forked from OSchip/llvm-project
[DebugInfo] Ignore DBG_VALUE instructions in PostRA Machine Sink
Summary: The logic for handling the sinking of COPY instructions was generating different code when building with debug flags. The original code did not take into consideration debug instructions. This resulted in the registers in the DBG_VALUE instructions being treated as used, and prevented the COPY from being sunk. This patch avoids analyzing debug instructions when trying to sink COPY instructions. This patch also creates a routine from the code in MachineSinking::SinkInstruction to perform the logic of sinking an instruction along with its debug instructions. This functionality is used in multiple places, including the code for sinking COPY instrs. Reviewers: junbuml, javed.absar, MatzeB, bjope Reviewed By: bjope Subscribers: aprantl, probinson, thegameg, jonpa, bjope, vsk, kristof.beyls, JDevlieghere, llvm-commits Tags: #debug-info Differential Revision: https://reviews.llvm.org/D45637 llvm-svn: 335264
This commit is contained in:
Matt Davis
parent
59a1be3acf
commit
d041f21810
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@ -753,6 +753,37 @@ static bool SinkingPreventsImplicitNullCheck(MachineInstr &MI,
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MBP.LHS.getReg() == BaseReg;
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}
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/// Sink an instruction and its associated debug instructions.
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static void performSink(MachineInstr &MI, MachineBasicBlock &SuccToSinkTo,
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MachineBasicBlock::iterator InsertPos) {
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// Collect matching debug values.
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SmallVector<MachineInstr *, 2> DbgValuesToSink;
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collectDebugValues(MI, DbgValuesToSink);
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// If we cannot find a location to use (merge with), then we erase the debug
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// location to prevent debug-info driven tools from potentially reporting
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// wrong location information.
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if (!SuccToSinkTo.empty() && InsertPos != SuccToSinkTo.end())
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MI.setDebugLoc(DILocation::getMergedLocation(MI.getDebugLoc(),
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InsertPos->getDebugLoc()));
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else
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MI.setDebugLoc(DebugLoc());
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// Move the instruction.
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MachineBasicBlock *ParentBlock = MI.getParent();
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SuccToSinkTo.splice(InsertPos, ParentBlock, MI,
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++MachineBasicBlock::iterator(MI));
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// Move previously adjacent debug value instructions to the insert position.
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for (SmallVectorImpl<MachineInstr *>::iterator DBI = DbgValuesToSink.begin(),
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DBE = DbgValuesToSink.end();
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DBI != DBE; ++DBI) {
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MachineInstr *DbgMI = *DBI;
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SuccToSinkTo.splice(InsertPos, ParentBlock, DbgMI,
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++MachineBasicBlock::iterator(DbgMI));
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}
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}
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/// SinkInstruction - Determine whether it is safe to sink the specified machine
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/// instruction out of its current block into a successor.
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bool MachineSinking::SinkInstruction(MachineInstr &MI, bool &SawStore,
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@ -866,30 +897,7 @@ bool MachineSinking::SinkInstruction(MachineInstr &MI, bool &SawStore,
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while (InsertPos != SuccToSinkTo->end() && InsertPos->isPHI())
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++InsertPos;
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// collect matching debug values.
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SmallVector<MachineInstr *, 2> DbgValuesToSink;
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collectDebugValues(MI, DbgValuesToSink);
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// Merge or erase debug location to ensure consistent stepping in profilers
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// and debuggers.
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if (!SuccToSinkTo->empty() && InsertPos != SuccToSinkTo->end())
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MI.setDebugLoc(DILocation::getMergedLocation(MI.getDebugLoc(),
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InsertPos->getDebugLoc()));
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else
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MI.setDebugLoc(DebugLoc());
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// Move the instruction.
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SuccToSinkTo->splice(InsertPos, ParentBlock, MI,
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++MachineBasicBlock::iterator(MI));
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// Move previously adjacent debug value instructions to the insert position.
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for (SmallVectorImpl<MachineInstr *>::iterator DBI = DbgValuesToSink.begin(),
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DBE = DbgValuesToSink.end(); DBI != DBE; ++DBI) {
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MachineInstr *DbgMI = *DBI;
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SuccToSinkTo->splice(InsertPos, ParentBlock, DbgMI,
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++MachineBasicBlock::iterator(DbgMI));
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}
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performSink(MI, *SuccToSinkTo, InsertPos);
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// Conservatively, clear any kill flags, since it's possible that they are no
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// longer correct.
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@ -1118,6 +1126,9 @@ bool PostRAMachineSinking::tryToSinkCopy(MachineBasicBlock &CurBB,
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MachineInstr *MI = &*I;
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++I;
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if (MI->isDebugInstr())
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continue;
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// Do not move any instruction across function call.
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if (MI->isCall())
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return false;
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@ -1158,7 +1169,7 @@ bool PostRAMachineSinking::tryToSinkCopy(MachineBasicBlock &CurBB,
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// block.
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clearKillFlags(MI, CurBB, UsedOpsInCopy, UsedRegUnits, TRI);
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MachineBasicBlock::iterator InsertPos = SuccBB->getFirstNonPHI();
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SuccBB->splice(InsertPos, &CurBB, MI);
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performSink(*MI, *SuccBB, InsertPos);
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updateLiveIn(MI, SuccBB, UsedOpsInCopy, DefedRegsInCopy);
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Changed = true;
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@ -0,0 +1,88 @@
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# RUN: llc -mtriple=x86_64-none-linux-gnu -run-pass=postra-machine-sink -verify-machineinstrs -o - %s | FileCheck %s
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#
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# This test was originally generated from the following sample:
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#
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# int x0;
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# extern void x3(int, int);
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# void x1(int x2) {
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# if (x0)
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# x3(0, x2);
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# }
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#
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# The code generates a COPY instruction which the PostRA Machine Sink pass will
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# try to sink. Earlier versions were not performing the sink due to a
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# DBG_VALUE instruction confusing the sinking algorithm.
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--- |
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@x0 = common dso_local global i32 0, align 4, !dbg !0
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define dso_local void @x1(i32) !dbg !11 {
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%2 = alloca i32, align 4
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store i32 %0, i32* %2, align 4
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call void @llvm.dbg.declare(metadata i32* %2, metadata !14, metadata !DIExpression()), !dbg !16
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%3 = load i32, i32* @x0, align 4, !dbg !16
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%4 = icmp ne i32 %3, 0, !dbg !16
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br i1 %4, label %5, label %7, !dbg !16
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; <label>:5: ; preds = %1
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%6 = load i32, i32* %2, align 4, !dbg !16
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call void @x3(i32 0, i32 %6), !dbg !16
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br label %7, !dbg !16
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; <label>:7: ; preds = %5, %1
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ret void, !dbg !16
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}
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declare void @llvm.dbg.declare(metadata, metadata, metadata)
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declare dso_local void @x3(i32, i32)
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!llvm.dbg.cu = !{!2}
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!llvm.module.flags = !{!7, !8}
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!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
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!1 = distinct !DIGlobalVariable(name: "x0", scope: !2, file: !3, line: 1, type: !6, isLocal: false, isDefinition: true)
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!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5)
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!3 = !DIFile(filename: "test.c", directory: "")
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!4 = !{}
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!5 = !{!0}
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!6 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
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!7 = !{i32 2, !"Dwarf Version", i32 4}
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!8 = !{i32 2, !"Debug Info Version", i32 3}
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!11 = distinct !DISubprogram(name: "x1", scope: !3, file: !3, line: 3, type: !12, isLocal: false, isDefinition: true, scopeLine: 3, flags: DIFlagPrototyped, isOptimized: false, unit: !2)
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!12 = !DISubroutineType(types: !13)
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!13 = !{null, !6}
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!14 = !DILocalVariable(name: "x2", arg: 1, scope: !11, file: !3, line: 3, type: !6)
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!15 = distinct !DILexicalBlock(scope: !11, file: !3, line: 4, column: 7)
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!16 = !DILocation(line: 4, column: 7, scope: !15)
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...
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---
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# CHECK: name: x1
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# CHECK: bb.0:
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# CHECK-NOT: $eax = COPY $edi
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# CHECK: bb.1:
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# CHECK: renamable $eax = COPY $edi
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# CHECK-NEXT: DBG_VALUE debug-use $eax,
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# CHECK: bb.2:
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name: x1
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alignment: 4
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tracksRegLiveness: true
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body: |
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bb.0:
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successors: %bb.2, %bb.1; %bb.2, %bb.1
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liveins: $edi
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DBG_VALUE debug-use $edi, debug-use $noreg, !14, !DIExpression(), debug-location !16
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renamable $eax = COPY $edi
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DBG_VALUE debug-use $eax, debug-use $noreg, !14, !DIExpression(), debug-location !16
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CMP32mi8 $rip, 1, $noreg, @x0, $noreg, 0, implicit-def $eflags, debug-location !16
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JE_1 %bb.2, implicit killed $eflags, debug-location !16
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JMP_1 %bb.1, debug-location !16
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bb.1:
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liveins: $eax
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$edi = MOV32r0 implicit-def dead $eflags, debug-location !16
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$esi = COPY killed renamable $eax, debug-location !16
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bb.2:
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RET 0, debug-location !16
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...
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