diff options
Diffstat (limited to 'compiler/rustc_codegen_cranelift/src/num.rs')
| -rw-r--r-- | compiler/rustc_codegen_cranelift/src/num.rs | 17 |
1 files changed, 10 insertions, 7 deletions
diff --git a/compiler/rustc_codegen_cranelift/src/num.rs b/compiler/rustc_codegen_cranelift/src/num.rs index 2ebf30da2d8..b6d378a5fe1 100644 --- a/compiler/rustc_codegen_cranelift/src/num.rs +++ b/compiler/rustc_codegen_cranelift/src/num.rs @@ -271,14 +271,17 @@ pub(crate) fn codegen_checked_int_binop<'tcx>( let val_hi = fx.bcx.ins().umulhi(lhs, rhs); fx.bcx.ins().icmp_imm(IntCC::NotEqual, val_hi, 0) } else { + // Based on LLVM's instruction sequence for compiling + // a.checked_mul(b).is_some() to riscv64gc: + // mulh a2, a0, a1 + // mul a0, a0, a1 + // srai a0, a0, 63 + // xor a0, a0, a2 + // snez a0, a0 let val_hi = fx.bcx.ins().smulhi(lhs, rhs); - let not_all_zero = fx.bcx.ins().icmp_imm(IntCC::NotEqual, val_hi, 0); - let not_all_ones = fx.bcx.ins().icmp_imm( - IntCC::NotEqual, - val_hi, - u64::try_from((1u128 << ty.bits()) - 1).unwrap() as i64, - ); - fx.bcx.ins().band(not_all_zero, not_all_ones) + let val_sign = fx.bcx.ins().sshr_imm(val, i64::from(ty.bits() - 1)); + let xor = fx.bcx.ins().bxor(val_hi, val_sign); + fx.bcx.ins().icmp_imm(IntCC::NotEqual, xor, 0) }; (val, has_overflow) } |