llvm-project

a3eb13b5 - [X86] remove unnecessary movs when %rdx is an input to mulx (#184462)

[X86] remove unnecessary movs when %rdx is an input to mulx (#184462) Closes: https://github.com/llvm/llvm-project/issues/174912 When generating a `mulx` instruction for a widening multiplication, even if one input is placed in %rdx, LLVM won't place it in the implicit first slot, instead it'll generate two movs before calling mulx to swap the registers, which are unnecessary. GCC already has this optimization (as shown in the issue) so this puts the two compilers closer to each other on that front. Co-authored-by: Aiden Grossman <aidengrossman@google.com>