1# RUN: llc %s -mtriple=x86_64 -run-pass=livedebugvalues -o - \ 2# RUN: -experimental-debug-variable-locations=true \ 3# RUN: | FileCheck %s -implicit-check-not=DBG_VALUE \ 4# RUN: --check-prefixes=CHECK,COMMON 5# 6# This test is designed to stimulate a simplification of variable-value 7# propagation in InstrRefBasedLDV. When we only have a single assignment of 8# a variable, we don't have to completely enumerate all the PHIs the variable 9# has and then value propagate through them: the variable value is available 10# only in those blocks dominated by the assignment. Example in this test: 11# 12# entry 13# / | \ 14# / v \ 15# / bb1 \ <--- Single variable assignment happens here 16# / / \ \ 17# / v v \ 18# | bb2 bb3 | 19# | \ / | 20# | v v | 21# | bb4 | 22# \ / \ / 23# v v v v 24# bb5 bb6 <--- Dominance frontier is here 25# 26# The general InstrRefBasedLDV algorithm takes this CFG, places PHIs at bb5 and 27# bb6, then value-propagates until it's determined that they can't be 28# eliminated. Then, we determine that there's no machine location for such PHIs, 29# and no variable location is emitted. 30# 31# The fast way of doing this: observe that the variable value can never extend 32# past the dominance frontier of the block where the assignment happens. So 33# just propagate the variable value into the dominated blocks, and avoid the 34# general algorithm. 35# 36# Doing so introduces a functional change: VarLocBasedLDV won't propagate 37# variable locations through out-of-scope blocks, and InstrRefBasedLDV tries to 38# replicate VarLocBasedLDV most of the time. In the MIR below, bb2 is out of 39# scope. This effectively becomes another variable assignment (of undef), which 40# requires full SSA and value propagation to emulate what VarLocBasedLDV did. 41# Applying this speed optimisation makes us diverge from what VarLocBasedLDV 42# does by not treating the out-of-scope block as an effective undef assignment, 43# hence this test. 44# 45# CHECK-LABEL: bb.1: 46# CHECK: DBG_VALUE 47# CHECK-LABEL: bb.2: 48## No location here because it's out-of-scope. 49# CHECK-LABEL: bb.3: 50# CHECK: DBG_VALUE 51# CHECK-LABEL: bb.4: 52# CHECK: DBG_VALUE 53# 54## VarLocBasedLDV will take the DBG_VALUE in the assignment block, propagate 55## to bb.3, but not into bb.4 because of the intervening out-of-scope block. 56## Disabled actual testing of this because it's just for comparison purposes. 57# 58# varloc-label: bb.1: 59# varloc: DBG_VALUE 60# varloc-label: bb.2: 61## No location here because it's out-of-scope. 62# varloc-label: bb.3: 63# varloc: DBG_VALUE 64# 65## Common tail for 'test2' -- this is checking that the assignment of undef or 66## $noreg in single-assignment mode doesn't lead to trouble further down the 67## line, specifically assertion failures. 68# 69# COMMON-LABEL: name: test2 70# COMMON: DBG_VALUE $noreg 71--- | 72 define i32 @_Z8bb_to_bb() local_unnamed_addr !dbg !12 { 73 entry: 74 ret i32 0, !dbg !17 75 } 76 77 define i32 @test2() local_unnamed_addr !dbg !112 { 78 entry: 79 ret i32 0, !dbg !117 80 } 81 82 !llvm.dbg.cu = !{!0} 83 !llvm.module.flags = !{!7, !8, !9, !10} 84 !llvm.ident = !{!11} 85 86 !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) 87 !1 = !DIFile(filename: "main.cpp", directory: "F:\") 88 !2 = !{} 89 !3 = !{!4} 90 !4 = !DIGlobalVariableExpression(var: !5, expr: !DIExpression()) 91 !5 = distinct !DIGlobalVariable(name: "start", scope: !0, file: !1, line: 4, type: !6, isLocal: false, isDefinition: true) 92 !6 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed) 93 !7 = !{i32 2, !"Dwarf Version", i32 4} 94 !8 = !{i32 2, !"Debug Info Version", i32 3} 95 !9 = !{i32 1, !"wchar_size", i32 2} 96 !10 = !{i32 7, !"PIC Level", i32 2} 97 !11 = !{!"clang"} 98 !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) 99 !13 = !DISubroutineType(types: !14) 100 !14 = !{!6, !6} 101 !15 = !{!16} 102 !16 = !DILocalVariable(name: "myVar", scope: !18, file: !1, line: 7, type: !6) 103 !17 = !DILocation(line: 10, scope: !18) 104 !18 = distinct !DILexicalBlock(scope: !12, file: !1, line: 1, column: 1) 105 !19 = distinct !DILexicalBlock(scope: !12, file: !1, line: 1, column: 1) 106 !20 = !DILocation(line: 10, scope: !19) 107 !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) 108 !115 = !{!116} 109 !116 = !DILocalVariable(name: "myVar", scope: !118, file: !1, line: 7, type: !6) 110 !117 = !DILocation(line: 10, scope: !118) 111 !118 = distinct !DILexicalBlock(scope: !112, file: !1, line: 1, column: 1) 112 !119 = distinct !DILexicalBlock(scope: !112, file: !1, line: 1, column: 1) 113 !120 = !DILocation(line: 10, scope: !119) 114 115... 116--- 117name: _Z8bb_to_bb 118debugInstrRef: true 119debugValueSubstitutions: 120 - { srcinst: 4, srcop: 0, dstinst: 3, dstop: 0, subreg: 0 } 121body: | 122 bb.0.entry: 123 successors: %bb.1, %bb.5, %bb.6 124 125 $rax = MOV64ri 1, debug-instr-number 1, debug-location !17 126 JCC_1 %bb.5, 1, implicit $eflags 127 JCC_1 %bb.6, 2, implicit $eflags 128 JMP_1 %bb.1 129 130 bb.1: 131 successors: %bb.2, %bb.3 132 133 DBG_VALUE $rax, $noreg, !16, !DIExpression(), debug-location !17 134 JCC_1 %bb.3, 1, implicit $eflags, debug-location !17 135 136 bb.2: 137 successors: %bb.4 138 139 JMP_1 %bb.4, debug-location !20 140 141 bb.3: 142 successors: %bb.4 143 144 JMP_1 %bb.4, debug-location !17 145 146 bb.4: 147 successors: %bb.5, %bb.6 148 149 JCC_1 %bb.5, 1, implicit $eflags, debug-location !17 150 JMP_1 %bb.6, debug-location !17 151 152 bb.5: 153 RET 0, debug-location !17 154 155 bb.6: 156 RET 0, debug-location !17 157... 158--- 159name: test2 160debugValueSubstitutions: 161 - { srcinst: 4, srcop: 0, dstinst: 3, dstop: 0, subreg: 0 } 162body: | 163 bb.0.entry: 164 successors: %bb.1, %bb.5, %bb.6 165 166 $rax = MOV64ri 1, debug-instr-number 1, debug-location !117 167 JCC_1 %bb.5, 1, implicit $eflags 168 JCC_1 %bb.6, 2, implicit $eflags 169 JMP_1 %bb.1 170 171 bb.1: 172 successors: %bb.2, %bb.3 173 174 DBG_VALUE $noreg, $noreg, !116, !DIExpression(), debug-location !117 175 JCC_1 %bb.3, 1, implicit $eflags, debug-location !117 176 177 bb.2: 178 successors: %bb.4 179 180 JMP_1 %bb.4, debug-location !120 181 182 bb.3: 183 successors: %bb.4 184 185 JMP_1 %bb.4, debug-location !117 186 187 bb.4: 188 successors: %bb.5, %bb.6 189 190 JCC_1 %bb.5, 1, implicit $eflags, debug-location !117 191 JMP_1 %bb.6, debug-location !117 192 193 bb.5: 194 RET 0, debug-location !117 195 196 bb.6: 197 RET 0, debug-location !117 198