1 files changed, 13 insertions, 1 deletions

diff --git a/contrib/llvm-project/clang/lib/CodeGen/CGStmt.cpp b/contrib/llvm-project/clang/lib/CodeGen/CGStmt.cpp
index 0f79a2e861d2..b89017de0bcf 100644
--- a/contrib/llvm-project/clang/lib/CodeGen/CGStmt.cpp
+++ b/contrib/llvm-project/clang/lib/CodeGen/CGStmt.cpp
@@ -837,7 +837,19 @@ void CodeGenFunction::EmitIfStmt(const IfStmt &S) {
   if (!ThenCount && !getCurrentProfileCount() &&
       CGM.getCodeGenOpts().OptimizationLevel)
     LH = Stmt::getLikelihood(S.getThen(), S.getElse());
-  EmitBranchOnBoolExpr(S.getCond(), ThenBlock, ElseBlock, ThenCount, LH);
+
+  // When measuring MC/DC, always fully evaluate the condition up front using
+  // EvaluateExprAsBool() so that the test vector bitmap can be updated prior to
+  // executing the body of the if.then or if.else. This is useful for when
+  // there is a 'return' within the body, but this is particularly beneficial
+  // when one if-stmt is nested within another if-stmt so that all of the MC/DC
+  // updates are kept linear and consistent.
+  if (!CGM.getCodeGenOpts().MCDCCoverage)
+    EmitBranchOnBoolExpr(S.getCond(), ThenBlock, ElseBlock, ThenCount, LH);
+  else {
+    llvm::Value *BoolCondVal = EvaluateExprAsBool(S.getCond());
+    Builder.CreateCondBr(BoolCondVal, ThenBlock, ElseBlock);
+  }
 
   // Emit the 'then' code.
   EmitBlock(ThenBlock);