[PATCH] D107692: [DAGCombine] Prevent the transform of combine for multi-use operand

[Allen zhong via Phabricator via llvm-commits]

Allen added a comment.

In D107692#2946669 <https://reviews.llvm.org/D107692#2946669>, @lebedev.ri wrote:

> Please,
>
> 1. either add a comment explaining why the one-use check needed
> 2. or rewrite the transform the right way, so that the lack of one-use check shows up as extra instruction bloat and not a miscompilation

ok, I'll add a comment as  compare between current change and rewritting the transform , current change has more effective code (less inst) .

the following code is with  rewritting the transform in your comment.

  adrp	x8, :got:g
  	ldr	x8, [x8, :got_lo12:g]
  	mov	w9, #50
  	mov	w10, #65535
  	ldrh	w8, [x8]
  	eor	w9, w8, w9
  	add	w9, w9, w10
  	sub	w8, w8, #1
  	and	w0, w8, w9, lsr #16
  	ret



================
Comment at: llvm/test/CodeGen/AArch64/arm64-srl-and.ll:7
+ at g = dso_local local_unnamed_addr global i16 0, align 4
+define dso_local noundef i32 @srl_and() local_unnamed_addr  {
+; CHECK-LABEL: srl_and:
----------------
RKSimon wrote:
> do you need all the dso_local/noundef/local_unnamed_addr attributes?
yes, they are not essential, and i'll delete them later


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https://reviews.llvm.org/D107692