Use less branches

chakra-core · Apr 15, 2024 · 62873f5 · 62873f5
1 parent 2e96c32
commit 62873f5
Show file tree

Hide file tree

Showing 2 changed files with 14 additions and 17 deletions.
diff --git a/lib/Runtime/ByteCode/ByteCodeEmitter.cpp b/lib/Runtime/ByteCode/ByteCodeEmitter.cpp
@@ -22,22 +22,18 @@ void VisitClearTmpRegs(ParseNode * pnode, ByteCodeGenerator * byteCodeGenerator,
 
 /**
  * This function generates the common code for null-propagation / optional-chaining.
- * This works similar to how the c# compiler emits byte-code for optional-chaining.
  */
 static void EmitNullPropagation(Js::RegSlot targetObjectSlot, ByteCodeGenerator *byteCodeGenerator, FuncInfo *funcInfo, bool isNullPropagating) {
  if (!isNullPropagating)
  return;
 
  Assert(funcInfo->currentOptionalChain != 0);
 
- Js::ByteCodeLabel continueLabel = byteCodeGenerator->Writer()->DefineLabel();
- byteCodeGenerator->Writer()->BrReg2(Js::OpCode::BrNeq_A, continueLabel, targetObjectSlot, funcInfo->nullConstantRegister);
- // if (targetObject == null)
- {
- byteCodeGenerator->Writer()->Reg1(Js::OpCode::LdUndef, funcInfo->currentOptionalChain->resultSlot); // result = undefined
- byteCodeGenerator->Writer()->Br(funcInfo->currentOptionalChain->skipLabel);
- }
- byteCodeGenerator->Writer()->MarkLabel(continueLabel);
+ // if (targetObject == null) goto chainEnd;
+ byteCodeGenerator->Writer()->BrReg2(
+ Js::OpCode::BrEq_A, funcInfo->currentOptionalChain->skipLabel,
+ targetObjectSlot, funcInfo->nullConstantRegister
+ );
 }
 
 bool CallTargetIsArray(ParseNode *pnode)
@@ -11627,18 +11623,21 @@ void Emit(ParseNode* pnode, ByteCodeGenerator* byteCodeGenerator, FuncInfo* func
  }
 
  case knopOptChain: {
- Js::ByteCodeLabel skipLabel = byteCodeGenerator->Writer()->DefineLabel();
- Js::RegSlot targetRegSlot = funcInfo->AcquireLoc(pnode);
+ FuncInfo::OptionalChainInfo *previousChain = funcInfo->currentOptionalChain;
 
- FuncInfo::OptionalChainInfo* previousChain = funcInfo->currentOptionalChain;
- FuncInfo::OptionalChainInfo currentOptionalChain = FuncInfo::OptionalChainInfo(skipLabel, targetRegSlot);
+ Js::ByteCodeLabel skipLabel = byteCodeGenerator->Writer()->DefineLabel();
+ FuncInfo::OptionalChainInfo currentOptionalChain = FuncInfo::OptionalChainInfo(skipLabel);
  funcInfo->currentOptionalChain = &currentOptionalChain;
 
+ Js::RegSlot resultSlot = funcInfo->AcquireLoc(pnode);
+ byteCodeGenerator->Writer()->Reg1(Js::OpCode::LdUndef, resultSlot); // result = undefined
+
+ // emit chain
  ParseNodePtr innerNode = pnode->AsParseNodeUni()->pnode1;
  Emit(innerNode, byteCodeGenerator, funcInfo, false);
 
  // Copy result
- byteCodeGenerator->Writer()->Reg2(Js::OpCode::Ld_A, targetRegSlot, innerNode->location);
+ byteCodeGenerator->Writer()->Reg2(Js::OpCode::Ld_A, resultSlot, innerNode->location);
  funcInfo->ReleaseLoc(innerNode);
 
  byteCodeGenerator->Writer()->MarkLabel(skipLabel);

diff --git a/lib/Runtime/ByteCode/FuncInfo.h b/lib/Runtime/ByteCode/FuncInfo.h
@@ -98,11 +98,9 @@ class FuncInfo
  uint currentInnerScopeIndex;
  struct OptionalChainInfo {
  Js::ByteCodeLabel skipLabel;
- Js::RegSlot resultSlot;
 
- OptionalChainInfo(Js::ByteCodeLabel skipLabel, Js::RegSlot resultSlot) {
+ OptionalChainInfo(Js::ByteCodeLabel skipLabel) {
  this->skipLabel = skipLabel;
- this->resultSlot = resultSlot;
  }
  } *currentOptionalChain;
 #if DBG