[PATCH] D148710: [DAGCombiner] Limit 'hoist add/sub binop w/ constant op' to the same divergency property

[chenglin.bi via Phabricator via llvm-commits]

bcl5980 created this revision.
bcl5980 added reviewers: RKSimon, foad.
Herald added subscribers: StephenFan, ecnelises, hiraditya.
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If the patterns have different property we prefer uniform value to add/sub constant.


https://reviews.llvm.org/D148710

Files:
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp


Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -3871,30 +3871,32 @@
   }
 
   // Hoist one-use addition by non-opaque constant:
-  //   (x + C) - y  ->  (x - y) + C
-  if (N0.getOpcode() == ISD::ADD && N0.hasOneUse() &&
-      isConstantOrConstantVector(N0.getOperand(1), /*NoOpaques=*/true)) {
-    SDValue Sub = DAG.getNode(ISD::SUB, DL, VT, N0.getOperand(0), N1);
-    return DAG.getNode(ISD::ADD, DL, VT, Sub, N0.getOperand(1));
-  }
-  // y - (x + C)  ->  (y - x) - C
-  if (N1.getOpcode() == ISD::ADD && N1.hasOneUse() &&
-      isConstantOrConstantVector(N1.getOperand(1), /*NoOpaques=*/true)) {
-    SDValue Sub = DAG.getNode(ISD::SUB, DL, VT, N0, N1.getOperand(0));
-    return DAG.getNode(ISD::SUB, DL, VT, Sub, N1.getOperand(1));
-  }
-  // (x - C) - y  ->  (x - y) - C
-  // This is necessary because SUB(X,C) -> ADD(X,-C) doesn't work for vectors.
-  if (N0.getOpcode() == ISD::SUB && N0.hasOneUse() &&
-      isConstantOrConstantVector(N0.getOperand(1), /*NoOpaques=*/true)) {
-    SDValue Sub = DAG.getNode(ISD::SUB, DL, VT, N0.getOperand(0), N1);
-    return DAG.getNode(ISD::SUB, DL, VT, Sub, N0.getOperand(1));
-  }
-  // (C - x) - y  ->  C - (x + y)
-  if (N0.getOpcode() == ISD::SUB && N0.hasOneUse() &&
-      isConstantOrConstantVector(N0.getOperand(0), /*NoOpaques=*/true)) {
-    SDValue Add = DAG.getNode(ISD::ADD, DL, VT, N0.getOperand(1), N1);
-    return DAG.getNode(ISD::SUB, DL, VT, N0.getOperand(0), Add);
+  if (N0->isDivergent() == N1->isDivergent()) {
+    //   (x + C) - y  ->  (x - y) + C
+    if (N0.getOpcode() == ISD::ADD && N0.hasOneUse() &&
+        isConstantOrConstantVector(N0.getOperand(1), /*NoOpaques=*/true)) {
+      SDValue Sub = DAG.getNode(ISD::SUB, DL, VT, N0.getOperand(0), N1);
+      return DAG.getNode(ISD::ADD, DL, VT, Sub, N0.getOperand(1));
+    }
+    // y - (x + C)  ->  (y - x) - C
+    if (N1.getOpcode() == ISD::ADD && N1.hasOneUse() &&
+        isConstantOrConstantVector(N1.getOperand(1), /*NoOpaques=*/true)) {
+      SDValue Sub = DAG.getNode(ISD::SUB, DL, VT, N0, N1.getOperand(0));
+      return DAG.getNode(ISD::SUB, DL, VT, Sub, N1.getOperand(1));
+    }
+    // (x - C) - y  ->  (x - y) - C
+    // This is necessary because SUB(X,C) -> ADD(X,-C) doesn't work for vectors.
+    if (N0.getOpcode() == ISD::SUB && N0.hasOneUse() &&
+        isConstantOrConstantVector(N0.getOperand(1), /*NoOpaques=*/true)) {
+      SDValue Sub = DAG.getNode(ISD::SUB, DL, VT, N0.getOperand(0), N1);
+      return DAG.getNode(ISD::SUB, DL, VT, Sub, N0.getOperand(1));
+    }
+    // (C - x) - y  ->  C - (x + y)
+    if (N0.getOpcode() == ISD::SUB && N0.hasOneUse() &&
+        isConstantOrConstantVector(N0.getOperand(0), /*NoOpaques=*/true)) {
+      SDValue Add = DAG.getNode(ISD::ADD, DL, VT, N0.getOperand(1), N1);
+      return DAG.getNode(ISD::SUB, DL, VT, N0.getOperand(0), Add);
+    }
   }
 
   // If the target's bool is represented as 0/-1, prefer to make this 'add 0/-1'


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