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[committed][PR rtl-optimization/116544] Fix test for promoted subregs

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This is a small bug in the ext-dce code's handling of promoted subregs.

Essentially when we see a promoted subreg we need to make additional bit groups
live as various parts of the RTL path know that an extension of a suitably
promoted subreg can be trivially eliminated.

When I added support for dealing with this quirk I failed to account for the
larger modes properly and it ignored the case when the size of the inner object
was > 32 bits.  Opps.

This does _not_ fix the outstanding x86 issue.  That's caused by something
completely different and more concerning ;(

Bootstrapped and regression tested on x86.  Obviously fixes the testcase on
riscv as well.

Pushing to the trunk.

	PR rtl-optimization/116544
gcc/
	* ext-dce.cc (ext_dce_process_uses): Fix thinko in promoted subreg
	handling.

gcc/testsuite/
	* gcc.dg/torture/pr116544.c: New test.
This commit is contained in:
Jeff Law 2024-09-01 22:16:04 -06:00
parent f77435aa39
commit 0562976d62
2 changed files with 23 additions and 1 deletions
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2
gcc/ext-dce.cc
View file

@ -846,7 +846,7 @@ ext_dce_process_uses (rtx_insn *insn, rtx obj,
bitmap_set_bit (livenow, rn + 1);
if (size > 16)
bitmap_set_bit (livenow, rn + 2);
if (size == 32)
if (size >= 32)
bitmap_set_bit (livenow, rn + 3);
iter.skip_subrtxes ();
}

22
gcc/testsuite/gcc.dg/torture/pr116544.c Normal file
View file

@ -0,0 +1,22 @@
/* { dg-options "-fno-strict-aliasing -fwrapv" }
/* { dg-do run { target longlong64 } } */
extern void abort (void);
long long a;
signed char b[60];
signed char c;
long long d[60];
int e[30];
long long *f = d;
static void g(long long *j, long k) { *j = k; }
int main() {
d[5] = 0x100000000;
for (int h = 2; h < 7; h += 3)
for (int i = 0; i < (c || b[h]) + 10; i += 11)
e[2] = f[h];
g(&a, e[2]);
if (a != 0)
abort ();
return 0;
}