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[Mem2Reg] Create merged debug locations for inserted phis

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Track the debug locations of the incoming values to newly-created phis,
and apply merged debug locations to the phis.

A merged location will be on line 0, but will have the correct scope
set. This improves crash reporting when an inlined instruction with a
merged location triggers a machine exception. A debugger will be able to
narrow down the crash to the correct inlined scope, instead of simply
pointing to the outer scope of the caller.

Taken together with a change allows generating merged line-0 locations
for  instructions which aren't calls, this results in a 0.5% increase in
the uncompressed size of the .debug_line section of a stage2+Release
build of clang (-O3 -g).

rdar://33858697

Differential Revision: https://reviews.llvm.org/D45397

llvm-svn: 330227
This commit is contained in:
Vedant Kumar 2018-04-17 22:03:08 +00:00
parent 0fc6c6248c
commit 1bdfe2db7c
2 changed files with 142 additions and 6 deletions
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38
lib/Transforms/Utils/PromoteMemoryToRegister.cpp
View File

@ -167,13 +167,15 @@ struct AllocaInfo {
/// Data package used by RenamePass().
struct RenamePassData {
using ValVector = std::vector<Value *>;
using LocationVector = std::vector<DebugLoc>;
RenamePassData(BasicBlock *B, BasicBlock *P, ValVector V)
: BB(B), Pred(P), Values(std::move(V)) {}
RenamePassData(BasicBlock *B, BasicBlock *P, ValVector V, LocationVector L)
: BB(B), Pred(P), Values(std::move(V)), Locations(std::move(L)) {}
BasicBlock *BB;
BasicBlock *Pred;
ValVector Values;
LocationVector Locations;
};
/// \brief This assigns and keeps a per-bb relative ordering of load/store
@ -302,6 +304,7 @@ private:
SmallPtrSetImpl<BasicBlock *> &LiveInBlocks);
void RenamePass(BasicBlock *BB, BasicBlock *Pred,
RenamePassData::ValVector &IncVals,
RenamePassData::LocationVector &IncLocs,
std::vector<RenamePassData> &Worklist);
bool QueuePhiNode(BasicBlock *BB, unsigned AllocaIdx, unsigned &Version);
};
@ -652,15 +655,20 @@ void PromoteMem2Reg::run() {
for (unsigned i = 0, e = Allocas.size(); i != e; ++i)
Values[i] = UndefValue::get(Allocas[i]->getAllocatedType());
// When handling debug info, treat all incoming values as if they have unknown
// locations until proven otherwise.
RenamePassData::LocationVector Locations(Allocas.size());
// Walks all basic blocks in the function performing the SSA rename algorithm
// and inserting the phi nodes we marked as necessary
std::vector<RenamePassData> RenamePassWorkList;
RenamePassWorkList.emplace_back(&F.front(), nullptr, std::move(Values));
RenamePassWorkList.emplace_back(&F.front(), nullptr, std::move(Values),
std::move(Locations));
do {
RenamePassData RPD = std::move(RenamePassWorkList.back());
RenamePassWorkList.pop_back();
// RenamePass may add new worklist entries.
RenamePass(RPD.BB, RPD.Pred, RPD.Values, RenamePassWorkList);
RenamePass(RPD.BB, RPD.Pred, RPD.Values, RPD.Locations, RenamePassWorkList);
} while (!RenamePassWorkList.empty());
// The renamer uses the Visited set to avoid infinite loops. Clear it now.
@ -867,6 +875,16 @@ bool PromoteMem2Reg::QueuePhiNode(BasicBlock *BB, unsigned AllocaNo,
return true;
}
/// Update the debug location of a phi. \p ApplyMergedLoc indicates whether to
/// create a merged location incorporating \p DL, or to set \p DL directly.
static void updateForIncomingValueLocation(PHINode *PN, DebugLoc DL,
bool ApplyMergedLoc) {
if (ApplyMergedLoc)
PN->applyMergedLocation(PN->getDebugLoc(), DL);
else
PN->setDebugLoc(DL);
}
/// \brief Recursively traverse the CFG of the function, renaming loads and
/// stores to the allocas which we are promoting.
///
@ -874,6 +892,7 @@ bool PromoteMem2Reg::QueuePhiNode(BasicBlock *BB, unsigned AllocaNo,
/// predecessor block Pred.
void PromoteMem2Reg::RenamePass(BasicBlock *BB, BasicBlock *Pred,
RenamePassData::ValVector &IncomingVals,
RenamePassData::LocationVector &IncomingLocs,
std::vector<RenamePassData> &Worklist) {
NextIteration:
// If we are inserting any phi nodes into this BB, they will already be in the
@ -898,6 +917,10 @@ NextIteration:
do {
unsigned AllocaNo = PhiToAllocaMap[APN];
// Update the location of the phi node.
updateForIncomingValueLocation(APN, IncomingLocs[AllocaNo],
APN->getNumIncomingValues() > 0);
// Add N incoming values to the PHI node.
for (unsigned i = 0; i != NumEdges; ++i)
APN->addIncoming(IncomingVals[AllocaNo], Pred);
@ -959,8 +982,11 @@ NextIteration:
continue;
// what value were we writing?
IncomingVals[ai->second] = SI->getOperand(0);
unsigned AllocaNo = ai->second;
IncomingVals[AllocaNo] = SI->getOperand(0);
// Record debuginfo for the store before removing it.
IncomingLocs[AllocaNo] = SI->getDebugLoc();
for (DbgInfoIntrinsic *DII : AllocaDbgDeclares[ai->second])
ConvertDebugDeclareToDebugValue(DII, SI, DIB);
BB->getInstList().erase(SI);
@ -983,7 +1009,7 @@ NextIteration:
for (; I != E; ++I)
if (VisitedSuccs.insert(*I).second)
Worklist.emplace_back(*I, Pred, IncomingVals);
Worklist.emplace_back(*I, Pred, IncomingVals, IncomingLocs);
goto NextIteration;
}

110
test/Transforms/Mem2Reg/dbg-inline-scope-for-phi.ll Normal file
View File

@ -0,0 +1,110 @@
; RUN: opt -S < %s -mem2reg -verify | FileCheck %s
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.13.0"
; Original source (with some whitespace removed):
;
; extern int *getp();
; extern int cond();
; int get1() { return *getp(); }
; int get2(int *p) { return *p; }
; int bug(int *p) {
; if (cond()) return get1();
; else return get2(p);
; }
define i32 @get1() !dbg !8 {
%1 = call i32* (...) @getp(), !dbg !12
%2 = load i32, i32* %1, align 4, !dbg !13
ret i32 %2, !dbg !14
}
declare i32* @getp(...)
define i32 @get2(i32*) !dbg !15 {
%2 = alloca i32*, align 8
store i32* %0, i32** %2, align 8
call void @llvm.dbg.declare(metadata i32** %2, metadata !19, metadata !DIExpression()), !dbg !20
%3 = load i32*, i32** %2, align 8, !dbg !21
%4 = load i32, i32* %3, align 4, !dbg !22
ret i32 %4, !dbg !23
}
declare void @llvm.dbg.declare(metadata, metadata, metadata)
; CHECK-LABEL: define i32 @bug
define i32 @bug(i32*) !dbg !24 {
%2 = alloca i32, align 4
%3 = alloca i32*, align 8
store i32* %0, i32** %3, align 8
call void @llvm.dbg.declare(metadata i32** %3, metadata !25, metadata !DIExpression()), !dbg !26
%4 = call i32 (...) @cond(), !dbg !27
%5 = icmp ne i32 %4, 0, !dbg !27
br i1 %5, label %6, label %8, !dbg !29
; <label>:6: ; preds = %1
%7 = call i32 @get1(), !dbg !30
store i32 %7, i32* %2, align 4, !dbg !31
br label %11, !dbg !31
; <label>:8: ; preds = %1
%9 = load i32*, i32** %3, align 8, !dbg !32
%10 = call i32 @get2(i32* %9), !dbg !33
store i32 %10, i32* %2, align 4, !dbg !34
br label %11, !dbg !34
; <label>:11: ; preds = %8, %6
%12 = load i32, i32* %2, align 4, !dbg !35
ret i32 %12, !dbg !35
; CHECK: [[phi:%.*]] = phi i32 [ {{.*}} ], [ {{.*}} ], !dbg [[mergedLoc:![0-9]+]]
; CHECK-NEXT: ret i32 [[phi]], !dbg [[retLoc:![0-9]+]]
}
; CHECK: [[commonScope:![0-9]+]] = distinct !DILexicalBlock(scope: {{.*}}, file: !1, line: 15, column: 7)
; CHECK: [[mergedLoc]] = !DILocation(line: 0, scope: [[commonScope]])
; CHECK: [[retLoc]] = !DILocation(line: 23, column: 1
declare i32 @cond(...)
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!3, !4, !5, !6}
!llvm.ident = !{!7}
!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "Apple LLVM version 9.1.0 (clang-902.2.37.2)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
!1 = !DIFile(filename: "bug.c", directory: "/bug")
!2 = !{}
!3 = !{i32 2, !"Dwarf Version", i32 4}
!4 = !{i32 2, !"Debug Info Version", i32 3}
!5 = !{i32 1, !"wchar_size", i32 4}
!6 = !{i32 7, !"PIC Level", i32 2}
!7 = !{!"Apple LLVM version 9.1.0 (clang-902.2.37.2)"}
!8 = distinct !DISubprogram(name: "get1", scope: !1, file: !1, line: 6, type: !9, isLocal: false, isDefinition: true, scopeLine: 6, isOptimized: false, unit: !0, variables: !2)
!9 = !DISubroutineType(types: !10)
!10 = !{!11}
!11 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!12 = !DILocation(line: 7, column: 11, scope: !8)
!13 = !DILocation(line: 7, column: 10, scope: !8)
!14 = !DILocation(line: 7, column: 3, scope: !8)
!15 = distinct !DISubprogram(name: "get2", scope: !1, file: !1, line: 10, type: !16, isLocal: false, isDefinition: true, scopeLine: 10, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
!16 = !DISubroutineType(types: !17)
!17 = !{!11, !18}
!18 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !11, size: 64)
!19 = !DILocalVariable(name: "p", arg: 1, scope: !15, file: !1, line: 10, type: !18)
!20 = !DILocation(line: 10, column: 15, scope: !15)
!21 = !DILocation(line: 11, column: 11, scope: !15)
!22 = !DILocation(line: 11, column: 10, scope: !15)
!23 = !DILocation(line: 11, column: 3, scope: !15)
!24 = distinct !DISubprogram(name: "bug", scope: !1, file: !1, line: 14, type: !16, isLocal: false, isDefinition: true, scopeLine: 14, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
!25 = !DILocalVariable(name: "p", arg: 1, scope: !24, file: !1, line: 14, type: !18)
!26 = !DILocation(line: 14, column: 14, scope: !24)
!27 = !DILocation(line: 15, column: 7, scope: !28)
!28 = distinct !DILexicalBlock(scope: !24, file: !1, line: 15, column: 7)
!29 = !DILocation(line: 15, column: 7, scope: !24)
!30 = !DILocation(line: 16, column: 12, scope: !28)
!31 = !DILocation(line: 16, column: 5, scope: !28)
!32 = !DILocation(line: 18, column: 17, scope: !28)
!33 = !DILocation(line: 18, column: 12, scope: !28)
!34 = !DILocation(line: 18, column: 5, scope: !28)
!35 = !DILocation(line: 23, column: 1, scope: !24)