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[LVI] Don't traverse uses when calculating range at use
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This effectively reverts 5c38c6a and 4f772b0.

A recently introduced LazyValueInfo::getConstantRangeAtUse returns incorrect
ranges for values in certain cases. One such example is described in PR60629.
The issue has something to do with traversing PHI uses of a value transitively.
As nikic pointed out, we're effectively reasoning about values from different
loop iterations.

In the faulting test case, CVP made a miscompilation because the calculated
range for a shift argument was incorrect. It returned empty-set, however it is
clearly not a dead code. CVP then erased the shift instruction because
of empty range.
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@d-makogon
d-makogon committed Feb 10, 2023
1 parent 0737770 commit c77c186
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Showing 3 changed files with 33 additions and 43 deletions.
2 changes: 1 addition & 1 deletion llvm/lib/Analysis/LazyValueInfo.cpp
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Expand Up @@ -1662,7 +1662,7 @@ ConstantRange LazyValueInfo::getConstantRangeAtUse(const Use &U,
// position where V can be constrained by a select or branch condition.
const Use *CurrU = &U;
// TODO: Increase limit?
const unsigned MaxUsesToInspect = 3;
const unsigned MaxUsesToInspect = 0;
for (unsigned I = 0; I < MaxUsesToInspect; ++I) {
std::optional<ValueLatticeElement> CondVal;
auto *CurrI = cast<Instruction>(CurrU->getUser());
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2 changes: 0 additions & 2 deletions llvm/test/Analysis/LazyValueAnalysis/pr60629.ll
View file
@@ -1,8 +1,6 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -passes=correlated-propagation -S %s | FileCheck %s

; XFAIL: *

; Check that shift is not removed by CVP because of incorrect range returned by LVI::getConstantRangeAtUse.
; https://github.com/llvm/llvm-project/issues/60629

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72 changes: 32 additions & 40 deletions llvm/test/Transforms/CorrelatedValuePropagation/cond-at-use.ll
View file
Expand Up @@ -9,9 +9,9 @@ declare i16 @llvm.abs.i16(i16, i1)

define i16 @sel_true_cond(i16 %x) {
; CHECK-LABEL: @sel_true_cond(
; CHECK-NEXT: [[SUB1:%.*]] = sub nuw i16 [[X:%.*]], 10
; CHECK-NEXT: [[SUB:%.*]] = call i16 @llvm.usub.sat.i16(i16 [[X:%.*]], i16 10)
; CHECK-NEXT: [[CMP:%.*]] = icmp uge i16 [[X]], 10
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i16 [[SUB1]], i16 42
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i16 [[SUB]], i16 42
; CHECK-NEXT: ret i16 [[SEL]]
;
%sub = call i16 @llvm.usub.sat.i16(i16 %x, i16 10)
Expand Down Expand Up @@ -76,8 +76,8 @@ define i16 @sel_true_cond_extra_use(i16 %x) {

define i16 @sel_true_cond_chain_speculatable(i16 %x) {
; CHECK-LABEL: @sel_true_cond_chain_speculatable(
; CHECK-NEXT: [[SUB1:%.*]] = add nuw i16 [[X:%.*]], 1
; CHECK-NEXT: [[EXTRA:%.*]] = mul i16 [[SUB1]], 3
; CHECK-NEXT: [[SUB:%.*]] = call i16 @llvm.uadd.sat.i16(i16 [[X:%.*]], i16 1)
; CHECK-NEXT: [[EXTRA:%.*]] = mul i16 [[SUB]], 3
; CHECK-NEXT: [[CMP:%.*]] = icmp ne i16 [[X]], -1
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i16 [[EXTRA]], i16 42
; CHECK-NEXT: ret i16 [[SEL]]
Expand Down Expand Up @@ -125,9 +125,9 @@ define i16 @sel_true_cond_longer_chain(i16 %x) {

define i16 @sel_false_cond(i16 %x) {
; CHECK-LABEL: @sel_false_cond(
; CHECK-NEXT: [[SUB1:%.*]] = sub nuw i16 [[X:%.*]], 10
; CHECK-NEXT: [[SUB:%.*]] = call i16 @llvm.usub.sat.i16(i16 [[X:%.*]], i16 10)
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i16 [[X]], 10
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i16 42, i16 [[SUB1]]
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i16 42, i16 [[SUB]]
; CHECK-NEXT: ret i16 [[SEL]]
;
%sub = call i16 @llvm.usub.sat.i16(i16 %x, i16 10)
Expand All @@ -152,13 +152,13 @@ define i16 @sel_false_cond_insufficient(i16 %x) {
define i16 @phi_true_cond(i16 %x) {
; CHECK-LABEL: @phi_true_cond(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[SUB1:%.*]] = sub nuw i16 [[X:%.*]], 10
; CHECK-NEXT: [[SUB:%.*]] = call i16 @llvm.usub.sat.i16(i16 [[X:%.*]], i16 10)
; CHECK-NEXT: [[CMP:%.*]] = icmp uge i16 [[X]], 10
; CHECK-NEXT: br i1 [[CMP]], label [[JOIN:%.*]], label [[SPLIT:%.*]]
; CHECK: split:
; CHECK-NEXT: br label [[JOIN]]
; CHECK: join:
; CHECK-NEXT: [[PHI:%.*]] = phi i16 [ [[SUB1]], [[ENTRY:%.*]] ], [ 42, [[SPLIT]] ]
; CHECK-NEXT: [[PHI:%.*]] = phi i16 [ [[SUB]], [[ENTRY:%.*]] ], [ 42, [[SPLIT]] ]
; CHECK-NEXT: ret i16 [[PHI]]
;
entry:
Expand Down Expand Up @@ -229,13 +229,13 @@ join:
define i16 @phi_false_cond(i16 %x) {
; CHECK-LABEL: @phi_false_cond(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[SUB1:%.*]] = sub nuw i16 [[X:%.*]], 10
; CHECK-NEXT: [[SUB:%.*]] = call i16 @llvm.usub.sat.i16(i16 [[X:%.*]], i16 10)
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i16 [[X]], 10
; CHECK-NEXT: br i1 [[CMP]], label [[SPLIT:%.*]], label [[JOIN:%.*]]
; CHECK: split:
; CHECK-NEXT: br label [[JOIN]]
; CHECK: join:
; CHECK-NEXT: [[PHI:%.*]] = phi i16 [ [[SUB1]], [[ENTRY:%.*]] ], [ 42, [[SPLIT]] ]
; CHECK-NEXT: [[PHI:%.*]] = phi i16 [ [[SUB]], [[ENTRY:%.*]] ], [ 42, [[SPLIT]] ]
; CHECK-NEXT: ret i16 [[PHI]]
;
entry:
Expand Down Expand Up @@ -308,10 +308,10 @@ define i16 @loop_cond() {
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi i16 [ 1000, [[ENTRY:%.*]] ], [ [[IV_NEXT1:%.*]], [[LOOP]] ]
; CHECK-NEXT: [[IV:%.*]] = phi i16 [ 1000, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
; CHECK-NEXT: [[COUNT:%.*]] = phi i16 [ 0, [[ENTRY]] ], [ [[COUNT_NEXT:%.*]], [[LOOP]] ]
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i16 [[IV]], 0
; CHECK-NEXT: [[IV_NEXT1]] = sub nuw i16 [[IV]], 1
; CHECK-NEXT: [[IV_NEXT]] = call i16 @llvm.usub.sat.i16(i16 [[IV]], i16 1)
; CHECK-NEXT: [[COUNT_NEXT]] = add i16 [[COUNT]], 1
; CHECK-NEXT: br i1 [[CMP]], label [[EXIT:%.*]], label [[LOOP]]
; CHECK: exit:
Expand All @@ -334,8 +334,9 @@ exit:

define i16 @urem_elide(i16 %x) {
; CHECK-LABEL: @urem_elide(
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i16 [[X:%.*]], 42
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i16 [[X]], i16 24
; CHECK-NEXT: [[UREM:%.*]] = urem i16 [[X:%.*]], 42
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i16 [[X]], 42
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i16 [[UREM]], i16 24
; CHECK-NEXT: ret i16 [[SEL]]
;
%urem = urem i16 %x, 42
Expand All @@ -346,10 +347,7 @@ define i16 @urem_elide(i16 %x) {

define i16 @urem_expand(i16 %x) {
; CHECK-LABEL: @urem_expand(
; CHECK-NEXT: [[X_FROZEN:%.*]] = freeze i16 [[X:%.*]]
; CHECK-NEXT: [[UREM_UREM:%.*]] = sub nuw i16 [[X_FROZEN]], 42
; CHECK-NEXT: [[UREM_CMP:%.*]] = icmp ult i16 [[X_FROZEN]], 42
; CHECK-NEXT: [[UREM:%.*]] = select i1 [[UREM_CMP]], i16 [[X_FROZEN]], i16 [[UREM_UREM]]
; CHECK-NEXT: [[UREM:%.*]] = urem i16 [[X:%.*]], 42
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i16 [[X]], 84
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i16 [[UREM]], i16 24
; CHECK-NEXT: ret i16 [[SEL]]
Expand All @@ -362,11 +360,9 @@ define i16 @urem_expand(i16 %x) {

define i16 @urem_narrow(i16 %x) {
; CHECK-LABEL: @urem_narrow(
; CHECK-NEXT: [[UREM_LHS_TRUNC:%.*]] = trunc i16 [[X:%.*]] to i8
; CHECK-NEXT: [[UREM1:%.*]] = urem i8 [[UREM_LHS_TRUNC]], 42
; CHECK-NEXT: [[UREM_ZEXT:%.*]] = zext i8 [[UREM1]] to i16
; CHECK-NEXT: [[UREM:%.*]] = urem i16 [[X:%.*]], 42
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i16 [[X]], 85
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i16 [[UREM_ZEXT]], i16 24
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i16 [[UREM]], i16 24
; CHECK-NEXT: ret i16 [[SEL]]
;
%urem = urem i16 %x, 42
Expand All @@ -390,10 +386,11 @@ define i16 @urem_insufficient(i16 %x) {

define i16 @srem_elide(i16 %x) {
; CHECK-LABEL: @srem_elide(
; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i16 [[X:%.*]], 42
; CHECK-NEXT: [[SREM:%.*]] = srem i16 [[X:%.*]], 42
; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i16 [[X]], 42
; CHECK-NEXT: [[CMP2:%.*]] = icmp sgt i16 [[X]], -42
; CHECK-NEXT: [[AND:%.*]] = and i1 [[CMP1]], [[CMP2]]
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[AND]], i16 [[X]], i16 24
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[AND]], i16 [[SREM]], i16 24
; CHECK-NEXT: ret i16 [[SEL]]
;
%srem = srem i16 %x, 42
Expand All @@ -406,13 +403,11 @@ define i16 @srem_elide(i16 %x) {

define i16 @srem_narrow(i16 %x) {
; CHECK-LABEL: @srem_narrow(
; CHECK-NEXT: [[SREM_LHS_TRUNC:%.*]] = trunc i16 [[X:%.*]] to i8
; CHECK-NEXT: [[SREM1:%.*]] = srem i8 [[SREM_LHS_TRUNC]], 42
; CHECK-NEXT: [[SREM_SEXT:%.*]] = sext i8 [[SREM1]] to i16
; CHECK-NEXT: [[SREM:%.*]] = srem i16 [[X:%.*]], 42
; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i16 [[X]], 43
; CHECK-NEXT: [[CMP2:%.*]] = icmp sgt i16 [[X]], -43
; CHECK-NEXT: [[AND:%.*]] = and i1 [[CMP1]], [[CMP2]]
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[AND]], i16 [[SREM_SEXT]], i16 24
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[AND]], i16 [[SREM]], i16 24
; CHECK-NEXT: ret i16 [[SEL]]
;
%srem = srem i16 %x, 42
Expand All @@ -425,11 +420,9 @@ define i16 @srem_narrow(i16 %x) {

define i16 @srem_convert(i16 %x) {
; CHECK-LABEL: @srem_convert(
; CHECK-NEXT: [[X_NONNEG:%.*]] = sub i16 0, [[X:%.*]]
; CHECK-NEXT: [[SREM1:%.*]] = urem i16 [[X_NONNEG]], 42
; CHECK-NEXT: [[SREM1_NEG:%.*]] = sub i16 0, [[SREM1]]
; CHECK-NEXT: [[SREM:%.*]] = srem i16 [[X:%.*]], 42
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i16 [[X]], 0
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i16 [[SREM1_NEG]], i16 24
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i16 [[SREM]], i16 24
; CHECK-NEXT: ret i16 [[SEL]]
;
%srem = srem i16 %x, 42
Expand All @@ -440,11 +433,9 @@ define i16 @srem_convert(i16 %x) {

define i16 @sdiv_convert(i16 %x) {
; CHECK-LABEL: @sdiv_convert(
; CHECK-NEXT: [[X_NONNEG:%.*]] = sub i16 0, [[X:%.*]]
; CHECK-NEXT: [[SREM1:%.*]] = udiv i16 [[X_NONNEG]], 42
; CHECK-NEXT: [[SREM1_NEG:%.*]] = sub i16 0, [[SREM1]]
; CHECK-NEXT: [[SREM:%.*]] = sdiv i16 [[X:%.*]], 42
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i16 [[X]], 0
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i16 [[SREM1_NEG]], i16 24
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i16 [[SREM]], i16 24
; CHECK-NEXT: ret i16 [[SEL]]
;
%srem = sdiv i16 %x, 42
Expand Down Expand Up @@ -507,7 +498,7 @@ define i16 @umin_elide(i16 %x) {

define i16 @ashr_convert(i16 %x, i16 %y) {
; CHECK-LABEL: @ashr_convert(
; CHECK-NEXT: [[ASHR:%.*]] = lshr i16 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[ASHR:%.*]] = ashr i16 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp sge i16 [[X]], 0
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i16 [[ASHR]], i16 24
; CHECK-NEXT: ret i16 [[SEL]]
Expand All @@ -520,7 +511,7 @@ define i16 @ashr_convert(i16 %x, i16 %y) {

define i32 @sext_convert(i16 %x) {
; CHECK-LABEL: @sext_convert(
; CHECK-NEXT: [[EXT:%.*]] = zext i16 [[X:%.*]] to i32
; CHECK-NEXT: [[EXT:%.*]] = sext i16 [[X:%.*]] to i32
; CHECK-NEXT: [[CMP:%.*]] = icmp sge i16 [[X]], 0
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i32 [[EXT]], i32 24
; CHECK-NEXT: ret i32 [[SEL]]
Expand All @@ -546,8 +537,9 @@ define i16 @infer_flags(i16 %x) {

define i16 @and_elide(i16 %x) {
; CHECK-LABEL: @and_elide(
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i16 [[X:%.*]], 8
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i16 [[X]], i16 24
; CHECK-NEXT: [[AND:%.*]] = and i16 [[X:%.*]], 7
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i16 [[X]], 8
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i16 [[AND]], i16 24
; CHECK-NEXT: ret i16 [[SEL]]
;
%and = and i16 %x, 7
Expand Down

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