1575583f2a
This patch adds support to the instruction-referencing LiveDebugValues implementation for emitting entry values. The instruction referencing implementations tracking by value rather than location means that we can get around two of the issues with VarLocs. DBG_VALUE instructions that re-assign the same value to a variable are no longer a problem, because we can "see through" to the value being assigned. We also don't need to do anything special during the dataflow stages: the "variable value problem" doesn't need to know whether a value is available most of the time, and the times it deoes need to know are always when entry values need to be terminated. The patch modifies the "TransferTracker" class, adding methods to identify when a variable ias an entry value candidate, and when a machine value is an entry value. recoverAsEntryValue tests these two things and emits an entry-value expression if they're true. It's used when we clobber or otherwise lose a value and can't find a replacement location for the value it contained. Differential Revision: https://reviews.llvm.org/D88406
114 lines
4.5 KiB
YAML
114 lines
4.5 KiB
YAML
--- |
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; RUN: llc %s -march=x86-64 -run-pass=livedebugvalues -o - -experimental-debug-variable-locations -emulate-old-livedebugvalues=0 | FileCheck %s -implicit-check-not=DBG_VALUE
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; Sometimes, variables can have multiple locations, and when control flow
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; merges LiveDebugValues has a hard time picking which one the variable lives
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; in. Test two of these scenarios that old LiveDebugValues can't handle: when
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; a value is in two registers, and when a value is both in a register and
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; on the stack.
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; In a register:
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; CHECK-LABEL: bb.0.entry:
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; CHECK: DBG_VALUE $rbp, $noreg, !16, !DIExpression()
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; CHECK-LABEL: bb.1.bb1:
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; CHECK: DBG_VALUE $rbp, $noreg, !16, !DIExpression()
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; CHECK: DBG_VALUE $rbp, $noreg, !16, !DIExpression()
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; CHECK-LABEL: bb.2.bb2:
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; CHECK: DBG_VALUE $rbp, $noreg, !16, !DIExpression()
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; CHECK-LABEL: bb.3.bb3:
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; CHECK: DBG_VALUE $rbp, $noreg, !16, !DIExpression()
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; On the stack: we move from $rbp to a stack slot in bb4, but join back on
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; $rbp in bb6.
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; CHECK-LABEL: bb.4:
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; CHECK: DBG_VALUE $rbp, $noreg, !16, !DIExpression()
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; CHECK: DBG_VALUE $rsp, 0, !16, !DIExpression()
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; CHECK-LABEL: bb.5:
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; CHECK: DBG_VALUE $rbp, $noreg, !16, !DIExpression()
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; CHECK-LABEL: bb.6:
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; CHECK: DBG_VALUE $rbp, $noreg, !16, !DIExpression()
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declare i64 @bees(i64 %arg);
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define i32 @_Z8bb_to_bb(i64 %arg) local_unnamed_addr !dbg !12 {
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entry:
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br label %bb1, !dbg !17
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bb1:
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br label %bb2, !dbg !17
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bb2:
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br label %bb3, !dbg !17
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bb3:
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ret i32 0, !dbg !17
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}
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!llvm.dbg.cu = !{!0}
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!llvm.module.flags = !{!7, !8, !9, !10}
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!llvm.ident = !{!11}
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!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 10.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, globals: !3, debugInfoForProfiling: true, nameTableKind: None)
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!1 = !DIFile(filename: "main.cpp", directory: "F:\")
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!2 = !{}
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!3 = !{!4}
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!4 = !DIGlobalVariableExpression(var: !5, expr: !DIExpression())
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!5 = distinct !DIGlobalVariable(name: "start", scope: !0, file: !1, line: 4, type: !6, isLocal: false, isDefinition: true)
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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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!9 = !{i32 1, !"wchar_size", i32 2}
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!10 = !{i32 7, !"PIC Level", i32 2}
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!11 = !{!"clang version 10.0.0"}
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!12 = distinct !DISubprogram(name: "bb_to_bb", linkageName: "bb_to_bb", scope: !1, file: !1, line: 6, type: !13, scopeLine: 6, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !15)
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!13 = !DISubroutineType(types: !14)
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!14 = !{!6, !6}
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!15 = !{!16}
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!16 = !DILocalVariable(name: "myVar", scope: !12, file: !1, line: 7, type: !6)
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!17 = !DILocation(line: 10, scope: !12)
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...
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---
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name: _Z8bb_to_bb
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tracksRegLiveness: true
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liveins:
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- { reg: '$rdi', virtual-reg: '' }
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stack:
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- { id: 0, name: '', type: spill-slot, offset: -8, size: 8, alignment: 8,
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stack-id: default, callee-saved-register: '', callee-saved-restored: true,
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debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
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body: |
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bb.0.entry:
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liveins: $rdi
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successors: %bb.1, %bb.2
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$rbp = MOV64rr $rdi, debug-location !17
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DBG_VALUE $rbp, $noreg, !16, !DIExpression(), debug-location !17
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dead $rcx = MOV64ri 0, debug-location !17
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CALL64pcrel32 @bees, csr_64, implicit $rsp, implicit $ssp, implicit $rdi, implicit-def $rsp, implicit-def $ssp, implicit-def $rax, debug-location !17
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CMP64ri8 renamable $rax, 1, implicit-def $eflags, debug-location !17
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JCC_1 %bb.2, 4, implicit killed $eflags, debug-location !17
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bb.1.bb1:
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liveins: $rax, $rbp
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successors: %bb.3
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$rbp = MOV64ri 0, debug-location !17
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DBG_VALUE $rbp, $noreg, !16, !DIExpression(), debug-location !17
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JMP_1 %bb.3
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bb.2.bb2:
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liveins: $rax, $rbp
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successors: %bb.3
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$rax = MOV64ri 0, debug-location !17
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bb.3.bb3:
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liveins: $rax, $rbp
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$rdi = MOV64rr $rbp, debug-location !17
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CALL64pcrel32 @bees, csr_64, implicit $rsp, implicit $ssp, implicit $rdi, implicit-def $rsp, implicit-def $ssp, implicit-def $rax, debug-location !17
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CMP64ri8 renamable $rax, 1, implicit-def $eflags, debug-location !17
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JCC_1 %bb.5, 4, implicit killed $eflags, debug-location !17
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bb.4:
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liveins: $rax, $rbp
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MOV64mr $rsp, 1, $noreg, 8, $noreg, killed renamable $rbp :: (store (s64) into %stack.0)
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JMP_1 %bb.6
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bb.5:
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liveins: $rax, $rbp
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bb.6:
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liveins: $rax, $rbp
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RETQ $rax, debug-location !17
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...
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