LGTM. Thanks!
在 2022/11/9 下午3:26, 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. --- v1 -> v2: break instead of continue if the inc/dec will overflow. So the logic wouldn't be changed if signed overflow was defined to wrap. Bootstrapped and regtested on loongarch64-linux-gnu. Ok for trunk? gcc/config/loongarch/loongarch.cc | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/gcc/config/loongarch/loongarch.cc b/gcc/config/loongarch/loongarch.cc index f54c233f90c..8d5d8d965dd 100644 --- a/gcc/config/loongarch/loongarch.cc +++ b/gcc/config/loongarch/loongarch.cc @@ -4178,10 +4178,13 @@ loongarch_emit_int_compare (enum rtx_code *code, rtx *op0, rtx *op1) if (!increment && !decrement) continue;+ if ((increment && rhs == HOST_WIDE_INT_MAX)+ || (decrement && rhs == HOST_WIDE_INT_MIN)) + break; + 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];
