| Message ID | 20221104063942.1594844-1-xry111@xry111.site |
|---|---|
| State | New |
| Headers | show |
| Series | LoongArch: fix signed overflow in loongarch_emit_int_compare | expand |
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];
On Sun, 2022-11-06 at 09:46 +0800, Lulu Cheng wrote: > 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]. Ah yes, I misread the code :(.
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];