[gcc r14-4643] combine: Fix handling of unsigned constants

[gcc r14-4643] combine: Fix handling of unsigned constants

[Stefan Schulze Frielinghaus]

https://gcc.gnu.org/g:648d30716d0cdb5dec96b2da9ed23328bad7cb9f

commit r14-4643-g648d30716d0cdb5dec96b2da9ed23328bad7cb9f
Author: Stefan Schulze Frielinghaus <stefansf@linux.ibm.com>
Date:   Sun Oct 15 11:20:01 2023 +0200

    combine: Fix handling of unsigned constants
    
    If a CONST_INT represents an integer of a mode with fewer bits than in
    HOST_WIDE_INT, then the integer is sign extended.  For those two
    optimizations touched by this patch, the integers of interest have only
    the most significant bit set w.r.t their mode, therefore, they were sign
    extended.  Thus in order to get the integer of interest, we have to chop
    off the high bits.
    
    gcc/ChangeLog:
    
            * combine.cc (simplify_compare_const): Fix handling of unsigned
            constants.

Diff:
---
 gcc/combine.cc | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/gcc/combine.cc b/gcc/combine.cc
index 360aa2f25e6..cb48e7f5b97 100644
--- a/gcc/combine.cc
+++ b/gcc/combine.cc
@@ -11923,7 +11923,7 @@ simplify_compare_const (enum rtx_code code, machine_mode mode,
       /* (unsigned) < 0x80000000 is equivalent to >= 0.  */
       else if (is_a <scalar_int_mode> (mode, &int_mode)
 	       && GET_MODE_PRECISION (int_mode) - 1 < HOST_BITS_PER_WIDE_INT
-	       && ((unsigned HOST_WIDE_INT) const_op
+	       && (((unsigned HOST_WIDE_INT) const_op & GET_MODE_MASK (int_mode))
 		   == HOST_WIDE_INT_1U << (GET_MODE_PRECISION (int_mode) - 1)))
 	{
 	  const_op = 0;
@@ -11962,7 +11962,7 @@ simplify_compare_const (enum rtx_code code, machine_mode mode,
       /* (unsigned) >= 0x80000000 is equivalent to < 0.  */
       else if (is_a <scalar_int_mode> (mode, &int_mode)
 	       && GET_MODE_PRECISION (int_mode) - 1 < HOST_BITS_PER_WIDE_INT
-	       && ((unsigned HOST_WIDE_INT) const_op
+	       && (((unsigned HOST_WIDE_INT) const_op & GET_MODE_MASK (int_mode))
 		   == HOST_WIDE_INT_1U << (GET_MODE_PRECISION (int_mode) - 1)))
 	{
 	  const_op = 0;