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[DebugInfo] Correctly update debug users of SSA values in tail duplication

During tail duplication, SSA values may be updated and have their uses
replaced with a virtual register, and any debug instructions that use
that value are deleted. This patch fixes the implementation of the debug
instruction deletion to work correctly for debug instructions that use
the SSA value multiple times, by batching deletions so that we don't
attempt to delete the same instruction twice.

Differential Revision: https://reviews.llvm.org/D106557
This commit is contained in:
Stephen Tozer 2021-07-26 09:59:20 +01:00
parent e67bfc0f97
commit 27b2ac2965
2 changed files with 133 additions and 1 deletions

View File

@ -216,6 +216,9 @@ bool TailDuplicator::tailDuplicateAndUpdate(
// Rewrite uses that are outside of the original def's block.
MachineRegisterInfo::use_iterator UI = MRI->use_begin(VReg);
// Only remove instructions after loop, as DBG_VALUE_LISTs with multiple
// uses of VReg may invalidate the use iterator when erased.
SmallPtrSet<MachineInstr *, 4> InstrsToRemove;
while (UI != MRI->use_end()) {
MachineOperand &UseMO = *UI;
MachineInstr *UseMI = UseMO.getParent();
@ -225,13 +228,15 @@ bool TailDuplicator::tailDuplicateAndUpdate(
// a debug instruction that is a kill.
// FIXME: Should it SSAUpdate job to delete debug instructions
// instead of replacing the use with undef?
UseMI->eraseFromParent();
InstrsToRemove.insert(UseMI);
continue;
}
if (UseMI->getParent() == DefBB && !UseMI->isPHI())
continue;
SSAUpdate.RewriteUse(UseMO);
}
for (auto *MI : InstrsToRemove)
MI->eraseFromParent();
}
SSAUpdateVRs.clear();

View File

@ -0,0 +1,127 @@
# RUN: llc -run-pass=early-tailduplication -mtriple=x86_64-unknown-linux-gnu %s -o - | FileCheck %s
# Tail Duplication may update SSA values and invalidate any DBG_VALUEs that
# use those values; those DBG_VALUEs should be deleted. This behaviour is tested
# for DBG_VALUE users, and DBG_VALUE_LISTs that use the value multiple times.
# CHECK-NOT: DBG_VALUE
--- |
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
define dso_local void @main() local_unnamed_addr #0 !dbg !15 {
entry:
br label %L.outer
L: ; preds = %L, %L.outer
%tobool2.not = icmp eq i32 undef, 0
br i1 %tobool2.not, label %if.end4, label %L
if.end4: ; preds = %L
call void @llvm.dbg.value(metadata !DIArgList(i32 %f.0.ph, i32 1, i32 %f.0.ph), metadata !19, metadata !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_LLVM_arg, 1, DW_OP_LLVM_arg, 2, DW_OP_and, DW_OP_or, DW_OP_stack_value)), !dbg !21
%cmp = icmp slt i32 %f.0.ph, undef
br i1 %cmp, label %if.then5, label %if.end6
if.then5: ; preds = %if.end4
call void @h() #2
br label %L.outer
L.outer: ; preds = %if.then5, %entry
%f.0.ph = phi i32 [ 0, %if.then5 ], [ 1, %entry ]
br label %L
if.end6: ; preds = %if.end4
ret void
}
declare dso_local void @h() local_unnamed_addr
declare void @llvm.dbg.value(metadata, metadata, metadata)
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!13, !14}
!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 13.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, globals: !3, splitDebugInlining: false, nameTableKind: None)
!1 = !DIFile(filename: "tail-dup-debugvalue.c", directory: "/tmp")
!2 = !{}
!3 = !{!4, !7, !9, !11}
!4 = !DIGlobalVariableExpression(var: !5, expr: !DIExpression())
!5 = distinct !DIGlobalVariable(name: "a", scope: !0, file: !1, line: 2, type: !6, isLocal: false, isDefinition: true)
!6 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!7 = !DIGlobalVariableExpression(var: !8, expr: !DIExpression())
!8 = distinct !DIGlobalVariable(name: "b", scope: !0, file: !1, line: 2, type: !6, isLocal: false, isDefinition: true)
!9 = !DIGlobalVariableExpression(var: !10, expr: !DIExpression())
!10 = distinct !DIGlobalVariable(name: "c", scope: !0, file: !1, line: 2, type: !6, isLocal: false, isDefinition: true)
!11 = !DIGlobalVariableExpression(var: !12, expr: !DIExpression())
!12 = distinct !DIGlobalVariable(name: "d", scope: !0, file: !1, line: 2, type: !6, isLocal: false, isDefinition: true)
!13 = !{i32 2, !"Debug Info Version", i32 3}
!14 = !{i32 7, !"uwtable", i32 1}
!15 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 3, type: !16, scopeLine: 3, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !18)
!16 = !DISubroutineType(types: !17)
!17 = !{!6}
!18 = !{!19, !20}
!19 = !DILocalVariable(name: "j", scope: !15, file: !1, line: 14, type: !6)
!20 = !DILocalVariable(name: "k", scope: !15, file: !1, line: 14, type: !6)
!21 = !DILocation(line: 0, scope: !15)
...
---
name: main
alignment: 16
tracksRegLiveness: true
registers:
- { id: 0, class: gr32 }
- { id: 1, class: gr32 }
- { id: 2, class: gr32 }
- { id: 3, class: gr8 }
- { id: 4, class: gr32 }
- { id: 5, class: gr32 }
- { id: 6, class: gr32 }
frameInfo:
maxAlignment: 1
hasCalls: true
machineFunctionInfo: {}
body: |
bb.0.entry:
successors: %bb.4(0x80000000)
%1:gr32 = MOV32ri 1
JMP_1 %bb.4
bb.1.L:
successors: %bb.2(0x04000000), %bb.1(0x7c000000)
%2:gr32 = MOV32r0 implicit-def dead $eflags
%3:gr8 = COPY %2.sub_8bit
TEST8rr %3, %3, implicit-def $eflags
JCC_1 %bb.1, 5, implicit $eflags
JMP_1 %bb.2
bb.2.if.end4:
successors: %bb.3(0x783e0f0f), %bb.5(0x07c1f0f1)
DBG_VALUE_LIST !19, !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_LLVM_arg, 1, DW_OP_LLVM_arg, 2, DW_OP_and, DW_OP_or, DW_OP_stack_value), %0, 1, %0, debug-location !21
DBG_VALUE %0, $noreg, !20, !DIExpression(), debug-location !21
%5:gr32 = IMPLICIT_DEF
%4:gr32 = SUB32rr %0, killed %5, implicit-def $eflags
JCC_1 %bb.5, 13, implicit $eflags
JMP_1 %bb.3
bb.3.if.then5:
successors: %bb.4(0x80000000)
ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
CALL64pcrel32 @h, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp
ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
%6:gr32 = MOV32r0 implicit-def dead $eflags
bb.4.L.outer:
successors: %bb.1(0x80000000)
%0:gr32 = PHI %1, %bb.0, %6, %bb.3
JMP_1 %bb.1
bb.5.if.end6:
RET 0
...