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[DebugInfo] Replace debug uses in replaceUsesOutsideBlock 

Value::replaceUsesOutsideBlock doesn't replace debug uses which leads to an
unnecessary reduction in variable location coverage. Fix this, add a unittest for
it, and add a regression test demonstrating the change through instcombine's
replacedSelectWithOperand.

Reviewed By: djtodoro

Differential Revision: https://reviews.llvm.org/D99169
This commit is contained in:
OCHyams 2021-04-15 16:05:30 +01:00
parent 2a95cb5858
commit 96a1e6b7cf
3 changed files with 205 additions and 0 deletions
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13
llvm/lib/IR/Value.cpp
View File

@ -33,6 +33,7 @@
#include "llvm/Support/ErrorHandling.h" #include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/ManagedStatic.h" #include "llvm/Support/ManagedStatic.h"
#include "llvm/Support/raw_ostream.h" #include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/Local.h"
#include <algorithm> #include <algorithm>
using namespace llvm; using namespace llvm;
@ -531,6 +532,17 @@ void Value::replaceNonMetadataUsesWith(Value *New) {
doRAUW(New, ReplaceMetadataUses::No); doRAUW(New, ReplaceMetadataUses::No);
} }
/// Replace llvm.dbg.* uses of MetadataAsValue(ValueAsMetadata(V)) outside BB
/// with New.
static void replaceDbgUsesOutsideBlock(Value *V, Value *New, BasicBlock *BB) {
SmallVector<DbgVariableIntrinsic *> DbgUsers;
findDbgUsers(DbgUsers, V);
for (auto *DVI : DbgUsers) {
if (DVI->getParent() != BB)
DVI->replaceVariableLocationOp(V, New);
}
}
// Like replaceAllUsesWith except it does not handle constants or basic blocks. // Like replaceAllUsesWith except it does not handle constants or basic blocks.
// This routine leaves uses within BB. // This routine leaves uses within BB.
void Value::replaceUsesOutsideBlock(Value *New, BasicBlock *BB) { void Value::replaceUsesOutsideBlock(Value *New, BasicBlock *BB) {
@ -541,6 +553,7 @@ void Value::replaceUsesOutsideBlock(Value *New, BasicBlock *BB) {
"replaceUses of value with new value of different type!"); "replaceUses of value with new value of different type!");
assert(BB && "Basic block that may contain a use of 'New' must be defined\n"); assert(BB && "Basic block that may contain a use of 'New' must be defined\n");
replaceDbgUsesOutsideBlock(this, New, BB);
replaceUsesWithIf(New, [BB](Use &U) { replaceUsesWithIf(New, [BB](Use &U) {
auto *I = dyn_cast<Instruction>(U.getUser()); auto *I = dyn_cast<Instruction>(U.getUser());
// Don't replace if it's an instruction in the BB basic block. // Don't replace if it's an instruction in the BB basic block.

127
llvm/test/DebugInfo/Generic/instcombine-replaced-select-with-operand.ll Normal file
View File

@ -0,0 +1,127 @@
; RUN: opt -instcombine -S %s | FileCheck %s
;; Ensure that debug uses of a select are replaced when the select is replaced
;; with one of its operands in InstCombine's replacedSelectWithOperand.
;; Based on IR generated from this source, compiled with -O2 -g:
;;
;; extern void* glob;
;; struct Thing {
;; void *ptr;
;; void *get() {return ptr;}
;; };
;; Thing *two(void *in) {
;; if ((long)in & 1)
;; return nullptr;
;; return static_cast<Thing *>(in);
;; }
;; void one() {
;; if (Thing *a = two(glob))
;; // Without the fix we lose 'this' (a) in the inlined call below.
;; glob = a->get();
;; }
;; Look at the instruction:
;; %retval.0.i = select i1 %tobool.not.i, %struct.Thing* %2, %struct.Thing* null
;; Note that %2 is a bitcast of %0.
;; InstCombine replaces the use of %retval.0.i in if.then with %0 because
;; if.then is only branched to when retval.0.is not null. Ensure that debug use
;; of %retval.0.i is also replaced with %0.
; CHECK: if.then:
; CHECK-NEXT: call void @llvm.dbg.value(metadata i8* %0, metadata ![[THIS:[0-9]+]], metadata !DIExpression())
; CHECK: ![[THIS]] = !DILocalVariable(name: "this",
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
%struct.Thing = type { i8* }
@glob = external dso_local local_unnamed_addr global i8*, align 8
define dso_local void @_Z3onev() local_unnamed_addr !dbg !29 {
entry:
%0 = load i8*, i8** @glob, align 8, !dbg !35
call void @llvm.dbg.value(metadata i8* %0, metadata !22, metadata !DIExpression()), !dbg !40
%1 = ptrtoint i8* %0 to i64, !dbg !42
%and.i = and i64 %1, 1, !dbg !43
%tobool.not.i = icmp eq i64 %and.i, 0, !dbg !42
%2 = bitcast i8* %0 to %struct.Thing*, !dbg !44
%retval.0.i = select i1 %tobool.not.i, %struct.Thing* %2, %struct.Thing* null, !dbg !44
call void @llvm.dbg.value(metadata %struct.Thing* %retval.0.i, metadata !33, metadata !DIExpression()), !dbg !45
%tobool.not = icmp eq %struct.Thing* %retval.0.i, null, !dbg !46
br i1 %tobool.not, label %if.end, label %if.then, !dbg !47
if.then: ; preds = %entry
call void @llvm.dbg.value(metadata %struct.Thing* %retval.0.i, metadata !48, metadata !DIExpression()), !dbg !51
%ptr.i = getelementptr inbounds %struct.Thing, %struct.Thing* %retval.0.i, i64 0, i32 0, !dbg !53
%3 = load i8*, i8** %ptr.i, align 8, !dbg !53
store i8* %3, i8** @glob, align 8, !dbg !56
br label %if.end, !dbg !57
if.end: ; preds = %if.then, %entry
ret void, !dbg !58
}
declare void @llvm.dbg.value(metadata, metadata, metadata)
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!14, !15, !16}
!llvm.ident = !{!17}
!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 13.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !3, splitDebugInlining: false, nameTableKind: None)
!1 = !DIFile(filename: "test.cpp", directory: "/")
!2 = !{}
!3 = !{!4, !5}
!4 = !DIBasicType(name: "long int", size: 64, encoding: DW_ATE_signed)
!5 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !6, size: 64)
!6 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "Thing", file: !1, line: 2, size: 64, flags: DIFlagTypePassByValue, elements: !7, identifier: "_ZTS5Thing")
!7 = !{!8, !10}
!8 = !DIDerivedType(tag: DW_TAG_member, name: "ptr", scope: !6, file: !1, line: 3, baseType: !9, size: 64)
!9 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: null, size: 64)
!10 = !DISubprogram(name: "get", linkageName: "_ZN5Thing3getEv", scope: !6, file: !1, line: 4, type: !11, scopeLine: 4, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized)
!11 = !DISubroutineType(types: !12)
!12 = !{!9, !13}
!13 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !6, size: 64, flags: DIFlagArtificial | DIFlagObjectPointer)
!14 = !{i32 7, !"Dwarf Version", i32 4}
!15 = !{i32 2, !"Debug Info Version", i32 3}
!16 = !{i32 1, !"wchar_size", i32 4}
!17 = !{!"clang version 13.0.0"}
!18 = distinct !DISubprogram(name: "two", linkageName: "_Z3twoPv", scope: !1, file: !1, line: 6, type: !19, scopeLine: 6, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !21)
!19 = !DISubroutineType(types: !20)
!20 = !{!5, !9}
!21 = !{!22}
!22 = !DILocalVariable(name: "in", arg: 1, scope: !18, file: !1, line: 6, type: !9)
!23 = !DILocation(line: 0, scope: !18)
!24 = !DILocation(line: 7, column: 7, scope: !25)
!25 = distinct !DILexicalBlock(scope: !18, file: !1, line: 7, column: 7)
!26 = !DILocation(line: 7, column: 16, scope: !25)
!27 = !DILocation(line: 7, column: 7, scope: !18)
!28 = !DILocation(line: 10, column: 1, scope: !18)
!29 = distinct !DISubprogram(name: "one", linkageName: "_Z3onev", scope: !1, file: !1, line: 11, type: !30, scopeLine: 11, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !32)
!30 = !DISubroutineType(types: !31)
!31 = !{null}
!32 = !{!33}
!33 = !DILocalVariable(name: "a", scope: !34, file: !1, line: 12, type: !5)
!34 = distinct !DILexicalBlock(scope: !29, file: !1, line: 12, column: 14)
!35 = !DILocation(line: 12, column: 22, scope: !34)
!40 = !DILocation(line: 0, scope: !18, inlinedAt: !41)
!41 = distinct !DILocation(line: 12, column: 18, scope: !34)
!42 = !DILocation(line: 7, column: 7, scope: !25, inlinedAt: !41)
!43 = !DILocation(line: 7, column: 16, scope: !25, inlinedAt: !41)
!44 = !DILocation(line: 7, column: 7, scope: !18, inlinedAt: !41)
!45 = !DILocation(line: 0, scope: !34)
!46 = !DILocation(line: 12, column: 14, scope: !34)
!47 = !DILocation(line: 12, column: 14, scope: !29)
!48 = !DILocalVariable(name: "this", arg: 1, scope: !49, type: !5, flags: DIFlagArtificial | DIFlagObjectPointer)
!49 = distinct !DISubprogram(name: "get", linkageName: "_ZN5Thing3getEv", scope: !6, file: !1, line: 4, type: !11, scopeLine: 4, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, declaration: !10, retainedNodes: !50)
!50 = !{!48}
!51 = !DILocation(line: 0, scope: !49, inlinedAt: !52)
!52 = distinct !DILocation(line: 14, column: 15, scope: !34)
!53 = !DILocation(line: 4, column: 23, scope: !49, inlinedAt: !52)
!56 = !DILocation(line: 14, column: 10, scope: !34)
!57 = !DILocation(line: 14, column: 5, scope: !34)
!58 = !DILocation(line: 15, column: 1, scope: !29)
!59 = !DILocation(line: 0, scope: !49)
!60 = !DILocation(line: 4, column: 23, scope: !49)
!61 = !DILocation(line: 4, column: 16, scope: !49)

65
llvm/unittests/IR/ValueTest.cpp
View File

@ -9,6 +9,7 @@
#include "llvm/IR/Value.h" #include "llvm/IR/Value.h"
#include "llvm/AsmParser/Parser.h" #include "llvm/AsmParser/Parser.h"
#include "llvm/IR/Function.h" #include "llvm/IR/Function.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/LLVMContext.h" #include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h" #include "llvm/IR/Module.h"
#include "llvm/IR/ModuleSlotTracker.h" #include "llvm/IR/ModuleSlotTracker.h"
@ -247,4 +248,68 @@ TEST(ValueTest, getLocalSlotDeath) {
} }
#endif #endif
TEST(ValueTest, replaceUsesOutsideBlock) {
// Check that Value::replaceUsesOutsideBlock(New, BB) replaces uses outside
// BB, including dbg.* uses of MetadataAsValue(ValueAsMetadata(this)).
const auto *IR = R"(
define i32 @f() !dbg !6 {
entry:
%a = add i32 0, 1, !dbg !15
%b = add i32 0, 2, !dbg !15
%c = add i32 %a, 2, !dbg !15
call void @llvm.dbg.value(metadata i32 %a, metadata !9, metadata !DIExpression()), !dbg !15
br label %exit, !dbg !15
exit:
call void @llvm.dbg.value(metadata i32 %a, metadata !11, metadata !DIExpression()), !dbg !16
ret i32 %a, !dbg !16
}
declare void @llvm.dbg.value(metadata, metadata, metadata)
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!5}
!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "debugify", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
!1 = !DIFile(filename: "test.ll", directory: "/")
!2 = !{}
!5 = !{i32 2, !"Debug Info Version", i32 3}
!6 = distinct !DISubprogram(name: "f", linkageName: "f", scope: null, file: !1, line: 1, type: !7, isLocal: false, isDefinition: true, scopeLine: 1, isOptimized: true, unit: !0, retainedNodes: !8)
!7 = !DISubroutineType(types: !2)
!8 = !{!9, !11}
!9 = !DILocalVariable(name: "1", scope: !6, file: !1, line: 1, type: !10)
!10 = !DIBasicType(name: "ty32", size: 32, encoding: DW_ATE_signed)
!11 = !DILocalVariable(name: "2", scope: !6, file: !1, line: 2, type: !12)
!12 = !DIBasicType(name: "ty64", size: 64, encoding: DW_ATE_signed)
!15 = !DILocation(line: 1, column: 1, scope: !6)
!16 = !DILocation(line: 5, column: 1, scope: !6)
)";
LLVMContext Ctx;
SMDiagnostic Err;
std::unique_ptr<Module> M = parseAssemblyString(IR, Err, Ctx);
if (!M)
Err.print("ValueTest", errs());
auto GetNext = [](auto *I) { return &*++I->getIterator(); };
Function *F = M->getFunction("f");
// Entry.
BasicBlock *Entry = &F->front();
Instruction *A = &Entry->front();
Instruction *B = GetNext(A);
Instruction *C = GetNext(B);
auto *EntryDbg = cast<DbgValueInst>(GetNext(C));
// Exit.
BasicBlock *Exit = GetNext(Entry);
auto *ExitDbg = cast<DbgValueInst>(&Exit->front());
Instruction *Ret = GetNext(ExitDbg);
A->replaceUsesOutsideBlock(B, Entry);
// These users are in Entry so shouldn't be changed.
ASSERT_TRUE(C->getOperand(0) == cast<Value>(A));
ASSERT_TRUE(EntryDbg->getValue(0) == cast<Value>(A));
// These users are outside Entry so should be changed.
ASSERT_TRUE(ExitDbg->getValue(0) == cast<Value>(B));
ASSERT_TRUE(Ret->getOperand(0) == cast<Value>(B));
}
} // end anonymous namespace } // end anonymous namespace