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LowerDbgDeclare: look through bitcasts. 

Summary:
Emit a value debug intrinsic (with OP_deref) when an alloca address is
passed to a function call after going through a bitcast.

This generates an FP or SP-relative location for the local variable in
the following case:
  int x;
  use((void *)&x;

Reviewers: aprantl, vsk, pcc

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70752
This commit is contained in:
Evgenii Stepanov 2019-11-25 15:45:17 -08:00
parent c8a2882a97
commit 6f89cbc429
2 changed files with 74 additions and 16 deletions
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42
llvm/lib/Transforms/Utils/Local.cpp
View File

@ -1421,22 +1421,32 @@ bool llvm::LowerDbgDeclare(Function &F) {
}))
continue;
for (auto &AIUse : AI->uses()) {
User *U = AIUse.getUser();
if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
if (AIUse.getOperandNo() == 1)
ConvertDebugDeclareToDebugValue(DDI, SI, DIB);
} else if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
ConvertDebugDeclareToDebugValue(DDI, LI, DIB);
} else if (CallInst *CI = dyn_cast<CallInst>(U)) {
// This is a call by-value or some other instruction that takes a
// pointer to the variable. Insert a *value* intrinsic that describes
// the variable by dereferencing the alloca.
DebugLoc NewLoc = getDebugValueLoc(DDI, nullptr);
auto *DerefExpr =
DIExpression::append(DDI->getExpression(), dwarf::DW_OP_deref);
DIB.insertDbgValueIntrinsic(AI, DDI->getVariable(), DerefExpr, NewLoc,
CI);
SmallVector<const Value *, 8> WorkList;
WorkList.push_back(AI);
while (!WorkList.empty()) {
const Value *V = WorkList.pop_back_val();
for (auto &AIUse : V->uses()) {
User *U = AIUse.getUser();
if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
if (AIUse.getOperandNo() == 1)
ConvertDebugDeclareToDebugValue(DDI, SI, DIB);
} else if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
ConvertDebugDeclareToDebugValue(DDI, LI, DIB);
} else if (CallInst *CI = dyn_cast<CallInst>(U)) {
// This is a call by-value or some other instruction that takes a
// pointer to the variable. Insert a *value* intrinsic that describes
// the variable by dereferencing the alloca.
if (!CI->isLifetimeStartOrEnd()) {
DebugLoc NewLoc = getDebugValueLoc(DDI, nullptr);
auto *DerefExpr =
DIExpression::append(DDI->getExpression(), dwarf::DW_OP_deref);
DIB.insertDbgValueIntrinsic(AI, DDI->getVariable(), DerefExpr,
NewLoc, CI);
}
} else if (BitCastInst *BI = dyn_cast<BitCastInst>(U)) {
if (BI->getType()->isPointerTy())
WorkList.push_back(BI);
}
}
}
DDI->eraseFromParent();

48
llvm/test/Transforms/Util/dbg-call-bitcast.ll Normal file
View File

@ -0,0 +1,48 @@
; RUN: opt -instcombine -S %s | FileCheck %s
define dso_local void @_Z1fv() {
%1 = alloca i32, align 4
%2 = bitcast i32* %1 to i8*
call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull %2)
call void @llvm.dbg.declare(metadata i32* %1, metadata !16, metadata !DIExpression()), !dbg !19
; CHECK: %[[A:.*]] = alloca i32, align 4
; CHECK: call void @llvm.dbg.value(metadata i32* %[[A]], {{.*}}, metadata !DIExpression(DW_OP_deref)
; CHECK: call void @_Z1gPv
call void @_Z1gPv(i8* nonnull %2)
%3 = bitcast i32* %1 to i8*
; CHECK: call void @llvm.dbg.value(metadata i32* %[[A]], {{.*}}, metadata !DIExpression(DW_OP_deref)
; CHECK: call void @_Z1gPv
call void @_Z1gPv(i8* nonnull %3)
call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull %2)
ret void, !dbg !21
}
declare void @llvm.lifetime.start.p0i8(i64 immarg, i8* nocapture)
declare void @llvm.dbg.declare(metadata, metadata, metadata)
declare dso_local void @_Z1gPv(i8*)
declare void @llvm.lifetime.end.p0i8(i64 immarg, i8* nocapture)
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!8, !9, !10}
!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 10.0.0 (git@github.com:llvm/llvm-project.git cab64b5708f614c71d275ec9d134e68b8c3baedd)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !3, nameTableKind: None)
!1 = !DIFile(filename: "dbg.cc", directory: "/tmp")
!2 = !{}
!3 = !{!4, !5}
!4 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: null, size: 64)
!5 = !DISubprogram(name: "g", linkageName: "_Z1gPv", scope: !1, file: !1, line: 1, type: !6, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized, retainedNodes: !2)
!6 = !DISubroutineType(types: !7)
!7 = !{null, !4}
!8 = !{i32 7, !"Dwarf Version", i32 4}
!9 = !{i32 2, !"Debug Info Version", i32 3}
!10 = !{i32 1, !"wchar_size", i32 4}
!12 = distinct !DISubprogram(name: "f", linkageName: "_Z1fv", scope: !1, file: !1, line: 2, type: !13, scopeLine: 2, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !15)
!13 = !DISubroutineType(types: !14)
!14 = !{null}
!15 = !{!16}
!16 = !DILocalVariable(name: "x", scope: !12, file: !1, line: 3, type: !17)
!17 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!18 = !DILocation(line: 3, column: 3, scope: !12)
!19 = !DILocation(line: 3, column: 7, scope: !12)
!20 = !DILocation(line: 4, column: 3, scope: !12)
!21 = !DILocation(line: 5, column: 1, scope: !12)