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d4879d7690
MemLocFragmentFill uses an IntervalMap to track which bits of each variable are stack-homed. Intervals with the same value (same stack location base address) are automatically coalesced by the map. This patch changes the analysis to take advantage of that and insert a new dbg loc after each def if any coalescing took place. This results in some additional redundant defs (we insert a def, then another that by definition shadows the previous one if any coalescing took place) but they're all cleaned up thanks to the previous patch in this stack. This reduces the total number of fragments created by AssignmentTrackingAnalysis which reduces compile time because LiveDebugValues computes SSA for every fragment it encounters. There's a geomean reduction in instructions retired in a CTMark LTO-O3-g build of 0.3% with these two patches. One small caveat is that this technique can produce partially overlapping fragments (e.g. slice [0, 32) and slice [16, 64)), which we know LiveDebugVariables doesn't really handle correctly. Used in combination with instruction-referencing this isn't a problem, since LiveDebugVariables is effectively side-stepped in instruction-referencing mode. Given this, the coalescing is only enabled when instruction-referencing is enabled (but the behaviour can be overriden using -debug-ata-coalesce-frags=<bool>). Reviewed By: jmorse Differential Revision: https://reviews.llvm.org/D146980
149 lines
7.5 KiB
LLVM
149 lines
7.5 KiB
LLVM
; RUN: llc %s -stop-before finalize-isel -o - \
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; RUN: -experimental-debug-variable-locations=false \
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; RUN: -debug-ata-coalesce-frags=true \
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; RUN: | FileCheck %s --implicit-check-not=DBG_
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; RUN: llc %s -stop-before finalize-isel -o - \
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; RUN: -experimental-debug-variable-locations=true \
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; RUN: | FileCheck %s --implicit-check-not=DBG_
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;; Check that the mem-loc-frag-fill pseudo-pass works on a simple CFG. When
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;; LLVM sees a dbg.value with an overlapping fragment it essentially considers
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;; the previous location as valid for all bits in that fragment. The pass
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;; tracks which bits are in memory and inserts dbg.values preserve memory
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;; locations for bits in memory when overlapping fragments are encountered.
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;; nums lives in mem, except prior to the second call to step() where there has
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;; been some DSE. At this point, the memory loc for nums.c is invalid. But the
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;; rest of num's bits, [0, 64), are in memory, so check there's a dbg.value for
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;; them.
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;; $ cat test.cpp
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;; struct Nums { int a, b, c; };
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;;
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;; void esc1(struct Nums*);
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;; void esc2(struct Nums*);
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;; bool step();
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;;
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;; int main() {
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;; struct Nums nums = { 1, 2, 1 };
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;; if (step())
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;; esc1(&nums);
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;; else
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;; esc2(&nums);
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;;
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;; nums.c = 2; //< Include some DSE to force a non-mem location.
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;; step();
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;;
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;; nums.c = nums.a;
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;;
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;; esc1(&nums);
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;; return 0;
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;; }
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;;
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;; $ clang++ test.cpp -O2 -g -Xclang -fexperimental-assignment-tracking -emit-llvm -S -o -
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;; Most check lines are inline in main.
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; CHECK: ![[nums:[0-9]+]] = !DILocalVariable(name: "nums",
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target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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%struct.Nums = type { i32, i32, i32 }
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@__const.main.nums = private unnamed_addr constant %struct.Nums { i32 1, i32 2, i32 1 }, align 4
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declare void @_Z4esc1P4Nums(ptr nocapture noundef readonly %p)
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declare void @_Z4esc2P4Nums(ptr nocapture noundef readonly %p)
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; Function Attrs: mustprogress norecurse uwtable
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define dso_local noundef i32 @main() local_unnamed_addr #3 !dbg !40 {
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; CHECK: name: main
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entry:
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%nums = alloca %struct.Nums, align 4, !DIAssignID !45
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call void @llvm.dbg.assign(metadata i1 undef, metadata !44, metadata !DIExpression(), metadata !45, metadata ptr %nums, metadata !DIExpression()), !dbg !46
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; CHECK: DBG_VALUE %stack.0.nums, $noreg, ![[nums]], !DIExpression(DW_OP_deref)
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call void @llvm.memcpy.p0i8.p0i8.i64(ptr noundef nonnull align 4 dereferenceable(12) %nums, ptr noundef nonnull align 4 dereferenceable(12) %nums, i64 12, i1 false), !dbg !48, !DIAssignID !49
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call void @llvm.dbg.assign(metadata i1 undef, metadata !44, metadata !DIExpression(), metadata !49, metadata ptr %nums, metadata !DIExpression()), !dbg !46
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%call = tail call noundef zeroext i1 @_Z4stepv(), !dbg !50
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br i1 %call, label %if.then, label %if.else, !dbg !52
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if.then: ; preds = %entry
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call void @_Z4esc1P4Nums(ptr noundef nonnull %nums), !dbg !53
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br label %if.end, !dbg !53
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if.else: ; preds = %entry
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call void @_Z4esc2P4Nums(ptr noundef nonnull %nums), !dbg !54
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br label %if.end
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if.end: ; preds = %if.else, %if.then
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; CHECK: bb.3.if.end:
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; CHECK-NEXT: DBG_VALUE 2, $noreg, ![[nums]], !DIExpression(DW_OP_LLVM_fragment, 64, 32), debug-location
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; CHECK-NEXT: DBG_VALUE %stack.0.nums, $noreg, ![[nums]], !DIExpression(DW_OP_deref, DW_OP_LLVM_fragment, 0, 64)
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%c = getelementptr inbounds %struct.Nums, ptr %nums, i64 0, i32 2, !dbg !55
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call void @llvm.dbg.assign(metadata i32 2, metadata !44, metadata !DIExpression(DW_OP_LLVM_fragment, 64, 32), metadata !56, metadata ptr %c, metadata !DIExpression()), !dbg !46
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%call1 = tail call noundef zeroext i1 @_Z4stepv(), !dbg !57
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store i32 1, ptr %c, align 4, !dbg !58, !DIAssignID !61
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;; Store to bits 64 to 96 - the whole variable is in memory again.
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; CHECK: MOV32mi %stack.0.nums, 1, $noreg, 8, $noreg, 1
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; CHECK-NEXT: DBG_VALUE %stack.0.nums, $noreg, ![[nums]], !DIExpression(DW_OP_deref)
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call void @llvm.dbg.assign(metadata i32 1, metadata !44, metadata !DIExpression(DW_OP_LLVM_fragment, 64, 32), metadata !61, metadata ptr %c, metadata !DIExpression()), !dbg !46
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call void @_Z4esc1P4Nums(ptr noundef nonnull %nums), !dbg !62
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ret i32 0, !dbg !64
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}
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declare void @llvm.lifetime.start.p0i8(i64 immarg, ptr nocapture) #4
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declare !dbg !65 dso_local noundef zeroext i1 @_Z4stepv() local_unnamed_addr #5
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declare void @llvm.lifetime.end.p0i8(i64 immarg, ptr nocapture) #4
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declare void @llvm.memcpy.p0i8.p0i8.i64(ptr noalias nocapture writeonly, ptr noalias nocapture readonly, i64, i1 immarg) #1
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declare void @llvm.dbg.assign(metadata, metadata, metadata, metadata, metadata, metadata) #2
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!llvm.dbg.cu = !{!2}
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!llvm.module.flags = !{!11, !12, !13, !14, !1000}
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!llvm.ident = !{!15}
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!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
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!1 = distinct !DIGlobalVariable(name: "glob", scope: !2, file: !3, line: 2, type: !5, isLocal: false, isDefinition: true)
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!2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !3, producer: "clang version 14.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, globals: !4, splitDebugInlining: false, nameTableKind: None)
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!3 = !DIFile(filename: "test.cpp", directory: "/")
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!4 = !{!0}
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!5 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "Nums", file: !3, line: 1, size: 96, flags: DIFlagTypePassByValue, elements: !6, identifier: "_ZTS4Nums")
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!6 = !{!7, !9, !10}
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!7 = !DIDerivedType(tag: DW_TAG_member, name: "a", scope: !5, file: !3, line: 1, baseType: !8, size: 32)
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!8 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
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!9 = !DIDerivedType(tag: DW_TAG_member, name: "b", scope: !5, file: !3, line: 1, baseType: !8, size: 32, offset: 32)
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!10 = !DIDerivedType(tag: DW_TAG_member, name: "c", scope: !5, file: !3, line: 1, baseType: !8, size: 32, offset: 64)
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!11 = !{i32 7, !"Dwarf Version", i32 5}
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!12 = !{i32 2, !"Debug Info Version", i32 3}
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!13 = !{i32 1, !"wchar_size", i32 4}
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!14 = !{i32 7, !"uwtable", i32 1}
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!15 = !{!"clang version 14.0.0"}
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!40 = distinct !DISubprogram(name: "main", scope: !3, file: !3, line: 7, type: !41, scopeLine: 7, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !43)
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!41 = !DISubroutineType(types: !42)
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!42 = !{!8}
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!43 = !{!44}
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!44 = !DILocalVariable(name: "nums", scope: !40, file: !3, line: 8, type: !5)
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!45 = distinct !DIAssignID()
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!46 = !DILocation(line: 0, scope: !40)
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!47 = !DILocation(line: 8, column: 3, scope: !40)
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!48 = !DILocation(line: 8, column: 15, scope: !40)
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!49 = distinct !DIAssignID()
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!50 = !DILocation(line: 9, column: 7, scope: !51)
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!51 = distinct !DILexicalBlock(scope: !40, file: !3, line: 9, column: 7)
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!52 = !DILocation(line: 9, column: 7, scope: !40)
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!53 = !DILocation(line: 10, column: 5, scope: !51)
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!54 = !DILocation(line: 12, column: 5, scope: !51)
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!55 = !DILocation(line: 14, column: 8, scope: !40)
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!56 = distinct !DIAssignID()
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!57 = !DILocation(line: 15, column: 3, scope: !40)
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!58 = !DILocation(line: 17, column: 10, scope: !40)
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!61 = distinct !DIAssignID()
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!62 = !DILocation(line: 19, column: 3, scope: !40)
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!63 = !DILocation(line: 21, column: 1, scope: !40)
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!64 = !DILocation(line: 20, column: 3, scope: !40)
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!65 = !DISubprogram(name: "step", linkageName: "_Z4stepv", scope: !3, file: !3, line: 5, type: !66, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized, retainedNodes: !69)
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!66 = !DISubroutineType(types: !67)
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!67 = !{!68}
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!68 = !DIBasicType(name: "bool", size: 8, encoding: DW_ATE_boolean)
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!69 = !{}
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!1000 = !{i32 7, !"debug-info-assignment-tracking", i1 true}
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