Implements [[likely]] and [[unlikely]] in IfStmt.

This is the initial part of the implementation of the C++20 likelihood
attributes. It handles the attributes in an if statement.

Differential Revision: https://reviews.llvm.org/D85091

1 files changed, 23 insertions, 19 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 8f79cc77..e7f8108 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -1462,16 +1462,15 @@ bool CodeGenFunction::ConstantFoldsToSimpleInteger(const Expr *Cond,
   return true;
 }
 
-
-
 /// EmitBranchOnBoolExpr - Emit a branch on a boolean condition (e.g. for an if
 /// statement) to the specified blocks.  Based on the condition, this might try
 /// to simplify the codegen of the conditional based on the branch.
-///
+/// \param Weights The weights determined by the likelihood attributes.
 void CodeGenFunction::EmitBranchOnBoolExpr(const Expr *Cond,
                                            llvm::BasicBlock *TrueBlock,
                                            llvm::BasicBlock *FalseBlock,
-                                           uint64_t TrueCount) {
+                                           uint64_t TrueCount,
+                                           llvm::MDNode *Weights) {
   Cond = Cond->IgnoreParens();
 
   if (const BinaryOperator *CondBOp = dyn_cast<BinaryOperator>(Cond)) {
@@ -1486,7 +1485,7 @@ void CodeGenFunction::EmitBranchOnBoolExpr(const Expr *Cond,
         // br(1 && X) -> br(X).
         incrementProfileCounter(CondBOp);
         return EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock,
-                                    TrueCount);
+                                    TrueCount, Weights);
       }
 
       // If we have "X && 1", simplify the code to use an uncond branch.
@@ -1495,7 +1494,7 @@ void CodeGenFunction::EmitBranchOnBoolExpr(const Expr *Cond,
           ConstantBool) {
         // br(X && 1) -> br(X).
         return EmitBranchOnBoolExpr(CondBOp->getLHS(), TrueBlock, FalseBlock,
-                                    TrueCount);
+                                    TrueCount, Weights);
       }
 
       // Emit the LHS as a conditional.  If the LHS conditional is false, we
@@ -1508,7 +1507,8 @@ void CodeGenFunction::EmitBranchOnBoolExpr(const Expr *Cond,
       ConditionalEvaluation eval(*this);
       {
         ApplyDebugLocation DL(*this, Cond);
-        EmitBranchOnBoolExpr(CondBOp->getLHS(), LHSTrue, FalseBlock, RHSCount);
+        EmitBranchOnBoolExpr(CondBOp->getLHS(), LHSTrue, FalseBlock, RHSCount,
+                             Weights);
         EmitBlock(LHSTrue);
       }
 
@@ -1517,7 +1517,8 @@ void CodeGenFunction::EmitBranchOnBoolExpr(const Expr *Cond,
 
       // Any temporaries created here are conditional.
       eval.begin(*this);
-      EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock, TrueCount);
+      EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock, TrueCount,
+                           Weights);
       eval.end(*this);
 
       return;
@@ -1532,7 +1533,7 @@ void CodeGenFunction::EmitBranchOnBoolExpr(const Expr *Cond,
         // br(0 || X) -> br(X).
         incrementProfileCounter(CondBOp);
         return EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock,
-                                    TrueCount);
+                                    TrueCount, Weights);
       }
 
       // If we have "X || 0", simplify the code to use an uncond branch.
@@ -1541,7 +1542,7 @@ void CodeGenFunction::EmitBranchOnBoolExpr(const Expr *Cond,
           !ConstantBool) {
         // br(X || 0) -> br(X).
         return EmitBranchOnBoolExpr(CondBOp->getLHS(), TrueBlock, FalseBlock,
-                                    TrueCount);
+                                    TrueCount, Weights);
       }
 
       // Emit the LHS as a conditional.  If the LHS conditional is true, we
@@ -1557,7 +1558,8 @@ void CodeGenFunction::EmitBranchOnBoolExpr(const Expr *Cond,
       ConditionalEvaluation eval(*this);
       {
         ApplyDebugLocation DL(*this, Cond);
-        EmitBranchOnBoolExpr(CondBOp->getLHS(), TrueBlock, LHSFalse, LHSCount);
+        EmitBranchOnBoolExpr(CondBOp->getLHS(), TrueBlock, LHSFalse, LHSCount,
+                             Weights);
         EmitBlock(LHSFalse);
       }
 
@@ -1566,7 +1568,8 @@ void CodeGenFunction::EmitBranchOnBoolExpr(const Expr *Cond,
 
       // Any temporaries created here are conditional.
       eval.begin(*this);
-      EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock, RHSCount);
+      EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock, RHSCount,
+                           Weights);
 
       eval.end(*this);
 
@@ -1581,7 +1584,7 @@ void CodeGenFunction::EmitBranchOnBoolExpr(const Expr *Cond,
       uint64_t FalseCount = getCurrentProfileCount() - TrueCount;
       // Negate the condition and swap the destination blocks.
       return EmitBranchOnBoolExpr(CondUOp->getSubExpr(), FalseBlock, TrueBlock,
-                                  FalseCount);
+                                  FalseCount, Weights);
     }
   }
 
@@ -1592,7 +1595,7 @@ void CodeGenFunction::EmitBranchOnBoolExpr(const Expr *Cond,
 
     ConditionalEvaluation cond(*this);
     EmitBranchOnBoolExpr(CondOp->getCond(), LHSBlock, RHSBlock,
-                         getProfileCount(CondOp));
+                         getProfileCount(CondOp), Weights);
 
     // When computing PGO branch weights, we only know the overall count for
     // the true block. This code is essentially doing tail duplication of the
@@ -1612,14 +1615,14 @@ void CodeGenFunction::EmitBranchOnBoolExpr(const Expr *Cond,
     {
       ApplyDebugLocation DL(*this, Cond);
       EmitBranchOnBoolExpr(CondOp->getLHS(), TrueBlock, FalseBlock,
-                           LHSScaledTrueCount);
+                           LHSScaledTrueCount, Weights);
     }
     cond.end(*this);
 
     cond.begin(*this);
     EmitBlock(RHSBlock);
     EmitBranchOnBoolExpr(CondOp->getRHS(), TrueBlock, FalseBlock,
-                         TrueCount - LHSScaledTrueCount);
+                         TrueCount - LHSScaledTrueCount, Weights);
     cond.end(*this);
 
     return;
@@ -1650,9 +1653,10 @@ void CodeGenFunction::EmitBranchOnBoolExpr(const Expr *Cond,
 
   // Create branch weights based on the number of times we get here and the
   // number of times the condition should be true.
-  uint64_t CurrentCount = std::max(getCurrentProfileCount(), TrueCount);
-  llvm::MDNode *Weights =
-      createProfileWeights(TrueCount, CurrentCount - TrueCount);
+  if (!Weights) {
+    uint64_t CurrentCount = std::max(getCurrentProfileCount(), TrueCount);
+    Weights = createProfileWeights(TrueCount, CurrentCount - TrueCount);
+  }
 
   // Emit the code with the fully general case.
   llvm::Value *CondV;