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[DebugInfo][GlobalOpt] Preserve source locs for optimized loads #134828

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Merged
merged 2 commits into from
Apr 24, 2025
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[DebugInfo][GlobalOpt] Preserve source locs for optimized loads #134828

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520d3ec
[DebugInfo][GlobalOpt] Preserve source locs for optimized loads
SLTozer Apr 7, 2025
c6a1d8a
Also preserve DebugLoc for replacement stores
SLTozer Apr 22, 2025
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18 changes: 13 additions & 5 deletions llvm/lib/Transforms/IPO/GlobalOpt.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -965,11 +965,12 @@ OptimizeGlobalAddressOfAllocation(GlobalVariable *GV, CallInst *CI,
if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
// The global is initialized when the store to it occurs. If the stored
// value is null value, the global bool is set to false, otherwise true.
new StoreInst(ConstantInt::getBool(
GV->getContext(),
!isa<ConstantPointerNull>(SI->getValueOperand())),
InitBool, false, Align(1), SI->getOrdering(),
SI->getSyncScopeID(), SI->getIterator());
auto *NewSI = new StoreInst(
ConstantInt::getBool(GV->getContext(), !isa<ConstantPointerNull>(
SI->getValueOperand())),
InitBool, false, Align(1), SI->getOrdering(), SI->getSyncScopeID(),
SI->getIterator());
NewSI->setDebugLoc(SI->getDebugLoc());
SI->eraseFromParent();
continue;
}
Expand All @@ -988,6 +989,11 @@ OptimizeGlobalAddressOfAllocation(GlobalVariable *GV, CallInst *CI,
InitBool->getName() + ".val", false, Align(1),
LI->getOrdering(), LI->getSyncScopeID(),
LI->getIterator());
// FIXME: Should we use the DebugLoc of the load used by the predicate, or
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I see new StoreInst above which looks like it does similar straightforward replacement, should we carry over the sloc there?

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It certainly looks like it - I'll find a test case and add it (and any other nearby cases if I spot any).

// the predicate? The load seems most appropriate, but there's an argument
// that the new load does not represent the old load, but is simply a
// component of recomputing the predicate.
cast<LoadInst>(LV)->setDebugLoc(LI->getDebugLoc());
InitBoolUsed = true;
switch (ICI->getPredicate()) {
default: llvm_unreachable("Unknown ICmp Predicate!");
Expand All @@ -1000,6 +1006,7 @@ OptimizeGlobalAddressOfAllocation(GlobalVariable *GV, CallInst *CI,
case ICmpInst::ICMP_ULE:
case ICmpInst::ICMP_EQ:
LV = BinaryOperator::CreateNot(LV, "notinit", ICI->getIterator());
cast<BinaryOperator>(LV)->setDebugLoc(ICI->getDebugLoc());
break;
case ICmpInst::ICMP_NE:
case ICmpInst::ICMP_UGT:
Expand Down Expand Up @@ -1276,6 +1283,7 @@ static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) {
new LoadInst(NewGV->getValueType(), NewGV, LI->getName() + ".b",
false, Align(1), LI->getOrdering(),
LI->getSyncScopeID(), LI->getIterator());
cast<LoadInst>(StoreVal)->setDebugLoc(LI->getDebugLoc());
} else {
assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) &&
"This is not a form that we understand!");
Expand Down
99 changes: 99 additions & 0 deletions llvm/test/Transforms/GlobalOpt/X86/preserve-dbgloc-of-load-store-to-bool.ll
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@@ -0,0 +1,99 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
; RUN: opt < %s -p=globalopt -S | FileCheck %s

;; Test that when we are able to simplify uses of global variables with loads of
;; newly generated bool values, we transfer debuglocs over correctly.

target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

@global = internal global i32 0
@global.1 = internal unnamed_addr global ptr null, align 8

define void @ham() !dbg !7 {
; CHECK-LABEL: define void @ham(
; CHECK-SAME: ) local_unnamed_addr !dbg [[DBG4:![0-9]+]] {
; CHECK-NEXT: [[BB:.*:]]
; CHECK-NEXT: [[LOAD_B:%.*]] = load i1, ptr @global, align 1, !dbg [[DBG6:![0-9]+]]
; CHECK-NEXT: [[LOAD_B1:%.*]] = load i1, ptr @global, align 1, !dbg [[DBG6]]
; CHECK-NEXT: [[LOAD:%.*]] = zext i1 [[LOAD_B1]] to i32, !dbg [[DBG6]]
; CHECK-NEXT: store i1 [[LOAD_B]], ptr @global, align 1
; CHECK-NEXT: ret void
;
bb:
%load = load i32, ptr @global, align 4, !dbg !4
store i32 %load, ptr @global, align 4
ret void
}

define void @hoge() {
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What's this function testing?

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@SLTozer SLTozer Apr 24, 2025 •
edited
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This function is necessary for GlobalOpt to make the decisions that trigger the bug.

; CHECK-LABEL: define void @hoge() local_unnamed_addr {
; CHECK-NEXT: [[BB:.*:]]
; CHECK-NEXT: store i1 true, ptr @global, align 1
; CHECK-NEXT: ret void
;
bb:
store i32 1, ptr @global, align 4
ret void
}

define void @bar() !dbg !13 {
; CHECK-LABEL: define void @bar(
; CHECK-SAME: ) local_unnamed_addr !dbg [[DBG8:![0-9]+]] {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: store i1 true, ptr @global.1.init, align 1, !dbg [[DBG9:![0-9]+]]
; CHECK-NEXT: ret void
;
entry:
%call = tail call noalias nonnull dereferenceable(48) ptr @_Znwm(i64 48)
store ptr %call, ptr @global.1, align 8, !dbg !14
ret void
}

define void @pluto() !dbg !10 {
; CHECK-LABEL: define void @pluto(
; CHECK-SAME: ) local_unnamed_addr !dbg [[DBG10:![0-9]+]] {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[GLOBAL_1_INIT_VAL:%.*]] = load i1, ptr @global.1.init, align 1, !dbg [[DBG11:![0-9]+]]
; CHECK-NEXT: [[NOTINIT:%.*]] = xor i1 [[GLOBAL_1_INIT_VAL]], true, !dbg [[DBG12:![0-9]+]]
; CHECK-NEXT: unreachable
;
entry:
%0 = load ptr, ptr @global.1, align 8, !dbg !11
%.not = icmp eq ptr %0, null, !dbg !12
unreachable
}

declare ptr @_Znwm(i64)

!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!3}

!0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang version 20.0.0git", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !2, globals: !2, splitDebugInlining: false, nameTableKind: None)
!1 = !DIFile(filename: "preserve-load-dbgloc.c", directory: "/tmp")
!2 = !{}
!3 = !{i32 2, !"Debug Info Version", i32 3}
!4 = !DILocation(line: 10, column: 1, scope: !5)
!5 = distinct !DILexicalBlock(scope: !7, file: !6, line: 1524, column: 3)
!6 = !DIFile(filename: "preserve-load-dbgloc.c", directory: "/tmp")
!7 = distinct !DISubprogram(name: "ham", scope: !6, file: !6, line: 10, type: !8, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !2)
!8 = distinct !DISubroutineType(types: !2)
!10 = distinct !DISubprogram(name: "pluto", scope: !6, file: !6, line: 20, type: !8, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !2)
!11 = !DILocation(line: 20, column: 2, scope: !10)
!12 = !DILocation(line: 21, column: 3, scope: !10)
!13 = distinct !DISubprogram(name: "bar", scope: !6, file: !6, line: 230, type: !8, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !2)
!14 = !DILocation(line: 11, column: 4, scope: !13)
;.
; CHECK: [[META0:![0-9]+]] = distinct !DICompileUnit(language: DW_LANG_C11, file: [[META1:![0-9]+]], producer: "{{.*}}clang version {{.*}}", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: [[META2:![0-9]+]], retainedTypes: [[META2]], globals: [[META2]], splitDebugInlining: false, nameTableKind: None)
; CHECK: [[META1]] = !DIFile(filename: "preserve-load-dbgloc.c", directory: {{.*}})
; CHECK: [[META2]] = !{}
; CHECK: [[DBG4]] = distinct !DISubprogram(name: "ham", scope: [[META1]], file: [[META1]], line: 10, type: [[META5:![0-9]+]], flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: [[META0]], retainedNodes: [[META2]])
; CHECK: [[META5]] = distinct !DISubroutineType(types: [[META2]])
; CHECK: [[DBG6]] = !DILocation(line: 10, column: 1, scope: [[META7:![0-9]+]])
; CHECK: [[META7]] = distinct !DILexicalBlock(scope: [[DBG4]], file: [[META1]], line: 1524, column: 3)
; CHECK: [[DBG8]] = distinct !DISubprogram(name: "bar", scope: [[META1]], file: [[META1]], line: 230, type: [[META5]], flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: [[META0]], retainedNodes: [[META2]])
; CHECK: [[DBG9]] = !DILocation(line: 11, column: 4, scope: [[DBG8]])
; CHECK: [[DBG10]] = distinct !DISubprogram(name: "pluto", scope: [[META1]], file: [[META1]], line: 20, type: [[META5]], flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: [[META0]], retainedNodes: [[META2]])
; CHECK: [[DBG11]] = !DILocation(line: 20, column: 2, scope: [[DBG10]])
; CHECK: [[DBG12]] = !DILocation(line: 21, column: 3, scope: [[DBG10]])
;.
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