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Implement __builtin_signbitl for PowerPC 

PowerPC uses the special PPC_FP128 type for long double on Linux, which is
composed of two 64-bit doubles. The higher-order double (which contains the
overall sign) comes first, and so the __builtin_signbitl implementation
requires special handling to extract the sign bit.

Fixes PR20691.

llvm-svn: 216341
This commit is contained in:
Hal Finkel 2014-08-24 03:47:06 +00:00
parent c2b7f7a6ab
commit 6208251923
2 changed files with 19 additions and 2 deletions
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10
clang/lib/CodeGen/CGBuiltin.cpp
View File

@ -1347,11 +1347,17 @@ RValue CodeGenFunction::EmitBuiltinExpr(const FunctionDecl *FD,
Value *Arg = EmitScalarExpr(E->getArg(0));
llvm::Type *ArgTy = Arg->getType();
if (ArgTy->isPPC_FP128Ty())
break; // FIXME: I'm not sure what the right implementation is here.
int ArgWidth = ArgTy->getPrimitiveSizeInBits();
llvm::Type *ArgIntTy = llvm::IntegerType::get(C, ArgWidth);
Value *BCArg = Builder.CreateBitCast(Arg, ArgIntTy);
if (ArgTy->isPPC_FP128Ty()) {
// The higher-order double comes first, and so we need to truncate the
// pair to extract the overall sign. The order of the pair is the same
// in both little- and big-Endian modes.
ArgWidth >>= 1;
ArgIntTy = llvm::IntegerType::get(C, ArgWidth);
BCArg = Builder.CreateTrunc(BCArg, ArgIntTy);
}
Value *ZeroCmp = llvm::Constant::getNullValue(ArgIntTy);
Value *Result = Builder.CreateICmpSLT(BCArg, ZeroCmp);
return RValue::get(Builder.CreateZExt(Result, ConvertType(E->getType())));

11
clang/test/CodeGen/ppc-signbit.c Normal file
View File

@ -0,0 +1,11 @@
// RUN: %clang_cc1 %s -emit-llvm -o - -triple powerpc64-linux-gnu | FileCheck %s
// RUN: %clang_cc1 %s -emit-llvm -o - -triple powerpc64le-linux-gnu | FileCheck %s
int test(long double x) { return __builtin_signbitl(x); }
// CHECK-LABEL: define signext i32 @test(ppc_fp128 %x)
// CHECK: bitcast ppc_fp128 %{{.*}} to i128
// CHECK: trunc i128 %{{.*}} to i64
// CHECK: icmp slt i64 %{{.*}}, 0
// CHECK: zext i1 %{{.*}} to i32