[test] Add Clang side tests for -fdebug-info-for-profiling

[MaskRay]

Summary

There is currently a driver test but no test for its effect on linkageName & pass pipeline.

[dblaikie]

clang/test/CodeGenCXX/fdebug-info-for-profiling.cpp

14–16

What's this test for? (I'd hesitate to add a test that has to run llvm-profdata and use that profile, etc) I guess it's a different codepath that sets up the pass pipeline for this case compared to the previous case?

[MaskRay]

clang/test/CodeGenCXX/fdebug-info-for-profiling.cpp

14–16

Test that -fdebug-info-for-profiling affects both driver -fprofile-use (CC1 -fprofile-instrument-use-path) and driver -fprofile-generate (CC1 -fprofile-instrument-path). IIUC: generate/use needs to have compatible flags so that their CFG is identical.

The profile reading pass will error on an invalid file (e.g. an empty file).

I hesitated a bit for the usage of llvm-profdata, but I searched for llvm-profdata and there are 20+ other tests using llvm-profdata so I believe it is fine.

[dblaikie]

Sounds good

[MaskRay]

Verified with @wmi offline this is good. Committing...

clang/test/CodeGenCXX/fdebug-info-for-profiling.cpp

+/// Normally -g1 does not add linkageName. -fdebug-info-for-profiling adds linkageName.
+// RUN: %clang_cc1 -emit-llvm -triple %itanium_abi_triple -debug-info-kind=line-tables-only %s -o - | FileCheck %s --check-prefix=LINE
+// RUN: %clang_cc1 -emit-llvm -triple %itanium_abi_triple -debug-info-kind=line-tables-only -fdebug-info-for-profiling %s -o - | FileCheck %s
+
+// LINE: = distinct !DISubprogram(name: "foo", scope:
+
+// CHECK: = distinct !DICompileUnit({{.*}}, debugInfoForProfiling: true,
+// CHECK: = distinct !DISubprogram(name: "foo", linkageName: "_Z3foov", scope:
+
+/// Add a DWARF discriminators pass for PGO.
+// RUN: %clang_cc1 -emit-llvm -fno-legacy-pass-manager -fdebug-pass-manager -O1 -fprofile-instrument-path=a.profdata %s -o - 2>&1 | FileCheck %s --check-prefix=NODISCR
+// RUN: %clang_cc1 -emit-llvm -fno-legacy-pass-manager -fdebug-pass-manager -O1 -fprofile-instrument-path=a.profdata -fdebug-info-for-profiling %s -o - 2>&1 | FileCheck %s --check-prefix=DISCR
+
+// RUN: echo > %t.proftext
+// RUN: llvm-profdata merge %t.proftext -o %t.profdata
+// RUN: %clang_cc1 -emit-llvm -fno-legacy-pass-manager -fdebug-pass-manager -O1 -fprofile-instrument-use-path=%t.profdata -fdebug-info-for-profiling %s -o - 2>&1 | FileCheck %s --check-prefix=DISCR
+
+// NODISCR-NOT: Running pass: AddDiscriminatorsPass
+// DISCR:       Running pass: AddDiscriminatorsPass on {{.*}}
+
+void foo() {}