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-rw-r--r--clang/lib/CodeGen/CGStmt.cpp19
1 files changed, 19 insertions, 0 deletions
diff --git a/clang/lib/CodeGen/CGStmt.cpp b/clang/lib/CodeGen/CGStmt.cpp
index 4e95e2f3128..1ca119ef988 100644
--- a/clang/lib/CodeGen/CGStmt.cpp
+++ b/clang/lib/CodeGen/CGStmt.cpp
@@ -16,6 +16,7 @@
#include "CodeGenModule.h"
#include "TargetInfo.h"
#include "clang/AST/StmtVisitor.h"
+#include "clang/Basic/Builtins.h"
#include "clang/Basic/PrettyStackTrace.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/Sema/LoopHint.h"
@@ -25,6 +26,8 @@
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/IR/Intrinsics.h"
+#include "llvm/IR/MDBuilder.h"
+
using namespace clang;
using namespace CodeGen;
@@ -1517,6 +1520,22 @@ void CodeGenFunction::EmitSwitchStmt(const SwitchStmt &S) {
EmitBlock(SwitchExit.getBlock(), true);
incrementProfileCounter(&S);
+ // If the switch has a condition wrapped by __builtin_unpredictable,
+ // create metadata that specifies that the switch is unpredictable.
+ // Don't bother if not optimizing because that metadata would not be used.
+ if (CGM.getCodeGenOpts().OptimizationLevel != 0) {
+ if (const CallExpr *Call = dyn_cast<CallExpr>(S.getCond())) {
+ const Decl *TargetDecl = Call->getCalleeDecl();
+ if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(TargetDecl)) {
+ if (FD->getBuiltinID() == Builtin::BI__builtin_unpredictable) {
+ llvm::MDBuilder MDHelper(getLLVMContext());
+ SwitchInsn->setMetadata(llvm::LLVMContext::MD_unpredictable,
+ MDHelper.createUnpredictable());
+ }
+ }
+ }
+ }
+
if (SwitchWeights) {
assert(SwitchWeights->size() == 1 + SwitchInsn->getNumCases() &&
"switch weights do not match switch cases");
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