# RUN: llc %s -march=x86-64 -run-pass=livedebugvalues -o - \
# RUN: -experimental-debug-variable-locations=true \
# RUN: | FileCheck %s -implicit-check-not=DBG_VALUE \
# RUN: --check-prefixes=CHECK,COMMON
#
# This test is designed to stimulate a simplification of variable-value
# propagation in InstrRefBasedLDV. When we only have a single assignment of
# a variable, we don't have to completely enumerate all the PHIs the variable
# has and then value propagate through them: the variable value is available
# only in those blocks dominated by the assignment. Example in this test:
#
# entry
# / | \
# / v \
# / bb1 \ <--- Single variable assignment happens here
# / / \ \
# / v v \
# | bb2 bb3 |
# | \ / |
# | v v |
# | bb4 |
# \ / \ /
# v v v v
# bb5 bb6 <--- Dominance frontier is here
#
# The general InstrRefBasedLDV algorithm takes this CFG, places PHIs at bb5 and
# bb6, then value-propagates until it's determined that they can't be
# eliminated. Then, we determine that there's no machine location for such PHIs,
# and no variable location is emitted.
#
# The fast way of doing this: observe that the variable value can never extend
# past the dominance frontier of the block where the assignment happens. So
# just propagate the variable value into the dominated blocks, and avoid the
# general algorithm.
#
# Doing so introduces a functional change: VarLocBasedLDV won't propagate
# variable locations through out-of-scope blocks, and InstrRefBasedLDV tries to
# replicate VarLocBasedLDV most of the time. In the MIR below, bb2 is out of
# scope. This effectively becomes another variable assignment (of undef), which
# requires full SSA and value propagation to emulate what VarLocBasedLDV did.
# Applying this speed optimisation makes us diverge from what VarLocBasedLDV
# does by not treating the out-of-scope block as an effective undef assignment,
# hence this test.
#
# CHECK-LABEL: bb.1:
# CHECK: DBG_VALUE
# CHECK-LABEL: bb.2:
## No location here because it's out-of-scope.
# CHECK-LABEL: bb.3:
# CHECK: DBG_VALUE
# CHECK-LABEL: bb.4:
# CHECK: DBG_VALUE
#
## VarLocBasedLDV will take the DBG_VALUE in the assignment block, propagate
## to bb.3, but not into bb.4 because of the intervening out-of-scope block.
## Disabled actual testing of this because it's just for comparison purposes.
#
# varloc-label: bb.1:
# varloc: DBG_VALUE
# varloc-label: bb.2:
## No location here because it's out-of-scope.
# varloc-label: bb.3:
# varloc: DBG_VALUE
#
## Common tail for 'test2' -- this is checking that the assignment of undef or
## $noreg in single-assignment mode doesn't lead to trouble further down the
## line, specifically assertion failures.
#
# COMMON-LABEL: name: test2
# COMMON: DBG_VALUE $noreg
--- |
define i32 @_Z8bb_to_bb() local_unnamed_addr !dbg !12 {
entry:
ret i32 0, !dbg !17
}
define i32 @test2() local_unnamed_addr !dbg !112 {
entry:
ret i32 0, !dbg !117
}
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!7, !8, !9, !10}
!llvm.ident = !{!11}
!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, globals: !3, debugInfoForProfiling: true, nameTableKind: None)
!1 = !DIFile(filename: "main.cpp", directory: "F:\")
!2 = !{}
!3 = !{!4}
!4 = !DIGlobalVariableExpression(var: !5, expr: !DIExpression())
!5 = distinct !DIGlobalVariable(name: "start", scope: !0, file: !1, line: 4, type: !6, isLocal: false, isDefinition: true)
!6 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!7 = !{i32 2, !"Dwarf Version", i32 4}
!8 = !{i32 2, !"Debug Info Version", i32 3}
!9 = !{i32 1, !"wchar_size", i32 2}
!10 = !{i32 7, !"PIC Level", i32 2}
!11 = !{!"clang"}
!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)
!13 = !DISubroutineType(types: !14)
!14 = !{!6, !6}
!15 = !{!16}
!16 = !DILocalVariable(name: "myVar", scope: !18, file: !1, line: 7, type: !6)
!17 = !DILocation(line: 10, scope: !18)
!18 = distinct !DILexicalBlock(scope: !12, file: !1, line: 1, column: 1)
!19 = distinct !DILexicalBlock(scope: !12, file: !1, line: 1, column: 1)
!20 = !DILocation(line: 10, scope: !19)
!112 = distinct !DISubprogram(name: "test2", linkageName: "102", scope: !1, file: !1, line: 6, type: !13, scopeLine: 6, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !115)
!115 = !{!116}
!116 = !DILocalVariable(name: "myVar", scope: !118, file: !1, line: 7, type: !6)
!117 = !DILocation(line: 10, scope: !118)
!118 = distinct !DILexicalBlock(scope: !112, file: !1, line: 1, column: 1)
!119 = distinct !DILexicalBlock(scope: !112, file: !1, line: 1, column: 1)
!120 = !DILocation(line: 10, scope: !119)
...
---
name: _Z8bb_to_bb
debugInstrRef: true
debugValueSubstitutions:
- { srcinst: 4, srcop: 0, dstinst: 3, dstop: 0, subreg: 0 }
body: |
bb.0.entry:
successors: %bb.1, %bb.5, %bb.6
$rax = MOV64ri 1, debug-instr-number 1, debug-location !17
JCC_1 %bb.5, 1, implicit $eflags
JCC_1 %bb.6, 2, implicit $eflags
JMP_1 %bb.1
bb.1:
successors: %bb.2, %bb.3
DBG_VALUE $rax, $noreg, !16, !DIExpression(), debug-location !17
JCC_1 %bb.3, 1, implicit $eflags, debug-location !17
bb.2:
successors: %bb.4
JMP_1 %bb.4, debug-location !20
bb.3:
successors: %bb.4
JMP_1 %bb.4, debug-location !17
bb.4:
successors: %bb.5, %bb.6
JCC_1 %bb.5, 1, implicit $eflags, debug-location !17
JMP_1 %bb.6, debug-location !17
bb.5:
RET 0, debug-location !17
bb.6:
RET 0, debug-location !17
...
---
name: test2
debugValueSubstitutions:
- { srcinst: 4, srcop: 0, dstinst: 3, dstop: 0, subreg: 0 }
body: |
bb.0.entry:
successors: %bb.1, %bb.5, %bb.6
$rax = MOV64ri 1, debug-instr-number 1, debug-location !117
JCC_1 %bb.5, 1, implicit $eflags
JCC_1 %bb.6, 2, implicit $eflags
JMP_1 %bb.1
bb.1:
successors: %bb.2, %bb.3
DBG_VALUE $noreg, $noreg, !116, !DIExpression(), debug-location !117
JCC_1 %bb.3, 1, implicit $eflags, debug-location !117
bb.2:
successors: %bb.4
JMP_1 %bb.4, debug-location !120
bb.3:
successors: %bb.4
JMP_1 %bb.4, debug-location !117
bb.4:
successors: %bb.5, %bb.6
JCC_1 %bb.5, 1, implicit $eflags, debug-location !117
JMP_1 %bb.6, debug-location !117
bb.5:
RET 0, debug-location !117
bb.6:
RET 0, debug-location !117
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