[Bug tree-optimization/41089] New: [4.5 Regression] r147980 (New SRA) breaks stdargs

["ubizjak at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

r147980 [1] breaks stdargs on alpha [2]:

FAIL: gcc.c-torture/execute/stdarg-1.c execution,  -O3 -fomit-frame-pointer 
FAIL: gcc.c-torture/execute/stdarg-1.c execution,  -O3 -g 
FAIL: gcc.c-torture/execute/stdarg-4.c execution,  -O1 
FAIL: gcc.c-torture/execute/stdarg-4.c execution,  -O2 
FAIL: gcc.c-torture/execute/stdarg-4.c execution,  -O3 -fomit-frame-pointer 
FAIL: gcc.c-torture/execute/stdarg-4.c execution,  -O3 -g 
FAIL: gcc.c-torture/execute/stdarg-4.c execution,  -Os 
...
FAIL: gcc.dg/tree-ssa/stdarg-2.c scan-tree-dump stdarg "f15: va_list escapes 1,
needs to save all GPR units and all FPR units"

Before new SRA, stdarg dump for gcc.dg/tree-ssa/stdarg-2.c, f15 () showed:

--cut here--
va_list escapes in # .MEMD.2039_12 = VDEF <.MEMD.2039_2>
apD.2040 = apD.1263;

f15: va_list escapes 1, needs to save all GPR units and all FPR units.
--cut here--

With new SRA (r147980):

bb2 will be executed at most once for each va_start in bb2
bb3 will be executed at most once for each va_start in bb2
f15: va_list escapes 0, needs to save 8 GPR units and 0 FPR units.

The last OK testresults were from r147610 [3] and started to fail in r148747
[4]

The problem can be triggered by compiling following test (distilled from
stdarg-2.c) with a crosscompiler to alpha-linux-gnu:

--cut here--
typedef __builtin_va_list __gnuc_va_list;
typedef __gnuc_va_list va_list;

long x;

inline void __attribute__((always_inline))
f15_1 (va_list ap)
{
  x = __builtin_va_arg(ap,long);
}

void
f15 (int i, ...)
{
  va_list ap;
  __builtin_va_start(ap,i);
  f15_1 (ap);
  __builtin_va_end(ap);
}
--cut here--

gcc -O2 -fdump-tree-stdarg.

Runtime failure will be triggered by following test (sorry for the debug
printk's):

--cut here--
# 1 "t.c"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "t.c"
# 1 "/space/uros/gcc-build-44/gcc/include/stdarg.h" 1 3 4
# 40 "/space/uros/gcc-build-44/gcc/include/stdarg.h" 3 4
typedef __builtin_va_list __gnuc_va_list;
# 102 "/space/uros/gcc-build-44/gcc/include/stdarg.h" 3 4
typedef __gnuc_va_list va_list;
# 2 "t.c" 2

extern void abort (void);

int foo_arg;
long x;

void
foo (int v, va_list ap)
{
  printf ("__base = %p\n", ap.__base);
  printf ("__offset = %i\n", ap.__offset);
  switch (v)
    {
    case 5: foo_arg = __builtin_va_arg(ap,int);
    printf ("foo_arg = %i\n", foo_arg);
    break;
    default: abort ();
    }
  printf ("__base = %p\n", ap.__base);
  printf ("__offset = %i\n", ap.__offset);
}

void
__attribute__((noinline))
f4 (int i, ...)
{
  va_list ap;
  __builtin_va_start(ap,i);
  printf ("f4 __base = %p\n", ap.__base);
  printf ("f4 __offset = %i\n", ap.__offset);
  x = __builtin_va_arg(ap,double);


  foo (i, ap);

  printf ("f4 __base = %p\n", ap.__base);
  printf ("f4 __offset = %i\n", ap.__offset);
  __builtin_va_end(ap);
}

int
main (void)
{
f4 (5, 16.0, 128);
  if (x != 16 || foo_arg != 128)
    abort ();
return 0;
}
--cut here--

foo_arg will be 0 at the final test.

[1] http://gcc.gnu.org/ml/gcc-cvs/2009-05/msg00959.html

[2] http://gcc.gnu.org/ml/gcc-testresults/2009-08/msg01508.html
[3] http://gcc.gnu.org/ml/gcc-testresults/2009-05/msg01614.html
[4] http://gcc.gnu.org/ml/gcc-testresults/2009-06/msg01912.html


-- 
           Summary: [4.5 Regression] r147980 (New SRA) breaks stdargs
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: ubizjak at gmail dot com
GCC target triplet: alphaev68-unknown-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41089