[llvm] ValueTracking: Improve handling of fadd in computeKnownFPClass. (PR #174123)
Matt Arsenault via llvm-commits
llvm-commits at lists.llvm.org
Sat Jan 3 02:27:14 PST 2026
https://github.com/arsenm updated https://github.com/llvm/llvm-project/pull/174123
>From 44a75529260761b5f7f80d044145d209c13ac984 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Wed, 31 Dec 2025 20:50:38 +0100
Subject: [PATCH 1/5] ValueTracking: Improve handling of fadd in
computeKnownFPClass.
This already recognized that if both inputs are positive, the
result is positive. Extend this to the mirror situation with
negative inputs.
Also special case fadd x, x. Canonically, fmul x, 2 is fadd x, x.
We can tell the sign bit won't change, and 0 will propagate.
---
llvm/lib/Analysis/ValueTracking.cpp | 28 ++++++++--
llvm/test/Transforms/Attributor/nofpclass.ll | 58 ++++++++++----------
2 files changed, 53 insertions(+), 33 deletions(-)
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index a831736b35c26..b33d81db5172d 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -5619,14 +5619,22 @@ void computeKnownFPClass(const Value *V, const APInt &DemandedElts,
computeKnownFPClass(Op->getOperand(1), DemandedElts, InterestedSrcs,
KnownRHS, Q, Depth + 1);
+ // Special case fadd x, x, which is the canonical form of fmul x, 2.
+ bool SameOperands = Op->getOperand(0) == Op->getOperand(1);
+ if (SameOperands)
+ KnownLHS = KnownRHS;
+
if ((WantNaN && KnownRHS.isKnownNeverNaN()) ||
(WantNegative && KnownRHS.cannotBeOrderedLessThanZero()) ||
WantNegZero || Opc == Instruction::FSub) {
- // RHS is canonically cheaper to compute. Skip inspecting the LHS if
- // there's no point.
- computeKnownFPClass(Op->getOperand(0), DemandedElts, InterestedSrcs,
- KnownLHS, Q, Depth + 1);
+ if (!SameOperands) {
+ // RHS is canonically cheaper to compute. Skip inspecting the LHS if
+ // there's no point.
+ computeKnownFPClass(Op->getOperand(0), DemandedElts, InterestedSrcs,
+ KnownLHS, Q, Depth + 1);
+ }
+
// Adding positive and negative infinity produces NaN.
// TODO: Check sign of infinities.
if (KnownLHS.isKnownNeverNaN() && KnownRHS.isKnownNeverNaN() &&
@@ -5640,6 +5648,10 @@ void computeKnownFPClass(const Value *V, const APInt &DemandedElts,
if (KnownLHS.cannotBeOrderedLessThanZero() &&
KnownRHS.cannotBeOrderedLessThanZero())
Known.knownNot(KnownFPClass::OrderedLessThanZeroMask);
+ if (KnownLHS.cannotBeOrderedGreaterThanZero() &&
+ KnownRHS.cannotBeOrderedGreaterThanZero())
+ Known.knownNot(KnownFPClass::OrderedGreaterThanZeroMask);
+
if (!F)
break;
@@ -5647,6 +5659,14 @@ void computeKnownFPClass(const Value *V, const APInt &DemandedElts,
Op->getType()->getScalarType()->getFltSemantics();
DenormalMode Mode = F->getDenormalMode(FltSem);
+ if (SameOperands) {
+ // Doubling 0 will give the same 0.
+ if (KnownRHS.isKnownNeverLogicalPosZero(Mode))
+ Known.knownNot(fcPosZero);
+ if (KnownRHS.isKnownNeverLogicalNegZero(Mode))
+ Known.knownNot(fcNegZero);
+ }
+
// (fadd x, 0.0) is guaranteed to return +0.0, not -0.0.
if ((KnownLHS.isKnownNeverLogicalNegZero(Mode) ||
KnownRHS.isKnownNeverLogicalNegZero(Mode)) &&
diff --git a/llvm/test/Transforms/Attributor/nofpclass.ll b/llvm/test/Transforms/Attributor/nofpclass.ll
index 8540a2fb42659..58093df0ea67b 100644
--- a/llvm/test/Transforms/Attributor/nofpclass.ll
+++ b/llvm/test/Transforms/Attributor/nofpclass.ll
@@ -3054,7 +3054,7 @@ define float @fadd_double_no_inf(float noundef nofpclass(inf) %arg) {
define float @fadd_double_no_zero(float noundef nofpclass(zero) %arg) {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef nofpclass(nzero) float @fadd_double_no_zero
+; CHECK-LABEL: define noundef nofpclass(zero) float @fadd_double_no_zero
; CHECK-SAME: (float noundef nofpclass(zero) [[ARG:%.*]]) #[[ATTR3]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3087,7 +3087,7 @@ define float @fadd_double_known_positive(float noundef nofpclass(ninf nnorm nsub
define float @fadd_double_known_positive_non0(float noundef nofpclass(ninf nnorm nsub zero) %arg) {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef nofpclass(ninf nzero nsub nnorm) float @fadd_double_known_positive_non0
+; CHECK-LABEL: define noundef nofpclass(ninf zero nsub nnorm) float @fadd_double_known_positive_non0
; CHECK-SAME: (float noundef nofpclass(ninf zero nsub nnorm) [[ARG:%.*]]) #[[ATTR3]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3098,7 +3098,7 @@ define float @fadd_double_known_positive_non0(float noundef nofpclass(ninf nnorm
define float @fadd_double_known_negative_or_zero(float noundef nofpclass(pinf pnorm psub) %arg) {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef float @fadd_double_known_negative_or_zero
+; CHECK-LABEL: define noundef nofpclass(pinf psub pnorm) float @fadd_double_known_negative_or_zero
; CHECK-SAME: (float noundef nofpclass(pinf psub pnorm) [[ARG:%.*]]) #[[ATTR3]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3109,7 +3109,7 @@ define float @fadd_double_known_negative_or_zero(float noundef nofpclass(pinf pn
define float @fadd_double_known_negative(float noundef nofpclass(pinf pnorm psub pzero) %arg) {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef float @fadd_double_known_negative
+; CHECK-LABEL: define noundef nofpclass(pinf pzero psub pnorm) float @fadd_double_known_negative
; CHECK-SAME: (float noundef nofpclass(pinf pzero psub pnorm) [[ARG:%.*]]) #[[ATTR3]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3120,7 +3120,7 @@ define float @fadd_double_known_negative(float noundef nofpclass(pinf pnorm psub
define float @fadd_double_known_negative_non0(float noundef nofpclass(pinf pnorm psub zero) %arg) {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef nofpclass(nzero) float @fadd_double_known_negative_non0
+; CHECK-LABEL: define noundef nofpclass(pinf zero psub pnorm) float @fadd_double_known_negative_non0
; CHECK-SAME: (float noundef nofpclass(pinf zero psub pnorm) [[ARG:%.*]]) #[[ATTR3]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3175,7 +3175,7 @@ define float @fadd_double_no_nnorm_nsub(float noundef nofpclass(nnorm nsub) %arg
define float @fadd_double_no_nopsub_pzero(float noundef nofpclass(psub pzero) %arg) {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef float @fadd_double_no_nopsub_pzero
+; CHECK-LABEL: define noundef nofpclass(pzero) float @fadd_double_no_nopsub_pzero
; CHECK-SAME: (float noundef nofpclass(pzero psub) [[ARG:%.*]]) #[[ATTR3]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3197,7 +3197,7 @@ define float @fadd_double_no_nonsub_nzero(float noundef nofpclass(nsub nzero) %a
define float @fadd_double_no_nopsub_pzero__ieee_daz(float noundef nofpclass(psub pzero) %arg) #2 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef float @fadd_double_no_nopsub_pzero__ieee_daz
+; CHECK-LABEL: define noundef nofpclass(pzero) float @fadd_double_no_nopsub_pzero__ieee_daz
; CHECK-SAME: (float noundef nofpclass(pzero psub) [[ARG:%.*]]) #[[ATTR11]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3208,7 +3208,7 @@ define float @fadd_double_no_nopsub_pzero__ieee_daz(float noundef nofpclass(psub
define float @fadd_double_no_nopsub_pzero__ftz_daz(float noundef nofpclass(psub pzero) %arg) #0 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef float @fadd_double_no_nopsub_pzero__ftz_daz
+; CHECK-LABEL: define noundef nofpclass(pzero) float @fadd_double_no_nopsub_pzero__ftz_daz
; CHECK-SAME: (float noundef nofpclass(pzero psub) [[ARG:%.*]]) #[[ATTR10]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3230,7 +3230,7 @@ define float @fadd_double_no_nonsub_nzero__ieee_daz(float noundef nofpclass(nsub
define float @fadd_double_no_nonsub_nzero__ftz_daz(float noundef nofpclass(nsub nzero) %arg) #0 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef float @fadd_double_no_nonsub_nzero__ftz_daz
+; CHECK-LABEL: define noundef nofpclass(nzero) float @fadd_double_no_nonsub_nzero__ftz_daz
; CHECK-SAME: (float noundef nofpclass(nzero nsub) [[ARG:%.*]]) #[[ATTR10]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3263,7 +3263,7 @@ define float @fadd_double_no_nonsub_nzero__ieee_dynamic(float noundef nofpclass(
define float @fadd_double_known_positive_nonsub_ieee(float noundef nofpclass(ninf nnorm sub zero) %arg) {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef nofpclass(ninf nzero nsub nnorm) float @fadd_double_known_positive_nonsub_ieee
+; CHECK-LABEL: define noundef nofpclass(ninf zero nsub nnorm) float @fadd_double_known_positive_nonsub_ieee
; CHECK-SAME: (float noundef nofpclass(ninf zero sub nnorm) [[ARG:%.*]]) #[[ATTR3]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3274,7 +3274,7 @@ define float @fadd_double_known_positive_nonsub_ieee(float noundef nofpclass(nin
define float @fadd_double_known_positive_nonsub__ieee_daz(float noundef nofpclass(ninf nnorm sub zero) %arg) #2 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef nofpclass(ninf nzero nsub nnorm) float @fadd_double_known_positive_nonsub__ieee_daz
+; CHECK-LABEL: define noundef nofpclass(ninf zero nsub nnorm) float @fadd_double_known_positive_nonsub__ieee_daz
; CHECK-SAME: (float noundef nofpclass(ninf zero sub nnorm) [[ARG:%.*]]) #[[ATTR11]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3285,7 +3285,7 @@ define float @fadd_double_known_positive_nonsub__ieee_daz(float noundef nofpclas
define float @fadd_double_known_positive_nonsub__ftz_daz(float noundef nofpclass(ninf nnorm sub zero) %arg) #0 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef nofpclass(ninf nsub nnorm) float @fadd_double_known_positive_nonsub__ftz_daz
+; CHECK-LABEL: define noundef nofpclass(ninf zero nsub nnorm) float @fadd_double_known_positive_nonsub__ftz_daz
; CHECK-SAME: (float noundef nofpclass(ninf zero sub nnorm) [[ARG:%.*]]) #[[ATTR10]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3296,7 +3296,7 @@ define float @fadd_double_known_positive_nonsub__ftz_daz(float noundef nofpclass
define float @fadd_double_known_positive_nonsub__ieee_dynamic(float noundef nofpclass(ninf nnorm sub zero) %arg) #9 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef nofpclass(ninf nzero nsub nnorm) float @fadd_double_known_positive_nonsub__ieee_dynamic
+; CHECK-LABEL: define noundef nofpclass(ninf zero nsub nnorm) float @fadd_double_known_positive_nonsub__ieee_dynamic
; CHECK-SAME: (float noundef nofpclass(ninf zero sub nnorm) [[ARG:%.*]]) #[[ATTR17]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3307,7 +3307,7 @@ define float @fadd_double_known_positive_nonsub__ieee_dynamic(float noundef nofp
define float @fadd_double_known_negative_nonsub_ieee(float noundef nofpclass(pinf pnorm sub zero) %arg) {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef nofpclass(nzero) float @fadd_double_known_negative_nonsub_ieee
+; CHECK-LABEL: define noundef nofpclass(pinf zero psub pnorm) float @fadd_double_known_negative_nonsub_ieee
; CHECK-SAME: (float noundef nofpclass(pinf zero sub pnorm) [[ARG:%.*]]) #[[ATTR3]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3318,7 +3318,7 @@ define float @fadd_double_known_negative_nonsub_ieee(float noundef nofpclass(pin
define float @fadd_double_known_negative_nonsub__ieee_daz(float noundef nofpclass(pinf pnorm sub zero) %arg) #2 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef nofpclass(nzero) float @fadd_double_known_negative_nonsub__ieee_daz
+; CHECK-LABEL: define noundef nofpclass(pinf zero psub pnorm) float @fadd_double_known_negative_nonsub__ieee_daz
; CHECK-SAME: (float noundef nofpclass(pinf zero sub pnorm) [[ARG:%.*]]) #[[ATTR11]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3329,7 +3329,7 @@ define float @fadd_double_known_negative_nonsub__ieee_daz(float noundef nofpclas
define float @fadd_double_known_negative_nonsub__ftz_daz(float noundef nofpclass(pinf pnorm sub zero) %arg) #0 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef float @fadd_double_known_negative_nonsub__ftz_daz
+; CHECK-LABEL: define noundef nofpclass(pinf zero psub pnorm) float @fadd_double_known_negative_nonsub__ftz_daz
; CHECK-SAME: (float noundef nofpclass(pinf zero sub pnorm) [[ARG:%.*]]) #[[ATTR10]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3340,7 +3340,7 @@ define float @fadd_double_known_negative_nonsub__ftz_daz(float noundef nofpclass
define float @fadd_double_known_negative_nonsub_dynamic(float noundef nofpclass(pinf pnorm sub zero) %arg) #9 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef nofpclass(nzero) float @fadd_double_known_negative_nonsub_dynamic
+; CHECK-LABEL: define noundef nofpclass(pinf zero psub pnorm) float @fadd_double_known_negative_nonsub_dynamic
; CHECK-SAME: (float noundef nofpclass(pinf zero sub pnorm) [[ARG:%.*]]) #[[ATTR17]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3406,7 +3406,7 @@ define float @fadd_known_negative_rhs(float %arg0, float nofpclass(pinf psub pno
define float @fadd_known_negative(float nofpclass(pinf psub pnorm) %arg0, float nofpclass(pinf psub pnorm) %arg1) {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define float @fadd_known_negative
+; CHECK-LABEL: define nofpclass(pinf psub pnorm) float @fadd_known_negative
; CHECK-SAME: (float nofpclass(pinf psub pnorm) [[ARG0:%.*]], float nofpclass(pinf psub pnorm) [[ARG1:%.*]]) #[[ATTR3]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG0]], [[ARG1]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3417,7 +3417,7 @@ define float @fadd_known_negative(float nofpclass(pinf psub pnorm) %arg0, float
define float @fadd_known_negative_daz(float nofpclass(pinf psub pnorm) %arg0, float nofpclass(pinf psub pnorm) %arg1) #2 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define float @fadd_known_negative_daz
+; CHECK-LABEL: define nofpclass(pinf psub pnorm) float @fadd_known_negative_daz
; CHECK-SAME: (float nofpclass(pinf psub pnorm) [[ARG0:%.*]], float nofpclass(pinf psub pnorm) [[ARG1:%.*]]) #[[ATTR11]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG0]], [[ARG1]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3428,7 +3428,7 @@ define float @fadd_known_negative_daz(float nofpclass(pinf psub pnorm) %arg0, fl
define float @fadd_known_negative_pzero_lhs(float nofpclass(pinf psub pnorm pzero) %arg0, float nofpclass(pinf psub pnorm) %arg1) {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define float @fadd_known_negative_pzero_lhs
+; CHECK-LABEL: define nofpclass(pinf psub pnorm) float @fadd_known_negative_pzero_lhs
; CHECK-SAME: (float nofpclass(pinf pzero psub pnorm) [[ARG0:%.*]], float nofpclass(pinf psub pnorm) [[ARG1:%.*]]) #[[ATTR3]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG0]], [[ARG1]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3439,7 +3439,7 @@ define float @fadd_known_negative_pzero_lhs(float nofpclass(pinf psub pnorm pzer
define float @fadd_known_negative_pzero_rhs(float nofpclass(pinf psub pnorm) %arg0, float nofpclass(pinf psub pnorm pzero) %arg1) {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define float @fadd_known_negative_pzero_rhs
+; CHECK-LABEL: define nofpclass(pinf psub pnorm) float @fadd_known_negative_pzero_rhs
; CHECK-SAME: (float nofpclass(pinf psub pnorm) [[ARG0:%.*]], float nofpclass(pinf pzero psub pnorm) [[ARG1:%.*]]) #[[ATTR3]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG0]], [[ARG1]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3450,7 +3450,7 @@ define float @fadd_known_negative_pzero_rhs(float nofpclass(pinf psub pnorm) %ar
define float @fadd_known_negative_pzero(float nofpclass(pinf psub pnorm pzero) %arg0, float nofpclass(pinf psub pnorm pzero) %arg1) {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define float @fadd_known_negative_pzero
+; CHECK-LABEL: define nofpclass(pinf psub pnorm) float @fadd_known_negative_pzero
; CHECK-SAME: (float nofpclass(pinf pzero psub pnorm) [[ARG0:%.*]], float nofpclass(pinf pzero psub pnorm) [[ARG1:%.*]]) #[[ATTR3]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG0]], [[ARG1]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3461,7 +3461,7 @@ define float @fadd_known_negative_pzero(float nofpclass(pinf psub pnorm pzero) %
define float @fadd_known_negative_pzero_ftz_daz(float nofpclass(pinf psub pnorm pzero) %arg0, float nofpclass(pinf psub pnorm pzero) %arg1) #0 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define float @fadd_known_negative_pzero_ftz_daz
+; CHECK-LABEL: define nofpclass(pinf psub pnorm) float @fadd_known_negative_pzero_ftz_daz
; CHECK-SAME: (float nofpclass(pinf pzero psub pnorm) [[ARG0:%.*]], float nofpclass(pinf pzero psub pnorm) [[ARG1:%.*]]) #[[ATTR10]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG0]], [[ARG1]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3472,7 +3472,7 @@ define float @fadd_known_negative_pzero_ftz_daz(float nofpclass(pinf psub pnorm
define float @fadd_known_negative_pzero_ftz(float nofpclass(pinf psub pnorm pzero) %arg0, float nofpclass(pinf psub pnorm pzero) %arg1) #1 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define float @fadd_known_negative_pzero_ftz
+; CHECK-LABEL: define nofpclass(pinf psub pnorm) float @fadd_known_negative_pzero_ftz
; CHECK-SAME: (float nofpclass(pinf pzero psub pnorm) [[ARG0:%.*]], float nofpclass(pinf pzero psub pnorm) [[ARG1:%.*]]) #[[ATTR13]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG0]], [[ARG1]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3483,7 +3483,7 @@ define float @fadd_known_negative_pzero_ftz(float nofpclass(pinf psub pnorm pzer
define float @fadd_known_negative_pzero_daz(float nofpclass(pinf psub pnorm pzero) %arg0, float nofpclass(pinf psub pnorm pzero) %arg1) #2 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define float @fadd_known_negative_pzero_daz
+; CHECK-LABEL: define nofpclass(pinf psub pnorm) float @fadd_known_negative_pzero_daz
; CHECK-SAME: (float nofpclass(pinf pzero psub pnorm) [[ARG0:%.*]], float nofpclass(pinf pzero psub pnorm) [[ARG1:%.*]]) #[[ATTR11]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG0]], [[ARG1]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3539,7 +3539,7 @@ define float @fadd_known_negative_normal_dapz(float nofpclass(pinf pnorm pzero)
; Cannot conclude this can't return +0 due to undef.
define float @fadd_double_no_zero_maybe_undef(float nofpclass(zero) %arg) {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define nofpclass(nzero) float @fadd_double_no_zero_maybe_undef
+; CHECK-LABEL: define nofpclass(zero) float @fadd_double_no_zero_maybe_undef
; CHECK-SAME: (float nofpclass(zero) [[ARG:%.*]]) #[[ATTR3]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3594,7 +3594,7 @@ define float @fadd_double_no_nzero_maybe_undef(float nofpclass(nzero) %arg) {
define float @fadd_double_no_pzero_maybe_undef(float nofpclass(pzero) %arg) {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define float @fadd_double_no_pzero_maybe_undef
+; CHECK-LABEL: define nofpclass(pzero) float @fadd_double_no_pzero_maybe_undef
; CHECK-SAME: (float nofpclass(pzero) [[ARG:%.*]]) #[[ATTR3]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3607,7 +3607,7 @@ define float @fadd_double_no_pzero_maybe_undef(float nofpclass(pzero) %arg) {
; still be flushed.
define float @fadd_double_no_zero__output_only_is_ftz(float noundef nofpclass(zero) %arg) #7 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef float @fadd_double_no_zero__output_only_is_ftz
+; CHECK-LABEL: define noundef nofpclass(zero) float @fadd_double_no_zero__output_only_is_ftz
; CHECK-SAME: (float noundef nofpclass(zero) [[ARG:%.*]]) #[[ATTR13]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3620,7 +3620,7 @@ define float @fadd_double_no_zero__output_only_is_ftz(float noundef nofpclass(ze
; still be flushed.
define float @fadd_double_no_zero__output_only_is_dynamic(float noundef nofpclass(zero) %arg) #8 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef float @fadd_double_no_zero__output_only_is_dynamic
+; CHECK-LABEL: define noundef nofpclass(zero) float @fadd_double_no_zero__output_only_is_dynamic
; CHECK-SAME: (float noundef nofpclass(zero) [[ARG:%.*]]) #[[ATTR18:[0-9]+]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
>From c3a3151ffaf33824da6d3ffaa3f6470c8608f1c3 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Fri, 2 Jan 2026 11:42:09 +0100
Subject: [PATCH 2/5] Check isGuaranteedNotToBeUndef
---
llvm/lib/Analysis/ValueTracking.cpp | 10 ++++++----
llvm/test/Transforms/Attributor/nofpclass.ll | 4 ++--
2 files changed, 8 insertions(+), 6 deletions(-)
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index b33d81db5172d..d083ccf8d7e79 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -5620,15 +5620,17 @@ void computeKnownFPClass(const Value *V, const APInt &DemandedElts,
KnownRHS, Q, Depth + 1);
// Special case fadd x, x, which is the canonical form of fmul x, 2.
- bool SameOperands = Op->getOperand(0) == Op->getOperand(1);
- if (SameOperands)
+ bool SelfAdd = Op->getOperand(0) == Op->getOperand(1) &&
+ isGuaranteedNotToBeUndef(Op->getOperand(0), Q.AC, Q.CxtI,
+ Q.DT, Depth + 1);
+ if (SelfAdd)
KnownLHS = KnownRHS;
if ((WantNaN && KnownRHS.isKnownNeverNaN()) ||
(WantNegative && KnownRHS.cannotBeOrderedLessThanZero()) ||
WantNegZero || Opc == Instruction::FSub) {
- if (!SameOperands) {
+ if (!SelfAdd) {
// RHS is canonically cheaper to compute. Skip inspecting the LHS if
// there's no point.
computeKnownFPClass(Op->getOperand(0), DemandedElts, InterestedSrcs,
@@ -5659,7 +5661,7 @@ void computeKnownFPClass(const Value *V, const APInt &DemandedElts,
Op->getType()->getScalarType()->getFltSemantics();
DenormalMode Mode = F->getDenormalMode(FltSem);
- if (SameOperands) {
+ if (SelfAdd) {
// Doubling 0 will give the same 0.
if (KnownRHS.isKnownNeverLogicalPosZero(Mode))
Known.knownNot(fcPosZero);
diff --git a/llvm/test/Transforms/Attributor/nofpclass.ll b/llvm/test/Transforms/Attributor/nofpclass.ll
index 58093df0ea67b..d39177c0ce793 100644
--- a/llvm/test/Transforms/Attributor/nofpclass.ll
+++ b/llvm/test/Transforms/Attributor/nofpclass.ll
@@ -3539,7 +3539,7 @@ define float @fadd_known_negative_normal_dapz(float nofpclass(pinf pnorm pzero)
; Cannot conclude this can't return +0 due to undef.
define float @fadd_double_no_zero_maybe_undef(float nofpclass(zero) %arg) {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define nofpclass(zero) float @fadd_double_no_zero_maybe_undef
+; CHECK-LABEL: define nofpclass(nzero) float @fadd_double_no_zero_maybe_undef
; CHECK-SAME: (float nofpclass(zero) [[ARG:%.*]]) #[[ATTR3]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3594,7 +3594,7 @@ define float @fadd_double_no_nzero_maybe_undef(float nofpclass(nzero) %arg) {
define float @fadd_double_no_pzero_maybe_undef(float nofpclass(pzero) %arg) {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define nofpclass(pzero) float @fadd_double_no_pzero_maybe_undef
+; CHECK-LABEL: define float @fadd_double_no_pzero_maybe_undef
; CHECK-SAME: (float nofpclass(pzero) [[ARG:%.*]]) #[[ATTR3]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
>From e69004b1453dc2850a2f828bfd4a59fef20b8835 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Fri, 2 Jan 2026 14:00:04 +0100
Subject: [PATCH 3/5] Consider output denorm mode
---
llvm/lib/Analysis/ValueTracking.cpp | 7 +++++--
llvm/test/Transforms/Attributor/nofpclass.ll | 12 ++++++------
2 files changed, 11 insertions(+), 8 deletions(-)
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index d083ccf8d7e79..3b5ee85e2c938 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -5663,9 +5663,12 @@ void computeKnownFPClass(const Value *V, const APInt &DemandedElts,
if (SelfAdd) {
// Doubling 0 will give the same 0.
- if (KnownRHS.isKnownNeverLogicalPosZero(Mode))
+ if (KnownRHS.isKnownNeverLogicalPosZero(Mode) &&
+ Mode.Output == DenormalMode::IEEE)
Known.knownNot(fcPosZero);
- if (KnownRHS.isKnownNeverLogicalNegZero(Mode))
+ if (KnownRHS.isKnownNeverLogicalNegZero(Mode) &&
+ (Mode.Output == DenormalMode::IEEE ||
+ Mode.Output == DenormalMode::PositiveZero))
Known.knownNot(fcNegZero);
}
diff --git a/llvm/test/Transforms/Attributor/nofpclass.ll b/llvm/test/Transforms/Attributor/nofpclass.ll
index d39177c0ce793..b8e106a1813ef 100644
--- a/llvm/test/Transforms/Attributor/nofpclass.ll
+++ b/llvm/test/Transforms/Attributor/nofpclass.ll
@@ -3208,7 +3208,7 @@ define float @fadd_double_no_nopsub_pzero__ieee_daz(float noundef nofpclass(psub
define float @fadd_double_no_nopsub_pzero__ftz_daz(float noundef nofpclass(psub pzero) %arg) #0 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef nofpclass(pzero) float @fadd_double_no_nopsub_pzero__ftz_daz
+; CHECK-LABEL: define noundef float @fadd_double_no_nopsub_pzero__ftz_daz
; CHECK-SAME: (float noundef nofpclass(pzero psub) [[ARG:%.*]]) #[[ATTR10]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3230,7 +3230,7 @@ define float @fadd_double_no_nonsub_nzero__ieee_daz(float noundef nofpclass(nsub
define float @fadd_double_no_nonsub_nzero__ftz_daz(float noundef nofpclass(nsub nzero) %arg) #0 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef nofpclass(nzero) float @fadd_double_no_nonsub_nzero__ftz_daz
+; CHECK-LABEL: define noundef float @fadd_double_no_nonsub_nzero__ftz_daz
; CHECK-SAME: (float noundef nofpclass(nzero nsub) [[ARG:%.*]]) #[[ATTR10]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3285,7 +3285,7 @@ define float @fadd_double_known_positive_nonsub__ieee_daz(float noundef nofpclas
define float @fadd_double_known_positive_nonsub__ftz_daz(float noundef nofpclass(ninf nnorm sub zero) %arg) #0 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef nofpclass(ninf zero nsub nnorm) float @fadd_double_known_positive_nonsub__ftz_daz
+; CHECK-LABEL: define noundef nofpclass(ninf nsub nnorm) float @fadd_double_known_positive_nonsub__ftz_daz
; CHECK-SAME: (float noundef nofpclass(ninf zero sub nnorm) [[ARG:%.*]]) #[[ATTR10]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3329,7 +3329,7 @@ define float @fadd_double_known_negative_nonsub__ieee_daz(float noundef nofpclas
define float @fadd_double_known_negative_nonsub__ftz_daz(float noundef nofpclass(pinf pnorm sub zero) %arg) #0 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef nofpclass(pinf zero psub pnorm) float @fadd_double_known_negative_nonsub__ftz_daz
+; CHECK-LABEL: define noundef nofpclass(pinf psub pnorm) float @fadd_double_known_negative_nonsub__ftz_daz
; CHECK-SAME: (float noundef nofpclass(pinf zero sub pnorm) [[ARG:%.*]]) #[[ATTR10]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3607,7 +3607,7 @@ define float @fadd_double_no_pzero_maybe_undef(float nofpclass(pzero) %arg) {
; still be flushed.
define float @fadd_double_no_zero__output_only_is_ftz(float noundef nofpclass(zero) %arg) #7 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef nofpclass(zero) float @fadd_double_no_zero__output_only_is_ftz
+; CHECK-LABEL: define noundef float @fadd_double_no_zero__output_only_is_ftz
; CHECK-SAME: (float noundef nofpclass(zero) [[ARG:%.*]]) #[[ATTR13]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3620,7 +3620,7 @@ define float @fadd_double_no_zero__output_only_is_ftz(float noundef nofpclass(ze
; still be flushed.
define float @fadd_double_no_zero__output_only_is_dynamic(float noundef nofpclass(zero) %arg) #8 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef nofpclass(zero) float @fadd_double_no_zero__output_only_is_dynamic
+; CHECK-LABEL: define noundef float @fadd_double_no_zero__output_only_is_dynamic
; CHECK-SAME: (float noundef nofpclass(zero) [[ARG:%.*]]) #[[ATTR18:[0-9]+]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
>From 70a5cc6f66caa7f3940c281ae7200eb414c89dd3 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Fri, 2 Jan 2026 14:23:19 +0100
Subject: [PATCH 4/5] Neg 0 handling redundant
---
llvm/lib/Analysis/ValueTracking.cpp | 14 ++++----------
1 file changed, 4 insertions(+), 10 deletions(-)
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 3b5ee85e2c938..6a7521ee0b19a 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -5661,16 +5661,10 @@ void computeKnownFPClass(const Value *V, const APInt &DemandedElts,
Op->getType()->getScalarType()->getFltSemantics();
DenormalMode Mode = F->getDenormalMode(FltSem);
- if (SelfAdd) {
- // Doubling 0 will give the same 0.
- if (KnownRHS.isKnownNeverLogicalPosZero(Mode) &&
- Mode.Output == DenormalMode::IEEE)
- Known.knownNot(fcPosZero);
- if (KnownRHS.isKnownNeverLogicalNegZero(Mode) &&
- (Mode.Output == DenormalMode::IEEE ||
- Mode.Output == DenormalMode::PositiveZero))
- Known.knownNot(fcNegZero);
- }
+ // Doubling 0 will give the same 0.
+ if (SelfAdd && KnownRHS.isKnownNeverLogicalPosZero(Mode) &&
+ Mode.Output == DenormalMode::IEEE)
+ Known.knownNot(fcPosZero);
// (fadd x, 0.0) is guaranteed to return +0.0, not -0.0.
if ((KnownLHS.isKnownNeverLogicalNegZero(Mode) ||
>From 107b4d4be2e4ff01693848f69121376b2354bf1f Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Fri, 2 Jan 2026 14:25:58 +0100
Subject: [PATCH 5/5] More accurate double 0 handling
---
llvm/lib/Analysis/ValueTracking.cpp | 3 ++-
llvm/test/Transforms/Attributor/nofpclass.ll | 8 ++++----
2 files changed, 6 insertions(+), 5 deletions(-)
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 6a7521ee0b19a..d7d5daa348412 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -5663,7 +5663,8 @@ void computeKnownFPClass(const Value *V, const APInt &DemandedElts,
// Doubling 0 will give the same 0.
if (SelfAdd && KnownRHS.isKnownNeverLogicalPosZero(Mode) &&
- Mode.Output == DenormalMode::IEEE)
+ (Mode.Output == DenormalMode::IEEE ||
+ Mode.Output == DenormalMode::PreserveSign))
Known.knownNot(fcPosZero);
// (fadd x, 0.0) is guaranteed to return +0.0, not -0.0.
diff --git a/llvm/test/Transforms/Attributor/nofpclass.ll b/llvm/test/Transforms/Attributor/nofpclass.ll
index b8e106a1813ef..2faf703c83a03 100644
--- a/llvm/test/Transforms/Attributor/nofpclass.ll
+++ b/llvm/test/Transforms/Attributor/nofpclass.ll
@@ -3208,7 +3208,7 @@ define float @fadd_double_no_nopsub_pzero__ieee_daz(float noundef nofpclass(psub
define float @fadd_double_no_nopsub_pzero__ftz_daz(float noundef nofpclass(psub pzero) %arg) #0 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef float @fadd_double_no_nopsub_pzero__ftz_daz
+; CHECK-LABEL: define noundef nofpclass(pzero) float @fadd_double_no_nopsub_pzero__ftz_daz
; CHECK-SAME: (float noundef nofpclass(pzero psub) [[ARG:%.*]]) #[[ATTR10]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3285,7 +3285,7 @@ define float @fadd_double_known_positive_nonsub__ieee_daz(float noundef nofpclas
define float @fadd_double_known_positive_nonsub__ftz_daz(float noundef nofpclass(ninf nnorm sub zero) %arg) #0 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef nofpclass(ninf nsub nnorm) float @fadd_double_known_positive_nonsub__ftz_daz
+; CHECK-LABEL: define noundef nofpclass(ninf pzero nsub nnorm) float @fadd_double_known_positive_nonsub__ftz_daz
; CHECK-SAME: (float noundef nofpclass(ninf zero sub nnorm) [[ARG:%.*]]) #[[ATTR10]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3329,7 +3329,7 @@ define float @fadd_double_known_negative_nonsub__ieee_daz(float noundef nofpclas
define float @fadd_double_known_negative_nonsub__ftz_daz(float noundef nofpclass(pinf pnorm sub zero) %arg) #0 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef nofpclass(pinf psub pnorm) float @fadd_double_known_negative_nonsub__ftz_daz
+; CHECK-LABEL: define noundef nofpclass(pinf pzero psub pnorm) float @fadd_double_known_negative_nonsub__ftz_daz
; CHECK-SAME: (float noundef nofpclass(pinf zero sub pnorm) [[ARG:%.*]]) #[[ATTR10]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -3607,7 +3607,7 @@ define float @fadd_double_no_pzero_maybe_undef(float nofpclass(pzero) %arg) {
; still be flushed.
define float @fadd_double_no_zero__output_only_is_ftz(float noundef nofpclass(zero) %arg) #7 {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define noundef float @fadd_double_no_zero__output_only_is_ftz
+; CHECK-LABEL: define noundef nofpclass(pzero) float @fadd_double_no_zero__output_only_is_ftz
; CHECK-SAME: (float noundef nofpclass(zero) [[ARG:%.*]]) #[[ATTR13]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
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