[AArch64] The multiplication instruction is missing

[dianqk]

I tried the following code:

define i32 @shift_overflow(i32 %x) {
  %const = bitcast i32 2147483648 to i32
  %r = mul i32 %x, %const
  ret i32 %r
}

I expect to get a multiplication or alternative instruction on AArch64, but I can only get a ret instruction: https://llvm.godbolt.org/z/xcffaPT9s.

[llvmbot]

@llvm/issue-subscribers-backend-aarch64

Author: DianQK (DianQK)

I tried the following code:

define i32 @<!-- -->shift_overflow(i32 %x) {
  %const = bitcast i32 2147483648 to i32
  %r = mul i32 %x, %const
  ret i32 %r
}

I expect to get a multiplication or alternative instruction on AArch64, but I can only get a ret instruction: https://llvm.godbolt.org/z/xcffaPT9s.