https://gcc.gnu.org/g:76cbd678d123ed93f99c4c52456bc14290f19b7f
commit r16-1420-g76cbd678d123ed93f99c4c52456bc14290f19b7f
Author: Uros Bizjak <ubiz...@gmail.com>
Date: Wed Jun 11 14:12:33 2025 +0200
i386: Fix signed integer overflow in ix86_expand_int_movcc [PR120604]
Patch for PR120553 enabled full 64-bit DImode immediates in
ix86_expand_int_movcc. However, the function calculates the difference
between two immediate arguments using signed 64-bit HOST_WIDE_INT
subtractions that can cause signed integer overflow.
Avoid the overflow by casting operands of subtractions to
(unsigned HOST_WIDE_INT).
PR target/120604
gcc/ChangeLog:
* config/i386/i386-expand.cc (ix86_expand_int_movcc): Cast operands
of
signed 64-bit HOST_WIDE_INT subtractions to (unsigned
HOST_WIDE_INT).
Diff:
---
gcc/config/i386/i386-expand.cc | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)
diff --git a/gcc/config/i386/i386-expand.cc b/gcc/config/i386/i386-expand.cc
index 181e64a86bf6..5c8c18f98834 100644
--- a/gcc/config/i386/i386-expand.cc
+++ b/gcc/config/i386/i386-expand.cc
@@ -3609,7 +3609,7 @@ ix86_expand_int_movcc (rtx operands[])
negate_cc_compare_p = true;
}
- diff = ct - cf;
+ diff = (unsigned HOST_WIDE_INT) ct - (unsigned HOST_WIDE_INT) cf;
/* Sign bit compares are better done using shifts than we do by using
sbb. */
if (sign_bit_compare_p
@@ -3667,7 +3667,8 @@ ix86_expand_int_movcc (rtx operands[])
PUT_CODE (compare_op,
reverse_condition (GET_CODE (compare_op)));
}
- diff = ct - cf;
+
+ diff = (unsigned HOST_WIDE_INT) ct - (unsigned HOST_WIDE_INT) cf;
if (reg_overlap_mentioned_p (out, compare_op))
tmp = gen_reg_rtx (mode);
@@ -3685,7 +3686,8 @@ ix86_expand_int_movcc (rtx operands[])
else
{
std::swap (ct, cf);
- diff = ct - cf;
+ diff = (unsigned HOST_WIDE_INT) ct
+ - (unsigned HOST_WIDE_INT) cf;
}
tmp = emit_store_flag (tmp, code, op0, op1, VOIDmode, 0, -1);
}
@@ -3752,9 +3754,11 @@ ix86_expand_int_movcc (rtx operands[])
tmp = expand_simple_unop (mode, NOT, tmp, copy_rtx (tmp), 1);
}
+ HOST_WIDE_INT ival = (unsigned HOST_WIDE_INT) cf
+ - (unsigned HOST_WIDE_INT) ct;
tmp = expand_simple_binop (mode, AND,
copy_rtx (tmp),
- gen_int_mode (cf - ct, mode),
+ gen_int_mode (ival, mode),
copy_rtx (tmp), 1, OPTAB_DIRECT);
if (ct)
tmp = expand_simple_binop (mode, PLUS,
@@ -3791,7 +3795,7 @@ ix86_expand_int_movcc (rtx operands[])
if (new_code != UNKNOWN)
{
std::swap (ct, cf);
- diff = -diff;
+ diff = (unsigned HOST_WIDE_INT) ct - (unsigned HOST_WIDE_INT) cf;
code = new_code;
}
}
@@ -3994,8 +3998,10 @@ ix86_expand_int_movcc (rtx operands[])
copy_rtx (out), 1, OPTAB_DIRECT);
}
+ HOST_WIDE_INT ival = (unsigned HOST_WIDE_INT) cf
+ - (unsigned HOST_WIDE_INT) ct;
out = expand_simple_binop (mode, AND, copy_rtx (out),
- gen_int_mode (cf - ct, mode),
+ gen_int_mode (ival, mode),
copy_rtx (out), 1, OPTAB_DIRECT);
if (ct)
out = expand_simple_binop (mode, PLUS, copy_rtx (out), GEN_INT (ct),
