[PATCH][PR66013] Update address_taken after ifn_va_arg expansion

[Tom de Vries <Tom_deVries at mentor dot com>]

Hi,

this patch fixes PR66013.


I.

Consider this test-case, with a va_list passed from f2 to f2_1:
...
#include <stdarg.h>

inline int __attribute__((always_inline))
f2_1 (va_list ap)
{
  return va_arg (ap, int);
}

int
f2 (int i, ...)
{
  int res;
  va_list ap;

  va_start (ap, i);
  res = f2_1 (ap);
  va_end (ap);

  return res;
}
...

When compiling at -O2 with -m32, before pass_stdarg we see that va_start and 
va_arg (in the same function after inlining) use different aps (with the same 
value though):
...
  # .MEM_2 = VDEF <.MEM_1(D)>
  # USE = nonlocal escaped
  # CLB = nonlocal escaped { D.1809 }
  __builtin_va_startD.1021 (&apD.1809, 0);

  # VUSE <.MEM_2>
  # PT = nonlocal
  ap.0_3 = apD.1809;

  # .MEM_4 = VDEF <.MEM_2>
  apD.1820 = ap.0_3;

  # .MEM_8 = VDEF <.MEM_4>
  # USE = nonlocal null { D.1820 } (escaped)
  # CLB = nonlocal null { D.1820 } (escaped)
  _7 = VA_ARG (&apD.1820, 0B, 1);
...

After expand_ifn_va_arg_1, we have this representation, and that's the one the 
pass_stdarg optimization operates on:
...
  # .MEM_2 = VDEF <.MEM_1(D)>
  # USE = nonlocal escaped
  # CLB = nonlocal escaped { D.1809 }
  __builtin_va_startD.1021 (&apD.1809, 0);

  # VUSE <.MEM_2>
  # PT = nonlocal
  ap.0_3 = apD.1809;

  # .MEM_4 = VDEF <.MEM_2>
  apD.1820 = ap.0_3;

  # VUSE <.MEM_4>
  ap.4_9 = apD.1820;

  ap.5_10 = ap.4_9 + 4;

  # .MEM_11 = VDEF <.MEM_4>
  apD.1820 = ap.5_10;

  # VUSE <.MEM_11>
  _7 = MEM[(intD.1 *)ap.4_9];
...

The optimization in pass_stdarg fails:
...
f2: va_list escapes 1, needs to save all GPR units and all FPR units.
...

The optimization fails because this assignment makes the va_list escape:
...
va_list escapes in # .MEM_4 = VDEF <.MEM_2>
apD.1820 = ap.0_3;
...


II.

By recalculating address_taken after expanding the ifn_va_arg, we get instead:
...
  # .MEM_2 = VDEF <.MEM_1(D)>
  # USE = nonlocal escaped
  # CLB = nonlocal escaped { D.1809 }
  __builtin_va_startD.1021 (&apD.1809, 0);

  # VUSE <.MEM_2>
  # PT = nonlocal
  ap.0_3 = apD.1809;

  ap_11 = ap.0_3;

  ap.4_9 = ap_11;

  ap.5_10 = ap.4_9 + 4;

  ap_4 = ap.5_10;

  # VUSE <.MEM_2>
  _7 = MEM[(intD.1 *)ap.4_9];
...

and the pass_stdarg optimization succeeds now:
...
f2: va_list escapes 0, needs to save 4 GPR units and all FPR units.
...

Bootstrapped and reg-tested on x86_64 with and without -m32.

OK for trunk?

Thanks,
- Tom

Update address_taken after ifn_va_arg expansion

2015-05-08  Tom de Vries  <tom@codesourcery.com>

	PR tree-optimization/66013
	* tree-stdarg.c: Include tree-ssa.h.
	(expand_ifn_va_arg_1): Call execute_update_addresses_taken after
	TODO_update_ssa.

	* gcc.dg/tree-ssa/stdarg-2.c: Add ia32 scan for 'va_list escapes 0'.
---
 gcc/testsuite/gcc.dg/tree-ssa/stdarg-2.c | 2 ++
 gcc/tree-stdarg.c                        | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/stdarg-2.c b/gcc/testsuite/gcc.dg/tree-ssa/stdarg-2.c
index f09b5de..3b1bc2c 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/stdarg-2.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/stdarg-2.c
@@ -300,6 +300,8 @@ f15 (int i, ...)
 /* We may be able to improve upon this after fixing PR66010/PR66013.  */
 /* { dg-final { scan-tree-dump "f15: va_list escapes 1, needs to save all GPR units and all FPR units" "stdarg" { target alpha*-*-linux* } } } */
 
+/* { dg-final { scan-tree-dump "f15: va_list escapes 0" "stdarg" { target { { i?86-*-* x86_64-*-* } && ia32 } } } } */
+
 /* { dg-final { scan-tree-dump-not "f15: va_list escapes 0, needs to save 0 GPR units" "stdarg" { target { { i?86-*-* x86_64-*-* } && ia32 } } } } */
 /* { dg-final { scan-tree-dump-not "f15: va_list escapes 0, needs to save 0 GPR units" "stdarg" { target ia64-*-* } } } */
 /* { dg-final { scan-tree-dump-not "f15: va_list escapes 0, needs to save 0 GPR units" "stdarg" { target { powerpc*-*-* && lp64 } } } } */
diff --git a/gcc/tree-stdarg.c b/gcc/tree-stdarg.c
index 1356374..64e6224 100644
--- a/gcc/tree-stdarg.c
+++ b/gcc/tree-stdarg.c
@@ -62,6 +62,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "tree-cfg.h"
 #include "tree-pass.h"
 #include "tree-stdarg.h"
+#include "tree-ssa.h"
 
 /* A simple pass that attempts to optimize stdarg functions on architectures
    that need to save register arguments to stack on entry to stdarg functions.
@@ -1108,6 +1109,7 @@ expand_ifn_va_arg_1 (function *fun)
 
   free_dominance_info (CDI_DOMINATORS);
   update_ssa (TODO_update_ssa);
+  execute_update_addresses_taken ();
 }
 
 /* Expand IFN_VA_ARGs in FUN, if necessary.  */
-- 
1.9.1