[llvm] [AArch64] Remove cmp/cmn "tiebreaker" (PR #191929)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-aarch64

Author: SiliconA-Z

<details>
<summary>Changes</summary>

We do not need it and it is confusing/misleading in cmp/cmn side-chooser

---
Full diff: https://github.com/llvm/llvm-project/pull/191929.diff


1 Files Affected:

- (modified) llvm/lib/Target/AArch64/AArch64ISelLowering.cpp (+4-6) 


``````````diff
diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index ece24767bdbb9..1f2bb86b66725 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -4248,13 +4248,11 @@ static SDValue getAArch64Cmp(SDValue LHS, SDValue RHS, ISD::CondCode CC,
   // can be turned into:
   //    cmp     w12, w11, lsl #1
   if (!isa<ConstantSDNode>(RHS) || !isLegalCmpImmed(RHS->getAsAPIntVal())) {
-    bool LHSIsCMN = isCMN(LHS, CC, DAG);
-    bool RHSIsCMN = isCMN(RHS, CC, DAG);
-    SDValue TheLHS = LHSIsCMN ? LHS.getOperand(1) : LHS;
-    SDValue TheRHS = RHSIsCMN ? RHS.getOperand(1) : RHS;
+    SDValue TheLHS = isCMN(LHS, CC, DAG) ? LHS.getOperand(1) : LHS;
+    SDValue TheRHS = isCMN(RHS, CC, DAG) ? RHS.getOperand(1) : RHS;
 
-    if (getCmpOperandFoldingProfit(TheLHS) + (LHSIsCMN ? 1 : 0) >
-        getCmpOperandFoldingProfit(TheRHS) + (RHSIsCMN ? 1 : 0)) {
+    if (getCmpOperandFoldingProfit(TheLHS) >
+        getCmpOperandFoldingProfit(TheRHS)) {
       std::swap(LHS, RHS);
       CC = ISD::getSetCCSwappedOperands(CC);
     }

``````````

</details>


https://github.com/llvm/llvm-project/pull/191929