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[CSSPGO] Fix missing debug info of dangling pseudo probe

While doing speculative execution opt, it conservatively drops all insn's debug info in the merged `ThenBB`(see the loop at line 2384) including the dangling probe. The missing debug info of the dangling probe will cause the wrong inference computation.

So we should avoid dropping the debug info from pseudo probe, this change try to fix this by moving the to-be dangling probe to the merging target BB before the debug info is dropped.

Reviewed By: hoy, wenlei

Differential Revision: https://reviews.llvm.org/D101195
This commit is contained in:
wlei 2021-04-23 12:35:12 -07:00
parent d61fdd44b0
commit 1f3e5b2188
2 changed files with 198 additions and 10 deletions

View File

@ -2371,22 +2371,24 @@ bool SimplifyCFGOpt::SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *ThenBB,
SpeculatedStore->getDebugLoc());
}
// Metadata can be dependent on the condition we are hoisting above.
// Conservatively strip all metadata on the instruction. Drop the debug loc
// to avoid making it appear as if the condition is a constant, which would
// be misleading while debugging.
for (auto &I : *ThenBB) {
if (!SpeculatedStoreValue || &I != SpeculatedStore)
I.setDebugLoc(DebugLoc());
I.dropUnknownNonDebugMetadata();
}
// A hoisted conditional probe should be treated as dangling so that it will
// not be over-counted when the samples collected on the non-conditional path
// are counted towards the conditional path. We leave it for the counts
// inference algorithm to figure out a proper count for a danglng probe.
moveAndDanglePseudoProbes(ThenBB, BI);
// Metadata can be dependent on the condition we are hoisting above.
// Conservatively strip all metadata on the instruction. Drop the debug loc
// to avoid making it appear as if the condition is a constant, which would
// be misleading while debugging.
for (auto &I : *ThenBB) {
assert(!isa<PseudoProbeInst>(I) &&
"Should not drop debug info from any pseudo probes.");
if (!SpeculatedStoreValue || &I != SpeculatedStore)
I.setDebugLoc(DebugLoc());
I.dropUnknownNonDebugMetadata();
}
// Hoist the instructions.
BB->getInstList().splice(BI->getIterator(), ThenBB->getInstList(),
ThenBB->begin(), std::prev(ThenBB->end()));

View File

@ -0,0 +1,186 @@
; REQUIRES: x86_64-linux
; RUN: opt < %s -simplifycfg -S -o %t
; RUN: FileCheck %s < %t
; Test to make sure the dangling probe's metadata not being dropped.
; CHECK: define dso_local i32 @foo
; CHECK: call void @llvm.pseudoprobe(i64 -4224472938262609671, i64 5, i32 2, i64 -1), !dbg ![[#]]
; Function Attrs: nounwind uwtable
define dso_local i32 @foo(i32* nocapture %marker, i32* nocapture %move_ordering, i32* nocapture %moves, i32 %num_moves) local_unnamed_addr #0 !dbg !10 {
entry:
call void @llvm.dbg.value(metadata i32* %marker, metadata !19, metadata !DIExpression()), !dbg !28
call void @llvm.dbg.value(metadata i32* %move_ordering, metadata !20, metadata !DIExpression()), !dbg !28
call void @llvm.dbg.value(metadata i32* %moves, metadata !21, metadata !DIExpression()), !dbg !28
call void @llvm.dbg.value(metadata i32 %num_moves, metadata !22, metadata !DIExpression()), !dbg !28
call void @llvm.pseudoprobe(i64 -4224472938262609671, i64 1, i32 0, i64 -1), !dbg !29
call void @llvm.dbg.value(metadata i32 -1000000, metadata !25, metadata !DIExpression()), !dbg !28
%0 = load i32, i32* %marker, align 4, !dbg !30, !tbaa !31
%inc = add nsw i32 %0, 1, !dbg !30
store i32 %inc, i32* %marker, align 4, !dbg !30, !tbaa !31
call void @llvm.dbg.value(metadata i32 %inc, metadata !27, metadata !DIExpression()), !dbg !28
%cmp = icmp slt i32 %0, 9, !dbg !35
br i1 %cmp, label %for.cond, label %if.else, !dbg !37
for.cond: ; preds = %entry, %for.inc
%i.0 = phi i32 [ %inc6, %for.inc ], [ %inc, %entry ], !dbg !38
%best.0 = phi i32 [ %best.1, %for.inc ], [ -1000000, %entry ], !dbg !28
%tmp.0 = phi i32 [ %tmp.1, %for.inc ], [ undef, %entry ]
call void @llvm.pseudoprobe(i64 -4224472938262609671, i64 2, i32 2, i64 -1), !dbg !41
call void @llvm.dbg.value(metadata i32 %tmp.0, metadata !26, metadata !DIExpression()), !dbg !28
call void @llvm.dbg.value(metadata i32 %best.0, metadata !25, metadata !DIExpression()), !dbg !28
call void @llvm.dbg.value(metadata i32 %i.0, metadata !24, metadata !DIExpression()), !dbg !28
call void @llvm.pseudoprobe(i64 -4224472938262609671, i64 3, i32 0, i64 -1), !dbg !42
%cmp1 = icmp slt i32 %i.0, %num_moves, !dbg !44
br i1 %cmp1, label %for.body, label %if.end12, !dbg !45
for.body: ; preds = %for.cond
call void @llvm.pseudoprobe(i64 -4224472938262609671, i64 4, i32 0, i64 -1), !dbg !46
%idxprom = sext i32 %i.0 to i64, !dbg !46
%arrayidx = getelementptr inbounds i32, i32* %move_ordering, i64 %idxprom, !dbg !46
%1 = load i32, i32* %arrayidx, align 4, !dbg !46, !tbaa !31
%cmp2 = icmp sgt i32 %1, %best.0, !dbg !49
br i1 %cmp2, label %if.then3, label %for.inc, !dbg !50
if.then3: ; preds = %for.body
call void @llvm.pseudoprobe(i64 -4224472938262609671, i64 5, i32 0, i64 -1), !dbg !51
call void @llvm.dbg.value(metadata i32 %1, metadata !25, metadata !DIExpression()), !dbg !28
call void @llvm.dbg.value(metadata i32 %i.0, metadata !26, metadata !DIExpression()), !dbg !28
br label %for.inc, !dbg !53
for.inc: ; preds = %for.body, %if.then3
%best.1 = phi i32 [ %1, %if.then3 ], [ %best.0, %for.body ], !dbg !28
%tmp.1 = phi i32 [ %i.0, %if.then3 ], [ %tmp.0, %for.body ]
call void @llvm.dbg.value(metadata i32 %tmp.1, metadata !26, metadata !DIExpression()), !dbg !28
call void @llvm.dbg.value(metadata i32 %best.1, metadata !25, metadata !DIExpression()), !dbg !28
call void @llvm.pseudoprobe(i64 -4224472938262609671, i64 6, i32 0, i64 -1), !dbg !54
call void @llvm.pseudoprobe(i64 -4224472938262609671, i64 7, i32 0, i64 -1), !dbg !55
%inc6 = add nsw i32 %i.0, 1, !dbg !55
call void @llvm.dbg.value(metadata i32 %inc6, metadata !24, metadata !DIExpression()), !dbg !28
br label %for.cond, !dbg !56, !llvm.loop !57
if.else: ; preds = %entry
call void @llvm.pseudoprobe(i64 -4224472938262609671, i64 9, i32 0, i64 -1), !dbg !59
%cmp7 = icmp slt i32 %inc, %num_moves, !dbg !61
br i1 %cmp7, label %cleanup, label %if.end12, !dbg !62
if.end12: ; preds = %if.else, %for.cond
%best.2 = phi i32 [ %best.0, %for.cond ], [ -1000000, %if.else ], !dbg !63
%tmp.2 = phi i32 [ %tmp.0, %for.cond ], [ undef, %if.else ]
call void @llvm.dbg.value(metadata i32 %tmp.2, metadata !26, metadata !DIExpression()), !dbg !28
call void @llvm.dbg.value(metadata i32 %best.2, metadata !25, metadata !DIExpression()), !dbg !28
call void @llvm.pseudoprobe(i64 -4224472938262609671, i64 11, i32 2, i64 -1), !dbg !28
call void @llvm.pseudoprobe(i64 -4224472938262609671, i64 8, i32 2, i64 -1), !dbg !64
call void @llvm.pseudoprobe(i64 -4224472938262609671, i64 12, i32 0, i64 -1), !dbg !65
%cmp13 = icmp sgt i32 %best.2, -1000000, !dbg !67
br i1 %cmp13, label %if.then14, label %cleanup, !dbg !68
if.then14: ; preds = %if.end12
call void @llvm.pseudoprobe(i64 -4224472938262609671, i64 13, i32 0, i64 -1), !dbg !69
br label %cleanup, !dbg !78
cleanup: ; preds = %if.end12, %if.else, %if.then14
%retval.0 = phi i32 [ 1, %if.then14 ], [ 1, %if.else ], [ 0, %if.end12 ], !dbg !28
call void @llvm.pseudoprobe(i64 -4224472938262609671, i64 14, i32 2, i64 -1), !dbg !79
ret i32 %retval.0, !dbg !83
}
; Function Attrs: inaccessiblememonly nounwind willreturn mustprogress
declare void @llvm.pseudoprobe(i64, i64, i32, i64) #1
; Function Attrs: nofree nosync nounwind readnone speculatable willreturn
declare void @llvm.dbg.value(metadata, metadata, metadata) #2
attributes #0 = { nounwind uwtable "disable-tail-calls"="true" "frame-pointer"="all" "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
attributes #1 = { inaccessiblememonly nounwind willreturn mustprogress }
attributes #2 = { nofree nosync nounwind readnone speculatable willreturn }
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!3, !4, !5, !6, !7}
!llvm.ident = !{!8}
!llvm.pseudo_probe_desc = !{!9}
!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 13.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, splitDebugInlining: false, nameTableKind: None)
!1 = !DIFile(filename: "test.cpp", directory: "")
!2 = !{}
!3 = !{i32 7, !"Dwarf Version", i32 4}
!4 = !{i32 2, !"Debug Info Version", i32 3}
!5 = !{i32 1, !"wchar_size", i32 4}
!6 = !{i32 1, !"ThinLTO", i32 0}
!7 = !{i32 1, !"EnableSplitLTOUnit", i32 1}
!8 = !{!"clang version 13.0.0"}
!9 = !{i64 -4224472938262609671, i64 328037311046, !"foo", null}
!10 = distinct !DISubprogram(name: "remove_one_fast", linkageName: "foo", scope: !1, file: !1, line: 8, type: !11, scopeLine: 9, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !18)
!11 = !DISubroutineType(types: !12)
!12 = !{!13, !14, !14, !15, !17}
!13 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!14 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !13, size: 64)
!15 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !16, size: 64)
!16 = !DIDerivedType(tag: DW_TAG_typedef, name: "move_s", file: !1, line: 6, baseType: !13)
!17 = !DIDerivedType(tag: DW_TAG_const_type, baseType: !13)
!18 = !{!19, !20, !21, !22, !23, !24, !25, !26, !27}
!19 = !DILocalVariable(name: "marker", arg: 1, scope: !10, file: !1, line: 8, type: !14)
!20 = !DILocalVariable(name: "move_ordering", arg: 2, scope: !10, file: !1, line: 8, type: !14)
!21 = !DILocalVariable(name: "moves", arg: 3, scope: !10, file: !1, line: 9, type: !15)
!22 = !DILocalVariable(name: "num_moves", arg: 4, scope: !10, file: !1, line: 9, type: !17)
!23 = !DILocalVariable(name: "tmpmv", scope: !10, file: !1, line: 10, type: !16)
!24 = !DILocalVariable(name: "i", scope: !10, file: !1, line: 11, type: !13)
!25 = !DILocalVariable(name: "best", scope: !10, file: !1, line: 11, type: !13)
!26 = !DILocalVariable(name: "tmp", scope: !10, file: !1, line: 12, type: !13)
!27 = !DILocalVariable(name: "mark", scope: !10, file: !1, line: 12, type: !13)
!28 = !DILocation(line: 0, scope: !10)
!29 = !DILocation(line: 10, column: 5, scope: !10)
!30 = !DILocation(line: 14, column: 14, scope: !10)
!31 = !{!32, !32, i64 0}
!32 = !{!"int", !33, i64 0}
!33 = !{!"omnipotent char", !34, i64 0}
!34 = !{!"Simple C++ TBAA"}
!35 = !DILocation(line: 17, column: 14, scope: !36)
!36 = distinct !DILexicalBlock(scope: !10, file: !1, line: 17, column: 9)
!37 = !DILocation(line: 17, column: 9, scope: !10)
!38 = !DILocation(line: 0, scope: !39)
!39 = distinct !DILexicalBlock(scope: !40, file: !1, line: 18, column: 9)
!40 = distinct !DILexicalBlock(scope: !36, file: !1, line: 17, column: 20)
!41 = !DILocation(line: 18, column: 18, scope: !39)
!42 = !DILocation(line: 18, column: 24, scope: !43)
!43 = distinct !DILexicalBlock(scope: !39, file: !1, line: 18, column: 9)
!44 = !DILocation(line: 18, column: 26, scope: !43)
!45 = !DILocation(line: 18, column: 9, scope: !39)
!46 = !DILocation(line: 19, column: 17, scope: !47)
!47 = distinct !DILexicalBlock(scope: !48, file: !1, line: 19, column: 17)
!48 = distinct !DILexicalBlock(scope: !43, file: !1, line: 18, column: 44)
!49 = !DILocation(line: 19, column: 34, scope: !47)
!50 = !DILocation(line: 19, column: 17, scope: !48)
!51 = !DILocation(line: 20, column: 24, scope: !52)
!52 = distinct !DILexicalBlock(scope: !47, file: !1, line: 19, column: 42)
!53 = !DILocation(line: 22, column: 13, scope: !52)
!54 = !DILocation(line: 23, column: 9, scope: !48)
!55 = !DILocation(line: 18, column: 40, scope: !43)
!56 = !DILocation(line: 18, column: 9, scope: !43)
!57 = distinct !{!57, !45, !58}
!58 = !DILocation(line: 23, column: 9, scope: !39)
!59 = !DILocation(line: 24, column: 16, scope: !60)
!60 = distinct !DILexicalBlock(scope: !36, file: !1, line: 24, column: 16)
!61 = !DILocation(line: 24, column: 21, scope: !60)
!62 = !DILocation(line: 24, column: 16, scope: !36)
!63 = !DILocation(line: 11, column: 12, scope: !10)
!64 = !DILocation(line: 24, column: 5, scope: !40)
!65 = !DILocation(line: 31, column: 9, scope: !66)
!66 = distinct !DILexicalBlock(scope: !10, file: !1, line: 31, column: 9)
!67 = !DILocation(line: 31, column: 14, scope: !66)
!68 = !DILocation(line: 31, column: 9, scope: !10)
!69 = !DILocation(line: 35, column: 30, scope: !70)
!70 = distinct !DILexicalBlock(scope: !66, file: !1, line: 31, column: 22)
!71 = !DILocation(line: 35, column: 9, scope: !70)
!72 = !DILocation(line: 35, column: 28, scope: !70)
!73 = !DILocation(line: 36, column: 29, scope: !70)
!74 = !DILocation(line: 38, column: 17, scope: !70)
!75 = !DILocation(line: 39, column: 23, scope: !70)
!76 = !DILocation(line: 39, column: 21, scope: !70)
!77 = !DILocation(line: 40, column: 20, scope: !70)
!78 = !DILocation(line: 42, column: 9, scope: !70)
!79 = !DILocation(line: 44, column: 9, scope: !80)
!80 = distinct !DILexicalBlock(scope: !66, file: !1, line: 43, column: 12)
!81 = !DILocation(line: 25, column: 16, scope: !82)
!82 = distinct !DILexicalBlock(scope: !60, file: !1, line: 24, column: 34)
!83 = !DILocation(line: 46, column: 1, scope: !10)