InstCombine: Enable SimplifyDemandedUseFPClass and remove flag (#81108)

This completes the unrevert of ef38833.

Author: arsenm

clang/test/Headers/__clang_hip_math.hip

@@ -2557,33 +2557,65 @@ extern "C" __device__ double test_nan(const char *tag) {
   return nan(tag);
 }
 
-// CHECK-LABEL: @test_nanf_emptystr(
-// CHECK-NEXT:  entry:
-// CHECK-NEXT:    ret float 0x7FF8000000000000
+// DEFAULT-LABEL: @test_nanf_emptystr(
+// DEFAULT-NEXT:  entry:
+// DEFAULT-NEXT:    ret float 0x7FF8000000000000
+//
+// FINITEONLY-LABEL: @test_nanf_emptystr(
+// FINITEONLY-NEXT:  entry:
+// FINITEONLY-NEXT:    ret float poison
+//
+// APPROX-LABEL: @test_nanf_emptystr(
+// APPROX-NEXT:  entry:
+// APPROX-NEXT:    ret float 0x7FF8000000000000
 //
 extern "C" __device__ float test_nanf_emptystr() {
   return nanf("");
 }
 
-// CHECK-LABEL: @test_nan_emptystr(
-// CHECK-NEXT:  entry:
-// CHECK-NEXT:    ret double 0x7FF8000000000000
+// DEFAULT-LABEL: @test_nan_emptystr(
+// DEFAULT-NEXT:  entry:
+// DEFAULT-NEXT:    ret double 0x7FF8000000000000
+//
+// FINITEONLY-LABEL: @test_nan_emptystr(
+// FINITEONLY-NEXT:  entry:
+// FINITEONLY-NEXT:    ret double poison
+//
+// APPROX-LABEL: @test_nan_emptystr(
+// APPROX-NEXT:  entry:
+// APPROX-NEXT:    ret double 0x7FF8000000000000
 //
 extern "C" __device__ double test_nan_emptystr() {
   return nan("");
 }
 
-// CHECK-LABEL: @test_nanf_fill(
-// CHECK-NEXT:  entry:
-// CHECK-NEXT:    ret float 0x7FF8000000000000
+// DEFAULT-LABEL: @test_nanf_fill(
+// DEFAULT-NEXT:  entry:
+// DEFAULT-NEXT:    ret float 0x7FF8000000000000
+//
+// FINITEONLY-LABEL: @test_nanf_fill(
+// FINITEONLY-NEXT:  entry:
+// FINITEONLY-NEXT:    ret float poison
+//
+// APPROX-LABEL: @test_nanf_fill(
+// APPROX-NEXT:  entry:
+// APPROX-NEXT:    ret float 0x7FF8000000000000
 //
 extern "C" __device__ float test_nanf_fill() {
   return nanf("0x456");
 }
 
-// CHECK-LABEL: @test_nan_fill(
-// CHECK-NEXT:  entry:
-// CHECK-NEXT:    ret double 0x7FF8000000000000
+// DEFAULT-LABEL: @test_nan_fill(
+// DEFAULT-NEXT:  entry:
+// DEFAULT-NEXT:    ret double 0x7FF8000000000000
+//
+// FINITEONLY-LABEL: @test_nan_fill(
+// FINITEONLY-NEXT:  entry:
+// FINITEONLY-NEXT:    ret double poison
+//
+// APPROX-LABEL: @test_nan_fill(
+// APPROX-NEXT:  entry:
+// APPROX-NEXT:    ret double 0x7FF8000000000000
 //
 extern "C" __device__ double test_nan_fill() {
   return nan("0x123");

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

@@ -142,12 +142,6 @@ static cl::opt<unsigned>
 MaxArraySize("instcombine-maxarray-size", cl::init(1024),
              cl::desc("Maximum array size considered when doing a combine"));
 
-// TODO: Remove this option
-static cl::opt<bool> EnableSimplifyDemandedUseFPClass(
-    "instcombine-simplify-demanded-fp-class",
-    cl::desc("Enable demanded floating-point class optimizations"),
-    cl::init(false));
-
 // FIXME: Remove this flag when it is no longer necessary to convert
 // llvm.dbg.declare to avoid inaccurate debug info. Setting this to false
 // increases variable availability at the cost of accuracy. Variables that
@@ -3111,9 +3105,6 @@ Instruction *InstCombinerImpl::visitFree(CallInst &FI, Value *Op) {
 }
 
 Instruction *InstCombinerImpl::visitReturnInst(ReturnInst &RI) {
-  if (!EnableSimplifyDemandedUseFPClass)
-    return nullptr;
-
   Value *RetVal = RI.getReturnValue();
   if (!RetVal || !AttributeFuncs::isNoFPClassCompatibleType(RetVal->getType()))
     return nullptr;

llvm/test/Transforms/InstCombine/simplify-demanded-fpclass.ll

@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 2
-; RUN: opt -S -passes=instcombine -instcombine-simplify-demanded-fp-class < %s | FileCheck %s
+; RUN: opt -S -passes=instcombine < %s | FileCheck %s
 
 declare float @llvm.fabs.f32(float)
 declare float @llvm.copysign.f32(float, float)