make __builtin_isfinite more efficient (PR27145)

[spatel]

Summary

isinf (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: I noticed this while looking at D18513.

[chandlerc]

LGTM, nice!

cfe/trunk/lib/CodeGen/CGBuiltin.cpp

case Builtin::BI__builtin_isunordered: {
     return RValue::get(Builder.CreateZExt(LHS, ConvertType(E->getType())));
   }
   case Builtin::BI__builtin_isnan: {
     Value *V = EmitScalarExpr(E->getArg(0));
     V = Builder.CreateFCmpUNO(V, V, "cmp");
     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: {
     // isinf_sign(x) -> fabs(x) == infinity ? (signbit(x) ? -1 : 1) : 0
     Value *Arg = EmitScalarExpr(E->getArg(0));
     Value *AbsArg = EmitFAbs(*this, Arg);
     Value *IsInf = Builder.CreateFCmpOEQ(
         AbsArg, ConstantFP::getInfinity(Arg->getType()), "isinf");
case Builtin::BI__builtin_isnormal: {
     Value *IsNormal =
       Builder.CreateFCmpUGE(Abs, ConstantFP::get(V->getContext(), Smallest),
                             "isnormal");
     V = Builder.CreateAnd(Eq, IsLessThanInf, "and");
     V = Builder.CreateAnd(V, IsNormal, "and");
     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());
 
     // Create Result
     BasicBlock *Begin = Builder.GetInsertBlock();
     BasicBlock *End = createBasicBlock("fpclassify_end", this->CurFn);
     Builder.SetInsertPoint(End);

cfe/trunk/test/CodeGen/builtins.c

void test_float_builtins(float F, double D, long double LD) {
   // CHECK:  %[[ABS:.*]] = call x86_fp80 @llvm.fabs.f80(x86_fp80 %[[ARG:.*]])
   // CHECK:  %[[ISINF:.*]] = fcmp oeq x86_fp80 %[[ABS]], 0xK7FFF8000000000000000
   // CHECK:  %[[BITCAST:.*]] = bitcast x86_fp80 %[[ARG]] to i80
   // CHECK:  %[[ISNEG:.*]] = icmp slt i80 %[[BITCAST]], 0
   // CHECK:  %[[SIGN:.*]] = select i1 %[[ISNEG]], i32 -1, i32 1
   // 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
   // CHECK: call float @llvm.fabs.f32(float
   // CHECK: fcmp ult float {{.*}}, 0x7FF0000000000000
   // CHECK: fcmp uge float {{.*}}, 0x3810000000000000
   // CHECK: and i1
   // CHECK: and i1