| --- | |
| ; RUN: llc %s -march=x86-64 -run-pass=livedebugvalues -o - -experimental-debug-variable-locations | FileCheck %s -implicit-check-not=DBG_VALUE |
| |
| ; The MIR below represents a pathalogical case for value-tracking |
| ; LiveDebugValues. The code structure is eight nested loops, with loop heads |
| ; from bb.1 to bb.8, a central block bb.9 that does nothing, and loop ends |
| ; from bb.10 to bb.17. The CMP's and jumps might be broken; the only |
| ; important part is that it looks like nested loops to LiveDebugValues. |
| ; |
| ; The variable location is always $rsi, which enters the function live. |
| ; There's also a def of $rsi in bb.14, in a loop tail, half way into the |
| ; loop nest.s. |
| ; |
| ; This presents a serious problem: the outer four loops each implicitly have |
| ; a PHI value for $rsi, because the block could be entered on a path straight |
| ; from entry, or from bb.14 where $rsi is def'd. While the innermost four |
| ; loops have a value of $rsi that is live-through each loop from bb.5 |
| ; onwards. |
| ; |
| ; Value-tracking LiveDebugValues _must_ correctly identify each PHI value. |
| ; Observe the DBG_VALUE in bb.2: this variable location musn't be propagated |
| ; any further, because there's a path to either successor that goes through |
| ; bb.14 where the value is overwritten.Value tracking needs to identify the |
| ; PHI value on entry to the block; and that each successor has a different |
| ; PHI value in that register. |
| ; |
| ; Likewise, we mustn't identify values as PHIs which aren't. Entering bb.5 |
| ; has a PHI value (from bb.4) in $rsi. There are no paths to bb.5 that pass |
| ; through the clobbering bb.14, which don't also pass through bb.4: thus |
| ; that value is live-through the innermost four loops. If we |
| ; over-approximated where PHIs happened, we would lose variable location |
| ; coverage here, by not propagating the variable location through the inner |
| ; loops. |
| ; |
| ; Getting this right requires the lattice descent (described in the |
| ; implementation) to search loop head PHI values, until one is found that is |
| ; live-through a loop. |
| |
| ; This location in bb.2 should not be propagated further, |
| ; CHECK-LABEL: bb.2: |
| ; CHECK: DBG_VALUE $rsi, $noreg |
| |
| ; This location should be live through the inner loops, til bb.14 |
| ; CHECK-LABEL: bb.5: |
| ; CHECK: DBG_VALUE $rsi, $noreg |
| ; CHECK-LABEL: bb.6: |
| ; CHECK: DBG_VALUE $rsi, $noreg |
| ; CHECK-LABEL: bb.7: |
| ; CHECK: DBG_VALUE $rsi, $noreg |
| ; CHECK-LABEL: bb.8: |
| ; CHECK: DBG_VALUE $rsi, $noreg |
| ; CHECK-LABEL: bb.9: |
| ; CHECK: DBG_VALUE $rsi, $noreg |
| ; CHECK-LABEL: bb.10: |
| ; CHECK: DBG_VALUE $rsi, $noreg |
| ; CHECK-LABEL: bb.11: |
| ; CHECK: DBG_VALUE $rsi, $noreg |
| ; CHECK-LABEL: bb.12: |
| ; CHECK: DBG_VALUE $rsi, $noreg |
| ; CHECK-LABEL: bb.13: |
| ; CHECK: DBG_VALUE $rsi, $noreg |
| |
| declare i64 @bees(i64 %arg); |
| |
| define i32 @chiasm(i64 %arg) local_unnamed_addr !dbg !12 { |
| entry: |
| br label %bb1, !dbg !17 |
| bb1: |
| br label %bb2, !dbg !17 |
| bb2: |
| br label %bb3, !dbg !17 |
| bb3: |
| ret i32 0, !dbg !17 |
| } |
| |
| !llvm.dbg.cu = !{!0} |
| !llvm.module.flags = !{!7, !8, !9, !10} |
| !llvm.ident = !{!11} |
| !0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 10.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, globals: !3, debugInfoForProfiling: true, nameTableKind: None) |
| !1 = !DIFile(filename: "main.cpp", directory: "F:\") |
| !2 = !{} |
| !3 = !{!4} |
| !4 = !DIGlobalVariableExpression(var: !5, expr: !DIExpression()) |
| !5 = distinct !DIGlobalVariable(name: "start", scope: !0, file: !1, line: 4, type: !6, isLocal: false, isDefinition: true) |
| !6 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed) |
| !7 = !{i32 2, !"Dwarf Version", i32 4} |
| !8 = !{i32 2, !"Debug Info Version", i32 3} |
| !9 = !{i32 1, !"wchar_size", i32 2} |
| !10 = !{i32 7, !"PIC Level", i32 2} |
| !11 = !{!"clang version 10.0.0"} |
| !12 = distinct !DISubprogram(name: "bb_to_bb", linkageName: "bb_to_bb", scope: !1, file: !1, line: 6, type: !13, scopeLine: 6, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !15) |
| !13 = !DISubroutineType(types: !14) |
| !14 = !{!6, !6} |
| !15 = !{!16} |
| !16 = !DILocalVariable(name: "myVar", scope: !12, file: !1, line: 7, type: !6) |
| !17 = !DILocation(line: 10, scope: !12) |
| |
| ... |
| --- |
| name: chiasm |
| tracksRegLiveness: true |
| liveins: |
| - { reg: '$rdi', virtual-reg: '' } |
| stack: |
| - { id: 0, name: '', type: spill-slot, offset: -8, size: 8, alignment: 8, |
| stack-id: default, callee-saved-register: '', callee-saved-restored: true, |
| debug-info-variable: '', debug-info-expression: '', debug-info-location: '' } |
| body: | |
| bb.0.entry: |
| liveins: $rdi, $rsi |
| |
| bb.1: |
| liveins: $rsi, $rdi |
| CMP64ri8 renamable $rdi, 1, implicit-def $eflags, debug-location !17 |
| JCC_1 %bb.17, 4, implicit $eflags, debug-location !17 |
| |
| bb.2: |
| liveins: $rsi, $rdi |
| DBG_VALUE $rsi, $noreg, !16, !DIExpression(), debug-location !17 |
| CMP64ri8 renamable $rdi, 2, implicit-def $eflags, debug-location !17 |
| JCC_1 %bb.16, 4, implicit $eflags, debug-location !17 |
| |
| bb.3: |
| liveins: $rsi, $rdi |
| CMP64ri8 renamable $rdi, 3, implicit-def $eflags, debug-location !17 |
| JCC_1 %bb.15, 4, implicit $eflags, debug-location !17 |
| |
| bb.4: |
| liveins: $rsi, $rdi |
| CMP64ri8 renamable $rdi, 4, implicit-def $eflags, debug-location !17 |
| JCC_1 %bb.14, 4, implicit $eflags, debug-location !17 |
| |
| bb.5: |
| liveins: $rsi, $rdi |
| DBG_VALUE $rsi, $noreg, !16, !DIExpression(), debug-location !17 |
| CMP64ri8 renamable $rdi, 4, implicit-def $eflags, debug-location !17 |
| JCC_1 %bb.13, 4, implicit $eflags, debug-location !17 |
| |
| bb.6: |
| liveins: $rsi, $rdi |
| CMP64ri8 renamable $rdi, 4, implicit-def $eflags, debug-location !17 |
| JCC_1 %bb.12, 4, implicit $eflags, debug-location !17 |
| |
| bb.7: |
| liveins: $rsi, $rdi |
| CMP64ri8 renamable $rdi, 4, implicit-def $eflags, debug-location !17 |
| JCC_1 %bb.11, 4, implicit $eflags, debug-location !17 |
| |
| bb.8: |
| liveins: $rsi, $rdi |
| CMP64ri8 renamable $rdi, 4, implicit-def $eflags, debug-location !17 |
| JCC_1 %bb.10, 4, implicit $eflags, debug-location !17 |
| |
| bb.9: |
| liveins: $rsi, $rdi, $eflags |
| ;$rsi = MOV64ri 0, debug-location !17 |
| ;JMP_1 %bb.1, debug-location !17 |
| |
| bb.10: |
| liveins: $rsi, $rdi, $eflags |
| JCC_1 %bb.8, 4, implicit $eflags, debug-location !17 |
| |
| bb.11: |
| liveins: $rsi, $rdi, $eflags |
| JCC_1 %bb.7, 4, implicit $eflags, debug-location !17 |
| |
| bb.12: |
| liveins: $rsi, $rdi, $eflags |
| JCC_1 %bb.6, 4, implicit $eflags, debug-location !17 |
| |
| bb.13: |
| liveins: $rsi, $rdi, $eflags |
| JCC_1 %bb.5, 4, implicit $eflags, debug-location !17 |
| |
| bb.14: |
| liveins: $rsi, $rdi, $eflags |
| $rsi = MOV64ri 0, debug-location !17 |
| JCC_1 %bb.4, 4, implicit $eflags, debug-location !17 |
| |
| bb.15: |
| liveins: $rsi, $rdi, $eflags |
| JCC_1 %bb.3, 4, implicit $eflags, debug-location !17 |
| |
| bb.16: |
| liveins: $rsi, $rdi, $eflags |
| JCC_1 %bb.2, 4, implicit $eflags, debug-location !17 |
| |
| bb.17: |
| liveins: $rsi, $rdi, $eflags |
| JCC_1 %bb.1, 4, implicit $eflags, debug-location !17 |
| |
| bb.18: |
| liveins: $rsi, $rdi, $eflags |
| RETQ |
| |
| ... |
