InstCombine: Fold out is_fpclass inf checks from test mask for known finite sources

[arsenm]

Summary

Make the partner transform already done for nnan sources.

[sepavloff]

LGTM

[arsenm]

Also handle negated case

[arsenm]

Don't bother with replaceOperand for the constant, it doesn't need to go to the worklist

[arsenm]

5ccbd07dd607bac8a05016d80e3fa34f2d393279

llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp

Instruction *InstCombinerImpl::foldIntrinsicIsFPClass(IntrinsicInst &II) {
   }
 
   // fp_class (nnan x), ~(qnan|snan) -> true
   if (Mask == (~fcNan & fcAllFlags) &&
       isKnownNeverNaN(Src0, &getTargetLibraryInfo())) {
     return replaceInstUsesWith(II, ConstantInt::get(II.getType(), true));
   }
 
+  // fp_class (ninf x), ninf|pinf|other -> fp_class (ninf x), other
+  if ((Mask & fcInf) && isKnownNeverInfinity(Src0, &getTargetLibraryInfo())) {
+    II.setArgOperand(1, ConstantInt::get(Src1->getType(), Mask & ~fcInf));
+    return ⅈ
+  }
+
+  // fp_class (ninf x), ~(ninf|pinf) -> true
+  if (Mask == (~fcInf & fcAllFlags) &&
+      isKnownNeverInfinity(Src0, &getTargetLibraryInfo())) {
+    return replaceInstUsesWith(II, ConstantInt::get(II.getType(), true));
+  }
+
   return nullptr;
 }
 
 static Optional<bool> getKnownSign(Value *Op, Instruction *CxtI,
                                    const DataLayout &DL, AssumptionCache *AC,
                                    DominatorTree *DT) {
   KnownBits Known = computeKnownBits(Op, DL, 0, AC, CxtI, DT);
   if (Known.isNonNegative())

llvm/test/Transforms/InstCombine/is_fpclass.ll

 }
 
 ; --------------------------------------------------------------------
 ; llvm.is.fpclass with ninf sources
 ; --------------------------------------------------------------------
 
 define i1 @test_class_is_ninf_pinf_ninf_src(float %x) {
 ; CHECK-LABEL: @test_class_is_ninf_pinf_ninf_src(
-; CHECK-NEXT:    [[NINF:%.*]] = fadd ninf float [[X:%.*]], 1.000000e+00
-; CHECK-NEXT:    [[CLASS:%.*]] = call i1 @llvm.is.fpclass.f32(float [[NINF]], i32 516)
-; CHECK-NEXT:    ret i1 [[CLASS]]
+; CHECK-NEXT:    ret i1 false
 ;
   %ninf = fadd ninf float %x, 1.0
   %class = call i1 @llvm.is.fpclass.f32(float %ninf, i32 516)
   ret i1 %class
 }
 
 define i1 @test_class_is_ninf_ninf_src(float %x) {
 ; CHECK-LABEL: @test_class_is_ninf_ninf_src(
-; CHECK-NEXT:    [[NINF:%.*]] = fadd ninf float [[X:%.*]], 1.000000e+00
-; CHECK-NEXT:    [[CLASS:%.*]] = call i1 @llvm.is.fpclass.f32(float [[NINF]], i32 4)
-; CHECK-NEXT:    ret i1 [[CLASS]]
+; CHECK-NEXT:    ret i1 false
 ;
   %ninf = fadd ninf float %x, 1.0
   %class = call i1 @llvm.is.fpclass.f32(float %ninf, i32 4)
   ret i1 %class
 }
 
 define i1 @test_class_is_pinf_ninf_src(float %x) {
 ; CHECK-LABEL: @test_class_is_pinf_ninf_src(
-; CHECK-NEXT:    [[NINF:%.*]] = fadd ninf float [[X:%.*]], 1.000000e+00
-; CHECK-NEXT:    [[CLASS:%.*]] = call i1 @llvm.is.fpclass.f32(float [[NINF]], i32 512)
-; CHECK-NEXT:    ret i1 [[CLASS]]
+; CHECK-NEXT:    ret i1 false
 ;
   %ninf = fadd ninf float %x, 1.0
   %class = call i1 @llvm.is.fpclass.f32(float %ninf, i32 512)
   ret i1 %class
 }
 
 define i1 @test_class_is_ninf_pinf_pnormal_ninf_src(float %x) {
 ; CHECK-LABEL: @test_class_is_ninf_pinf_pnormal_ninf_src(
 ; CHECK-NEXT:    [[NINF:%.*]] = fadd ninf float [[X:%.*]], 1.000000e+00
-; CHECK-NEXT:    [[CLASS:%.*]] = call i1 @llvm.is.fpclass.f32(float [[NINF]], i32 772)
+; CHECK-NEXT:    [[CLASS:%.*]] = call i1 @llvm.is.fpclass.f32(float [[NINF]], i32 256)
 ; CHECK-NEXT:    ret i1 [[CLASS]]
 ;
   %ninf = fadd ninf float %x, 1.0
   %class = call i1 @llvm.is.fpclass.f32(float %ninf, i32 772)
   ret i1 %class
 }
 
 define i1 @test_class_is_not_inf_ninf_src(float %x) {
 ; CHECK-LABEL: @test_class_is_not_inf_ninf_src(
-; CHECK-NEXT:    [[NINF:%.*]] = fadd ninf float [[X:%.*]], 1.000000e+00
-; CHECK-NEXT:    [[CLASS:%.*]] = call i1 @llvm.is.fpclass.f32(float [[NINF]], i32 507)
-; CHECK-NEXT:    ret i1 [[CLASS]]
+; CHECK-NEXT:    ret i1 true
 ;
   %ninf = fadd ninf float %x, 1.0
   %class = call i1 @llvm.is.fpclass.f32(float %ninf, i32 507) ; ~fcInf & fcAllFlags
   ret i1 %class
 }
 
 define i1 @test_class_is_not_inf_ninf_src_strict(float %x) {
 ; CHECK-LABEL: @test_class_is_not_inf_ninf_src_strict(
-; CHECK-NEXT:    [[NINF:%.*]] = fadd ninf float [[X:%.*]], 1.000000e+00
-; CHECK-NEXT:    [[CLASS:%.*]] = call i1 @llvm.is.fpclass.f32(float [[NINF]], i32 507) #[[ATTR3]]
-; CHECK-NEXT:    ret i1 [[CLASS]]
+; CHECK-NEXT:    ret i1 true
 ;
   %ninf = fadd ninf float %x, 1.0
   %class = call i1 @llvm.is.fpclass.f32(float %ninf, i32 507) strictfp ; ~fcInf & fcAllFlags
   ret i1 %class
 }
 
 ; --------------------------------------------------------------------
 ; Negation of llvm.is.fpclass