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make __builtin_isfinite more efficient (PR27145) 

isinf (is infinite) and isfinite should be implemented with the same function
except we change the comparison operator.

See PR27145 for more details:
https://llvm.org/bugs/show_bug.cgi?id=27145

Ref: forked off of the discussion in D18513.

Differential Revision: http://reviews.llvm.org/D18648

llvm-svn: 265675
This commit is contained in:
Sanjay Patel 2016-04-07 14:29:05 +00:00
parent f90ec0e82e
commit ae7a9df7bf
2 changed files with 13 additions and 22 deletions
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31
clang/lib/CodeGen/CGBuiltin.cpp
View File

@ -786,13 +786,19 @@ RValue CodeGenFunction::EmitBuiltinExpr(const FunctionDecl *FD,
return RValue::get(Builder.CreateZExt(V, ConvertType(E->getType())));
}
case Builtin::BI__builtin_isinf: {
// isinf(x) --> fabs(x) == infinity
case Builtin::BI__builtin_isinf:
case Builtin::BI__builtin_isfinite: {
// isinf(x) --> fabs(x) == infinity
// isfinite(x) --> fabs(x) != infinity
// x != NaN via the ordered compare in either case.
Value *V = EmitScalarExpr(E->getArg(0));
V = EmitFAbs(*this, V);
V = Builder.CreateFCmpOEQ(V, ConstantFP::getInfinity(V->getType()),"isinf");
return RValue::get(Builder.CreateZExt(V, ConvertType(E->getType())));
Value *Fabs = EmitFAbs(*this, V);
Constant *Infinity = ConstantFP::getInfinity(V->getType());
CmpInst::Predicate Pred = (BuiltinID == Builtin::BI__builtin_isinf)
? CmpInst::FCMP_OEQ
: CmpInst::FCMP_ONE;
Value *FCmp = Builder.CreateFCmp(Pred, Fabs, Infinity, "cmpinf");
return RValue::get(Builder.CreateZExt(FCmp, ConvertType(E->getType())));
}
case Builtin::BI__builtin_isinf_sign: {
@ -830,19 +836,6 @@ RValue CodeGenFunction::EmitBuiltinExpr(const FunctionDecl *FD,
return RValue::get(Builder.CreateZExt(V, ConvertType(E->getType())));
}
case Builtin::BI__builtin_isfinite: {
// isfinite(x) --> x == x && fabs(x) != infinity;
Value *V = EmitScalarExpr(E->getArg(0));
Value *Eq = Builder.CreateFCmpOEQ(V, V, "iseq");
Value *Abs = EmitFAbs(*this, V);
Value *IsNotInf =
Builder.CreateFCmpUNE(Abs, ConstantFP::getInfinity(V->getType()),"isinf");
V = Builder.CreateAnd(Eq, IsNotInf, "and");
return RValue::get(Builder.CreateZExt(V, ConvertType(E->getType())));
}
case Builtin::BI__builtin_fpclassify: {
Value *V = EmitScalarExpr(E->getArg(5));
llvm::Type *Ty = ConvertType(E->getArg(5)->getType());

4
clang/test/CodeGen/builtins.c
View File

@ -217,10 +217,8 @@ void test_float_builtins(float F, double D, long double LD) {
// CHECK: select i1 %[[ISINF]], i32 %[[SIGN]], i32 0
res = __builtin_isfinite(F);
// CHECK: fcmp oeq float
// CHECK: call float @llvm.fabs.f32(float
// CHECK: fcmp une float {{.*}}, 0x7FF0000000000000
// CHECK: and i1
// CHECK: fcmp one float {{.*}}, 0x7FF0000000000000
res = __builtin_isnormal(F);
// CHECK: fcmp oeq float