[all-commits] [llvm/llvm-project] d337c1: [AArch64] Use SUBXrx64 for dynamic stack to refer ...

[chenglin.bi via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: d337c1f2565a748bcf3f162d0754a362b2c597a4
      https://github.com/llvm/llvm-project/commit/d337c1f2565a748bcf3f162d0754a362b2c597a4
  Author: chenglin.bi <chenglin.bi at linaro.org>
  Date:   2022-07-20 (Wed, 20 Jul 2022)

  Changed paths:
    M llvm/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp
    M llvm/lib/Target/AArch64/AArch64InstrFormats.td
    M llvm/lib/Target/AArch64/AArch64InstrInfo.td
    M llvm/test/CodeGen/AArch64/win-alloca.ll
    M llvm/test/CodeGen/AArch64/win64_vararg.ll

  Log Message:
  -----------
  [AArch64] Use SUBXrx64 for dynamic stack to refer to sp

When we lower dynamic stack, we need to substract pattern `x15 << 4`  from sp.
Subtract instruction with arith shifted register(SUBXrs) can't refer to sp. So for now we need two extra mov like:

```
mov x0, sp
sub x0, x0, x15, lsl #4
mov sp, x0
```
If we want to refer to sp in subtract instruction like this:
```
sub	sp, sp, x15, lsl #4
```
We must use arith extended register version(SUBXrx).
So in this patch when we find sub have sp operand on src0, try to select to SubXrx64.

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D129932