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ConstantFolding: Constant fold denormal inputs to canonicalize for IEEE
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This makes it possible to use canonicalize to perform a dynamic check
for whether denormal flushing is enabled, which will fold out when the
denormal mode is known. Previously it would only fold if denormal
flushing were known enabled.

https://reviews.llvm.org/D156107
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@arsenm
arsenm committed Jul 24, 2023
1 parent 68b7d3f commit a09d9b4
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Showing 2 changed files with 244 additions and 12 deletions.
3 changes: 1 addition & 2 deletions llvm/lib/Analysis/ConstantFolding.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1973,9 +1973,8 @@ static Constant *constantFoldCanonicalize(const Type *Ty, const CallBase *CI,
DenormalMode DenormMode =
CI->getFunction()->getDenormalMode(Src.getSemantics());

// TODO: Should allow folding for pure IEEE.
if (DenormMode == DenormalMode::getIEEE())
return nullptr;
return ConstantFP::get(CI->getContext(), Src);

if (DenormMode.Input == DenormalMode::Dynamic)
return nullptr;
Expand Down
253 changes: 243 additions & 10 deletions llvm/test/Transforms/InstSimplify/canonicalize.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -75,8 +75,7 @@ define <2 x float> @canonicalize_poison_vector() {

define float @canonicalize_denorm() {
; CHECK-LABEL: @canonicalize_denorm(
; CHECK-NEXT: [[RET:%.*]] = call float @llvm.canonicalize.f32(float 0x380FFFFFC0000000)
; CHECK-NEXT: ret float [[RET]]
; CHECK-NEXT: ret float 0x380FFFFFC0000000
;
%ret = call float @llvm.canonicalize.f32(float bitcast (i32 8388607 to float))
ret float %ret
Expand Down Expand Up @@ -370,8 +369,7 @@ define double @canonicalize_1.0_f64() {

define double @canonicalize_0x00000000000001_f64() {
; CHECK-LABEL: @canonicalize_0x00000000000001_f64(
; CHECK-NEXT: [[RET:%.*]] = call double @llvm.canonicalize.f64(double 4.940660e-324)
; CHECK-NEXT: ret double [[RET]]
; CHECK-NEXT: ret double 4.940660e-324
;
%ret = call double @llvm.canonicalize.f64(double 0x00000000000001)
ret double %ret
Expand Down Expand Up @@ -415,8 +413,7 @@ define half @canonicalize_1.0_f16() {

define half @canonicalize_0x0001_f16() {
; CHECK-LABEL: @canonicalize_0x0001_f16(
; CHECK-NEXT: [[RET:%.*]] = call half @llvm.canonicalize.f16(half 0xH0001)
; CHECK-NEXT: ret half [[RET]]
; CHECK-NEXT: ret half 0xH0001
;
%ret = call half @llvm.canonicalize.f16(half 0xH0001)
ret half %ret
Expand Down Expand Up @@ -460,8 +457,7 @@ define fp128 @canonicalize_1.0_fp128() {

define fp128 @canonicalize_0x00000000000000000000000000000001_fp128() {
; CHECK-LABEL: @canonicalize_0x00000000000000000000000000000001_fp128(
; CHECK-NEXT: [[RET:%.*]] = call fp128 @llvm.canonicalize.f128(fp128 0xL00000000000000000000000000000001)
; CHECK-NEXT: ret fp128 [[RET]]
; CHECK-NEXT: ret fp128 0xL00000000000000000000000000000001
;
%ret = call fp128 @llvm.canonicalize.fp128(fp128 0xL00000000000000000000000000000001)
ret fp128 %ret
Expand Down Expand Up @@ -514,8 +510,7 @@ define bfloat @canonicalize_1.0_bf16() {

define bfloat @canonicalize_0x0001_bf16() {
; CHECK-LABEL: @canonicalize_0x0001_bf16(
; CHECK-NEXT: [[RET:%.*]] = call bfloat @llvm.canonicalize.bf16(bfloat 0xR0001)
; CHECK-NEXT: ret bfloat [[RET]]
; CHECK-NEXT: ret bfloat 0xR0001
;
%ret = call bfloat @llvm.canonicalize.bf16(bfloat 0xR0001)
ret bfloat %ret
Expand Down Expand Up @@ -767,6 +762,243 @@ define ppc_fp128 @canonicalize_neg1.0_ppcf128() {
ret ppc_fp128 %ret
}

; --------------------------------------------------------------------
; Test folds of using canonicalize + is.fpclass to inspect the denormal mode.
; --------------------------------------------------------------------

define i1 @is_poszero_daz_enabled_check_dynamic() "denormal-fp-math"="ieee,dynamic" {
; CHECK-LABEL: @is_poszero_daz_enabled_check_dynamic(
; CHECK-NEXT: [[CANONICAL:%.*]] = call float @llvm.canonicalize.f32(float 0x36A0000000000000)
; CHECK-NEXT: [[IS_POS_ZERO:%.*]] = call i1 @llvm.is.fpclass.f32(float [[CANONICAL]], i32 64)
; CHECK-NEXT: ret i1 [[IS_POS_ZERO]]
;
%canonical = call float @llvm.canonicalize.f32(float bitcast (i32 1 to float))
%is.pos.zero = call i1 @llvm.is.fpclass.f32(float %canonical, i32 64)
ret i1 %is.pos.zero
}

define i1 @is_preserve_sign_daz_enabled_check_dynamic() "denormal-fp-math"="ieee,dynamic" {
; CHECK-LABEL: @is_preserve_sign_daz_enabled_check_dynamic(
; CHECK-NEXT: [[CANONICAL:%.*]] = call float @llvm.canonicalize.f32(float 0xB6A0000000000000)
; CHECK-NEXT: [[IS_NEG_ZERO:%.*]] = call i1 @llvm.is.fpclass.f32(float [[CANONICAL]], i32 32)
; CHECK-NEXT: ret i1 [[IS_NEG_ZERO]]
;
%canonical = call float @llvm.canonicalize.f32(float bitcast (i32 -2147483647 to float))
%is.neg.zero = call i1 @llvm.is.fpclass.f32(float %canonical, i32 32)
ret i1 %is.neg.zero
}

define i1 @is_positive_zero_daz_enabled_check_dynamic() "denormal-fp-math"="ieee,dynamic" {
; CHECK-LABEL: @is_positive_zero_daz_enabled_check_dynamic(
; CHECK-NEXT: [[CANONICAL:%.*]] = call float @llvm.canonicalize.f32(float 0xB6A0000000000000)
; CHECK-NEXT: [[IS_POS_ZERO:%.*]] = call i1 @llvm.is.fpclass.f32(float [[CANONICAL]], i32 64)
; CHECK-NEXT: ret i1 [[IS_POS_ZERO]]
;
%canonical = call float @llvm.canonicalize.f32(float bitcast (i32 -2147483647 to float))
%is.pos.zero = call i1 @llvm.is.fpclass.f32(float %canonical, i32 64)
ret i1 %is.pos.zero
}

define i1 @is_any_daz_enabled_check_dynamic() "denormal-fp-math"="ieee,dynamic" {
; CHECK-LABEL: @is_any_daz_enabled_check_dynamic(
; CHECK-NEXT: [[CANONICAL:%.*]] = call float @llvm.canonicalize.f32(float 0xB6A0000000000000)
; CHECK-NEXT: [[IS_ANY_ZERO:%.*]] = call i1 @llvm.is.fpclass.f32(float [[CANONICAL]], i32 96)
; CHECK-NEXT: ret i1 [[IS_ANY_ZERO]]
;
%canonical = call float @llvm.canonicalize.f32(float bitcast (i32 -2147483647 to float))
%is.any.zero = call i1 @llvm.is.fpclass.f32(float %canonical, i32 96)
ret i1 %is.any.zero
}

define i1 @is_not_daz_enabled_check_dynamic() "denormal-fp-math"="ieee,dynamic" {
; CHECK-LABEL: @is_not_daz_enabled_check_dynamic(
; CHECK-NEXT: [[CANONICAL:%.*]] = call float @llvm.canonicalize.f32(float 0x36A0000000000000)
; CHECK-NEXT: [[IS_NOT_POS_ZERO:%.*]] = call i1 @llvm.is.fpclass.f32(float [[CANONICAL]], i32 959)
; CHECK-NEXT: ret i1 [[IS_NOT_POS_ZERO]]
;
%canonical = call float @llvm.canonicalize.f32(float bitcast (i32 1 to float))
%is.not.pos.zero = call i1 @llvm.is.fpclass.f32(float %canonical, i32 959)
ret i1 %is.not.pos.zero
}

define i1 @is_poszero_daz_enabled_check_ieee() "denormal-fp-math"="ieee,ieee" {
; CHECK-LABEL: @is_poszero_daz_enabled_check_ieee(
; CHECK-NEXT: ret i1 false
;
%canonical = call float @llvm.canonicalize.f32(float bitcast (i32 1 to float))
%is.pos.zero = call i1 @llvm.is.fpclass.f32(float %canonical, i32 64)
ret i1 %is.pos.zero
}

define i1 @is_preserve_sign_daz_enabled_check_ieee() "denormal-fp-math"="ieee,ieee" {
; CHECK-LABEL: @is_preserve_sign_daz_enabled_check_ieee(
; CHECK-NEXT: ret i1 false
;
%canonical = call float @llvm.canonicalize.f32(float bitcast (i32 -2147483647 to float))
%is.neg.zero = call i1 @llvm.is.fpclass.f32(float %canonical, i32 32)
ret i1 %is.neg.zero
}

define i1 @is_positive_zero_daz_enabled_check_ieee() "denormal-fp-math"="ieee,ieee" {
; CHECK-LABEL: @is_positive_zero_daz_enabled_check_ieee(
; CHECK-NEXT: ret i1 false
;
%canonical = call float @llvm.canonicalize.f32(float bitcast (i32 -2147483647 to float))
%is.pos.zero = call i1 @llvm.is.fpclass.f32(float %canonical, i32 64)
ret i1 %is.pos.zero
}

define i1 @is_any_daz_enabled_check_ieee() "denormal-fp-math"="ieee,ieee" {
; CHECK-LABEL: @is_any_daz_enabled_check_ieee(
; CHECK-NEXT: ret i1 false
;
%canonical = call float @llvm.canonicalize.f32(float bitcast (i32 -2147483647 to float))
%is.any.zero = call i1 @llvm.is.fpclass.f32(float %canonical, i32 96)
ret i1 %is.any.zero
}

define i1 @is_not_daz_enabled_check_ieee() "denormal-fp-math"="ieee,ieee" {
; CHECK-LABEL: @is_not_daz_enabled_check_ieee(
; CHECK-NEXT: ret i1 true
;
%canonical = call float @llvm.canonicalize.f32(float bitcast (i32 1 to float))
%is.not.pos.zero = call i1 @llvm.is.fpclass.f32(float %canonical, i32 959)
ret i1 %is.not.pos.zero
}

define i1 @is_poszero_daz_enabled_check_preserve_sign() "denormal-fp-math"="ieee,preserve-sign" {
; CHECK-LABEL: @is_poszero_daz_enabled_check_preserve_sign(
; CHECK-NEXT: ret i1 true
;
%canonical = call float @llvm.canonicalize.f32(float bitcast (i32 1 to float))
%is.pos.zero = call i1 @llvm.is.fpclass.f32(float %canonical, i32 64)
ret i1 %is.pos.zero
}

define i1 @is_preserve_sign_daz_enabled_check_preserve_sign() "denormal-fp-math"="ieee,preserve-sign" {
; CHECK-LABEL: @is_preserve_sign_daz_enabled_check_preserve_sign(
; CHECK-NEXT: ret i1 true
;
%canonical = call float @llvm.canonicalize.f32(float bitcast (i32 -2147483647 to float))
%is.neg.zero = call i1 @llvm.is.fpclass.f32(float %canonical, i32 32)
ret i1 %is.neg.zero
}

define i1 @is_positive_zero_daz_enabled_check_preserve_sign() "denormal-fp-math"="ieee,preserve-sign" {
; CHECK-LABEL: @is_positive_zero_daz_enabled_check_preserve_sign(
; CHECK-NEXT: ret i1 false
;
%canonical = call float @llvm.canonicalize.f32(float bitcast (i32 -2147483647 to float))
%is.pos.zero = call i1 @llvm.is.fpclass.f32(float %canonical, i32 64)
ret i1 %is.pos.zero
}

define i1 @is_any_daz_enabled_check_preserve_sign() "denormal-fp-math"="ieee,preserve-sign" {
; CHECK-LABEL: @is_any_daz_enabled_check_preserve_sign(
; CHECK-NEXT: ret i1 true
;
%canonical = call float @llvm.canonicalize.f32(float bitcast (i32 -2147483647 to float))
%is.any.zero = call i1 @llvm.is.fpclass.f32(float %canonical, i32 96)
ret i1 %is.any.zero
}

define i1 @is_not_daz_enabled_check_preserve_sign() "denormal-fp-math"="ieee,preserve-sign" {
; CHECK-LABEL: @is_not_daz_enabled_check_preserve_sign(
; CHECK-NEXT: ret i1 false
;
%canonical = call float @llvm.canonicalize.f32(float bitcast (i32 1 to float))
%is.not.pos.zero = call i1 @llvm.is.fpclass.f32(float %canonical, i32 959)
ret i1 %is.not.pos.zero
}

define i1 @is_poszero_daz_enabled_check_positive_zero() "denormal-fp-math"="ieee,positive-zero" {
; CHECK-LABEL: @is_poszero_daz_enabled_check_positive_zero(
; CHECK-NEXT: ret i1 true
;
%canonical = call float @llvm.canonicalize.f32(float bitcast (i32 1 to float))
%is.pos.zero = call i1 @llvm.is.fpclass.f32(float %canonical, i32 64)
ret i1 %is.pos.zero
}

define i1 @is_preserve_sign_daz_enabled_check_positive_zero() "denormal-fp-math"="ieee,positive-zero" {
; CHECK-LABEL: @is_preserve_sign_daz_enabled_check_positive_zero(
; CHECK-NEXT: ret i1 false
;
%canonical = call float @llvm.canonicalize.f32(float bitcast (i32 -2147483647 to float))
%is.neg.zero = call i1 @llvm.is.fpclass.f32(float %canonical, i32 32)
ret i1 %is.neg.zero
}

define i1 @is_positive_zero_daz_enabled_check_positive_zero() "denormal-fp-math"="ieee,positive-zero" {
; CHECK-LABEL: @is_positive_zero_daz_enabled_check_positive_zero(
; CHECK-NEXT: ret i1 true
;
%canonical = call float @llvm.canonicalize.f32(float bitcast (i32 -2147483647 to float))
%is.pos.zero = call i1 @llvm.is.fpclass.f32(float %canonical, i32 64)
ret i1 %is.pos.zero
}

define i1 @is_any_daz_enabled_check_positive_zero() "denormal-fp-math"="ieee,positive-zero" {
; CHECK-LABEL: @is_any_daz_enabled_check_positive_zero(
; CHECK-NEXT: ret i1 true
;
%canonical = call float @llvm.canonicalize.f32(float bitcast (i32 -2147483647 to float))
%is.any.zero = call i1 @llvm.is.fpclass.f32(float %canonical, i32 96)
ret i1 %is.any.zero
}

define i1 @is_not_daz_enabled_check_positive_zero() "denormal-fp-math"="ieee,positive-zero" {
; CHECK-LABEL: @is_not_daz_enabled_check_positive_zero(
; CHECK-NEXT: ret i1 false
;
%canonical = call float @llvm.canonicalize.f32(float bitcast (i32 1 to float))
%is.not.pos.zero = call i1 @llvm.is.fpclass.f32(float %canonical, i32 959)
ret i1 %is.not.pos.zero
}

define i1 @is_poszero_daz_enabled_check_dynamic_bitcast() "denormal-fp-math"="ieee,dynamic" {
; CHECK-LABEL: @is_poszero_daz_enabled_check_dynamic_bitcast(
; CHECK-NEXT: [[CANONICAL:%.*]] = call float @llvm.canonicalize.f32(float 0x36A0000000000000)
; CHECK-NEXT: [[BITCAST:%.*]] = bitcast float [[CANONICAL]] to i32
; CHECK-NEXT: [[IS_POS_ZERO:%.*]] = icmp eq i32 [[BITCAST]], 0
; CHECK-NEXT: ret i1 [[IS_POS_ZERO]]
;
%canonical = call float @llvm.canonicalize.f32(float bitcast (i32 1 to float))
%bitcast = bitcast float %canonical to i32
%is.pos.zero = icmp eq i32 %bitcast, 0
ret i1 %is.pos.zero
}

define i1 @is_poszero_daz_enabled_check_preserve_sign_bitcast() "denormal-fp-math"="ieee,preserve-sign" {
; CHECK-LABEL: @is_poszero_daz_enabled_check_preserve_sign_bitcast(
; CHECK-NEXT: ret i1 true
;
%canonical = call float @llvm.canonicalize.f32(float bitcast (i32 1 to float))
%bitcast = bitcast float %canonical to i32
%is.pos.zero = icmp eq i32 %bitcast, 0
ret i1 %is.pos.zero
}

define i1 @is_poszero_daz_enabled_check_positive_zero_bitcast() "denormal-fp-math"="ieee,positive-zero" {
; CHECK-LABEL: @is_poszero_daz_enabled_check_positive_zero_bitcast(
; CHECK-NEXT: ret i1 true
;
%canonical = call float @llvm.canonicalize.f32(float bitcast (i32 1 to float))
%bitcast = bitcast float %canonical to i32
%is.pos.zero = icmp eq i32 %bitcast, 0
ret i1 %is.pos.zero
}

define i1 @is_poszero_daz_enabled_check_ieee_bitcast() "denormal-fp-math"="ieee,ieee" {
; CHECK-LABEL: @is_poszero_daz_enabled_check_ieee_bitcast(
; CHECK-NEXT: ret i1 false
;
%canonical = call float @llvm.canonicalize.f32(float bitcast (i32 1 to float))
%bitcast = bitcast float %canonical to i32
%is.pos.zero = icmp eq i32 %bitcast, 0
ret i1 %is.pos.zero
}

declare bfloat @llvm.canonicalize.bf16(bfloat)
declare half @llvm.canonicalize.f16(half)
declare float @llvm.canonicalize.f32(float)
Expand All @@ -775,3 +1007,4 @@ declare double @llvm.canonicalize.f64(double)
declare fp128 @llvm.canonicalize.fp128(fp128)
declare x86_fp80 @llvm.canonicalize.f80(x86_fp80)
declare ppc_fp128 @llvm.canonicalize.ppcf128(ppc_fp128)
declare i1 @llvm.is.fpclass.f32(float, i32 immarg)

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