[CSSPGO] Return error_code for missing probe profile (#102085)

wlei-llvm · web-flow · commit 0f28aa632cde · 2024-08-13T08:12:04.000-07:00
We should undo this https://reviews.llvm.org/D102007 after undoing https://reviews.llvm.org/D104477 to use missing probe to represent unknown count, zero count and unknown count are different to profile inference. It only affects post-inline(linker) pipeline(with `--overwrite-existing-weights` on ) and flow-sensitive FDO.
diff --git a/llvm/include/llvm/Transforms/Utils/SampleProfileLoaderBaseImpl.h b/llvm/include/llvm/Transforms/Utils/SampleProfileLoaderBaseImpl.h
@@ -449,9 +449,6 @@ SampleProfileLoaderBaseImpl<BT>::getInstWeightImpl(const InstructionT &Inst) {
   return R;
 }
 
-// Here use error_code to represent: 1) The dangling probe. 2) Ignore the weight
-// of non-probe instruction. So if all instructions of the BB give error_code,
-// tell the inference algorithm to infer the BB weight.
 template <typename BT>
 ErrorOr<uint64_t>
 SampleProfileLoaderBaseImpl<BT>::getProbeWeight(const InstructionT &Inst) {
@@ -464,17 +461,13 @@ SampleProfileLoaderBaseImpl<BT>::getProbeWeight(const InstructionT &Inst) {
     return std::error_code();
 
   const FunctionSamples *FS = findFunctionSamples(Inst);
-  // If none of the instruction has FunctionSample, we choose to return zero
-  // value sample to indicate the BB is cold. This could happen when the
-  // instruction is from inlinee and no profile data is found.
-  // FIXME: This should not be affected by the source drift issue as 1) if the
-  // newly added function is top-level inliner, it won't match the CFG checksum
-  // in the function profile or 2) if it's the inlinee, the inlinee should have
-  // a profile, otherwise it wouldn't be inlined. For non-probe based profile,
-  // we can improve it by adding a switch for profile-sample-block-accurate for
-  // block level counts in the future.
-  if (!FS)
-    return 0;
+  if (!FS) {
+    // If we can't find the function samples for a probe, it could be due to the
+    // probe is later optimized away or the inlining context is mismatced. We
+    // treat it as unknown, leaving it to profile inference instead of forcing a
+    // zero count.
+    return std::error_code();
+  }
 
   auto R = FS->findSamplesAt(Probe->Id, Probe->Discriminator);
   if (R) {
diff --git a/llvm/test/Transforms/SampleProfile/Inputs/pseudo-probe-missing-probe.prof b/llvm/test/Transforms/SampleProfile/Inputs/pseudo-probe-missing-probe.prof
@@ -0,0 +1,13 @@
+main:89650:0
+ 1: 0
+ 2: 16724
+ 3: 16724
+ 4: 14342
+ 5: 15026 bar:15026
+ 6: 1882
+ 8: 16724
+ 9: 0
+ !CFGChecksum: 563091374530180
+bar:15026:15026
+ 1: 15026
+ !CFGChecksum: 4294967295
diff --git a/llvm/test/Transforms/SampleProfile/pseudo-probe-missing-probe.ll b/llvm/test/Transforms/SampleProfile/pseudo-probe-missing-probe.ll
@@ -0,0 +1,243 @@
+; RUN: opt < %s -passes=sample-profile  -sample-profile-file=%S/Inputs/pseudo-probe-missing-probe.prof -S | FileCheck %s
+
+; CHECK:  br i1 %tobool.not.i, label %if.end.i, label %if.then.i, !dbg ![[#]], !prof ![[#PROF:]]
+
+; CHECK:  [[#PROF]] = !{!"branch_weights", i32 918, i32 918}
+; Verify the else branch is not set to a zero count
+; CHECK-NOT:  [[#PROF]] = !{!"branch_weights", i32 1698, i32 0}
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@x = dso_local global i32 0, align 4, !dbg !0
+
+; Function Attrs: nofree noinline norecurse nounwind memory(readwrite, argmem: none) uwtable
+define dso_local void @bar(i32 %i) local_unnamed_addr #0 !dbg !18 {
+entry:
+    #dbg_value(i32 poison, !22, !DIExpression(), !23)
+  call void @llvm.pseudoprobe(i64 -2012135647395072713, i64 1, i32 0, i64 -1), !dbg !24
+  %0 = load volatile i32, ptr @x, align 4, !dbg !24, !tbaa !25
+  %add = add nsw i32 %0, 5, !dbg !24
+  store volatile i32 %add, ptr @x, align 4, !dbg !24, !tbaa !25
+  ret void, !dbg !29
+}
+
+; Function Attrs: nofree norecurse nounwind memory(readwrite, argmem: none) uwtable
+define dso_local void @baz(i32 noundef %i) local_unnamed_addr #1 !dbg !30 {
+entry:
+    #dbg_value(i32 %i, !32, !DIExpression(), !33)
+  call void @llvm.pseudoprobe(i64 7546896869197086323, i64 1, i32 0, i64 -1), !dbg !34
+  %rem = srem i32 %i, 100, !dbg !36
+  %tobool.not = icmp eq i32 %rem, 0, !dbg !36
+  br i1 %tobool.not, label %if.end, label %if.then, !dbg !37
+
+if.then:                                          ; preds = %entry
+  call void @llvm.pseudoprobe(i64 7546896869197086323, i64 2, i32 0, i64 -1), !dbg !38
+  %0 = load volatile i32, ptr @x, align 4, !dbg !38, !tbaa !25
+  %inc = add nsw i32 %0, 1, !dbg !38
+  store volatile i32 %inc, ptr @x, align 4, !dbg !38, !tbaa !25
+  br label %if.end, !dbg !39
+
+if.end:                                           ; preds = %if.then, %entry
+  call void @llvm.pseudoprobe(i64 7546896869197086323, i64 3, i32 0, i64 -1), !dbg !40
+  %1 = load volatile i32, ptr @x, align 4, !dbg !40, !tbaa !25
+  %add = add nsw i32 %1, 2, !dbg !40
+  store volatile i32 %add, ptr @x, align 4, !dbg !40, !tbaa !25
+  %2 = and i32 %i, 1, !dbg !41
+  %tobool2.not = icmp eq i32 %2, 0, !dbg !41
+  br i1 %tobool2.not, label %if.else, label %if.end11, !dbg !43
+
+if.else:                                          ; preds = %if.end
+  call void @llvm.pseudoprobe(i64 7546896869197086323, i64 5, i32 0, i64 -1), !dbg !44
+  %rem5 = srem i32 %i, 3, !dbg !46
+  %tobool6.not = icmp eq i32 %rem5, 0, !dbg !46
+  %spec.select = select i1 %tobool6.not, i32 -1, i32 2, !dbg !47
+  br label %if.end11, !dbg !47
+
+if.end11:                                         ; preds = %if.else, %if.end
+  %.sink14 = phi i32 [ 1, %if.end ], [ %spec.select, %if.else ]
+  %3 = load volatile i32, ptr @x, align 4, !dbg !48, !tbaa !25
+  %add8 = add nsw i32 %3, %.sink14, !dbg !48
+  store volatile i32 %add8, ptr @x, align 4, !dbg !48, !tbaa !25
+  call void @llvm.pseudoprobe(i64 7546896869197086323, i64 9, i32 0, i64 -1), !dbg !49
+  ret void, !dbg !49
+}
+
+; Function Attrs: nofree norecurse nounwind uwtable
+define dso_local noundef i32 @main() local_unnamed_addr #2 !dbg !50 {
+entry:
+  call void @llvm.pseudoprobe(i64 -2624081020897602054, i64 1, i32 0, i64 -1), !dbg !55
+    #dbg_value(i32 0, !54, !DIExpression(), !56)
+  call void @llvm.pseudoprobe(i64 -2624081020897602054, i64 2, i32 0, i64 -1), !dbg !57
+  br label %while.body, !dbg !58
+
+while.body:                                       ; preds = %entry, %if.end
+  %inc7 = phi i32 [ 1, %entry ], [ %inc, %if.end ]
+  %i.06 = phi i32 [ 0, %entry ], [ %inc7, %if.end ]
+    #dbg_value(i32 %i.06, !54, !DIExpression(), !56)
+  call void @llvm.pseudoprobe(i64 -2624081020897602054, i64 3, i32 0, i64 -1), !dbg !59
+  %rem = urem i32 %inc7, 10, !dbg !62
+  %tobool.not = icmp eq i32 %rem, 0, !dbg !62
+  br i1 %tobool.not, label %if.else, label %if.then, !dbg !63
+
+if.then:                                          ; preds = %while.body
+  call void @llvm.pseudoprobe(i64 -2624081020897602054, i64 4, i32 0, i64 -1), !dbg !64
+  tail call void @bar(i32 poison), !dbg !65
+  br label %if.end, !dbg !67
+
+if.else:                                          ; preds = %while.body
+  call void @llvm.pseudoprobe(i64 -2624081020897602054, i64 6, i32 0, i64 -1), !dbg !68
+    #dbg_value(i32 %inc7, !32, !DIExpression(), !69)
+  call void @llvm.pseudoprobe(i64 7546896869197086323, i64 1, i32 0, i64 -1), !dbg !72
+  %rem.i4 = urem i32 %inc7, 100, !dbg !73
+  %tobool.not.i = icmp eq i32 %rem.i4, 0, !dbg !73
+  br i1 %tobool.not.i, label %if.end.i, label %if.then.i, !dbg !74
+
+if.then.i:                                        ; preds = %if.else
+  call void @llvm.pseudoprobe(i64 7546896869197086323, i64 2, i32 0, i64 -1), !dbg !75
+  %0 = load volatile i32, ptr @x, align 4, !dbg !75, !tbaa !25
+  %inc.i = add nsw i32 %0, 1, !dbg !75
+  store volatile i32 %inc.i, ptr @x, align 4, !dbg !75, !tbaa !25
+  br label %if.end.i, !dbg !76
+
+if.end.i:                                         ; preds = %if.then.i, %if.else
+  call void @llvm.pseudoprobe(i64 7546896869197086323, i64 3, i32 0, i64 -1), !dbg !77
+  %1 = load volatile i32, ptr @x, align 4, !dbg !77, !tbaa !25
+  %add.i = add nsw i32 %1, 2, !dbg !77
+  store volatile i32 %add.i, ptr @x, align 4, !dbg !77, !tbaa !25
+  %2 = and i32 %i.06, 1, !dbg !78
+  %tobool2.not.i.not = icmp eq i32 %2, 0, !dbg !78
+  br i1 %tobool2.not.i.not, label %baz.exit, label %if.else.i, !dbg !79
+
+if.else.i:                                        ; preds = %if.end.i
+  call void @llvm.pseudoprobe(i64 7546896869197086323, i64 5, i32 0, i64 -1), !dbg !80
+  %rem5.i5 = urem i32 %inc7, 3, !dbg !81
+  %tobool6.not.i = icmp eq i32 %rem5.i5, 0, !dbg !81
+  %spec.select.i = select i1 %tobool6.not.i, i32 -1, i32 2, !dbg !82
+  br label %baz.exit, !dbg !82
+
+baz.exit:                                         ; preds = %if.end.i, %if.else.i
+  %.sink14.i = phi i32 [ 1, %if.end.i ], [ %spec.select.i, %if.else.i ]
+  %3 = load volatile i32, ptr @x, align 4, !dbg !83, !tbaa !25
+  %add8.i = add nsw i32 %3, %.sink14.i, !dbg !83
+  store volatile i32 %add8.i, ptr @x, align 4, !dbg !83, !tbaa !25
+  call void @llvm.pseudoprobe(i64 7546896869197086323, i64 9, i32 0, i64 -1), !dbg !84
+  br label %if.end
+
+if.end:                                           ; preds = %baz.exit, %if.then
+  call void @llvm.pseudoprobe(i64 -2624081020897602054, i64 8, i32 0, i64 -1), !dbg !58
+    #dbg_value(i32 %inc7, !54, !DIExpression(), !56)
+  call void @llvm.pseudoprobe(i64 -2624081020897602054, i64 2, i32 0, i64 -1), !dbg !57
+  %inc = add nuw nsw i32 %inc7, 1, !dbg !57
+    #dbg_value(i32 %inc, !54, !DIExpression(), !56)
+  %exitcond.not = icmp eq i32 %inc, 160000001, !dbg !85
+  br i1 %exitcond.not, label %while.end, label %while.body, !dbg !58, !llvm.loop !86
+
+while.end:                                        ; preds = %if.end
+  call void @llvm.pseudoprobe(i64 -2624081020897602054, i64 9, i32 0, i64 -1), !dbg !89
+  ret i32 0, !dbg !89
+}
+
+; Function Attrs: mustprogress nocallback nofree nosync nounwind willreturn memory(inaccessiblemem: readwrite)
+declare void @llvm.pseudoprobe(i64, i64, i32, i64) #3
+
+attributes #0 = { nofree noinline norecurse nounwind memory(readwrite, argmem: none) uwtable "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
+attributes #1 = { nofree norecurse nounwind memory(readwrite, argmem: none) uwtable "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
+attributes #2 = { nofree norecurse nounwind uwtable "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" "use-sample-profile"}
+attributes #3 = { mustprogress nocallback nofree nosync nounwind willreturn memory(inaccessiblemem: readwrite) }
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!7, !8, !9, !10, !11, !12, !13}
+!llvm.ident = !{!14}
+!llvm.pseudo_probe_desc = !{!15, !16, !17}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "x", scope: !2, file: !3, line: 1, type: !5, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C11, file: !3, producer: "clang version 20.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, globals: !4, splitDebugInlining: false, nameTableKind: None)
+!3 = !DIFile(filename: "test.c", directory: "/home", checksumkind: CSK_MD5, checksum: "b67c15e928f76c51702a59639dbebb4c")
+!4 = !{!0}
+!5 = !DIDerivedType(tag: DW_TAG_volatile_type, baseType: !6)
+!6 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!7 = !{i32 7, !"Dwarf Version", i32 5}
+!8 = !{i32 2, !"Debug Info Version", i32 3}
+!9 = !{i32 1, !"wchar_size", i32 4}
+!10 = !{i32 8, !"PIC Level", i32 2}
+!11 = !{i32 7, !"PIE Level", i32 2}
+!12 = !{i32 7, !"uwtable", i32 2}
+!13 = !{i32 7, !"debug-info-assignment-tracking", i1 true}
+!14 = !{!"clang version 20.0.0"}
+!15 = !{i64 -2012135647395072713, i64 4294967295, !"bar"}
+!16 = !{i64 7546896869197086323, i64 191430930410, !"baz"}
+!17 = !{i64 -2624081020897602054, i64 563091374530180, !"main"}
+!18 = distinct !DISubprogram(name: "bar", scope: !3, file: !3, line: 3, type: !19, scopeLine: 3, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !21)
+!19 = !DISubroutineType(types: !20)
+!20 = !{null, !6}
+!21 = !{!22}
+!22 = !DILocalVariable(name: "i", arg: 1, scope: !18, file: !3, line: 3, type: !6)
+!23 = !DILocation(line: 0, scope: !18)
+!24 = !DILocation(line: 4, column: 5, scope: !18)
+!25 = !{!26, !26, i64 0}
+!26 = !{!"int", !27, i64 0}
+!27 = !{!"omnipotent char", !28, i64 0}
+!28 = !{!"Simple C/C++ TBAA"}
+!29 = !DILocation(line: 8, column: 1, scope: !18)
+!30 = distinct !DISubprogram(name: "baz", scope: !3, file: !3, line: 10, type: !19, scopeLine: 10, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !31)
+!31 = !{!32}
+!32 = !DILocalVariable(name: "i", arg: 1, scope: !30, file: !3, line: 10, type: !6)
+!33 = !DILocation(line: 0, scope: !30)
+!34 = !DILocation(line: 11, column: 6, scope: !35)
+!35 = distinct !DILexicalBlock(scope: !30, file: !3, line: 11, column: 6)
+!36 = !DILocation(line: 11, column: 7, scope: !35)
+!37 = !DILocation(line: 11, column: 6, scope: !30)
+!38 = !DILocation(line: 12, column: 6, scope: !35)
+!39 = !DILocation(line: 12, column: 5, scope: !35)
+!40 = !DILocation(line: 14, column: 5, scope: !30)
+!41 = !DILocation(line: 15, column: 9, scope: !42)
+!42 = distinct !DILexicalBlock(scope: !30, file: !3, line: 15, column: 7)
+!43 = !DILocation(line: 15, column: 7, scope: !30)
+!44 = !DILocation(line: 17, column: 12, scope: !45)
+!45 = distinct !DILexicalBlock(scope: !42, file: !3, line: 17, column: 12)
+!46 = !DILocation(line: 17, column: 14, scope: !45)
+!47 = !DILocation(line: 17, column: 12, scope: !42)
+!48 = !DILocation(line: 0, scope: !42)
+!49 = !DILocation(line: 21, column: 1, scope: !30)
+!50 = distinct !DISubprogram(name: "main", scope: !3, file: !3, line: 23, type: !51, scopeLine: 23, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !53)
+!51 = !DISubroutineType(types: !52)
+!52 = !{!6}
+!53 = !{!54}
+!54 = !DILocalVariable(name: "i", scope: !50, file: !3, line: 24, type: !6)
+!55 = !DILocation(line: 24, column: 7, scope: !50)
+!56 = !DILocation(line: 0, scope: !50)
+!57 = !DILocation(line: 25, column: 11, scope: !50)
+!58 = !DILocation(line: 25, column: 3, scope: !50)
+!59 = !DILocation(line: 26, column: 8, scope: !60)
+!60 = distinct !DILexicalBlock(scope: !61, file: !3, line: 26, column: 8)
+!61 = distinct !DILexicalBlock(scope: !50, file: !3, line: 25, column: 30)
+!62 = !DILocation(line: 26, column: 10, scope: !60)
+!63 = !DILocation(line: 26, column: 8, scope: !61)
+!64 = !DILocation(line: 27, column: 10, scope: !60)
+!65 = !DILocation(line: 27, column: 6, scope: !66)
+!66 = !DILexicalBlockFile(scope: !60, file: !3, discriminator: 455082031)
+!67 = !DILocation(line: 27, column: 6, scope: !60)
+!68 = !DILocation(line: 29, column: 10, scope: !60)
+!69 = !DILocation(line: 0, scope: !30, inlinedAt: !70)
+!70 = distinct !DILocation(line: 29, column: 6, scope: !71)
+!71 = !DILexicalBlockFile(scope: !60, file: !3, discriminator: 455082047)
+!72 = !DILocation(line: 11, column: 6, scope: !35, inlinedAt: !70)
+!73 = !DILocation(line: 11, column: 7, scope: !35, inlinedAt: !70)
+!74 = !DILocation(line: 11, column: 6, scope: !30, inlinedAt: !70)
+!75 = !DILocation(line: 12, column: 6, scope: !35, inlinedAt: !70)
+!76 = !DILocation(line: 12, column: 5, scope: !35, inlinedAt: !70)
+!77 = !DILocation(line: 14, column: 5, scope: !30, inlinedAt: !70)
+!78 = !DILocation(line: 15, column: 9, scope: !42, inlinedAt: !70)
+!79 = !DILocation(line: 15, column: 7, scope: !30, inlinedAt: !70)
+!80 = !DILocation(line: 17, column: 12, scope: !45, inlinedAt: !70)
+!81 = !DILocation(line: 17, column: 14, scope: !45, inlinedAt: !70)
+!82 = !DILocation(line: 17, column: 12, scope: !42, inlinedAt: !70)
+!83 = !DILocation(line: 0, scope: !42, inlinedAt: !70)
+!84 = !DILocation(line: 21, column: 1, scope: !30, inlinedAt: !70)
+!85 = !DILocation(line: 25, column: 14, scope: !50)
+!86 = distinct !{!86, !58, !87, !88}
+!87 = !DILocation(line: 30, column: 3, scope: !50)
+!88 = !{!"llvm.loop.mustprogress"}
+!89 = !DILocation(line: 31, column: 3, scope: !50)
