[clang] 87fd09b - [InstrProfiling] Generate runtime hook for ELF platforms
Petr Hosek via cfe-commits
cfe-commits at lists.llvm.org
Thu Mar 11 12:29:16 PST 2021
Author: Petr Hosek
Date: 2021-03-11T12:29:01-08:00
New Revision: 87fd09b25f8892e07b7ba11525baa9c3ec3e5d3f
URL: https://github.com/llvm/llvm-project/commit/87fd09b25f8892e07b7ba11525baa9c3ec3e5d3f
DIFF: https://github.com/llvm/llvm-project/commit/87fd09b25f8892e07b7ba11525baa9c3ec3e5d3f.diff
LOG: [InstrProfiling] Generate runtime hook for ELF platforms
When using -fprofile-list to selectively apply instrumentation only
to certain files or functions, we may end up with a binary that doesn't
have any counters in the case where no files were selected. However,
because on Linux and Fuchsia, we pass -u__llvm_profile_runtime, the
runtime would still be pulled in and incur some non-trivial overhead,
especially in the case when the continuous or runtime counter relocation
mode is being used. A better way would be to pull in the profile runtime
only when needed by declaring the __llvm_profile_runtime symbol in the
translation unit only when needed.
This approach was already used prior to 9a041a75221ca, but we changed it
to always generate the __llvm_profile_runtime due to a TAPI limitation.
Since TAPI is only used on Mach-O platforms, we could use the early
emission of __llvm_profile_runtime there, and on other platforms we
could change back to the earlier approach where the symbol is generated
later only when needed. We can stop passing -u__llvm_profile_runtime to
the linker on Linux and Fuchsia since the generated undefined symbol in
each translation unit that needed it serves the same purpose.
Differential Revision: https://reviews.llvm.org/D98061
Added:
Modified:
clang/docs/UsersManual.rst
clang/lib/Driver/ToolChains/Fuchsia.cpp
clang/lib/Driver/ToolChains/Fuchsia.h
clang/lib/Driver/ToolChains/Linux.cpp
clang/lib/Driver/ToolChains/Linux.h
clang/test/Driver/coverage-ld.c
clang/test/Driver/fuchsia.c
llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
llvm/test/Instrumentation/InstrProfiling/linkage.ll
llvm/test/Instrumentation/InstrProfiling/profiling.ll
Removed:
################################################################################
diff --git a/clang/docs/UsersManual.rst b/clang/docs/UsersManual.rst
index 28de4e3aac6f..8a369c88c2a5 100644
--- a/clang/docs/UsersManual.rst
+++ b/clang/docs/UsersManual.rst
@@ -2301,6 +2301,14 @@ In these cases, you can use the flag ``-fno-profile-instr-generate`` (or
Note that these flags should appear after the corresponding profile
flags to have an effect.
+.. note::
+
+ When none of the translation units inside a binary is instrumented, in the
+ case of ELF and COFF binary format the profile runtime will not be linked
+ into the binary and no profile will be produced, while in the case of Mach-O
+ the profile runtime will be linked and profile will be produced but there
+ will not be any counters.
+
Instrumenting only selected files or functions
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/Driver/ToolChains/Fuchsia.cpp b/clang/lib/Driver/ToolChains/Fuchsia.cpp
index 8e086010a984..4b27a102f218 100644
--- a/clang/lib/Driver/ToolChains/Fuchsia.cpp
+++ b/clang/lib/Driver/ToolChains/Fuchsia.cpp
@@ -394,13 +394,3 @@ SanitizerMask Fuchsia::getDefaultSanitizers() const {
}
return Res;
}
-
-void Fuchsia::addProfileRTLibs(const llvm::opt::ArgList &Args,
- llvm::opt::ArgStringList &CmdArgs) const {
- // Add linker option -u__llvm_profile_runtime to cause runtime
- // initialization module to be linked in.
- if (needsProfileRT(Args))
- CmdArgs.push_back(Args.MakeArgString(
- Twine("-u", llvm::getInstrProfRuntimeHookVarName())));
- ToolChain::addProfileRTLibs(Args, CmdArgs);
-}
diff --git a/clang/lib/Driver/ToolChains/Fuchsia.h b/clang/lib/Driver/ToolChains/Fuchsia.h
index 07adf9b7101d..1a0263ce3393 100644
--- a/clang/lib/Driver/ToolChains/Fuchsia.h
+++ b/clang/lib/Driver/ToolChains/Fuchsia.h
@@ -71,9 +71,6 @@ class LLVM_LIBRARY_VISIBILITY Fuchsia : public ToolChain {
SanitizerMask getSupportedSanitizers() const override;
SanitizerMask getDefaultSanitizers() const override;
- void addProfileRTLibs(const llvm::opt::ArgList &Args,
- llvm::opt::ArgStringList &CmdArgs) const override;
-
RuntimeLibType
GetRuntimeLibType(const llvm::opt::ArgList &Args) const override;
CXXStdlibType
diff --git a/clang/lib/Driver/ToolChains/Linux.cpp b/clang/lib/Driver/ToolChains/Linux.cpp
index ad98013dd4f0..5f5b069fe2df 100644
--- a/clang/lib/Driver/ToolChains/Linux.cpp
+++ b/clang/lib/Driver/ToolChains/Linux.cpp
@@ -925,16 +925,6 @@ SanitizerMask Linux::getSupportedSanitizers() const {
return Res;
}
-void Linux::addProfileRTLibs(const llvm::opt::ArgList &Args,
- llvm::opt::ArgStringList &CmdArgs) const {
- // Add linker option -u__llvm_profile_runtime to cause runtime
- // initialization module to be linked in.
- if (needsProfileRT(Args))
- CmdArgs.push_back(Args.MakeArgString(
- Twine("-u", llvm::getInstrProfRuntimeHookVarName())));
- ToolChain::addProfileRTLibs(Args, CmdArgs);
-}
-
llvm::DenormalMode
Linux::getDefaultDenormalModeForType(const llvm::opt::ArgList &DriverArgs,
const JobAction &JA,
diff --git a/clang/lib/Driver/ToolChains/Linux.h b/clang/lib/Driver/ToolChains/Linux.h
index 05e01a208456..605ba5431b81 100644
--- a/clang/lib/Driver/ToolChains/Linux.h
+++ b/clang/lib/Driver/ToolChains/Linux.h
@@ -43,8 +43,6 @@ class LLVM_LIBRARY_VISIBILITY Linux : public Generic_ELF {
bool isNoExecStackDefault() const override;
bool IsMathErrnoDefault() const override;
SanitizerMask getSupportedSanitizers() const override;
- void addProfileRTLibs(const llvm::opt::ArgList &Args,
- llvm::opt::ArgStringList &CmdArgs) const override;
std::string computeSysRoot() const override;
std::string getDynamicLinker(const llvm::opt::ArgList &Args) const override;
diff --git a/clang/test/Driver/coverage-ld.c b/clang/test/Driver/coverage-ld.c
index c15531fa05e9..fd13f7759609 100644
--- a/clang/test/Driver/coverage-ld.c
+++ b/clang/test/Driver/coverage-ld.c
@@ -12,9 +12,7 @@
// RUN: --sysroot=%S/Inputs/basic_linux_tree \
// RUN: | FileCheck --check-prefix=CHECK-LINUX-I386 %s
//
-// CHECK-LINUX-I386-NOT: "-u__llvm_profile_runtime"
// CHECK-LINUX-I386: /Inputs/resource_dir{{/|\\\\}}lib{{/|\\\\}}linux{{/|\\\\}}libclang_rt.profile-i386.a"
-// CHECK-LINUX-I386-NOT: "-u__llvm_profile_runtime"
// CHECK-LINUX-I386: "-lc"
//
// RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
diff --git a/clang/test/Driver/fuchsia.c b/clang/test/Driver/fuchsia.c
index 5d3b4c8d9fe3..9b03fea55a3a 100644
--- a/clang/test/Driver/fuchsia.c
+++ b/clang/test/Driver/fuchsia.c
@@ -249,7 +249,6 @@
// RUN: -fuse-ld=lld 2>&1 \
// RUN: | FileCheck %s -check-prefix=CHECK-PROFRT-AARCH64
// CHECK-PROFRT-AARCH64: "-resource-dir" "[[RESOURCE_DIR:[^"]+]]"
-// CHECK-PROFRT-AARCH64: "-u__llvm_profile_runtime"
// CHECK-PROFRT-AARCH64: "[[RESOURCE_DIR]]{{/|\\\\}}lib{{/|\\\\}}aarch64-fuchsia{{/|\\\\}}libclang_rt.profile.a"
// RUN: %clang %s -### --target=x86_64-fuchsia \
@@ -258,5 +257,4 @@
// RUN: -fuse-ld=lld 2>&1 \
// RUN: | FileCheck %s -check-prefix=CHECK-PROFRT-X86_64
// CHECK-PROFRT-X86_64: "-resource-dir" "[[RESOURCE_DIR:[^"]+]]"
-// CHECK-PROFRT-X86_64: "-u__llvm_profile_runtime"
// CHECK-PROFRT-X86_64: "[[RESOURCE_DIR]]{{/|\\\\}}lib{{/|\\\\}}x86_64-fuchsia{{/|\\\\}}libclang_rt.profile.a"
diff --git a/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp b/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
index 3c5b579cada1..998a8b9235c7 100644
--- a/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
+++ b/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
@@ -543,8 +543,10 @@ bool InstrProfiling::run(
UsedVars.clear();
TT = Triple(M.getTargetTriple());
- // Emit the runtime hook even if no counters are present.
- bool MadeChange = emitRuntimeHook();
+ bool MadeChange = false;
+ // Emit the runtime hook even if no counters are present in Mach-O.
+ if (TT.isOSBinFormatMachO())
+ MadeChange = emitRuntimeHook();
// Improve compile time by avoiding linear scans when there is no work.
GlobalVariable *CoverageNamesVar =
@@ -584,6 +586,8 @@ bool InstrProfiling::run(
emitVNodes();
emitNameData();
emitRegistration();
+ if (!TT.isOSBinFormatMachO())
+ emitRuntimeHook();
emitUses();
emitInitialization();
return true;
@@ -1058,11 +1062,6 @@ void InstrProfiling::emitRegistration() {
}
bool InstrProfiling::emitRuntimeHook() {
- // We expect the linker to be invoked with -u<hook_var> flag for Linux or
- // Fuchsia, in which case there is no need to emit the user function.
- if (TT.isOSLinux() || TT.isOSFuchsia())
- return false;
-
// If the module's provided its own runtime, we don't need to do anything.
if (M->getGlobalVariable(getInstrProfRuntimeHookVarName()))
return false;
diff --git a/llvm/test/Instrumentation/InstrProfiling/linkage.ll b/llvm/test/Instrumentation/InstrProfiling/linkage.ll
index 61fe9a52122b..81ba4d3c90d6 100644
--- a/llvm/test/Instrumentation/InstrProfiling/linkage.ll
+++ b/llvm/test/Instrumentation/InstrProfiling/linkage.ll
@@ -10,7 +10,6 @@
; RUN: opt < %s -mtriple=x86_64-pc-win32-coff -passes=instrprof -S | FileCheck %s --check-prefixes=COFF
; MACHO: @__llvm_profile_runtime = external global i32
-; ELF-NOT: @__llvm_profile_runtime = external global i32
; ELF: $__profd_foo = comdat noduplicates
; ELF: $__profd_foo_weak = comdat noduplicates
diff --git a/llvm/test/Instrumentation/InstrProfiling/profiling.ll b/llvm/test/Instrumentation/InstrProfiling/profiling.ll
index e2e47e0b20bb..76d319d2e6b9 100644
--- a/llvm/test/Instrumentation/InstrProfiling/profiling.ll
+++ b/llvm/test/Instrumentation/InstrProfiling/profiling.ll
@@ -1,14 +1,11 @@
; RUN: opt < %s -mtriple=x86_64 -passes=instrprof -S | FileCheck %s --check-prefixes=CHECK,ELF,ELF_GENERIC
; RUN: opt < %s -mtriple=x86_64-linux -passes=instrprof -S | FileCheck %s --check-prefixes=CHECK,ELF_LINUX
; RUN: opt < %s -mtriple=x86_64-apple-macosx10.10.0 -passes=instrprof -S | FileCheck %s --check-prefixes=CHECK,MACHO
-; RUN: opt < %s -mtriple=x86_64-windows -passes=instrprof -S | FileCheck %s --check-prefixes=CHECK,WIN
+; RUN: opt < %s -mtriple=x86_64-windows -passes=instrprof -S | FileCheck %s --check-prefixes=CHECK,COFF
; RUN: opt < %s -mtriple=x86_64-apple-macosx10.10.0 -instrprof -S | FileCheck %s
-; ELF_GENERIC: @__llvm_profile_runtime = external global i32
-; ELF_LINUX-NOT: @__llvm_profile_runtime
; MACHO: @__llvm_profile_runtime = external global i32
-; WIN: @__llvm_profile_runtime = external global i32
@__profn_foo = hidden constant [3 x i8] c"foo"
; CHECK-NOT: __profn_foo
@@ -21,8 +18,8 @@
; ELF: @__profd_foo = hidden {{.*}}, section "__llvm_prf_data", comdat, align 8
; MACHO: @__profc_foo = hidden global [1 x i64] zeroinitializer, section "__DATA,__llvm_prf_cnts", align 8
; MACHO: @__profd_foo = hidden {{.*}}, section "__DATA,__llvm_prf_data,regular,live_support", align 8
-; WIN: @__profc_foo = internal global [1 x i64] zeroinitializer, section ".lprfc$M", align 8
-; WIN: @__profd_foo = internal {{.*}}, section ".lprfd$M", align 8
+; COFF: @__profc_foo = internal global [1 x i64] zeroinitializer, section ".lprfc$M", align 8
+; COFF: @__profd_foo = internal {{.*}}, section ".lprfd$M", align 8
define void @foo() {
call void @llvm.instrprof.increment(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @__profn_foo, i32 0, i32 0), i64 0, i32 1, i32 0)
ret void
@@ -32,8 +29,8 @@ define void @foo() {
; ELF: @__profd_bar = hidden {{.*}}, section "__llvm_prf_data", comdat, align 8
; MACHO: @__profc_bar = hidden global [1 x i64] zeroinitializer, section "__DATA,__llvm_prf_cnts", align 8
; MACHO: @__profd_bar = hidden {{.*}}, section "__DATA,__llvm_prf_data,regular,live_support", align 8
-; WIN: @__profc_bar = internal global [1 x i64] zeroinitializer, section ".lprfc$M", align 8
-; WIN: @__profd_bar = internal {{.*}}, section ".lprfd$M", align 8
+; COFF: @__profc_bar = internal global [1 x i64] zeroinitializer, section ".lprfc$M", align 8
+; COFF: @__profd_bar = internal {{.*}}, section ".lprfd$M", align 8
define void @bar() {
call void @llvm.instrprof.increment(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @__profn_bar, i32 0, i32 0), i64 0, i32 1, i32 0)
ret void
@@ -43,8 +40,8 @@ define void @bar() {
; ELF: @__profd_baz = hidden {{.*}}, section "__llvm_prf_data", comdat, align 8
; MACHO: @__profc_baz = hidden global [3 x i64] zeroinitializer, section "__DATA,__llvm_prf_cnts", align 8
; MACHO: @__profd_baz = hidden {{.*}}, section "__DATA,__llvm_prf_data,regular,live_support", align 8
-; WIN: @__profc_baz = internal global [3 x i64] zeroinitializer, section ".lprfc$M", align 8
-; WIN: @__profd_baz = internal {{.*}}, section ".lprfd$M", align 8
+; COFF: @__profc_baz = internal global [3 x i64] zeroinitializer, section ".lprfc$M", align 8
+; COFF: @__profd_baz = internal {{.*}}, section ".lprfd$M", align 8
define void @baz() {
call void @llvm.instrprof.increment(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @__profn_baz, i32 0, i32 0), i64 0, i32 3, i32 0)
call void @llvm.instrprof.increment(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @__profn_baz, i32 0, i32 0), i64 0, i32 3, i32 1)
@@ -54,12 +51,14 @@ define void @baz() {
declare void @llvm.instrprof.increment(i8*, i64, i32, i32)
-; ELF: @llvm.compiler.used = appending global {{.*}} @__llvm_profile_runtime {{.*}} @__profd_foo {{.*}} @__profd_bar {{.*}} @__profd_baz
+; ELF: @__llvm_profile_runtime = external global i32
+; COFF: @__llvm_profile_runtime = external global i32
+
+; ELF: @llvm.compiler.used = appending global {{.*}} @__profd_foo {{.*}} @__profd_bar {{.*}} @__profd_baz {{.*}} @__llvm_profile_runtime
; MACHO: @llvm.used = appending global {{.*}} @__llvm_profile_runtime {{.*}} @__profd_foo {{.*}} @__profd_bar {{.*}} @__profd_baz
-; WIN: @llvm.used = appending global {{.*}} @__llvm_profile_runtime {{.*}} @__profd_foo {{.*}} @__profd_bar {{.*}} @__profd_baz
+; COFF: @llvm.used = appending global {{.*}} @__profd_foo {{.*}} @__profd_bar {{.*}} @__profd_baz {{.*}} @__llvm_profile_runtime
; ELF_GENERIC: define internal void @__llvm_profile_register_functions() unnamed_addr {
-; ELF_GENERIC-NEXT: call void @__llvm_profile_register_function(i8* bitcast (i32* @__llvm_profile_runtime to i8*))
; ELF_GENERIC-NEXT: call void @__llvm_profile_register_function(i8* bitcast ({ i64, i64, i64*, i8*, i8*, i32, [2 x i16] }* @__profd_foo to i8*))
; ELF_GENERIC-NEXT: call void @__llvm_profile_register_function(i8* bitcast ({ i64, i64, i64*, i8*, i8*, i32, [2 x i16] }* @__profd_bar to i8*))
; ELF_GENERIC-NEXT: call void @__llvm_profile_register_function(i8* bitcast ({ i64, i64, i64*, i8*, i8*, i32, [2 x i16] }* @__profd_baz to i8*))
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