在 2022/11/4 下午2:39, Xi Ruoyao 写道:
Signed overflow is an undefined behavior, so we need to prevent it from
happening, instead of "checking" the result.
gcc/ChangeLog:
* config/loongarch/loongarch.cc (loongarch_emit_int_compare):
Avoid signed overflow.
---
Bootstrapped and regtested on loongarch64-linux-gnu. OK for trunk?
gcc/config/loongarch/loongarch.cc | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/gcc/config/loongarch/loongarch.cc
b/gcc/config/loongarch/loongarch.cc
index f54c233f90c..032fb1474c7 100644
--- a/gcc/config/loongarch/loongarch.cc
+++ b/gcc/config/loongarch/loongarch.cc
@@ -4175,13 +4175,14 @@ loongarch_emit_int_compare (enum rtx_code *code, rtx
*op0, rtx *op1)
HOST_WIDE_INT new_rhs;
bool increment = *code == mag_comparisons[i][0];
bool decrement = *code == mag_comparisons[i][1];
- if (!increment && !decrement)
+ if ((!increment && !decrement)
+ || (increment && rhs == HOST_WIDE_INT_MAX)
+ || (decrement && rhs == HOST_WIDE_INT_MIN))
continue;
I think it should be here:
if (!increment && !decrement)
continue;
+ if ((increment && rhs == HOST_WIDE_INT_MAX)
+ || (decrement && rhs == HOST_WIDE_INT_MIN))
+ break;
+
It is not necessary to continue when *code matches one of
mag_comparisons[i].
new_rhs = rhs + (increment ? 1 : -1);
if (loongarch_integer_cost (new_rhs)
- < loongarch_integer_cost (rhs)
- && (rhs < 0) == (new_rhs < 0))
+ < loongarch_integer_cost (rhs))
{
*op1 = GEN_INT (new_rhs);
*code = mag_comparisons[i][increment];
