[llvm] [AArch64] - Fold and and cmp into tst (PR #110347)

[Jorge Botto via llvm-commits]

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@@ -4301,6 +4301,29 @@ static SDValue LowerPREFETCH(SDValue Op, SelectionDAG &DAG) {
                      Op.getOperand(1));
 }
 
+// Converts SETCC (AND X Y) Z ULT -> SETCC (AND X (Y & ~(Z - 1)) 0 EQ when Y is
+// a power of 2. This is then lowered to ANDS X (Y & ~(Z - 1)) instead of SUBS
+// (AND X Y) Z which produces a better opt with EmitComparison
+static void simplifySetCCIntoEq(ISD::CondCode &CC, SDValue &LHS, SDValue &RHS,
+                                SelectionDAG &DAG, const SDLoc dl) {
+  if (CC == ISD::SETULT && LHS.getOpcode() == ISD::AND && LHS->hasOneUse()) {
+    ConstantSDNode *LHSConstOp = dyn_cast<ConstantSDNode>(LHS.getOperand(1));
+    ConstantSDNode *RHSConst = dyn_cast<ConstantSDNode>(RHS);
+    if (LHSConstOp && RHSConst) {
+      uint64_t lhsConstValue = LHSConstOp->getZExtValue();
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jf-botto wrote:

Apologies, fixed it.

https://github.com/llvm/llvm-project/pull/110347