[llvm] efec3a2 - [DAG] visitADDSAT/visitSUBSAT - merge scalar/vector canonicalization and constant folding.

[Simon Pilgrim via llvm-commits]

Author: Simon Pilgrim
Date: 2021-12-19T13:19:40Z
New Revision: efec3a26b40c604e4f355d518e359d9fb480e98e

URL: https://github.com/llvm/llvm-project/commit/efec3a26b40c604e4f355d518e359d9fb480e98e
DIFF: https://github.com/llvm/llvm-project/commit/efec3a26b40c604e4f355d518e359d9fb480e98e.diff

LOG: [DAG] visitADDSAT/visitSUBSAT - merge scalar/vector canonicalization and constant folding.

Match order of most of the other integer opcode combines

Added: 
    

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

Removed: 
    


################################################################################
diff  --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index e70d3f98e5e0..8055eb9a82d6 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -2549,6 +2549,19 @@ SDValue DAGCombiner::visitADDSAT(SDNode *N) {
   EVT VT = N0.getValueType();
   SDLoc DL(N);
 
+  // fold (add_sat x, undef) -> -1
+  if (N0.isUndef() || N1.isUndef())
+    return DAG.getAllOnesConstant(DL, VT);
+
+  // fold (add_sat c1, c2) -> c3
+  if (SDValue C = DAG.FoldConstantArithmetic(Opcode, DL, VT, {N0, N1}))
+    return C;
+
+  // canonicalize constant to RHS
+  if (DAG.isConstantIntBuildVectorOrConstantInt(N0) &&
+      !DAG.isConstantIntBuildVectorOrConstantInt(N1))
+    return DAG.getNode(Opcode, DL, VT, N1, N0);
+
   // fold vector ops
   if (VT.isVector()) {
     // TODO SimplifyVBinOp
@@ -2556,20 +2569,6 @@ SDValue DAGCombiner::visitADDSAT(SDNode *N) {
     // fold (add_sat x, 0) -> x, vector edition
     if (ISD::isConstantSplatVectorAllZeros(N1.getNode()))
       return N0;
-    if (ISD::isConstantSplatVectorAllZeros(N0.getNode()))
-      return N1;
-  }
-
-  // fold (add_sat x, undef) -> -1
-  if (N0.isUndef() || N1.isUndef())
-    return DAG.getAllOnesConstant(DL, VT);
-
-  if (DAG.isConstantIntBuildVectorOrConstantInt(N0)) {
-    // canonicalize constant to RHS
-    if (!DAG.isConstantIntBuildVectorOrConstantInt(N1))
-      return DAG.getNode(Opcode, DL, VT, N1, N0);
-    // fold (add_sat c1, c2) -> c3
-    return DAG.FoldConstantArithmetic(Opcode, DL, VT, {N0, N1});
   }
 
   // fold (add_sat x, 0) -> x
@@ -3606,15 +3605,6 @@ SDValue DAGCombiner::visitSUBSAT(SDNode *N) {
   EVT VT = N0.getValueType();
   SDLoc DL(N);
 
-  // fold vector ops
-  if (VT.isVector()) {
-    // TODO SimplifyVBinOp
-
-    // fold (sub_sat x, 0) -> x, vector edition
-    if (ISD::isConstantSplatVectorAllZeros(N1.getNode()))
-      return N0;
-  }
-
   // fold (sub_sat x, undef) -> 0
   if (N0.isUndef() || N1.isUndef())
     return DAG.getConstant(0, DL, VT);
@@ -3627,6 +3617,15 @@ SDValue DAGCombiner::visitSUBSAT(SDNode *N) {
   if (SDValue C = DAG.FoldConstantArithmetic(N->getOpcode(), DL, VT, {N0, N1}))
     return C;
 
+  // fold vector ops
+  if (VT.isVector()) {
+    // TODO SimplifyVBinOp
+
+    // fold (sub_sat x, 0) -> x, vector edition
+    if (ISD::isConstantSplatVectorAllZeros(N1.getNode()))
+      return N0;
+  }
+
   // fold (sub_sat x, 0) -> x
   if (isNullConstant(N1))
     return N0;