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middle-end: fix epilog reductions when vector iters peeled [PR113364]

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This fixes a bug where vect_create_epilog_for_reduction does not handle the
case where all exits are early exits.  In this case we should do like induction
handling code does and not have a main exit.

This shows that some new miscompiles are happening (stage3 is likely miscompiled)
but that's unrelated to this patch and I'll look at it next.

gcc/ChangeLog:

	PR tree-optimization/113364
	* tree-vect-loop.cc (vect_create_epilog_for_reduction): If all exits all
	early exits then we must reduce from the first offset for all of them.

gcc/testsuite/ChangeLog:

	PR tree-optimization/113364
	* gcc.dg/vect/vect-early-break_107-pr113364.c: New test.
This commit is contained in:
Tamar Christina 2024-01-24 07:37:17 +00:00
parent d89537a141
commit 72429448fd
2 changed files with 24 additions and 1 deletions
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22
gcc/testsuite/gcc.dg/vect/vect-early-break_107-pr113364.c Normal file
View file

@ -0,0 +1,22 @@
/* { dg-do compile } */
/* { dg-add-options vect_early_break } */
/* { dg-require-effective-target vect_early_break } */
/* { dg-require-effective-target vect_int } */
/* { dg-additional-options "-w" } */
typedef const unsigned char *It;
It DecodeSLEB128(It begin, It end, int *v) {
int value = 0;
unsigned shift = 0;
unsigned char byte;
do
{
if (begin == end)
return begin;
byte = *(begin++);
int slice = byte & 0x7f;
value |= slice << shift;
} while (byte >= 128);
*v = value;
return begin;
}

3
gcc/tree-vect-loop.cc
View file

@ -5982,7 +5982,8 @@ vect_create_epilog_for_reduction (loop_vec_info loop_vinfo,
loop-closed PHI of the inner loop which we remember as
def for the reduction PHI generation. */
bool double_reduc = false;
bool main_exit_p = LOOP_VINFO_IV_EXIT (loop_vinfo) == loop_exit;
bool main_exit_p = LOOP_VINFO_IV_EXIT (loop_vinfo) == loop_exit
&& !LOOP_VINFO_EARLY_BREAKS_VECT_PEELED (loop_vinfo);
stmt_vec_info rdef_info = stmt_info;
if (STMT_VINFO_DEF_TYPE (stmt_info) == vect_double_reduction_def)
{