ValueTracking: Improve accuracy of 0 handling with PreserveSign (#173165)

If the source value is known not subnormal and not zero with the
same sign, we can infer the result is also not zero with the same
sign.

Author: arsenm

llvm/lib/Analysis/ValueTracking.cpp

@@ -5308,6 +5308,14 @@ void computeKnownFPClass(const Value *V, const APInt &DemandedElts,
       if (DenormMode.inputsAreZero() || DenormMode.outputsAreZero())
         Known.knownNot(fcSubnormal);
 
+      if (DenormMode == DenormalMode::getPreserveSign()) {
+        if (KnownSrc.isKnownNever(fcPosZero | fcPosSubnormal))
+          Known.knownNot(fcPosZero);
+        if (KnownSrc.isKnownNever(fcNegZero | fcNegSubnormal))
+          Known.knownNot(fcNegZero);
+        break;
+      }
+
       if (DenormMode.Input == DenormalMode::PositiveZero ||
           (DenormMode.Output == DenormalMode::PositiveZero &&
            DenormMode.Input == DenormalMode::IEEE))

llvm/test/Transforms/Attributor/nofpclass-canonicalize.ll

@@ -204,99 +204,99 @@ define float @ret_canonicalize_ieee_constant_snan() "denormal-fp-math"="ieee,iee
 }
 
 define float @ret_canonicalize_daz_constant_pos_denormal() "denormal-fp-math"="preserve-sign,preserve-sign" {
-; CHECK-LABEL: define noundef nofpclass(nan inf sub norm) float @ret_canonicalize_daz_constant_pos_denormal
+; CHECK-LABEL: define noundef nofpclass(nan inf nzero sub norm) float @ret_canonicalize_daz_constant_pos_denormal
 ; CHECK-SAME: () #[[ATTR10:[0-9]+]] {
-; CHECK-NEXT:    [[CALL:%.*]] = call noundef nofpclass(nan inf sub norm) float @llvm.canonicalize.f32(float noundef 0x36A0000000000000) #[[ATTR12]]
+; CHECK-NEXT:    [[CALL:%.*]] = call noundef nofpclass(nan inf nzero sub norm) float @llvm.canonicalize.f32(float noundef 0x36A0000000000000) #[[ATTR12]]
 ; CHECK-NEXT:    ret float [[CALL]]
 ;
   %call = call float @llvm.canonicalize.f32(float 0x36A0000000000000)
   ret float %call
 }
 
 define float @ret_canonicalize_daz_constant_neg_denormal() "denormal-fp-math"="preserve-sign,preserve-sign" {
-; CHECK-LABEL: define noundef nofpclass(nan inf sub norm) float @ret_canonicalize_daz_constant_neg_denormal
+; CHECK-LABEL: define noundef nofpclass(nan inf pzero sub norm) float @ret_canonicalize_daz_constant_neg_denormal
 ; CHECK-SAME: () #[[ATTR10]] {
-; CHECK-NEXT:    [[CALL:%.*]] = call noundef nofpclass(nan inf sub norm) float @llvm.canonicalize.f32(float noundef 0xB6A0000000000000) #[[ATTR12]]
+; CHECK-NEXT:    [[CALL:%.*]] = call noundef nofpclass(nan inf pzero sub norm) float @llvm.canonicalize.f32(float noundef 0xB6A0000000000000) #[[ATTR12]]
 ; CHECK-NEXT:    ret float [[CALL]]
 ;
   %call = call float @llvm.canonicalize.f32(float 0xb6A0000000000000)
   ret float %call
 }
 
 define float @ret_canonicalize_daz_constant_pos_zero() "denormal-fp-math"="preserve-sign,preserve-sign" {
-; CHECK-LABEL: define noundef nofpclass(nan inf sub norm) float @ret_canonicalize_daz_constant_pos_zero
+; CHECK-LABEL: define noundef nofpclass(nan inf nzero sub norm) float @ret_canonicalize_daz_constant_pos_zero
 ; CHECK-SAME: () #[[ATTR10]] {
-; CHECK-NEXT:    [[CALL:%.*]] = call noundef nofpclass(nan inf sub norm) float @llvm.canonicalize.f32(float noundef 0.000000e+00) #[[ATTR12]]
+; CHECK-NEXT:    [[CALL:%.*]] = call noundef nofpclass(nan inf nzero sub norm) float @llvm.canonicalize.f32(float noundef 0.000000e+00) #[[ATTR12]]
 ; CHECK-NEXT:    ret float [[CALL]]
 ;
   %call = call float @llvm.canonicalize.f32(float 0.0)
   ret float %call
 }
 
 define float @ret_canonicalize_daz_constant_neg_zero() "denormal-fp-math"="preserve-sign,preserve-sign" {
-; CHECK-LABEL: define noundef nofpclass(nan inf sub norm) float @ret_canonicalize_daz_constant_neg_zero
+; CHECK-LABEL: define noundef nofpclass(nan inf pzero sub norm) float @ret_canonicalize_daz_constant_neg_zero
 ; CHECK-SAME: () #[[ATTR10]] {
-; CHECK-NEXT:    [[CALL:%.*]] = call noundef nofpclass(nan inf sub norm) float @llvm.canonicalize.f32(float noundef -0.000000e+00) #[[ATTR12]]
+; CHECK-NEXT:    [[CALL:%.*]] = call noundef nofpclass(nan inf pzero sub norm) float @llvm.canonicalize.f32(float noundef -0.000000e+00) #[[ATTR12]]
 ; CHECK-NEXT:    ret float [[CALL]]
 ;
   %call = call float @llvm.canonicalize.f32(float -0.0)
   ret float %call
 }
 
 define float @ret_canonicalize_daz_constant_pos_normal() "denormal-fp-math"="preserve-sign,preserve-sign" {
-; CHECK-LABEL: define noundef nofpclass(nan inf sub nnorm) float @ret_canonicalize_daz_constant_pos_normal
+; CHECK-LABEL: define noundef nofpclass(nan inf zero sub nnorm) float @ret_canonicalize_daz_constant_pos_normal
 ; CHECK-SAME: () #[[ATTR10]] {
-; CHECK-NEXT:    [[CALL:%.*]] = call noundef nofpclass(nan inf sub nnorm) float @llvm.canonicalize.f32(float noundef 8.000000e+00) #[[ATTR12]]
+; CHECK-NEXT:    [[CALL:%.*]] = call noundef nofpclass(nan inf zero sub nnorm) float @llvm.canonicalize.f32(float noundef 8.000000e+00) #[[ATTR12]]
 ; CHECK-NEXT:    ret float [[CALL]]
 ;
   %call = call float @llvm.canonicalize.f32(float 8.0)
   ret float %call
 }
 
 define float @ret_canonicalize_daz_constant_neg_normal() "denormal-fp-math"="preserve-sign,preserve-sign" {
-; CHECK-LABEL: define noundef nofpclass(nan inf sub pnorm) float @ret_canonicalize_daz_constant_neg_normal
+; CHECK-LABEL: define noundef nofpclass(nan inf zero sub pnorm) float @ret_canonicalize_daz_constant_neg_normal
 ; CHECK-SAME: () #[[ATTR10]] {
-; CHECK-NEXT:    [[CALL:%.*]] = call noundef nofpclass(nan inf sub pnorm) float @llvm.canonicalize.f32(float noundef -8.000000e+00) #[[ATTR12]]
+; CHECK-NEXT:    [[CALL:%.*]] = call noundef nofpclass(nan inf zero sub pnorm) float @llvm.canonicalize.f32(float noundef -8.000000e+00) #[[ATTR12]]
 ; CHECK-NEXT:    ret float [[CALL]]
 ;
   %call = call float @llvm.canonicalize.f32(float -8.0)
   ret float %call
 }
 
 define float @ret_canonicalize_daz_constant_pos_inf() "denormal-fp-math"="preserve-sign,preserve-sign" {
-; CHECK-LABEL: define noundef nofpclass(nan ninf sub norm) float @ret_canonicalize_daz_constant_pos_inf
+; CHECK-LABEL: define noundef nofpclass(nan ninf zero sub norm) float @ret_canonicalize_daz_constant_pos_inf
 ; CHECK-SAME: () #[[ATTR10]] {
-; CHECK-NEXT:    [[CALL:%.*]] = call noundef nofpclass(nan ninf sub norm) float @llvm.canonicalize.f32(float noundef 0x7FF0000000000000) #[[ATTR12]]
+; CHECK-NEXT:    [[CALL:%.*]] = call noundef nofpclass(nan ninf zero sub norm) float @llvm.canonicalize.f32(float noundef 0x7FF0000000000000) #[[ATTR12]]
 ; CHECK-NEXT:    ret float [[CALL]]
 ;
   %call = call float @llvm.canonicalize.f32(float 0x7FF0000000000000)
   ret float %call
 }
 
 define float @ret_canonicalize_daz_constant_neg_inf() "denormal-fp-math"="preserve-sign,preserve-sign" {
-; CHECK-LABEL: define noundef nofpclass(nan pinf sub norm) float @ret_canonicalize_daz_constant_neg_inf
+; CHECK-LABEL: define noundef nofpclass(nan pinf zero sub norm) float @ret_canonicalize_daz_constant_neg_inf
 ; CHECK-SAME: () #[[ATTR10]] {
-; CHECK-NEXT:    [[CALL:%.*]] = call noundef nofpclass(nan pinf sub norm) float @llvm.canonicalize.f32(float noundef 0xFFF0000000000000) #[[ATTR12]]
+; CHECK-NEXT:    [[CALL:%.*]] = call noundef nofpclass(nan pinf zero sub norm) float @llvm.canonicalize.f32(float noundef 0xFFF0000000000000) #[[ATTR12]]
 ; CHECK-NEXT:    ret float [[CALL]]
 ;
   %call = call float @llvm.canonicalize.f32(float 0xFFF0000000000000)
   ret float %call
 }
 
 define float @ret_canonicalize_daz_constant_qnan() "denormal-fp-math"="preserve-sign,preserve-sign" {
-; CHECK-LABEL: define noundef nofpclass(snan inf sub norm) float @ret_canonicalize_daz_constant_qnan
+; CHECK-LABEL: define noundef nofpclass(snan inf zero sub norm) float @ret_canonicalize_daz_constant_qnan
 ; CHECK-SAME: () #[[ATTR10]] {
-; CHECK-NEXT:    [[CALL:%.*]] = call noundef nofpclass(snan inf sub norm) float @llvm.canonicalize.f32(float noundef 0x7FF8000000000000) #[[ATTR12]]
+; CHECK-NEXT:    [[CALL:%.*]] = call noundef nofpclass(snan inf zero sub norm) float @llvm.canonicalize.f32(float noundef 0x7FF8000000000000) #[[ATTR12]]
 ; CHECK-NEXT:    ret float [[CALL]]
 ;
   %call = call float @llvm.canonicalize.f32(float 0x7FF8000000000000)
   ret float %call
 }
 
 define float @ret_canonicalize_daz_constant_snan() "denormal-fp-math"="preserve-sign,preserve-sign" {
-; CHECK-LABEL: define noundef nofpclass(snan inf sub norm) float @ret_canonicalize_daz_constant_snan
+; CHECK-LABEL: define noundef nofpclass(snan inf zero sub norm) float @ret_canonicalize_daz_constant_snan
 ; CHECK-SAME: () #[[ATTR10]] {
-; CHECK-NEXT:    [[CALL:%.*]] = call noundef nofpclass(snan inf sub norm) float @llvm.canonicalize.f32(float noundef 0x7FF1000000000000) #[[ATTR12]]
+; CHECK-NEXT:    [[CALL:%.*]] = call noundef nofpclass(snan inf zero sub norm) float @llvm.canonicalize.f32(float noundef 0x7FF1000000000000) #[[ATTR12]]
 ; CHECK-NEXT:    ret float [[CALL]]
 ;
   %call = call float @llvm.canonicalize.f32(float 0x7FF1000000000000)
@@ -504,9 +504,9 @@ define float @ret_canonicalize_dynamic_constant_snan() "denormal-fp-math"="dynam
 }
 
 define float @ret_canonicalize_daz_not_nzero_not_nsub(float nofpclass(nzero nsub) %x) "denormal-fp-math"="preserve-sign,preserve-sign" {
-; CHECK-LABEL: define nofpclass(snan sub) float @ret_canonicalize_daz_not_nzero_not_nsub
+; CHECK-LABEL: define nofpclass(snan nzero sub) float @ret_canonicalize_daz_not_nzero_not_nsub
 ; CHECK-SAME: (float nofpclass(nzero nsub) [[X:%.*]]) #[[ATTR10]] {
-; CHECK-NEXT:    [[CALL:%.*]] = call nofpclass(snan sub) float @llvm.canonicalize.f32(float nofpclass(nzero nsub) [[X]]) #[[ATTR12]]
+; CHECK-NEXT:    [[CALL:%.*]] = call nofpclass(snan nzero sub) float @llvm.canonicalize.f32(float nofpclass(nzero nsub) [[X]]) #[[ATTR12]]
 ; CHECK-NEXT:    ret float [[CALL]]
 ;
   %call = call float @llvm.canonicalize.f32(float %x)
@@ -534,9 +534,9 @@ define float @ret_canonicalize_daz_not_nzero(float nofpclass(nzero) %x) "denorma
 }
 
 define float @ret_canonicalize_daz_not_pzero_not_psub(float nofpclass(pzero psub) %x) "denormal-fp-math"="preserve-sign,preserve-sign" {
-; CHECK-LABEL: define nofpclass(snan sub) float @ret_canonicalize_daz_not_pzero_not_psub
+; CHECK-LABEL: define nofpclass(snan pzero sub) float @ret_canonicalize_daz_not_pzero_not_psub
 ; CHECK-SAME: (float nofpclass(pzero psub) [[X:%.*]]) #[[ATTR10]] {
-; CHECK-NEXT:    [[CALL:%.*]] = call nofpclass(snan sub) float @llvm.canonicalize.f32(float nofpclass(pzero psub) [[X]]) #[[ATTR12]]
+; CHECK-NEXT:    [[CALL:%.*]] = call nofpclass(snan pzero sub) float @llvm.canonicalize.f32(float nofpclass(pzero psub) [[X]]) #[[ATTR12]]
 ; CHECK-NEXT:    ret float [[CALL]]
 ;
   %call = call float @llvm.canonicalize.f32(float %x)
@@ -584,9 +584,9 @@ define float @ret_canonicalize_daz_not_sub(float nofpclass(sub) %x) "denormal-fp
 }
 
 define float @ret_canonicalize_daz_not_sub_not_nzero(float nofpclass(sub nzero) %x) "denormal-fp-math"="preserve-sign,preserve-sign" {
-; CHECK-LABEL: define nofpclass(snan sub) float @ret_canonicalize_daz_not_sub_not_nzero
+; CHECK-LABEL: define nofpclass(snan nzero sub) float @ret_canonicalize_daz_not_sub_not_nzero
 ; CHECK-SAME: (float nofpclass(nzero sub) [[X:%.*]]) #[[ATTR10]] {
-; CHECK-NEXT:    [[CALL:%.*]] = call nofpclass(snan sub) float @llvm.canonicalize.f32(float nofpclass(nzero sub) [[X]]) #[[ATTR12]]
+; CHECK-NEXT:    [[CALL:%.*]] = call nofpclass(snan nzero sub) float @llvm.canonicalize.f32(float nofpclass(nzero sub) [[X]]) #[[ATTR12]]
 ; CHECK-NEXT:    ret float [[CALL]]
 ;
   %call = call float @llvm.canonicalize.f32(float %x)