diff options
Diffstat (limited to 'clang/lib/CodeGen/CGBuiltin.cpp')
| -rw-r--r-- | clang/lib/CodeGen/CGBuiltin.cpp | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp index 2060630c386..4c59286291b 100644 --- a/clang/lib/CodeGen/CGBuiltin.cpp +++ b/clang/lib/CodeGen/CGBuiltin.cpp @@ -1537,6 +1537,26 @@ RValue CodeGenFunction::EmitBuiltinExpr(const FunctionDecl *FD, return RValue::get(ComplexVal.second); } + case Builtin::BI__builtin_clrsb: + case Builtin::BI__builtin_clrsbl: + case Builtin::BI__builtin_clrsbll: { + // clrsb(x) -> clz(x < 0 ? ~x : x) - 1 or + Value *ArgValue = EmitScalarExpr(E->getArg(0)); + + llvm::Type *ArgType = ArgValue->getType(); + Value *F = CGM.getIntrinsic(Intrinsic::ctlz, ArgType); + + llvm::Type *ResultType = ConvertType(E->getType()); + Value *Zero = llvm::Constant::getNullValue(ArgType); + Value *IsNeg = Builder.CreateICmpSLT(ArgValue, Zero, "isneg"); + Value *Inverse = Builder.CreateNot(ArgValue, "not"); + Value *Tmp = Builder.CreateSelect(IsNeg, Inverse, ArgValue); + Value *Ctlz = Builder.CreateCall(F, {Tmp, Builder.getFalse()}); + Value *Result = Builder.CreateSub(Ctlz, llvm::ConstantInt::get(ArgType, 1)); + Result = Builder.CreateIntCast(Result, ResultType, /*isSigned*/true, + "cast"); + return RValue::get(Result); + } case Builtin::BI__builtin_ctzs: case Builtin::BI__builtin_ctz: case Builtin::BI__builtin_ctzl: |
