[PATCH] D14464: Add discriminators for call instructions that are from the same line and same basic block.

[Dehao Chen via llvm-commits]

danielcdh updated this revision to Diff 39709.
danielcdh added a comment.

Add explaination how this would affect sample based FDO.


http://reviews.llvm.org/D14464

Files:
  lib/Transforms/Utils/AddDiscriminators.cpp
  test/Transforms/AddDiscriminators/call.ll

Index: test/Transforms/AddDiscriminators/call.ll
===================================================================
--- /dev/null
+++ test/Transforms/AddDiscriminators/call.ll
@@ -0,0 +1,48 @@
+; RUN: opt < %s -add-discriminators -S | FileCheck %s
+
+; Discriminator support for calls that are defined in one line:
+; #1 void bar();
+; #2
+; #3 void foo() {
+; #4  bar();bar()/*discriminator 1*/;bar()/*discriminator 2*/;
+; #5 }
+
+; Function Attrs: uwtable
+define void @_Z3foov() #0 {
+  call void @_Z3barv(), !dbg !10
+; CHECK:  call void @_Z3barv(), !dbg ![[CALL0:[0-9]+]]
+  call void @_Z3barv(), !dbg !11
+; CHECK:  call void @_Z3barv(), !dbg ![[CALL1:[0-9]+]]
+  call void @_Z3barv(), !dbg !12
+; CHECK:  call void @_Z3barv(), !dbg ![[CALL2:[0-9]+]]
+  ret void, !dbg !13
+}
+
+declare void @_Z3barv() #1
+
+attributes #0 = { uwtable "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!7, !8}
+!llvm.ident = !{!9}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 3.8.0 (trunk 250915) (llvm/trunk 251830)", isOptimized: false, runtimeVersion: 0, emissionKind: 1, enums: !2, subprograms: !3)
+!1 = !DIFile(filename: "c.cc", directory: "/tmp")
+!2 = !{}
+!3 = !{!4}
+!4 = distinct !DISubprogram(name: "foo", linkageName: "_Z3foov", scope: !1, file: !1, line: 3, type: !5, isLocal: false, isDefinition: true, scopeLine: 3, flags: DIFlagPrototyped, isOptimized: false, variables: !2)
+!5 = !DISubroutineType(types: !6)
+!6 = !{null}
+!7 = !{i32 2, !"Dwarf Version", i32 4}
+!8 = !{i32 2, !"Debug Info Version", i32 3}
+!9 = !{!"clang version 3.8.0 (trunk 250915) (llvm/trunk 251830)"}
+!10 = !DILocation(line: 4, column: 3, scope: !4)
+!11 = !DILocation(line: 4, column: 9, scope: !4)
+!12 = !DILocation(line: 4, column: 15, scope: !4)
+!13 = !DILocation(line: 5, column: 1, scope: !4)
+
+; CHECK: ![[CALL1]] = !DILocation(line: 4, column: 9, scope: ![[CALL1BLOCK:[0-9]+]])
+; CHECK: ![[CALL1BLOCK]] = !DILexicalBlockFile({{.*}} discriminator: 1)
+; CHECK: ![[CALL2]] = !DILocation(line: 4, column: 15, scope: ![[CALL2BLOCK:[0-9]+]])
+; CHECK: ![[CALL2BLOCK]] = !DILexicalBlockFile({{.*}} discriminator: 2)
Index: lib/Transforms/Utils/AddDiscriminators.cpp
===================================================================
--- lib/Transforms/Utils/AddDiscriminators.cpp
+++ lib/Transforms/Utils/AddDiscriminators.cpp
@@ -224,5 +224,37 @@
       }
     }
   }
+
+  // Traverse all instructions and assign new discriminators to call
+  // instructions with the same lineno that are in the same basic block.
+  // Sample base profile needs to distinguish different function calls within
+  // a same source line for correct profile annotation.
+  for (BasicBlock &B : F) {
+    const DILocation *FirstDIL = NULL;
+    for (auto &I : B.getInstList()) {
+      CallInst *Current = dyn_cast<CallInst>(&I);
+      if (Current) {
+        DILocation *CurrentDIL = Current->getDebugLoc();
+        if (FirstDIL) {
+          if (CurrentDIL && CurrentDIL->getLine() == FirstDIL->getLine() &&
+              CurrentDIL->getFilename() == FirstDIL->getFilename()) {
+            auto *Scope = FirstDIL->getScope();
+            auto *File = Builder.createFile(FirstDIL->getFilename(),
+                                            Scope->getDirectory());
+            auto *NewScope = Builder.createLexicalBlockFile(
+                Scope, File, FirstDIL->computeNewDiscriminator());
+            Current->setDebugLoc(DILocation::get(
+                Ctx, CurrentDIL->getLine(), CurrentDIL->getColumn(), NewScope,
+                CurrentDIL->getInlinedAt()));
+            Changed = true;
+          } else {
+            FirstDIL = CurrentDIL;
+          }
+        } else {
+          FirstDIL = CurrentDIL;
+        }
+      }
+    }
+  }
   return Changed;
 }


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