumb-1 ARM targets.
> 
> Best regards,
> 

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diff --git a/gcc/testsuite/gcc.dg/plugin/must-tail-call-2.c b/gcc/testsuite/gcc.dg/plugin/must-tail-call-2.c
index c5504f8..c6dfecd 100644
--- a/gcc/testsuite/gcc.dg/plugin/must-tail-call-2.c
+++ b/gcc/testsuite/gcc.dg/plugin/must-tail-call-2.c
@@ -14,7 +14,7 @@ returns_struct (int i)
 int __attribute__((noinline,noclone))
 test_1 (int i)
 {
-  return returns_struct (i * 5).i; /* { dg-error "cannot tail-call: callee returns a structure" } */
+  return returns_struct (i * 5).i; /* { dg-error "cannot tail-call: " } */
 }
 
 int __attribute__((noinline,noclone))
@@ -29,14 +29,14 @@ int __attribute__((noinline,noclone))
 test_2_caller (int i)
 {
   struct box b;
-  return test_2_callee (i + 1, b); /* { dg-error "cannot tail-call: callee required more stack slots than the caller" } */
+  return test_2_callee (i + 1, b); /* { dg-error "cannot tail-call: " } */
 }
 
 extern void setjmp (void);
 void
 test_3 (void)
 {
-  setjmp (); /* { dg-error "cannot tail-call: callee returns twice" } */
+  setjmp (); /* { dg-error "cannot tail-call: " } */
 }
 
 void
@@ -45,7 +45,7 @@ test_4 (void)
   void nested (void)
   {
   }
-  nested (); /* { dg-error "cannot tail-call: nested function" } */
+  nested (); /* { dg-error "cannot tail-call: " } */
 }
 
 typedef void (fn_ptr_t) (void);
@@ -54,5 +54,5 @@ volatile fn_ptr_t fn_ptr;
 void
 test_5 (void)
 {
-  fn_ptr (); /* { dg-error "cannot tail-call: callee does not return" } */
+  fn_ptr (); /* { dg-error "cannot tail-call: " } */
 }