[PATCH] D123881: [X86] Move some hasOneUse checks after checking what the opcode is.

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: spatel, RKSimon.
Herald added subscribers: StephenFan, pengfei, hiraditya.
Herald added a project: All.
craig.topper requested review of this revision.
Herald added a project: LLVM.

Calling hasOneUse can be expensive on nodes with multiple results.
Especially when some results are Chains. By checking the opcode first,
we can know avoid walking the uses if it isn't an interesting node,
and thus avoid calling hasOneUse on a node that might have many uses.

Found by profiling the IR given in D123857 <https://reviews.llvm.org/D123857>.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D123881

Files:
  llvm/lib/Target/X86/X86ISelLowering.cpp


Index: llvm/lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- llvm/lib/Target/X86/X86ISelLowering.cpp
+++ llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -48883,9 +48883,10 @@
   }
 
   // Try to fold a VTRUNCUS or VTRUNCS into a truncating store.
-  if (!St->isTruncatingStore() && StoredVal.hasOneUse() &&
+  if (!St->isTruncatingStore() &&
       (StoredVal.getOpcode() == X86ISD::VTRUNCUS ||
        StoredVal.getOpcode() == X86ISD::VTRUNCS) &&
+      StoredVal.hasOneUse() &&
       TLI.isTruncStoreLegal(StoredVal.getOperand(0).getValueType(), VT)) {
     bool IsSigned = StoredVal.getOpcode() == X86ISD::VTRUNCS;
     return EmitTruncSStore(IsSigned, St->getChain(),
@@ -48894,15 +48895,15 @@
   }
 
   // Try to fold a extract_element(VTRUNC) pattern into a truncating store.
-  if (!St->isTruncatingStore() && StoredVal.hasOneUse()) {
+  if (!St->isTruncatingStore()) {
     auto IsExtractedElement = [](SDValue V) {
-      if (V.getOpcode() == ISD::TRUNCATE && V.getOperand(0).hasOneUse())
+      if (V.getOpcode() == ISD::TRUNCATE && V.hasOneUse())
         V = V.getOperand(0);
       unsigned Opc = V.getOpcode();
-      if (Opc == ISD::EXTRACT_VECTOR_ELT || Opc == X86ISD::PEXTRW) {
-        if (V.getOperand(0).hasOneUse() && isNullConstant(V.getOperand(1)))
-          return V.getOperand(0);
-      }
+      if ((Opc == ISD::EXTRACT_VECTOR_ELT || Opc == X86ISD::PEXTRW) &&
+          V.hasOneUse() && V.getOperand(0).hasOneUse() &&
+          isNullConstant(V.getOperand(1)))
+        return V.getOperand(0);
       return SDValue();
     };
     if (SDValue Extract = IsExtractedElement(StoredVal)) {


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