[PATCH] D14033: [PGO] Eliminate emission of runtime hook user (Linux)

[Justin Bogner via llvm-commits]

David Li <davidxl at google.com> writes:
> davidxl updated this revision to Diff 38685.
> davidxl added a comment.
>
> Addressed review comments from Justin.
>
>
> http://reviews.llvm.org/D14033
>
> Files:
>   lib/Transforms/Instrumentation/InstrProfiling.cpp
>   test/Instrumentation/InstrProfiling/linkage.ll
>
> Index: test/Instrumentation/InstrProfiling/linkage.ll
> ===================================================================
> --- test/Instrumentation/InstrProfiling/linkage.ll
> +++ test/Instrumentation/InstrProfiling/linkage.ll
> @@ -1,36 +1,36 @@
>  ;; Check that runtime symbols get appropriate linkage.
>  
> -; RUN: opt < %s -mtriple=x86_64-apple-macosx10.10.0 -instrprof -S | FileCheck %s
> -; RUN: opt < %s -mtriple=x86_64-unknown-linux -instrprof -S | FileCheck %s
> +; RUN: opt < %s -mtriple=x86_64-apple-macosx10.10.0 -instrprof -S | FileCheck %s --check-prefix=OTHER --check-prefix=COMMON
> +; RUN: opt < %s -mtriple=x86_64-unknown-linux -instrprof -S | FileCheck %s --check-prefix=LINUX --check-prefix=COMMON
>  
>  @__llvm_profile_name_foo = hidden constant [3 x i8] c"foo"
>  @__llvm_profile_name_foo_weak = weak hidden constant [8 x i8] c"foo_weak"
>  @"__llvm_profile_name_linkage.ll:foo_internal" = internal constant [23 x i8] c"linkage.ll:foo_internal"
>  @__llvm_profile_name_foo_inline = linkonce_odr hidden constant [10 x i8] c"foo_inline"
>  
> -; CHECK: @__llvm_profile_counters_foo = hidden global
> -; CHECK: @__llvm_profile_data_foo = hidden constant
> +; COMMON: @__llvm_profile_counters_foo = hidden global
> +; COMMON: @__llvm_profile_data_foo = hidden constant
>  define void @foo() {
>    call void @llvm.instrprof.increment(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @__llvm_profile_name_foo, i32 0, i32 0), i64 0, i32 1, i32 0)
>    ret void
>  }
>  
> -; CHECK: @__llvm_profile_counters_foo_weak = weak hidden global
> -; CHECK: @__llvm_profile_data_foo_weak = weak hidden constant
> +; COMMON: @__llvm_profile_counters_foo_weak = weak hidden global
> +; COMMON: @__llvm_profile_data_foo_weak = weak hidden constant
>  define weak void @foo_weak() {
>    call void @llvm.instrprof.increment(i8* getelementptr inbounds ([8 x i8], [8 x i8]* @__llvm_profile_name_foo_weak, i32 0, i32 0), i64 0, i32 1, i32 0)
>    ret void
>  }
>  
> -; CHECK: @"__llvm_profile_counters_linkage.ll:foo_internal" = internal global
> -; CHECK: @"__llvm_profile_data_linkage.ll:foo_internal" = internal constant
> +; COMMON: @"__llvm_profile_counters_linkage.ll:foo_internal" = internal global
> +; COMMON: @"__llvm_profile_data_linkage.ll:foo_internal" = internal constant
>  define internal void @foo_internal() {
>    call void @llvm.instrprof.increment(i8* getelementptr inbounds ([23 x i8], [23 x i8]* @"__llvm_profile_name_linkage.ll:foo_internal", i32 0, i32 0), i64 0, i32 1, i32 0)
>    ret void
>  }
>  
> -; CHECK: @__llvm_profile_counters_foo_inline = linkonce_odr hidden global
> -; CHECK: @__llvm_profile_data_foo_inline = linkonce_odr hidden constant
> +; COMMON: @__llvm_profile_counters_foo_inline = linkonce_odr hidden global
> +; COMMON: @__llvm_profile_data_foo_inline = linkonce_odr hidden constant
>  define linkonce_odr void @foo_inline() {
>    call void @llvm.instrprof.increment(i8* getelementptr inbounds ([10 x i8], [10 x i8]* @__llvm_profile_name_foo_inline, i32 0, i32 0), i64 0, i32 1, i32 0)
>    ret void
> @@ -38,9 +38,12 @@
>  
>  declare void @llvm.instrprof.increment(i8*, i64, i32, i32)
>  
> -; CHECK: @__llvm_profile_runtime = external global i32
> +; OTHER: @__llvm_profile_runtime = external global i32
> +; LINUX-NOT: @__llvm_profile_runtime = external global i32
>  
> -; CHECK: define linkonce_odr hidden i32 @__llvm_profile_runtime_user() {{.*}} {
> -; CHECK:   %[[REG:.*]] = load i32, i32* @__llvm_profile_runtime
> -; CHECK:   ret i32 %[[REG]]
> -; CHECK: }
> +; OTHER: define linkonce_odr hidden i32 @__llvm_profile_runtime_user() {{.*}} {
> +; OTHER:   %[[REG:.*]] = load i32, i32* @__llvm_profile_runtime
> +; OTHER:   ret i32 %[[REG]]
> +; OTHER: }
> +; LINUX-NOT: define linkonce_odr hidden i32 @__llvm_profile_runtime_user() {{.*}} {
> +; LINUX-NOT:   %[[REG:.*]] = load i32, i32* @__llvm_profile_runtime
> Index: lib/Transforms/Instrumentation/InstrProfiling.cpp
> ===================================================================
> --- lib/Transforms/Instrumentation/InstrProfiling.cpp
> +++ lib/Transforms/Instrumentation/InstrProfiling.cpp
> @@ -288,6 +288,11 @@
>  
>  void InstrProfiling::emitRuntimeHook() {
>  
> +  // Clang driver inserts -u<hook_var> option at linker command line
> +  // for Linux thus there is no need to emit the hook user function.

I'd probably word this more like "We expect the driver to be invoked
with -u<hook_var> on linux, in which case there is no need to emit the
user function". The change LGTM.

> +  if (Triple(M->getTargetTriple()).isOSLinux())
> +    return;
> +
>    // If the module's provided its own runtime, we don't need to do anything.
>    if (M->getGlobalVariable(getInstrProfRuntimeHookVarName())) return;