Implementation of __builtin_ctlz.

llvm-svn: 51595

2 files changed, 18 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index a43649dc4bd..232f6d6d4af 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -192,6 +192,20 @@ RValue CodeGenFunction::EmitBuiltinExpr(unsigned BuiltinID, const CallExpr *E) {
       Result = Builder.CreateIntCast(Result, ResultType, "cast");
     return RValue::get(Result);
   }
+  case Builtin::BI__builtin_clz:
+  case Builtin::BI__builtin_clzl:
+  case Builtin::BI__builtin_clzll: {
+    Value *ArgValue = EmitScalarExpr(E->getArg(0));
+    
+    const llvm::Type *ArgType = ArgValue->getType();
+    Value *F = CGM.getIntrinsic(Intrinsic::ctlz, &ArgType, 1);
+
+    const llvm::Type *ResultType = ConvertType(E->getType());    
+    Value *Result = Builder.CreateCall(F, ArgValue, "tmp");
+    if (Result->getType() != ResultType)
+      Result = Builder.CreateIntCast(Result, ResultType, "cast");
+    return RValue::get(Result);
+  }
   case Builtin::BI__builtin_expect:
     return RValue::get(EmitScalarExpr(E->getArg(0)));
   case Builtin::BI__builtin_bswap32:
diff --git a/clang/test/CodeGen/builtin-count-zeros.c b/clang/test/CodeGen/builtin-count-zeros.c
new file mode 100644
index 00000000000..26b139aa8c4
--- /dev/null
+++ b/clang/test/CodeGen/builtin-count-zeros.c
@@ -0,0 +1,4 @@
+// RUN: clang -emit-llvm %s -o - | grep 'cttz' | count 2
+// RUN: clang -emit-llvm %s -o - | grep 'ctlz' | count 2
+
+int a(int a) {return __builtin_ctz(a) + __builtin_clz(a);}