[llvm] [KnownFPClass] Fix fsub input handling and improve fadd_self (PR #225605)
Eric Ross via llvm-commits
llvm-commits at lists.llvm.org
Sun Oct 4 20:50:17 PDT 2026
https://github.com/ZERICO2005 updated https://github.com/llvm/llvm-project/pull/225605
>From 100ce1a46fbef008628b9b2d3025d7b19dec3913 Mon Sep 17 00:00:00 2001
From: zerico <zerico2005 at gmail.com>
Date: Sun, 4 Oct 2026 21:37:58 -0600
Subject: [PATCH] [KnownFPClass] Fix fsub input denormal handling
---
llvm/lib/Support/KnownFPClass.cpp | 70 +++++-----
.../Attributor/nofpclass-fadd-fsub.ll | 122 ++++++++++++++----
2 files changed, 138 insertions(+), 54 deletions(-)
diff --git a/llvm/lib/Support/KnownFPClass.cpp b/llvm/lib/Support/KnownFPClass.cpp
index 96d6a9758b8f8..dbae26961f13c 100644
--- a/llvm/lib/Support/KnownFPClass.cpp
+++ b/llvm/lib/Support/KnownFPClass.cpp
@@ -462,9 +462,9 @@ KnownBits KnownFPClass::toKnownBits(const fltSemantics &FltSemantics) const {
return Known;
}
-// Handle known sign bit and nan cases for fadd.
+// Handle known sign bit and nan cases for fadd, fsub, and fma.
static KnownFPClass fadd_impl(const KnownFPClass &KnownLHS,
- const KnownFPClass &KnownRHS, DenormalMode Mode) {
+ const KnownFPClass &KnownRHS, bool IsFMA) {
KnownFPClass Known;
// Adding positive and negative infinity produces NaN, but only if both
@@ -494,47 +494,59 @@ static KnownFPClass fadd_impl(const KnownFPClass &KnownLHS,
Known.knownNot(fcZero | fcNegSubnormal);
}
+ if (!IsFMA) {
+ // (fadd x, +0.0) is guaranteed to return +0.0, not -0.0.
+ if (KnownLHS.isKnownNeverNegZero() || KnownRHS.isKnownNeverNegZero())
+ Known.knownNot(fcNegZero);
+
+ Known.propagateNonSNaN(KnownLHS, KnownRHS);
+ }
+
return Known;
}
-KnownFPClass KnownFPClass::fadd(const KnownFPClass &KnownLHS,
- const KnownFPClass &KnownRHS,
+KnownFPClass KnownFPClass::fadd(const KnownFPClass &KnownLHS_,
+ const KnownFPClass &KnownRHS_,
DenormalMode Mode) {
- KnownFPClass Known = fadd_impl(KnownLHS, KnownRHS, Mode);
-
- // (fadd x, 0.0) is guaranteed to return +0.0, not -0.0.
- if ((KnownLHS.isKnownNeverLogicalNegZero(Mode) ||
- KnownRHS.isKnownNeverLogicalNegZero(Mode)) &&
- // Make sure output negative denormal can't flush to -0
- (Mode.Output == DenormalMode::IEEE ||
- Mode.Output == DenormalMode::PositiveZero))
- Known.knownNot(fcNegZero);
+ KnownFPClass KnownLHS = applyInputDenormalMode(KnownLHS_, Mode);
+ KnownFPClass KnownRHS = applyInputDenormalMode(KnownRHS_, Mode);
- Known.propagateNonSNaN(KnownLHS, KnownRHS);
+ KnownFPClass Known = fadd_impl(KnownLHS, KnownRHS, /*IsFMA=*/false);
- return Known;
+ return applyOutputDenormalMode(Known, Mode);
}
-KnownFPClass KnownFPClass::fadd_self(const KnownFPClass &KnownSrc,
+KnownFPClass KnownFPClass::fadd_self(const KnownFPClass &KnownSrc_,
DenormalMode Mode) {
- KnownFPClass Known = fadd(KnownSrc, KnownSrc, Mode);
+ KnownFPClass KnownSrc = applyInputDenormalMode(KnownSrc_, Mode);
+
+ KnownFPClass Known = fadd_impl(KnownSrc, KnownSrc, /*IsFMA=*/false);
+
+ if (KnownSrc.isKnownNever(fcPosSubnormal))
+ Known.knownNot(fcPosSubnormal);
+ if (KnownSrc.isKnownNever(fcNegSubnormal))
+ Known.knownNot(fcNegSubnormal);
// Doubling 0 will give the same 0.
- if (KnownSrc.isKnownNeverLogicalPosZero(Mode) &&
- (Mode.Output == DenormalMode::IEEE ||
- (Mode.Output == DenormalMode::PreserveSign &&
- KnownSrc.isKnownNeverPosSubnormal()) ||
- (Mode.Output == DenormalMode::PositiveZero &&
- KnownSrc.isKnownNeverSubnormal())))
+ if (KnownSrc.isKnownNeverPosZero())
Known.knownNot(fcPosZero);
- return Known;
+ return applyOutputDenormalMode(Known, Mode);
}
-KnownFPClass KnownFPClass::fsub(const KnownFPClass &KnownLHS,
- const KnownFPClass &KnownRHS,
+KnownFPClass KnownFPClass::fsub(const KnownFPClass &KnownLHS_,
+ const KnownFPClass &KnownRHS_,
DenormalMode Mode) {
- return fadd(KnownLHS, fneg(KnownRHS), Mode);
+ KnownFPClass KnownLHS = applyInputDenormalMode(KnownLHS_, Mode);
+ KnownFPClass KnownRHS = applyInputDenormalMode(KnownRHS_, Mode);
+
+ // fsub(x, y) == fadd(x, -y) as long as we negate after subnormals are
+ // flushed.
+ KnownRHS.fneg();
+
+ KnownFPClass Known = fadd_impl(KnownLHS, KnownRHS, /*IsFMA=*/false);
+
+ return applyOutputDenormalMode(Known, Mode);
}
KnownFPClass KnownFPClass::fmul(const KnownFPClass &KnownLHS,
@@ -709,7 +721,7 @@ KnownFPClass KnownFPClass::fma(const KnownFPClass &KnownLHS,
//
// If the multiply is a -0 due to rounding, the final -0 + 0 will be -0,
// unlike for a separate fadd.
- KnownFPClass Known = fadd_impl(Mul, KnownAddend, Mode);
+ KnownFPClass Known = fadd_impl(Mul, KnownAddend, /*IsFMA=*/true);
// propagateNonSNaN for 3 arguments.
if (KnownLHS.isKnownNever(fcSNan) && KnownRHS.isKnownNever(fcSNan) &&
@@ -723,7 +735,7 @@ KnownFPClass KnownFPClass::fma_square(const KnownFPClass &KnownSquared,
const KnownFPClass &KnownAddend,
DenormalMode Mode) {
KnownFPClass Squared = square(KnownSquared, Mode);
- KnownFPClass Known = fadd_impl(Squared, KnownAddend, Mode);
+ KnownFPClass Known = fadd_impl(Squared, KnownAddend, /*IsFMA=*/true);
// Since we know the squared input must be positive, the add of opposite sign
// infinities nan hazard only applies for negative inf.
diff --git a/llvm/test/Transforms/Attributor/nofpclass-fadd-fsub.ll b/llvm/test/Transforms/Attributor/nofpclass-fadd-fsub.ll
index 890610488abf2..2385e189c1130 100644
--- a/llvm/test/Transforms/Attributor/nofpclass-fadd-fsub.ll
+++ b/llvm/test/Transforms/Attributor/nofpclass-fadd-fsub.ll
@@ -291,8 +291,8 @@ define float @fadd_p0_ieee_daz(float %arg0) #2 {
ret float %add
}
-define float @fadd_p0_dapz_ieee(float %arg0) #4 {
-; CHECK-LABEL: define nofpclass(nzero) float @fadd_p0_dapz_ieee(
+define float @fadd_p0_ftpz_ieee(float %arg0) #4 {
+; CHECK-LABEL: define nofpclass(nzero) float @fadd_p0_ftpz_ieee(
; CHECK-SAME: float [[ARG0:%.*]]) #[[ATTR5:[0-9]+]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG0]], 0.000000e+00
; CHECK-NEXT: ret float [[ADD]]
@@ -341,8 +341,18 @@ define float @fsub_p0_commute_ieee_daz(float %arg0) #2 {
ret float %sub
}
-define float @fsub_n0_commute_ieee_daz(float %arg0) #1 {
+define float @fsub_n0_commute_ieee_daz(float %arg0) #2 {
; CHECK-LABEL: define float @fsub_n0_commute_ieee_daz(
+; CHECK-SAME: float [[ARG0:%.*]]) #[[ATTR4]] {
+; CHECK-NEXT: [[SUB:%.*]] = fsub float -0.000000e+00, [[ARG0]]
+; CHECK-NEXT: ret float [[SUB]]
+;
+ %sub = fsub float -0.0, %arg0
+ ret float %sub
+}
+
+define float @fsub_n0_commute_ftz_ieee(float %arg0) #1 {
+; CHECK-LABEL: define float @fsub_n0_commute_ftz_ieee(
; CHECK-SAME: float [[ARG0:%.*]]) #[[ATTR6:[0-9]+]] {
; CHECK-NEXT: [[SUB:%.*]] = fsub float -0.000000e+00, [[ARG0]]
; CHECK-NEXT: ret float [[SUB]]
@@ -552,7 +562,7 @@ define float @fadd_known_positive_nzero(float nofpclass(ninf nsub nnorm nzero) %
}
define float @fadd_known_positive_nzero_ftz_daz(float nofpclass(ninf nsub nnorm nzero) %arg0, float nofpclass(ninf nsub nnorm nzero) %arg1) #0 {
-; CHECK-LABEL: define nofpclass(ninf nsub nnorm) float @fadd_known_positive_nzero_ftz_daz(
+; CHECK-LABEL: define nofpclass(ninf nzero nsub nnorm) float @fadd_known_positive_nzero_ftz_daz(
; CHECK-SAME: float nofpclass(ninf nzero nsub nnorm) [[ARG0:%.*]], float nofpclass(ninf nzero nsub nnorm) [[ARG1:%.*]]) #[[ATTR1]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG0]], [[ARG1]]
; CHECK-NEXT: ret float [[ADD]]
@@ -562,7 +572,7 @@ define float @fadd_known_positive_nzero_ftz_daz(float nofpclass(ninf nsub nnorm
}
define float @fadd_known_positive_nzero_ftz(float nofpclass(ninf nsub nnorm nzero) %arg0, float nofpclass(ninf nsub nnorm nzero) %arg1) #1 {
-; CHECK-LABEL: define nofpclass(ninf nsub nnorm) float @fadd_known_positive_nzero_ftz(
+; CHECK-LABEL: define nofpclass(ninf nzero nsub nnorm) float @fadd_known_positive_nzero_ftz(
; CHECK-SAME: float nofpclass(ninf nzero nsub nnorm) [[ARG0:%.*]], float nofpclass(ninf nzero nsub nnorm) [[ARG1:%.*]]) #[[ATTR6]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG0]], [[ARG1]]
; CHECK-NEXT: ret float [[ADD]]
@@ -764,7 +774,7 @@ define float @fadd_self_no_noninf_nnorm(float noundef nofpclass(ninf nnorm) %arg
}
define float @fadd_self_no_pnorm_psub(float noundef nofpclass(pnorm psub) %arg) {
-; CHECK-LABEL: define noundef float @fadd_self_no_pnorm_psub(
+; CHECK-LABEL: define noundef nofpclass(psub) float @fadd_self_no_pnorm_psub(
; CHECK-SAME: float noundef nofpclass(psub pnorm) [[ARG:%.*]]) #[[ATTR0]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -774,7 +784,7 @@ define float @fadd_self_no_pnorm_psub(float noundef nofpclass(pnorm psub) %arg)
}
define float @fadd_self_no_nnorm_nsub(float noundef nofpclass(nnorm nsub) %arg) {
-; CHECK-LABEL: define noundef float @fadd_self_no_nnorm_nsub(
+; CHECK-LABEL: define noundef nofpclass(nsub) float @fadd_self_no_nnorm_nsub(
; CHECK-SAME: float noundef nofpclass(nsub nnorm) [[ARG:%.*]]) #[[ATTR0]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -784,7 +794,7 @@ define float @fadd_self_no_nnorm_nsub(float noundef nofpclass(nnorm nsub) %arg)
}
define float @fadd_self_no_nopsub_pzero(float noundef nofpclass(psub pzero) %arg) {
-; CHECK-LABEL: define noundef nofpclass(pzero) float @fadd_self_no_nopsub_pzero(
+; CHECK-LABEL: define noundef nofpclass(pzero psub) float @fadd_self_no_nopsub_pzero(
; CHECK-SAME: float noundef nofpclass(pzero psub) [[ARG:%.*]]) #[[ATTR0]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -794,7 +804,7 @@ define float @fadd_self_no_nopsub_pzero(float noundef nofpclass(psub pzero) %arg
}
define float @fadd_self_no_nonsub_nzero(float noundef nofpclass(nsub nzero) %arg) {
-; CHECK-LABEL: define noundef nofpclass(nzero) float @fadd_self_no_nonsub_nzero(
+; CHECK-LABEL: define noundef nofpclass(nzero nsub) float @fadd_self_no_nonsub_nzero(
; CHECK-SAME: float noundef nofpclass(nzero nsub) [[ARG:%.*]]) #[[ATTR0]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -804,7 +814,7 @@ define float @fadd_self_no_nonsub_nzero(float noundef nofpclass(nsub nzero) %arg
}
define float @fadd_self_no_nopsub_pzero__ieee_daz(float noundef nofpclass(psub pzero) %arg) #2 {
-; CHECK-LABEL: define noundef nofpclass(pzero) float @fadd_self_no_nopsub_pzero__ieee_daz(
+; CHECK-LABEL: define noundef nofpclass(pzero psub) float @fadd_self_no_nopsub_pzero__ieee_daz(
; CHECK-SAME: float noundef nofpclass(pzero psub) [[ARG:%.*]]) #[[ATTR4]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -814,7 +824,7 @@ define float @fadd_self_no_nopsub_pzero__ieee_daz(float noundef nofpclass(psub p
}
define float @fadd_self_no_nopsub_pzero__ftz_daz(float noundef nofpclass(psub pzero) %arg) #0 {
-; CHECK-LABEL: define noundef nofpclass(pzero) float @fadd_self_no_nopsub_pzero__ftz_daz(
+; CHECK-LABEL: define noundef nofpclass(pzero psub) float @fadd_self_no_nopsub_pzero__ftz_daz(
; CHECK-SAME: float noundef nofpclass(pzero psub) [[ARG:%.*]]) #[[ATTR1]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -824,7 +834,7 @@ define float @fadd_self_no_nopsub_pzero__ftz_daz(float noundef nofpclass(psub pz
}
define float @fadd_self_no_nonsub_nzero__ieee_daz(float noundef nofpclass(nsub nzero) %arg) #2 {
-; CHECK-LABEL: define noundef nofpclass(nzero) float @fadd_self_no_nonsub_nzero__ieee_daz(
+; CHECK-LABEL: define noundef nofpclass(nzero nsub) float @fadd_self_no_nonsub_nzero__ieee_daz(
; CHECK-SAME: float noundef nofpclass(nzero nsub) [[ARG:%.*]]) #[[ATTR4]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -834,7 +844,7 @@ define float @fadd_self_no_nonsub_nzero__ieee_daz(float noundef nofpclass(nsub n
}
define float @fadd_self_no_nonsub_nzero__ftz_daz(float noundef nofpclass(nsub nzero) %arg) #0 {
-; CHECK-LABEL: define noundef float @fadd_self_no_nonsub_nzero__ftz_daz(
+; CHECK-LABEL: define noundef nofpclass(nzero nsub) float @fadd_self_no_nonsub_nzero__ftz_daz(
; CHECK-SAME: float noundef nofpclass(nzero nsub) [[ARG:%.*]]) #[[ATTR1]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -844,7 +854,7 @@ define float @fadd_self_no_nonsub_nzero__ftz_daz(float noundef nofpclass(nsub nz
}
define float @fadd_self_no_nopsub_pzero__ieee_dynamic(float noundef nofpclass(psub pzero) %arg) #9 {
-; CHECK-LABEL: define noundef float @fadd_self_no_nopsub_pzero__ieee_dynamic(
+; CHECK-LABEL: define noundef nofpclass(psub) float @fadd_self_no_nopsub_pzero__ieee_dynamic(
; CHECK-SAME: float noundef nofpclass(pzero psub) [[ARG:%.*]]) #[[ATTR8:[0-9]+]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -854,7 +864,7 @@ define float @fadd_self_no_nopsub_pzero__ieee_dynamic(float noundef nofpclass(ps
}
define float @fadd_self_no_nonsub_nzero__ieee_dynamic(float noundef nofpclass(nsub nzero) %arg) #9 {
-; CHECK-LABEL: define noundef nofpclass(nzero) float @fadd_self_no_nonsub_nzero__ieee_dynamic(
+; CHECK-LABEL: define noundef nofpclass(nzero nsub) float @fadd_self_no_nonsub_nzero__ieee_dynamic(
; CHECK-SAME: float noundef nofpclass(nzero nsub) [[ARG:%.*]]) #[[ATTR8]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -1134,9 +1144,9 @@ define float @fadd_self_no_nzero(float noundef nofpclass(nzero) %arg) {
ret float %add
}
-define float @fadd_self_no_nzero_dapz_dapz(float noundef nofpclass(nzero) %arg) #10 {
-; CHECK-LABEL: define noundef nofpclass(nzero) float @fadd_self_no_nzero_dapz_dapz(
-; CHECK-SAME: float noundef nofpclass(nzero) [[ARG:%.*]]) #[[ATTR0]] {
+define float @fadd_self_no_nzero_ftpz_dapz(float noundef nofpclass(nzero) %arg) #3 {
+; CHECK-LABEL: define noundef nofpclass(nzero) float @fadd_self_no_nzero_ftpz_dapz(
+; CHECK-SAME: float noundef nofpclass(nzero) [[ARG:%.*]]) #[[ATTR2]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
;
@@ -1144,8 +1154,8 @@ define float @fadd_self_no_nzero_dapz_dapz(float noundef nofpclass(nzero) %arg)
ret float %add
}
-define float @fadd_self_no_nzero_dapz_ieee(float noundef nofpclass(nzero) %arg) #4 {
-; CHECK-LABEL: define noundef nofpclass(nzero) float @fadd_self_no_nzero_dapz_ieee(
+define float @fadd_self_no_nzero_ftpz_ieee(float noundef nofpclass(nzero) %arg) #4 {
+; CHECK-LABEL: define noundef nofpclass(nzero) float @fadd_self_no_nzero_ftpz_ieee(
; CHECK-SAME: float noundef nofpclass(nzero) [[ARG:%.*]]) #[[ATTR5]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -1176,7 +1186,7 @@ define float @fadd_self_no_pzero_maybe_undef(float nofpclass(pzero) %arg) {
; The input is not logical 0 since it's IEEE, but the output could
; still be flushed.
-define float @fadd_self_no_zero__output_only_is_ftz(float noundef nofpclass(zero) %arg) #7 {
+define float @fadd_self_no_zero__output_only_is_ftz(float noundef nofpclass(zero) %arg) #1 {
; CHECK-LABEL: define noundef float @fadd_self_no_zero__output_only_is_ftz(
; CHECK-SAME: float noundef nofpclass(zero) [[ARG:%.*]]) #[[ATTR6]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
@@ -1211,7 +1221,7 @@ define float @fadd_self_no_zero__output_only_is_ftpz(float noundef nofpclass(zer
}
define float @fadd_self_no_zero_or_nsub__output_only_is_ftpz(float noundef nofpclass(zero nsub) %arg) #4 {
-; CHECK-LABEL: define noundef nofpclass(nzero) float @fadd_self_no_zero_or_nsub__output_only_is_ftpz(
+; CHECK-LABEL: define noundef nofpclass(nzero nsub) float @fadd_self_no_zero_or_nsub__output_only_is_ftpz(
; CHECK-SAME: float noundef nofpclass(zero nsub) [[ARG:%.*]]) #[[ATTR5]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -1221,7 +1231,7 @@ define float @fadd_self_no_zero_or_nsub__output_only_is_ftpz(float noundef nofpc
}
define float @fadd_self_no_zero_or_psub__output_only_is_ftpz(float noundef nofpclass(zero psub) %arg) #4 {
-; CHECK-LABEL: define noundef nofpclass(nzero) float @fadd_self_no_zero_or_psub__output_only_is_ftpz(
+; CHECK-LABEL: define noundef nofpclass(nzero psub) float @fadd_self_no_zero_or_psub__output_only_is_ftpz(
; CHECK-SAME: float noundef nofpclass(zero psub) [[ARG:%.*]]) #[[ATTR5]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -1231,7 +1241,7 @@ define float @fadd_self_no_zero_or_psub__output_only_is_ftpz(float noundef nofpc
}
define float @fadd_self_no_zero_or_sub__output_only_is_ftpz(float noundef nofpclass(zero sub) %arg) #4 {
-; CHECK-LABEL: define noundef nofpclass(zero) float @fadd_self_no_zero_or_sub__output_only_is_ftpz(
+; CHECK-LABEL: define noundef nofpclass(zero sub) float @fadd_self_no_zero_or_sub__output_only_is_ftpz(
; CHECK-SAME: float noundef nofpclass(zero sub) [[ARG:%.*]]) #[[ATTR5]] {
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[ARG]], [[ARG]]
; CHECK-NEXT: ret float [[ADD]]
@@ -1284,6 +1294,68 @@ define half @known_negative_normal_or_inf__fadd__known_negative_or_nan(half nofp
ret half %add
}
+define float @fsub__lhs_nzero__rhs_psub(float nofpclass(nan inf pzero sub norm) %lhs, float nofpclass(nan inf zero nsub norm) %rhs) {
+; CHECK-LABEL: define nofpclass(nan pinf nzero psub pnorm) float @fsub__lhs_nzero__rhs_psub(
+; CHECK-SAME: float nofpclass(nan inf pzero sub norm) [[LHS:%.*]], float nofpclass(nan inf zero nsub norm) [[RHS:%.*]]) #[[ATTR0]] {
+; CHECK-NEXT: [[SUB:%.*]] = fsub float [[LHS]], [[RHS]]
+; CHECK-NEXT: ret float [[SUB]]
+;
+ %sub = fsub float %lhs, %rhs
+ ret float %sub
+}
+
+; We shall not rule out negative zero: -0.0 - dapz(psub) == -0.0 - +0.0 == -0.0
+define float @fsub__lhs_nzero__rhs_psub__mode_ieee_dapz(float nofpclass(nan inf pzero sub norm) %lhs, float nofpclass(nan inf zero nsub norm) %rhs) #5 {
+; CHECK-LABEL: define nofpclass(nan pinf psub pnorm) float @fsub__lhs_nzero__rhs_psub__mode_ieee_dapz(
+; CHECK-SAME: float nofpclass(nan inf pzero sub norm) [[LHS:%.*]], float nofpclass(nan inf zero nsub norm) [[RHS:%.*]]) #[[ATTR7]] {
+; CHECK-NEXT: [[SUB:%.*]] = fsub float [[LHS]], [[RHS]]
+; CHECK-NEXT: ret float [[SUB]]
+;
+ %sub = fsub float %lhs, %rhs
+ ret float %sub
+}
+
+; We shall not rule out negative zero: -0.0 - daz(psub) == -0.0 - +0.0 == -0.0
+define float @fsub__lhs_nzero__rhs_psub__mode_ieee_daz(float nofpclass(nan inf pzero sub norm) %lhs, float nofpclass(nan inf zero nsub norm) %rhs) #2 {
+; CHECK-LABEL: define nofpclass(nan pinf psub pnorm) float @fsub__lhs_nzero__rhs_psub__mode_ieee_daz(
+; CHECK-SAME: float nofpclass(nan inf pzero sub norm) [[LHS:%.*]], float nofpclass(nan inf zero nsub norm) [[RHS:%.*]]) #[[ATTR4]] {
+; CHECK-NEXT: [[SUB:%.*]] = fsub float [[LHS]], [[RHS]]
+; CHECK-NEXT: ret float [[SUB]]
+;
+ %sub = fsub float %lhs, %rhs
+ ret float %sub
+}
+
+define float @fsub__lhs_nzero__rhs_psub__mode_ftpz_dapz(float nofpclass(nan inf pzero sub norm) %lhs, float nofpclass(nan inf zero nsub norm) %rhs) #3 {
+; CHECK-LABEL: define nofpclass(nan pinf psub pnorm) float @fsub__lhs_nzero__rhs_psub__mode_ftpz_dapz(
+; CHECK-SAME: float nofpclass(nan inf pzero sub norm) [[LHS:%.*]], float nofpclass(nan inf zero nsub norm) [[RHS:%.*]]) #[[ATTR2]] {
+; CHECK-NEXT: [[SUB:%.*]] = fsub float [[LHS]], [[RHS]]
+; CHECK-NEXT: ret float [[SUB]]
+;
+ %sub = fsub float %lhs, %rhs
+ ret float %sub
+}
+
+define float @fsub__lhs_nzero__rhs_psub__mode_dynamic_dapz(float nofpclass(nan inf pzero sub norm) %lhs, float nofpclass(nan inf zero nsub norm) %rhs) #7 {
+; CHECK-LABEL: define nofpclass(nan pinf psub pnorm) float @fsub__lhs_nzero__rhs_psub__mode_dynamic_dapz(
+; CHECK-SAME: float nofpclass(nan inf pzero sub norm) [[LHS:%.*]], float nofpclass(nan inf zero nsub norm) [[RHS:%.*]]) #[[ATTR10:[0-9]+]] {
+; CHECK-NEXT: [[SUB:%.*]] = fsub float [[LHS]], [[RHS]]
+; CHECK-NEXT: ret float [[SUB]]
+;
+ %sub = fsub float %lhs, %rhs
+ ret float %sub
+}
+
+define float @fsub__lhs_nzero__rhs_psub__mode_dynamic_dynamic(float nofpclass(nan inf pzero sub norm) %lhs, float nofpclass(nan inf zero nsub norm) %rhs) #6 {
+; CHECK-LABEL: define nofpclass(nan pinf psub pnorm) float @fsub__lhs_nzero__rhs_psub__mode_dynamic_dynamic(
+; CHECK-SAME: float nofpclass(nan inf pzero sub norm) [[LHS:%.*]], float nofpclass(nan inf zero nsub norm) [[RHS:%.*]]) #[[ATTR3]] {
+; CHECK-NEXT: [[SUB:%.*]] = fsub float [[LHS]], [[RHS]]
+; CHECK-NEXT: ret float [[SUB]]
+;
+ %sub = fsub float %lhs, %rhs
+ ret float %sub
+}
+
attributes #0 = { denormal_fpenv(preservesign) }
attributes #1 = { denormal_fpenv(preservesign|ieee) }
attributes #2 = { denormal_fpenv(ieee|preservesign) }
@@ -1291,6 +1363,6 @@ attributes #3 = { denormal_fpenv(positivezero|positivezero) }
attributes #4 = { denormal_fpenv(positivezero|ieee) }
attributes #5 = { denormal_fpenv(ieee|positivezero) }
attributes #6 = { denormal_fpenv(dynamic) }
-attributes #7 = { denormal_fpenv(preservesign|ieee) }
+attributes #7 = { denormal_fpenv(dynamic|positivezero) }
attributes #8 = { denormal_fpenv(dynamic|ieee) }
attributes #9 = { denormal_fpenv(ieee|dynamic) }
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