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rtl-optimization/110939 Really fix narrow comparison of memory and constant

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In the former fix in commit 41ef5a3416 I
completely missed the fact that the normal form of a CONST_INT for a
mode with fewer bits than in HOST_WIDE_INT is a sign extended version of
the actual constant.  This even holds true for unsigned constants.

Fixed by masking out the upper bits for the incoming constant and sign
extending the resulting unsigned constant.

gcc/ChangeLog:

	* combine.cc (simplify_compare_const): Properly handle unsigned
	constants while narrowing comparison of memory and constants.
This commit is contained in:
Stefan Schulze Frielinghaus
2023-10-01 16:11:32 +02:00
parent e4a4b8e983
commit 86b2ffc0b8
1 changed files with 10 additions and 9 deletions
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19
gcc/combine.cc
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@@ -12003,14 +12003,15 @@ simplify_compare_const (enum rtx_code code, machine_mode mode,
&& !MEM_VOLATILE_P (op0)
/* The optimization makes only sense for constants which are big enough
so that we have a chance to chop off something at all. */
&& (unsigned HOST_WIDE_INT) const_op > 0xff
/* Bail out, if the constant does not fit into INT_MODE. */
&& (unsigned HOST_WIDE_INT) const_op
< ((HOST_WIDE_INT_1U << (GET_MODE_PRECISION (int_mode) - 1) << 1) - 1)
&& ((unsigned HOST_WIDE_INT) const_op & GET_MODE_MASK (int_mode)) > 0xff
/* Ensure that we do not overflow during normalization. */
&& (code != GTU || (unsigned HOST_WIDE_INT) const_op < HOST_WIDE_INT_M1U))
&& (code != GTU
|| ((unsigned HOST_WIDE_INT) const_op & GET_MODE_MASK (int_mode))
< HOST_WIDE_INT_M1U)
&& trunc_int_for_mode (const_op, int_mode) == const_op)
{
unsigned HOST_WIDE_INT n = (unsigned HOST_WIDE_INT) const_op;
unsigned HOST_WIDE_INT n
= (unsigned HOST_WIDE_INT) const_op & GET_MODE_MASK (int_mode);
enum rtx_code adjusted_code;
/* Normalize code to either LEU or GEU. */
@@ -12051,15 +12052,15 @@ simplify_compare_const (enum rtx_code code, machine_mode mode,
HOST_WIDE_INT_PRINT_HEX ") to (MEM %s "
HOST_WIDE_INT_PRINT_HEX ").\n", GET_MODE_NAME (int_mode),
GET_MODE_NAME (narrow_mode_iter), GET_RTX_NAME (code),
(unsigned HOST_WIDE_INT)const_op, GET_RTX_NAME (adjusted_code),
n);
(unsigned HOST_WIDE_INT) const_op & GET_MODE_MASK (int_mode),
GET_RTX_NAME (adjusted_code), n);
}
poly_int64 offset = (BYTES_BIG_ENDIAN
? 0
: (GET_MODE_SIZE (int_mode)
- GET_MODE_SIZE (narrow_mode_iter)));
*pop0 = adjust_address_nv (op0, narrow_mode_iter, offset);
*pop1 = GEN_INT (n);
*pop1 = gen_int_mode (n, narrow_mode_iter);
return adjusted_code;
}
}