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widening_mul: Fix up further r14-8680 widening mul issues [PR119417]

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The following testcase is miscompiled since r14-8680 PR113560 changes.
I've already tried to fix some of the issues caused by that change in
r14-8823 PR113759, but apparently didn't get it right.

The problem is that the r14-8680 changes sometimes set *type_out to
a narrower type than the *new_rhs_out actually has (because it will
handle stuff like _1 = rhs1 & 0xffff; and imply from that HImode type_out.

Now, if in convert_mult_to_widen or convert_plusminus_to_widen we actually
get optab for the modes we've asked for (i.e. with from_mode and to_mode),
everything works fine, if the operands don't have the expected types,
they are converted to those (for INTEGER_CSTs with fold_convert,
otherwise with build_and_insert_cast).
On the following testcase on aarch64 that is not the case, we ask
for from_mode HImode and to_mode DImode, but get actual_mode SImode.
The mult_rhs1 operand already has SImode and we change type1 to unsigned int
and so no cast is actually done, except that the & 0xffff is lost that way.

The following patch ensures that if we change typeN because of wider
actual_mode (or because of a sign change), we first cast to the old
typeN (if the r14-8680 code was encountered, otherwise it would have the
same precision) and only then change it, and then perhaps cast again.

On the testcase on aarch64-linux the patch results in the expected
-       add     x19, x19, w0, uxtw 1
+       add     x19, x19, w0, uxth 1
difference.

2025-03-26  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/119417
	* tree-ssa-math-opts.cc (convert_mult_to_widen): Before changing
	typeN because actual_precision/from_unsignedN differs cast rhsN
	to typeN if it has a different type.
	(convert_plusminus_to_widen): Before changing
	typeN because actual_precision/from_unsignedN differs cast mult_rhsN
	to typeN if it has a different type.

	* gcc.dg/torture/pr119417.c: New test.
This commit is contained in:
Jakub Jelinek
2025-03-26 14:03:50 +01:00
committed by Jakub Jelinek
parent fb71d7c8e7
commit 02132faf4e
2 changed files with 68 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

24
gcc/testsuite/gcc.dg/torture/pr119417.c Normal file
View File

@@ -0,0 +1,24 @@
/* PR tree-optimization/119417 */
/* { dg-do run { target int32 } } */
__attribute__((noipa)) void
foo (unsigned long long x)
{
if (x != 0)
__builtin_abort ();
}
unsigned v = 0x10000;
int
main ()
{
unsigned long long a = 0;
while (1)
{
a = a + ((v & 0xFFFF) * 2);
foo (a);
if (v)
break;
}
}

48
gcc/tree-ssa-math-opts.cc
View File

@@ -2800,7 +2800,17 @@ convert_mult_to_widen (gimple *stmt, gimple_stmt_iterator *gsi)
return false;
if (actual_precision != TYPE_PRECISION (type1)
|| from_unsigned1 != TYPE_UNSIGNED (type1))
type1 = build_nonstandard_integer_type (actual_precision, from_unsigned1);
{
if (!useless_type_conversion_p (type1, TREE_TYPE (rhs1)))
{
if (TREE_CODE (rhs1) == INTEGER_CST)
rhs1 = fold_convert (type1, rhs1);
else
rhs1 = build_and_insert_cast (gsi, loc, type1, rhs1);
}
type1 = build_nonstandard_integer_type (actual_precision,
from_unsigned1);
}
if (!useless_type_conversion_p (type1, TREE_TYPE (rhs1)))
{
if (TREE_CODE (rhs1) == INTEGER_CST)
@@ -2810,7 +2820,17 @@ convert_mult_to_widen (gimple *stmt, gimple_stmt_iterator *gsi)
}
if (actual_precision != TYPE_PRECISION (type2)
|| from_unsigned2 != TYPE_UNSIGNED (type2))
type2 = build_nonstandard_integer_type (actual_precision, from_unsigned2);
{
if (!useless_type_conversion_p (type2, TREE_TYPE (rhs2)))
{
if (TREE_CODE (rhs2) == INTEGER_CST)
rhs2 = fold_convert (type2, rhs2);
else
rhs2 = build_and_insert_cast (gsi, loc, type2, rhs2);
}
type2 = build_nonstandard_integer_type (actual_precision,
from_unsigned2);
}
if (!useless_type_conversion_p (type2, TREE_TYPE (rhs2)))
{
if (TREE_CODE (rhs2) == INTEGER_CST)
@@ -3021,7 +3041,17 @@ convert_plusminus_to_widen (gimple_stmt_iterator *gsi, gimple *stmt,
actual_precision = GET_MODE_PRECISION (actual_mode);
if (actual_precision != TYPE_PRECISION (type1)
|| from_unsigned1 != TYPE_UNSIGNED (type1))
type1 = build_nonstandard_integer_type (actual_precision, from_unsigned1);
{
if (!useless_type_conversion_p (type1, TREE_TYPE (mult_rhs1)))
{
if (TREE_CODE (mult_rhs1) == INTEGER_CST)
mult_rhs1 = fold_convert (type1, mult_rhs1);
else
mult_rhs1 = build_and_insert_cast (gsi, loc, type1, mult_rhs1);
}
type1 = build_nonstandard_integer_type (actual_precision,
from_unsigned1);
}
if (!useless_type_conversion_p (type1, TREE_TYPE (mult_rhs1)))
{
if (TREE_CODE (mult_rhs1) == INTEGER_CST)
@@ -3031,7 +3061,17 @@ convert_plusminus_to_widen (gimple_stmt_iterator *gsi, gimple *stmt,
}
if (actual_precision != TYPE_PRECISION (type2)
|| from_unsigned2 != TYPE_UNSIGNED (type2))
type2 = build_nonstandard_integer_type (actual_precision, from_unsigned2);
{
if (!useless_type_conversion_p (type2, TREE_TYPE (mult_rhs2)))
{
if (TREE_CODE (mult_rhs2) == INTEGER_CST)
mult_rhs2 = fold_convert (type2, mult_rhs2);
else
mult_rhs2 = build_and_insert_cast (gsi, loc, type2, mult_rhs2);
}
type2 = build_nonstandard_integer_type (actual_precision,
from_unsigned2);
}
if (!useless_type_conversion_p (type2, TREE_TYPE (mult_rhs2)))
{
if (TREE_CODE (mult_rhs2) == INTEGER_CST)