[Hexagon] Use fast-math flags (#162274)

Use fast-math flag `afn` for `fmul` and remove UseUnsafeMath feature,
users now should use fast-math flags only, `unsafe-fp-math` attribute
support will be removed in future. Hopefully `afn` is the right option
This is the Hexagon part.

Author: paperchalice

llvm/lib/Target/Hexagon/Hexagon.td

@@ -110,8 +110,6 @@ def FeatureSmallData: SubtargetFeature<"small-data", "UseSmallData", "true",
       "Allow GP-relative addressing of global variables">;
 def FeatureDuplex: SubtargetFeature<"duplex", "EnableDuplex", "true",
       "Enable generation of duplex instruction">;
-def FeatureUnsafeFP: SubtargetFeature<"unsafe-fp", "UseUnsafeMath", "true",
-      "Use unsafe FP math">;
 def FeatureReservedR19: SubtargetFeature<"reserved-r19", "ReservedR19",
       "true", "Reserve register R19">;
 def FeatureNoreturnStackElim: SubtargetFeature<"noreturn-stack-elim",
@@ -167,7 +165,6 @@ def UseHVXQFloat       : Predicate<"HST->useHVXQFloatOps()">,
 def UseHVXFloatingPoint: Predicate<"HST->useHVXFloatingPoint()">;
 def HasMemNoShuf       : Predicate<"HST->hasMemNoShuf()">,
                          AssemblerPredicate<(all_of FeatureMemNoShuf)>;
-def UseUnsafeMath      : Predicate<"HST->useUnsafeMath()">;
 def NotOptTinyCore     : Predicate<"!HST->isTinyCore() ||"
                                    "MF->getFunction().hasOptSize()"> {
   let RecomputePerFunction = 1;

llvm/lib/Target/Hexagon/HexagonPatterns.td

@@ -1611,8 +1611,11 @@ def DfMpy: OutPatFrag<(ops node:$Rs, node:$Rt),
     $Rt, $Rs),
   $Rs, $Rt)>;
 
-let Predicates = [HasV67,UseUnsafeMath], AddedComplexity = 50 in {
-  def: Pat<(fmul F64:$Rs, F64:$Rt), (DfMpy $Rs, $Rt)>;
+def fmul_afn : PatFrag<(ops node:$a, node:$b), (fmul node:$a, node:$b), [{
+  return N->getFlags().hasApproximateFuncs();
+}]>;
+let Predicates = [HasV67], AddedComplexity = 50 in {
+  def : Pat<(fmul_afn F64:$Rs, F64:$Rt), (DfMpy $Rs, $Rt)>;
 }
 let Predicates = [HasV67] in {
   def: OpR_RR_pat<F2_dfmin,     pf2<fminimumnum>, f64, F64>;

llvm/lib/Target/Hexagon/HexagonSubtarget.h

@@ -54,7 +54,6 @@ class HexagonSubtarget : public HexagonGenSubtargetInfo {
   bool UseNewValueJumps = false;
   bool UseNewValueStores = false;
   bool UseSmallData = false;
-  bool UseUnsafeMath = false;
   bool UseZRegOps = false;
   bool UseHVXIEEEFPOps = false;
   bool UseHVXQFloatOps = false;
@@ -234,7 +233,6 @@ class HexagonSubtarget : public HexagonGenSubtargetInfo {
   bool useNewValueJumps() const { return UseNewValueJumps; }
   bool useNewValueStores() const { return UseNewValueStores; }
   bool useSmallData() const { return UseSmallData; }
-  bool useUnsafeMath() const { return UseUnsafeMath; }
   bool useZRegOps() const { return UseZRegOps; }
   bool useCabac() const { return UseCabac; }
 

llvm/lib/Target/Hexagon/HexagonTargetMachine.cpp

@@ -250,13 +250,6 @@ HexagonTargetMachine::getSubtargetImpl(const Function &F) const {
       CPUAttr.isValid() ? CPUAttr.getValueAsString().str() : TargetCPU;
   std::string FS =
       FSAttr.isValid() ? FSAttr.getValueAsString().str() : TargetFS;
-  // Append the preexisting target features last, so that +mattr overrides
-  // the "unsafe-fp-math" function attribute.
-  // Creating a separate target feature is not strictly necessary, it only
-  // exists to make "unsafe-fp-math" force creating a new subtarget.
-
-  if (F.getFnAttribute("unsafe-fp-math").getValueAsBool())
-    FS = FS.empty() ? "+unsafe-fp" : "+unsafe-fp," + FS;
 
   auto &I = SubtargetMap[CPU + FS];
   if (!I) {

llvm/test/CodeGen/Hexagon/fmul-v67.ll

@@ -29,7 +29,7 @@ b2:
 ; CHECK: [[R22]] += dfmpylh([[R20]],[[R21]])
 ; CHECK: [[R22]] += dfmpylh([[R21]],[[R20]])
 ; CHECK: [[R22]] += dfmpyhh([[R20]],[[R21]])
-define double @test_02(double %a0, double %a1) #2 {
+define double @test_02(double %a0, double %a1) #1 {
 b2:
   %v3 = fmul double %a0, %a1
   ret double %v3
@@ -40,13 +40,11 @@ b2:
 ; CHECK: [[R30]] += dfmpylh(r1:0,r3:2)
 ; CHECK: [[R30]] += dfmpylh(r3:2,r1:0)
 ; CHECK: [[R30]] += dfmpyhh(r1:0,r3:2)
-define double @test_03(double %a0, double %a1) #3 {
+define double @test_03(double %a0, double %a1) #1 {
 b2:
-  %v3 = fmul double %a0, %a1
+  %v3 = fmul afn double %a0, %a1
   ret double %v3
 }
 
 attributes #0 = { nounwind }
 attributes #1 = { nounwind "target-cpu"="hexagonv67" }
-attributes #2 = { nounwind "target-cpu"="hexagonv67" "unsafe-fp-math"="false" }
-attributes #3 = { nounwind "target-cpu"="hexagonv67" "unsafe-fp-math"="true" }