[PATCH] D49569: [X86] Remove what appear to be unnecessary uses of DCI.CombineTo

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: RKSimon, spatel.

CombineTo is most useful when you need to replace multiple results, avoid the worklist management, or you need to something else after the combine, etc. Otherwise you should be able to just return the new node and let DAGCombiner go through its usual worklist code.

All of the places changed in this patch look to be standard cases where we should be able to use the more stand behavior of just returning the new node.


https://reviews.llvm.org/D49569

Files:
  lib/Target/X86/X86ISelLowering.cpp


Index: lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- lib/Target/X86/X86ISelLowering.cpp
+++ lib/Target/X86/X86ISelLowering.cpp
@@ -30842,7 +30842,7 @@
 
   // Nuke no-op shuffles that show up after combining.
   if (isNoopShuffleMask(Mask))
-    return DCI.CombineTo(N.getNode(), N.getOperand(0), /*AddTo*/ true);
+    return N.getOperand(0);
 
   // Look for simplifications involving one or two shuffle instructions.
   SDValue V = N.getOperand(0);
@@ -31290,9 +31290,8 @@
     // a particular chain.
     if (SDValue Res = combineX86ShufflesRecursively(
             {Op}, 0, Op, {0}, {}, /*Depth*/ 1,
-            /*HasVarMask*/ false, DAG, Subtarget)) {
-      return DCI.CombineTo(N, Res);
-    }
+            /*HasVarMask*/ false, DAG, Subtarget))
+      return Res;
   }
 
   return SDValue();
@@ -34228,9 +34227,8 @@
   SDValue Op(N, 0);
   if (SDValue Res =
           combineX86ShufflesRecursively({Op}, 0, Op, {0}, {}, /*Depth*/ 1,
-                                        /*HasVarMask*/ false, DAG, Subtarget)) {
-    return DCI.CombineTo(N, Res);
-  }
+                                        /*HasVarMask*/ false, DAG, Subtarget))
+    return Res;
 
   return SDValue();
 }
@@ -34289,9 +34287,8 @@
     SDValue Op(N, 0);
     if (SDValue Res = combineX86ShufflesRecursively(
             {Op}, 0, Op, {0}, {}, /*Depth*/ 1,
-            /*HasVarMask*/ false, DAG, Subtarget)) {
-      return DCI.CombineTo(N, Res);
-    }
+            /*HasVarMask*/ false, DAG, Subtarget))
+      return Res;
   }
 
   // Constant Folding.
@@ -34329,9 +34326,8 @@
   SDValue Op(N, 0);
   if (SDValue Res =
           combineX86ShufflesRecursively({Op}, 0, Op, {0}, {}, /*Depth*/ 1,
-                                        /*HasVarMask*/ false, DAG, Subtarget)) {
-    return DCI.CombineTo(N, Res);
-  }
+                                        /*HasVarMask*/ false, DAG, Subtarget))
+    return Res;
 
   return SDValue();
 }
@@ -34785,9 +34781,8 @@
     SDValue Op(N, 0);
     if (SDValue Res = combineX86ShufflesRecursively(
             {Op}, 0, Op, {0}, {}, /*Depth*/ 1,
-            /*HasVarMask*/ false, DAG, Subtarget)) {
-      return DCI.CombineTo(N, Res);
-    }
+            /*HasVarMask*/ false, DAG, Subtarget))
+      return Res;
   }
 
   // Attempt to combine a scalar bitmask AND with an extracted shuffle.
@@ -37195,9 +37190,8 @@
     SDValue Op(N, 0);
     if (SDValue Res = combineX86ShufflesRecursively(
             {Op}, 0, Op, {0}, {}, /*Depth*/ 1,
-            /*HasVarMask*/ false, DAG, Subtarget)) {
-      return DCI.CombineTo(N, Res);
-    }
+            /*HasVarMask*/ false, DAG, Subtarget))
+      return Res;
   }
 
   return SDValue();


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