================
@@ -14944,6 +14945,51 @@ SDValue SITargetLowering::performAddCombine(SDNode *N,
return SDValue();
}
+SDValue SITargetLowering::performPtrAddCombine(SDNode *N,
+ DAGCombinerInfo &DCI) const {
+ SelectionDAG &DAG = DCI.DAG;
+ SDLoc DL(N);
+ SDValue N0 = N->getOperand(0);
+ SDValue N1 = N->getOperand(1);
+
+ if (N1.getOpcode() == ISD::ADD) {
+ // (ptradd x, (add y, z)) -> (ptradd (ptradd x, y), z) if z is a constant,
+ // y is not, and (add y, z) is used only once.
+ // (ptradd x, (add y, z)) -> (ptradd (ptradd x, z), y) if y is a constant,
+ // z is not, and (add y, z) is used only once.
+ // The goal is to move constant offsets to the outermost ptradd, to create
+ // more opportunities to fold offsets into memory instructions.
+ // Together with the generic combines in DAGCombiner.cpp, this also
+ // implements (ptradd (ptradd x, y), z) -> (ptradd (ptradd x, z), y)).
+ //
+ // This transform is here instead of in the general DAGCombiner as it can
+ // turn in-bounds pointer arithmetic out-of-bounds, which is problematic
for
+ // AArch64's CPA.
+ SDValue X = N0;
+ SDValue Y = N1.getOperand(0);
+ SDValue Z = N1.getOperand(1);
+ bool N1OneUse = N1.hasOneUse();
+ bool YIsConstant = DAG.isConstantIntBuildVectorOrConstantInt(Y);
+ bool ZIsConstant = DAG.isConstantIntBuildVectorOrConstantInt(Z);
+ if ((ZIsConstant != YIsConstant) && N1OneUse) {
+ SDNodeFlags Flags;
+ // If both additions in the original were NUW, the new ones are as well.
+ if (N->getFlags().hasNoUnsignedWrap() &&
+ N1->getFlags().hasNoUnsignedWrap())
+ Flags |= SDNodeFlags::NoUnsignedWrap;
----------------
arsenm wrote:
Can you do SDNodeFlags = (N->getFlags() & N1->getFlags()) &
SDNodeFlags::NoUnsignedWrap?
https://github.com/llvm/llvm-project/pull/142739
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