1 files changed, 22 insertions, 0 deletions
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index d6ae818d6a0..6b7ed4e8bfd 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -17,6 +17,7 @@
 #include "CodeGenFunction.h"
 #include "CodeGenModule.h"
 #include "ConstantEmitter.h"
+#include "PatternInit.h"
 #include "TargetInfo.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Decl.h"
@@ -44,6 +45,25 @@ int64_t clamp(int64_t Value, int64_t Low, int64_t High) {
   return std::min(High, std::max(Low, Value));
 }
 
+static void initializeAlloca(CodeGenFunction &CGF, AllocaInst *AI, Value *Size, unsigned AlignmentInBytes) {
+  ConstantInt *Byte;
+  switch (CGF.getLangOpts().getTrivialAutoVarInit()) {
+  case LangOptions::TrivialAutoVarInitKind::Uninitialized:
+    // Nothing to initialize.
+    return;
+  case LangOptions::TrivialAutoVarInitKind::Zero:
+    Byte = CGF.Builder.getInt8(0x00);
+    break;
+  case LangOptions::TrivialAutoVarInitKind::Pattern: {
+    llvm::Type *Int8 = llvm::IntegerType::getInt8Ty(CGF.CGM.getLLVMContext());
+    Byte = llvm::dyn_cast<llvm::ConstantInt>(
+        initializationPatternFor(CGF.CGM, Int8));
+    break;
+  }
+  }
+  CGF.Builder.CreateMemSet(AI, Byte, Size, AlignmentInBytes);
+}
+
 /// getBuiltinLibFunction - Given a builtin id for a function like
 /// "__builtin_fabsf", return a Function* for "fabsf".
 llvm::Constant *CodeGenModule::getBuiltinLibFunction(const FunctionDecl *FD,
@@ -2259,6 +2279,7 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
             .getQuantity();
     AllocaInst *AI = Builder.CreateAlloca(Builder.getInt8Ty(), Size);
     AI->setAlignment(SuitableAlignmentInBytes);
+    initializeAlloca(*this, AI, Size, SuitableAlignmentInBytes);
     return RValue::get(AI);
   }
 
@@ -2271,6 +2292,7 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
         CGM.getContext().toCharUnitsFromBits(AlignmentInBits).getQuantity();
     AllocaInst *AI = Builder.CreateAlloca(Builder.getInt8Ty(), Size);
     AI->setAlignment(AlignmentInBytes);
+    initializeAlloca(*this, AI, Size, AlignmentInBytes);
     return RValue::get(AI);
   }