1--- | 2 ; RUN: llc %s -march=x86-64 -run-pass=livedebugvalues -o - -experimental-debug-variable-locations | FileCheck %s -implicit-check-not=DBG_VALUE 3 4 ; The MIR below represents a pathalogical case for value-tracking 5 ; LiveDebugValues. The code structure is eight nested loops, with loop heads 6 ; from bb.1 to bb.8, a central block bb.9 that does nothing, and loop ends 7 ; from bb.10 to bb.17. The CMP's and jumps might be broken; the only 8 ; important part is that it looks like nested loops to LiveDebugValues. 9 ; 10 ; The variable location is always $rsi, which enters the function live. 11 ; There's also a def of $rsi in bb.14, in a loop tail, half way into the 12 ; loop nest.s. 13 ; 14 ; This presents a serious problem: the outer four loops each implicitly have 15 ; a PHI value for $rsi, because the block could be entered on a path straight 16 ; from entry, or from bb.14 where $rsi is def'd. While the innermost four 17 ; loops have a value of $rsi that is live-through each loop from bb.5 18 ; onwards. 19 ; 20 ; Value-tracking LiveDebugValues _must_ correctly identify each PHI value. 21 ; Observe the DBG_VALUE in bb.2: this variable location musn't be propagated 22 ; any further, because there's a path to either successor that goes through 23 ; bb.14 where the value is overwritten.Value tracking needs to identify the 24 ; PHI value on entry to the block; and that each successor has a different 25 ; PHI value in that register. 26 ; 27 ; Likewise, we mustn't identify values as PHIs which aren't. Entering bb.5 28 ; has a PHI value (from bb.4) in $rsi. There are no paths to bb.5 that pass 29 ; through the clobbering bb.14, which don't also pass through bb.4: thus 30 ; that value is live-through the innermost four loops. If we 31 ; over-approximated where PHIs happened, we would lose variable location 32 ; coverage here, by not propagating the variable location through the inner 33 ; loops. 34 ; 35 ; Getting this right requires the lattice descent (described in the 36 ; implementation) to search loop head PHI values, until one is found that is 37 ; live-through a loop. 38 39 ; This location in bb.2 should not be propagated further, 40 ; CHECK-LABEL: bb.2: 41 ; CHECK: DBG_VALUE $rsi, $noreg 42 43 ; This location should be live through the inner loops, til bb.14 44 ; CHECK-LABEL: bb.5: 45 ; CHECK: DBG_VALUE $rsi, $noreg 46 ; CHECK-LABEL: bb.6: 47 ; CHECK: DBG_VALUE $rsi, $noreg 48 ; CHECK-LABEL: bb.7: 49 ; CHECK: DBG_VALUE $rsi, $noreg 50 ; CHECK-LABEL: bb.8: 51 ; CHECK: DBG_VALUE $rsi, $noreg 52 ; CHECK-LABEL: bb.9: 53 ; CHECK: DBG_VALUE $rsi, $noreg 54 ; CHECK-LABEL: bb.10: 55 ; CHECK: DBG_VALUE $rsi, $noreg 56 ; CHECK-LABEL: bb.11: 57 ; CHECK: DBG_VALUE $rsi, $noreg 58 ; CHECK-LABEL: bb.12: 59 ; CHECK: DBG_VALUE $rsi, $noreg 60 ; CHECK-LABEL: bb.13: 61 ; CHECK: DBG_VALUE $rsi, $noreg 62 63 declare i64 @bees(i64 %arg); 64 65 define i32 @chiasm(i64 %arg) local_unnamed_addr !dbg !12 { 66 entry: 67 br label %bb1, !dbg !17 68 bb1: 69 br label %bb2, !dbg !17 70 bb2: 71 br label %bb3, !dbg !17 72 bb3: 73 ret i32 0, !dbg !17 74 } 75 76 !llvm.dbg.cu = !{!0} 77 !llvm.module.flags = !{!7, !8, !9, !10} 78 !llvm.ident = !{!11} 79 !0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 10.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, globals: !3, debugInfoForProfiling: true, nameTableKind: None) 80 !1 = !DIFile(filename: "main.cpp", directory: "F:\") 81 !2 = !{} 82 !3 = !{!4} 83 !4 = !DIGlobalVariableExpression(var: !5, expr: !DIExpression()) 84 !5 = distinct !DIGlobalVariable(name: "start", scope: !0, file: !1, line: 4, type: !6, isLocal: false, isDefinition: true) 85 !6 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed) 86 !7 = !{i32 2, !"Dwarf Version", i32 4} 87 !8 = !{i32 2, !"Debug Info Version", i32 3} 88 !9 = !{i32 1, !"wchar_size", i32 2} 89 !10 = !{i32 7, !"PIC Level", i32 2} 90 !11 = !{!"clang version 10.0.0"} 91 !12 = distinct !DISubprogram(name: "bb_to_bb", linkageName: "bb_to_bb", scope: !1, file: !1, line: 6, type: !13, scopeLine: 6, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !15) 92 !13 = !DISubroutineType(types: !14) 93 !14 = !{!6, !6} 94 !15 = !{!16} 95 !16 = !DILocalVariable(name: "myVar", scope: !12, file: !1, line: 7, type: !6) 96 !17 = !DILocation(line: 10, scope: !12) 97 98... 99--- 100name: chiasm 101tracksRegLiveness: true 102liveins: 103 - { reg: '$rdi', virtual-reg: '' } 104stack: 105 - { id: 0, name: '', type: spill-slot, offset: -8, size: 8, alignment: 8, 106 stack-id: default, callee-saved-register: '', callee-saved-restored: true, 107 debug-info-variable: '', debug-info-expression: '', debug-info-location: '' } 108body: | 109 bb.0.entry: 110 liveins: $rdi, $rsi 111 112 bb.1: 113 liveins: $rsi, $rdi 114 CMP64ri8 renamable $rdi, 1, implicit-def $eflags, debug-location !17 115 JCC_1 %bb.17, 4, implicit $eflags, debug-location !17 116 117 bb.2: 118 liveins: $rsi, $rdi 119 DBG_VALUE $rsi, $noreg, !16, !DIExpression(), debug-location !17 120 CMP64ri8 renamable $rdi, 2, implicit-def $eflags, debug-location !17 121 JCC_1 %bb.16, 4, implicit $eflags, debug-location !17 122 123 bb.3: 124 liveins: $rsi, $rdi 125 CMP64ri8 renamable $rdi, 3, implicit-def $eflags, debug-location !17 126 JCC_1 %bb.15, 4, implicit $eflags, debug-location !17 127 128 bb.4: 129 liveins: $rsi, $rdi 130 CMP64ri8 renamable $rdi, 4, implicit-def $eflags, debug-location !17 131 JCC_1 %bb.14, 4, implicit $eflags, debug-location !17 132 133 bb.5: 134 liveins: $rsi, $rdi 135 DBG_VALUE $rsi, $noreg, !16, !DIExpression(), debug-location !17 136 CMP64ri8 renamable $rdi, 4, implicit-def $eflags, debug-location !17 137 JCC_1 %bb.13, 4, implicit $eflags, debug-location !17 138 139 bb.6: 140 liveins: $rsi, $rdi 141 CMP64ri8 renamable $rdi, 4, implicit-def $eflags, debug-location !17 142 JCC_1 %bb.12, 4, implicit $eflags, debug-location !17 143 144 bb.7: 145 liveins: $rsi, $rdi 146 CMP64ri8 renamable $rdi, 4, implicit-def $eflags, debug-location !17 147 JCC_1 %bb.11, 4, implicit $eflags, debug-location !17 148 149 bb.8: 150 liveins: $rsi, $rdi 151 CMP64ri8 renamable $rdi, 4, implicit-def $eflags, debug-location !17 152 JCC_1 %bb.10, 4, implicit $eflags, debug-location !17 153 154 bb.9: 155 liveins: $rsi, $rdi, $eflags 156 ;$rsi = MOV64ri 0, debug-location !17 157 ;JMP_1 %bb.1, debug-location !17 158 159 bb.10: 160 liveins: $rsi, $rdi, $eflags 161 JCC_1 %bb.8, 4, implicit $eflags, debug-location !17 162 163 bb.11: 164 liveins: $rsi, $rdi, $eflags 165 JCC_1 %bb.7, 4, implicit $eflags, debug-location !17 166 167 bb.12: 168 liveins: $rsi, $rdi, $eflags 169 JCC_1 %bb.6, 4, implicit $eflags, debug-location !17 170 171 bb.13: 172 liveins: $rsi, $rdi, $eflags 173 JCC_1 %bb.5, 4, implicit $eflags, debug-location !17 174 175 bb.14: 176 liveins: $rsi, $rdi, $eflags 177 $rsi = MOV64ri 0, debug-location !17 178 JCC_1 %bb.4, 4, implicit $eflags, debug-location !17 179 180 bb.15: 181 liveins: $rsi, $rdi, $eflags 182 JCC_1 %bb.3, 4, implicit $eflags, debug-location !17 183 184 bb.16: 185 liveins: $rsi, $rdi, $eflags 186 JCC_1 %bb.2, 4, implicit $eflags, debug-location !17 187 188 bb.17: 189 liveins: $rsi, $rdi, $eflags 190 JCC_1 %bb.1, 4, implicit $eflags, debug-location !17 191 192 bb.18: 193 liveins: $rsi, $rdi, $eflags 194 RETQ 195 196... 197