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veclower: Fix up -fcompare-debug issue in expand_vector_comparison [PR104307]

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The following testcase fails -fcompare-debug, because expand_vector_comparison
since r11-1786-g1ac9258cca8030745d3c0b8f63186f0adf0ebc27 sets
vec_cond_expr_only when it sees some use other than VEC_COND_EXPR that uses
the lhs in its condition.
Obviously we should ignore debug stmts when doing so, e.g. by not pushing
them to uses.
That would be a 2 liner change, but while looking at it, I'm also worried
about VEC_COND_EXPRs that would use the lhs in more than one operand,
like VEC_COND_EXPR <lhs, lhs, something> or VEC_COND_EXPR <lhs, something, lhs>
(sure, they ought to be folded, but what if they weren't).  Because if
something like that happens, then FOR_EACH_IMM_USE_FAST would push the same
stmt multiple times and expand_vector_condition can return true even when
it modifies it (for vector bool masking).
And lastly, it seems quite wasteful to safe_push statements that will just
cause vec_cond_expr_only = false; and break; in the second loop, both for
cases like 1000 immediate non-VEC_COND_EXPR uses and for cases like
999 VEC_COND_EXPRs with lhs in cond followed by a single non-VEC_COND_EXPR
use.  So this patch only pushes VEC_COND_EXPRs there.

2022-02-01  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/104307
	* tree-vect-generic.cc (expand_vector_comparison): Don't push debug
	stmts to uses vector, just set vec_cond_expr_only to false for
	non-VEC_COND_EXPRs instead of pushing them into uses.  Treat
	VEC_COND_EXPRs that use lhs not just in rhs1, but rhs2 or rhs3 too
	like non-VEC_COND_EXPRs.

	* gcc.target/i386/pr104307.c: New test.
This commit is contained in:
Jakub Jelinek 2022-02-01 16:02:54 +01:00
parent 7e83607907
commit e9bf6d6b0e
2 changed files with 26 additions and 18 deletions
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6
gcc/testsuite/gcc.target/i386/pr104307.c Normal file
View File

@ -0,0 +1,6 @@
/* PR middle-end/104307 */
/* { dg-do compile } */
/* { dg-require-effective-target int128 } */
/* { dg-options "-O2 -mavx512f -fcompare-debug " } */
#include "pr78669.c"

26
gcc/tree-vect-generic.cc
View File

@ -436,14 +436,22 @@ expand_vector_comparison (gimple_stmt_iterator *gsi, tree type, tree op0,
feeding a VEC_COND_EXPR statement. */
auto_vec<gimple *> uses;
FOR_EACH_IMM_USE_FAST (use_p, iterator, lhs)
uses.safe_push (USE_STMT (use_p));
for (unsigned i = 0; i < uses.length (); i ++)
{
gassign *use = dyn_cast<gassign *> (uses[i]);
if (use != NULL
gimple *use = USE_STMT (use_p);
if (is_gimple_debug (use))
continue;
if (is_gimple_assign (use)
&& gimple_assign_rhs_code (use) == VEC_COND_EXPR
&& gimple_assign_rhs1 (use) == lhs)
&& gimple_assign_rhs1 (use) == lhs
&& gimple_assign_rhs2 (use) != lhs
&& gimple_assign_rhs3 (use) != lhs)
uses.safe_push (use);
else
vec_cond_expr_only = false;
}
if (vec_cond_expr_only)
for (gimple *use : uses)
{
gimple_stmt_iterator it = gsi_for_stmt (use);
if (!expand_vector_condition (&it, dce_ssa_names))
@ -452,12 +460,6 @@ expand_vector_comparison (gimple_stmt_iterator *gsi, tree type, tree op0,
break;
}
}
else
{
vec_cond_expr_only = false;
break;
}
}
if (!uses.is_empty () && vec_cond_expr_only)
return NULL_TREE;