Remove fold with unhandeable corner case

Author: rgwott

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -2627,11 +2627,11 @@ SDValue DAGCombiner::visitPTRADD(SDNode *N) {
   EVT IntVT = N1.getValueType();
   SDLoc DL(N);
 
-  // fold (ptradd und*f, y) -> und*f
+  // fold (ptradd undef, y) -> undef
   if (N0.isUndef())
     return N0;
 
-  // fold (ptradd x, und*f) -> und*f
+  // fold (ptradd x, undef) -> undef
   if (N1.isUndef())
     return DAG.getUNDEF(PtrVT);
 
@@ -2647,33 +2647,6 @@ SDValue DAGCombiner::visitPTRADD(SDNode *N) {
     bool N0OneUse = N0.hasOneUse();
     bool YIsConstant = DAG.isConstantIntBuildVectorOrConstantInt(Y);
     bool ZIsConstant = DAG.isConstantIntBuildVectorOrConstantInt(Z);
-
-    // (ptradd (ptradd x, y), z) -> (ptradd (ptradd x, z), y) if:
-    //   * (ptradd x, y) has one use; and
-    //   * y is a constant; and
-    //   * z is not a constant.
-    // Serves to expose constant y for subsequent folding.
-    if (N0OneUse && YIsConstant && !ZIsConstant) {
-      SDValue Add = DAG.getNode(ISD::PTRADD, DL, IntVT, {X, Z});
-
-      // Calling visit() can replace the Add node with ISD::DELETED_NODE if
-      // there aren't any users, so keep a handle around whilst we visit it.
-      HandleSDNode ADDHandle(Add);
-
-      SDValue VisitedAdd = visit(Add.getNode());
-      if (VisitedAdd) {
-        // If visit() returns the same node, it means the SDNode was RAUW'd, and
-        // therefore we have to load the new value to perform the checks whether
-        // the reassociation fold is profitable.
-        if (VisitedAdd.getNode() == Add.getNode())
-          Add = ADDHandle.getValue();
-        else
-          Add = VisitedAdd;
-      }
-
-      return DAG.getMemBasePlusOffset(Add, Y, DL, SDNodeFlags());
-    }
-
     bool ZOneUse = Z.hasOneUse();
 
     // (ptradd (ptradd x, y), z) -> (ptradd x, (add y, z)) if:

llvm/test/CodeGen/AArch64/cpa-selectiondag.ll

@@ -62,18 +62,20 @@ entry:
 
 define void @msubpt1(i32 %index, i32 %elem) {
 ; CHECK-CPA-O0-LABEL:    msubpt1:
-; CHECK-CPA-O0:          addpt	[[REG1:x[0-9]+]], x{{[0-9]+}}, x{{[0-9]+}}, lsl #4
-; CHECK-CPA-O0:          addpt	[[REG2:x[0-9]+]], [[REG1]], x{{[0-9]+}}
-; CHECK-CPA-O0:          addpt	[[REG3:x[0-9]+]], x{{[0-9]+}}, x{{[0-9]+}}
-; CHECK-CPA-O0:          ldr	q{{[0-9]+}}, [[[REG3]], #16]
-; CHECK-CPA-O0:          str	q{{[0-9]+}}, [[[REG1]], #288]
-; CHECK-CPA-O0:          str	q{{[0-9]+}}, [[[REG2]], #32]
+; CHECK-CPA-O0:          addpt	[[REG1:x[0-9]+]], x{{[0-9]+}}, [[REG1]]
+; CHECK-CPA-O0:          addpt	[[REG2:x[0-9]+]], x{{[0-9]+}}, [[REG2]]
+; CHECK-CPA-O0:          ldr	q{{[0-9]+}}, [[[REG2]], #16]
+; CHECK-CPA-O0:          ldr	q{{[0-9]+}}, [[[REG2]], #32]
+; CHECK-CPA-O0:          str	q{{[0-9]+}}, [[[REG1]], #32]
+; CHECK-CPA-O0:          str	q{{[0-9]+}}, [[[REG1]], #16]
+; CHECK-CPA-O0:          str	q{{[0-9]+}}, [[[REG1]]]
 ;
 ; CHECK-CPA-O3-LABEL:    msubpt1:
-; CHECK-CPA-O3:          addpt	[[REG1:x[0-9]+]], x{{[0-9]+}}, x{{[0-9]+}}, lsl #4
-; CHECK-CPA-O3:          addpt	[[REG2:x[0-9]+]], [[REG1]], x{{[0-9]+}}
-; CHECK-CPA-O3:          str	q{{[0-9]+}}, [[[REG1]], #288]
+; CHECK-CPA-O3:          addpt	[[REG1:x[0-9]+]], x{{[0-9]+}}, [[REG1]]
+; CHECK-CPA-O3:          ldp	q{{[0-9]+}}, q{{[0-9]+}}, [[[REG1]], #16]
+; CHECK-CPA-O3:          addpt	[[REG2:x[0-9]+]], x{{[0-9]+}}, [[REG2]]
 ; CHECK-CPA-O3:          stp	q{{[0-9]+}}, q{{[0-9]+}}, [[[REG2]], #16]
+; CHECK-CPA-O3:          str	q{{[0-9]+}}, [[[REG2]]]
 ;
 ; CHECK-NOCPA-O0-LABEL:  msubpt1:
 ; CHECK-NOCPA-O0:        mneg	[[REG1:x[0-9]+]], x{{[0-9]+}}, x{{[0-9]+}}
@@ -97,12 +99,12 @@ entry:
 
 define void @subpt1(i32 %index, i32 %elem) {
 ; CHECK-CPA-O0-LABEL:    subpt1:
-; CHECK-CPA-O0:          subpt	[[REG1:x[0-9]+]], x{{[0-9]+}}, x{{[0-9]+}}
-; CHECK-CPA-O0:          str	q{{[0-9]+}}, [[[REG1]], #96]
+; CHECK-CPA-O0:          addpt	[[REG1:x[0-9]+]], x{{[0-9]+}}, [[REG1]]
+; CHECK-CPA-O0:          str	q{{[0-9]+}}, [[[REG1]]]
 ;
 ; CHECK-CPA-O3-LABEL:    subpt1:
-; CHECK-CPA-O3:          subpt	[[REG1:x[0-9]+]], x{{[0-9]+}}, x{{[0-9]+}}
-; CHECK-CPA-O3:          str	q{{[0-9]+}}, [[[REG1]], #96]
+; CHECK-CPA-O3:          addpt	[[REG1:x[0-9]+]], x{{[0-9]+}}, [[REG1]]
+; CHECK-CPA-O3:          str	q{{[0-9]+}}, [[[REG1]]]
 ;
 ; CHECK-NOCPA-O0-LABEL:  subpt1:
 ; CHECK-NOCPA-O0:        subs	[[REG1:x[0-9]+]], x{{[0-9]+}}, x{{[0-9]+}}, lsl #8
@@ -121,12 +123,12 @@ entry:
 
 define void @subpt2(i32 %index, i32 %elem) {
 ; CHECK-CPA-O0-LABEL:    subpt2:
-; CHECK-CPA-O0:          addpt	[[REG1:x[0-9]+]], x{{[0-9]+}}, x{{[0-9]+}}, lsl #4
-; CHECK-CPA-O0:          str	q{{[0-9]+}}, [[[REG1]], #96]
+; CHECK-CPA-O0:          addpt	[[REG1:x[0-9]+]], x{{[0-9]+}}, [[REG1]]
+; CHECK-CPA-O0:          str	q{{[0-9]+}}, [[[REG1]]]
 ;
 ; CHECK-CPA-O3-LABEL:    subpt2:
-; CHECK-CPA-O3:          addpt	[[REG1:x[0-9]+]], x{{[0-9]+}}, x{{[0-9]+}}, lsl #4
-; CHECK-CPA-O3:          str	q{{[0-9]+}}, [[[REG1]], #96]
+; CHECK-CPA-O3:          addpt	[[REG1:x[0-9]+]], x{{[0-9]+}}, [[REG1]]
+; CHECK-CPA-O3:          str	q{{[0-9]+}}, [[[REG1]]]
 ;
 ; CHECK-NOCPA-O0-LABEL:  subpt2:
 ; CHECK-NOCPA-O0:        subs	[[REG1:x[0-9]+]], x{{[0-9]+}}, w{{[0-9]+}}, sxtw #4
@@ -401,7 +403,7 @@ define hidden void @multidim() {
 ; CHECK-CPA-O0:          mov	w9, w9
 ; CHECK-CPA-O0:          add	x9, x9, w10, uxtw #1
 ; CHECK-CPA-O0:          addpt	x8, x8, x9
-; CHECK-CPA-O0:          ldrb	w8, [x8, #2]
+; CHECK-CPA-O0:          ldrb	w8, [x8]
 ;
 ; CHECK-CPA-O3-LABEL:    multidim:
 ; CHECK-CPA-O3:          ret