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;
 
              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];
-- 
2.38.1

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