SamplePGO - Fix PR 25482 - Do not rely on llvm.dbg.cu for discriminators

The discriminators pass relied on the presence of llvm.dbg.cu to decide
whether to add discriminators, but this fails in the case where debug
info is only enabled partially when -fprofile-sample-use is active.

The reason llvm.dbg.cu is not present in these cases is to prevent
codegen from emitting debug info (as it is only used for the sample
profile pass).

This changes the discriminators pass to also emit discriminators even
when debug info is not being emitted.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@252763 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Utils/AddDiscriminators.cpp

@@ -98,8 +98,8 @@ FunctionPass *llvm::createAddDiscriminatorsPass() {
 }
 
 static bool hasDebugInfo(const Function &F) {
-  NamedMDNode *CUNodes = F.getParent()->getNamedMetadata("llvm.dbg.cu");
-  return CUNodes != nullptr;
+  DISubprogram *S = getDISubprogram(&F);
+  return S != nullptr;
 }
 
 /// \brief Assign DWARF discriminators.

test/Transforms/AddDiscriminators/basic.ll

@@ -37,7 +37,11 @@ if.end:                                           ; preds = %if.then, %entry
 
 attributes #0 = { nounwind uwtable "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" "unsafe-fp-math"="false" "use-soft-float"="false" }
 
-!llvm.dbg.cu = !{!0}
+; We should be able to add discriminators even in the absence of llvm.dbg.cu.
+; When using sample profiles, the front end will generate line tables but it
+; does not generate llvm.dbg.cu to prevent codegen from emitting debug info
+; to the final binary.
+; !llvm.dbg.cu = !{!0}
 !llvm.module.flags = !{!7, !8}
 !llvm.ident = !{!9}
 

test/Transforms/AddDiscriminators/call.ll

@@ -23,7 +23,11 @@ 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}
+; We should be able to add discriminators even in the absence of llvm.dbg.cu.
+; When using sample profiles, the front end will generate line tables but it
+; does not generate llvm.dbg.cu to prevent codegen from emitting debug info
+; to the final binary.
+; !llvm.dbg.cu = !{!0}
 !llvm.module.flags = !{!7, !8}
 !llvm.ident = !{!9}
 

test/Transforms/AddDiscriminators/first-only.ll

@@ -46,7 +46,11 @@ if.end:                                           ; preds = %if.then, %entry
 
 attributes #0 = { nounwind uwtable "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" "unsafe-fp-math"="false" "use-soft-float"="false" }
 
-!llvm.dbg.cu = !{!0}
+; We should be able to add discriminators even in the absence of llvm.dbg.cu.
+; When using sample profiles, the front end will generate line tables but it
+; does not generate llvm.dbg.cu to prevent codegen from emitting debug info
+; to the final binary.
+; !llvm.dbg.cu = !{!0}
 !llvm.module.flags = !{!7, !8}
 !llvm.ident = !{!9}
 

test/Transforms/AddDiscriminators/multiple.ll

@@ -47,7 +47,11 @@ if.end:                                           ; preds = %if.else, %if.then
 
 attributes #0 = { nounwind uwtable "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" "unsafe-fp-math"="false" "use-soft-float"="false" }
 
-!llvm.dbg.cu = !{!0}
+; We should be able to add discriminators even in the absence of llvm.dbg.cu.
+; When using sample profiles, the front end will generate line tables but it
+; does not generate llvm.dbg.cu to prevent codegen from emitting debug info
+; to the final binary.
+; !llvm.dbg.cu = !{!0}
 !llvm.module.flags = !{!7, !8}
 !llvm.ident = !{!9}
 

test/Transforms/AddDiscriminators/no-discriminators.ll

@@ -44,6 +44,10 @@ declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
 attributes #0 = { nounwind uwtable "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" "unsafe-fp-math"="false" "use-soft-float"="false" }
 attributes #1 = { nounwind readnone }
 
+; We should be able to add discriminators even in the absence of llvm.dbg.cu.
+; When using sample profiles, the front end will generate line tables but it
+; does not generate llvm.dbg.cu to prevent codegen from emitting debug info
+; to the final binary.
 !llvm.dbg.cu = !{!0}
 !llvm.module.flags = !{!10, !11}
 !llvm.ident = !{!12}

test/Transforms/AddDiscriminators/oneline.ll

@@ -54,7 +54,11 @@ declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
 attributes #0 = { nounwind uwtable "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "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 = { nounwind readnone }
 
-!llvm.dbg.cu = !{!0}
+; We should be able to add discriminators even in the absence of llvm.dbg.cu.
+; When using sample profiles, the front end will generate line tables but it
+; does not generate llvm.dbg.cu to prevent codegen from emitting debug info
+; to the final binary.
+; !llvm.dbg.cu = !{!0}
 !llvm.module.flags = !{!10, !11}
 !llvm.ident = !{!12}