[llvm] [ValueTracking] Fix computeKnownFPClass for fpext (PR #81972)
Yingwei Zheng via llvm-commits
llvm-commits at lists.llvm.org
Thu Feb 15 23:15:59 PST 2024
https://github.com/dtcxzyw created https://github.com/llvm/llvm-project/pull/81972
This patch adds the missing `subnormal -> normal` part for `fpext` in `computeKnownFPClass`.
Fixes the miscompilation reported by https://github.com/llvm/llvm-project/pull/80941#issuecomment-1947302100.
>From fc56dfc8dbe4bb77f07b75ba4fa33189aa2fba90 Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Fri, 16 Feb 2024 14:49:22 +0800
Subject: [PATCH 1/2] [ValueTracking] Add pre-commit tests. NFC.
---
.../Transforms/Attributor/nofpclass-fpext.ll | 30 +++++++++++++++++++
llvm/test/Transforms/InstCombine/pr80941.ll | 29 ++++++++++++++++++
2 files changed, 59 insertions(+)
create mode 100644 llvm/test/Transforms/InstCombine/pr80941.ll
diff --git a/llvm/test/Transforms/Attributor/nofpclass-fpext.ll b/llvm/test/Transforms/Attributor/nofpclass-fpext.ll
index 0ba114117ceec6..4f9d430d11e4b1 100644
--- a/llvm/test/Transforms/Attributor/nofpclass-fpext.ll
+++ b/llvm/test/Transforms/Attributor/nofpclass-fpext.ll
@@ -490,5 +490,35 @@ define double @ret_fpext_bf16_f64_nonorm(bfloat nofpclass(norm) %arg0) {
%ext = fpext bfloat %arg0 to double
ret double %ext
}
+
+define double @ret_fpext_bf16_f64_nonorm_psub(bfloat nofpclass(norm psub) %arg0) {
+; CHECK-LABEL: define nofpclass(sub norm) double @ret_fpext_bf16_f64_nonorm_psub
+; CHECK-SAME: (bfloat nofpclass(sub norm) [[ARG0:%.*]]) #[[ATTR0]] {
+; CHECK-NEXT: [[EXT:%.*]] = fpext bfloat [[ARG0]] to double
+; CHECK-NEXT: ret double [[EXT]]
+;
+ %ext = fpext bfloat %arg0 to double
+ ret double %ext
+}
+
+define double @ret_fpext_bf16_f64_nonorm_nsub(bfloat nofpclass(norm nsub) %arg0) {
+; CHECK-LABEL: define nofpclass(sub norm) double @ret_fpext_bf16_f64_nonorm_nsub
+; CHECK-SAME: (bfloat nofpclass(sub norm) [[ARG0:%.*]]) #[[ATTR0]] {
+; CHECK-NEXT: [[EXT:%.*]] = fpext bfloat [[ARG0]] to double
+; CHECK-NEXT: ret double [[EXT]]
+;
+ %ext = fpext bfloat %arg0 to double
+ ret double %ext
+}
+
+define double @ret_fpext_bf16_f64_nonorm_sub(bfloat nofpclass(norm sub) %arg0) {
+; CHECK-LABEL: define nofpclass(sub norm) double @ret_fpext_bf16_f64_nonorm_sub
+; CHECK-SAME: (bfloat nofpclass(sub norm) [[ARG0:%.*]]) #[[ATTR0]] {
+; CHECK-NEXT: [[EXT:%.*]] = fpext bfloat [[ARG0]] to double
+; CHECK-NEXT: ret double [[EXT]]
+;
+ %ext = fpext bfloat %arg0 to double
+ ret double %ext
+}
;; NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
; TUNIT: {{.*}}
diff --git a/llvm/test/Transforms/InstCombine/pr80941.ll b/llvm/test/Transforms/InstCombine/pr80941.ll
new file mode 100644
index 00000000000000..8a78cca57ccec2
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/pr80941.ll
@@ -0,0 +1,29 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
+; RUN: opt -S -passes=instcombine < %s | FileCheck %s
+
+define float @pr80941(float %arg) {
+; CHECK-LABEL: define float @pr80941(
+; CHECK-SAME: float [[ARG:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[COND:%.*]] = tail call i1 @llvm.is.fpclass.f32(float [[ARG]], i32 144)
+; CHECK-NEXT: br i1 [[COND]], label [[IF_THEN:%.*]], label [[IF_EXIT:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: br label [[IF_EXIT]]
+; CHECK: if.exit:
+; CHECK-NEXT: [[RET:%.*]] = phi float [ 0.000000e+00, [[IF_THEN]] ], [ [[ARG]], [[ENTRY:%.*]] ]
+; CHECK-NEXT: ret float [[RET]]
+;
+entry:
+ %cond = tail call i1 @llvm.is.fpclass.f32(float %arg, i32 144)
+ br i1 %cond, label %if.then, label %if.exit
+
+if.then:
+ %fpext = fpext float %arg to double
+ %sign = call double @llvm.copysign.f64(double 0.000000e+00, double %fpext)
+ %fptrunc = fptrunc double %sign to float
+ br label %if.exit
+
+if.exit:
+ %ret = phi float [ %fptrunc, %if.then ], [ %arg, %entry ]
+ ret float %ret
+}
>From e6f22f8d3affb2c60534388f6625796d22ff7a93 Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Fri, 16 Feb 2024 15:03:37 +0800
Subject: [PATCH 2/2] [ValueTracking] Fix computeKnownFPClass for fpext
---
llvm/lib/Analysis/ValueTracking.cpp | 7 ++++++-
llvm/test/Transforms/Attributor/nofpclass-fpext.ll | 8 ++++----
llvm/test/Transforms/InstCombine/pr80941.ll | 5 ++++-
3 files changed, 14 insertions(+), 6 deletions(-)
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index cc1d5b74dcfc53..1a076adb1bad0a 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -5173,8 +5173,13 @@ void computeKnownFPClass(const Value *V, const APInt &DemandedElts,
Op->getOperand(0)->getType()->getScalarType()->getFltSemantics();
// All subnormal inputs should be in the normal range in the result type.
- if (APFloat::isRepresentableAsNormalIn(SrcTy, DstTy))
+ if (APFloat::isRepresentableAsNormalIn(SrcTy, DstTy)) {
+ if (Known.KnownFPClasses & fcPosSubnormal)
+ Known.KnownFPClasses |= fcPosNormal;
+ if (Known.KnownFPClasses & fcNegSubnormal)
+ Known.KnownFPClasses |= fcNegNormal;
Known.knownNot(fcSubnormal);
+ }
// Sign bit of a nan isn't guaranteed.
if (!Known.isKnownNeverNaN())
diff --git a/llvm/test/Transforms/Attributor/nofpclass-fpext.ll b/llvm/test/Transforms/Attributor/nofpclass-fpext.ll
index 4f9d430d11e4b1..ee36f949529d4f 100644
--- a/llvm/test/Transforms/Attributor/nofpclass-fpext.ll
+++ b/llvm/test/Transforms/Attributor/nofpclass-fpext.ll
@@ -142,7 +142,7 @@ define double @ret_fpext_f32_to_f64_nosub(float nofpclass(sub) %arg0) {
}
define double @ret_fpext_f32_to_f64_nonorm(float nofpclass(norm) %arg0) {
-; CHECK-LABEL: define nofpclass(sub norm) double @ret_fpext_f32_to_f64_nonorm
+; CHECK-LABEL: define nofpclass(sub) double @ret_fpext_f32_to_f64_nonorm
; CHECK-SAME: (float nofpclass(sub norm) [[ARG0:%.*]]) #[[ATTR0]] {
; CHECK-NEXT: [[EXT:%.*]] = fpext float [[ARG0]] to double
; CHECK-NEXT: ret double [[EXT]]
@@ -482,7 +482,7 @@ define double @ret_fpext_bf16_f64_nosub(bfloat nofpclass(sub) %arg0) {
}
define double @ret_fpext_bf16_f64_nonorm(bfloat nofpclass(norm) %arg0) {
-; CHECK-LABEL: define nofpclass(sub norm) double @ret_fpext_bf16_f64_nonorm
+; CHECK-LABEL: define nofpclass(sub) double @ret_fpext_bf16_f64_nonorm
; CHECK-SAME: (bfloat nofpclass(sub norm) [[ARG0:%.*]]) #[[ATTR0]] {
; CHECK-NEXT: [[EXT:%.*]] = fpext bfloat [[ARG0]] to double
; CHECK-NEXT: ret double [[EXT]]
@@ -492,7 +492,7 @@ define double @ret_fpext_bf16_f64_nonorm(bfloat nofpclass(norm) %arg0) {
}
define double @ret_fpext_bf16_f64_nonorm_psub(bfloat nofpclass(norm psub) %arg0) {
-; CHECK-LABEL: define nofpclass(sub norm) double @ret_fpext_bf16_f64_nonorm_psub
+; CHECK-LABEL: define nofpclass(sub pnorm) double @ret_fpext_bf16_f64_nonorm_psub
; CHECK-SAME: (bfloat nofpclass(sub norm) [[ARG0:%.*]]) #[[ATTR0]] {
; CHECK-NEXT: [[EXT:%.*]] = fpext bfloat [[ARG0]] to double
; CHECK-NEXT: ret double [[EXT]]
@@ -502,7 +502,7 @@ define double @ret_fpext_bf16_f64_nonorm_psub(bfloat nofpclass(norm psub) %arg0)
}
define double @ret_fpext_bf16_f64_nonorm_nsub(bfloat nofpclass(norm nsub) %arg0) {
-; CHECK-LABEL: define nofpclass(sub norm) double @ret_fpext_bf16_f64_nonorm_nsub
+; CHECK-LABEL: define nofpclass(sub nnorm) double @ret_fpext_bf16_f64_nonorm_nsub
; CHECK-SAME: (bfloat nofpclass(sub norm) [[ARG0:%.*]]) #[[ATTR0]] {
; CHECK-NEXT: [[EXT:%.*]] = fpext bfloat [[ARG0]] to double
; CHECK-NEXT: ret double [[EXT]]
diff --git a/llvm/test/Transforms/InstCombine/pr80941.ll b/llvm/test/Transforms/InstCombine/pr80941.ll
index 8a78cca57ccec2..95242b1d1407bf 100644
--- a/llvm/test/Transforms/InstCombine/pr80941.ll
+++ b/llvm/test/Transforms/InstCombine/pr80941.ll
@@ -8,9 +8,12 @@ define float @pr80941(float %arg) {
; CHECK-NEXT: [[COND:%.*]] = tail call i1 @llvm.is.fpclass.f32(float [[ARG]], i32 144)
; CHECK-NEXT: br i1 [[COND]], label [[IF_THEN:%.*]], label [[IF_EXIT:%.*]]
; CHECK: if.then:
+; CHECK-NEXT: [[FPEXT:%.*]] = fpext float [[ARG]] to double
+; CHECK-NEXT: [[SIGN:%.*]] = call double @llvm.copysign.f64(double 0.000000e+00, double [[FPEXT]])
+; CHECK-NEXT: [[FPTRUNC:%.*]] = fptrunc double [[SIGN]] to float
; CHECK-NEXT: br label [[IF_EXIT]]
; CHECK: if.exit:
-; CHECK-NEXT: [[RET:%.*]] = phi float [ 0.000000e+00, [[IF_THEN]] ], [ [[ARG]], [[ENTRY:%.*]] ]
+; CHECK-NEXT: [[RET:%.*]] = phi float [ [[FPTRUNC]], [[IF_THEN]] ], [ [[ARG]], [[ENTRY:%.*]] ]
; CHECK-NEXT: ret float [[RET]]
;
entry:
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