r338209 - Revert r337456: [CodeGen] Disable aggressive structor optimizations at -O0, take 3
Chandler Carruth via cfe-commits
cfe-commits at lists.llvm.org
Sat Jul 28 20:05:07 PDT 2018
Author: chandlerc
Date: Sat Jul 28 20:05:07 2018
New Revision: 338209
URL: http://llvm.org/viewvc/llvm-project?rev=338209&view=rev
Log:
Revert r337456: [CodeGen] Disable aggressive structor optimizations at -O0, take 3
This commit increases the number of sections and overall output size of
.o files by 10% and sometimes a bit more. This alone is challenging for
some users, but it also appears to trigger an as-yet unexplained
behavior in the Gold linker where the memory usage increases
considerably more than 10% (we think).
The increase is also frustrating because in many (if not all) cases we
end up with almost all of the growth coming from the ELF overhead of
-ffunction-sections and such, not from actual extra code being emitted.
Richard Smith and Eric Christopher are both going to investigate this
and try to get to the bottom of what is triggering this and whether the
kinds of increases here are sustainable or what options we might have to
minimize the impact they have. However, this is currently breaking
a pretty large number of our users' builds so reverting it while we sort
out how to make progress here. I've seen a longer and more detailed
update to the commit thread.
Modified:
cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp
cfe/trunk/test/CodeGenCXX/ctor-dtor-alias.cpp
cfe/trunk/test/CodeGenCXX/float16-declarations.cpp
Modified: cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp?rev=338209&r1=338208&r2=338209&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp (original)
+++ cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp Sat Jul 28 20:05:07 2018
@@ -3744,22 +3744,12 @@ static StructorCodegen getCodegenToUse(C
}
llvm::GlobalValue::LinkageTypes Linkage = CGM.getFunctionLinkage(AliasDecl);
- // All discardable structors can be RAUWed, but we don't want to do that in
- // unoptimized code, as that makes complete structor symbol disappear
- // completely, which degrades debugging experience.
- // Symbols with private linkage can be safely aliased, so we special case them
- // here.
- if (llvm::GlobalValue::isLocalLinkage(Linkage))
- return CGM.getCodeGenOpts().OptimizationLevel > 0 ? StructorCodegen::RAUW
- : StructorCodegen::Alias;
+ if (llvm::GlobalValue::isDiscardableIfUnused(Linkage))
+ return StructorCodegen::RAUW;
- // Linkonce structors cannot be aliased nor placed in a comdat, so these need
- // to be emitted separately.
// FIXME: Should we allow available_externally aliases?
- if (llvm::GlobalValue::isDiscardableIfUnused(Linkage) ||
- !llvm::GlobalAlias::isValidLinkage(Linkage))
- return CGM.getCodeGenOpts().OptimizationLevel > 0 ? StructorCodegen::RAUW
- : StructorCodegen::Emit;
+ if (!llvm::GlobalAlias::isValidLinkage(Linkage))
+ return StructorCodegen::RAUW;
if (llvm::GlobalValue::isWeakForLinker(Linkage)) {
// Only ELF and wasm support COMDATs with arbitrary names (C5/D5).
Modified: cfe/trunk/test/CodeGenCXX/ctor-dtor-alias.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/ctor-dtor-alias.cpp?rev=338209&r1=338208&r2=338209&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/ctor-dtor-alias.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/ctor-dtor-alias.cpp Sat Jul 28 20:05:07 2018
@@ -1,7 +1,5 @@
-// RUN: %clang_cc1 %s -triple i686-linux -emit-llvm -o - -mconstructor-aliases > %t
-// RUN: FileCheck --check-prefix=NOOPT1 --input-file=%t %s
-// RUN: FileCheck --check-prefix=NOOPT2 --input-file=%t %s
-// RUN: FileCheck --check-prefix=NOOPT3 --input-file=%t %s
+// RUN: %clang_cc1 %s -triple i686-linux -emit-llvm -o - -mconstructor-aliases | FileCheck --check-prefix=NOOPT %s
+
// RUN: %clang_cc1 %s -triple i686-linux -emit-llvm -o - -mconstructor-aliases -O1 -disable-llvm-passes > %t
// RUN: FileCheck --check-prefix=CHECK1 --input-file=%t %s
// RUN: FileCheck --check-prefix=CHECK2 --input-file=%t %s
@@ -23,13 +21,6 @@ namespace test1 {
// CHECK1: define weak_odr void @_ZN5test16foobarIvED0Ev({{.*}} comdat($_ZN5test16foobarIvED5Ev)
// CHECK1-NOT: comdat
-// This should happen regardless of the opt level.
-// NOOPT1: @_ZN5test16foobarIvEC1Ev = weak_odr unnamed_addr alias void {{.*}} @_ZN5test16foobarIvEC2Ev
-// NOOPT1: @_ZN5test16foobarIvED1Ev = weak_odr unnamed_addr alias void (%"struct.test1::foobar"*), void (%"struct.test1::foobar"*)* @_ZN5test16foobarIvED2Ev
-// NOOPT1: define weak_odr void @_ZN5test16foobarIvEC2Ev({{.*}} comdat($_ZN5test16foobarIvEC5Ev)
-// NOOPT1: define weak_odr void @_ZN5test16foobarIvED2Ev({{.*}} comdat($_ZN5test16foobarIvED5Ev)
-// NOOPT1: define weak_odr void @_ZN5test16foobarIvED0Ev({{.*}} comdat($_ZN5test16foobarIvED5Ev)
-
// COFF doesn't support comdats with arbitrary names (C5/D5).
// COFF: define weak_odr {{.*}} void @_ZN5test16foobarIvEC2Ev({{.*}} comdat align
// COFF: define weak_odr {{.*}} void @_ZN5test16foobarIvEC1Ev({{.*}} comdat align
@@ -46,17 +37,12 @@ template struct foobar<void>;
}
namespace test2 {
-// test that when the destructor is linkonce_odr we just replace every use of
+// test that when the destrucor is linkonce_odr we just replace every use of
// C1 with C2.
// CHECK1: define internal void @__cxx_global_var_init()
// CHECK1: call void @_ZN5test26foobarIvEC2Ev
// CHECK1: define linkonce_odr void @_ZN5test26foobarIvEC2Ev({{.*}} comdat align
-
-// At -O0, we should still emit the complete constructor.
-// NOOPT1: define internal void @__cxx_global_var_init()
-// NOOPT1: call void @_ZN5test26foobarIvEC1Ev
-// NOOPT1: define linkonce_odr void @_ZN5test26foobarIvEC1Ev({{.*}} comdat align
void g();
template <typename T> struct foobar {
foobar() { g(); }
@@ -71,11 +57,6 @@ namespace test3 {
// CHECK1: define internal void @__cxx_global_var_init.1()
// CHECK1: call i32 @__cxa_atexit{{.*}}_ZN5test312_GLOBAL__N_11AD2Ev
// CHECK1: define internal void @_ZN5test312_GLOBAL__N_11AD2Ev(
-
-// We can use an alias for internal symbols at -O0.
-// NOOPT2: _ZN5test312_GLOBAL__N_11BD1Ev = internal unnamed_addr alias void {{.*}} @_ZN5test312_GLOBAL__N_11BD2Ev
-// NOOPT2: define internal void @__cxx_global_var_init.1()
-// NOOPT2: call i32 @__cxa_atexit{{.*}}_ZN5test312_GLOBAL__N_11BD1Ev
namespace {
struct A {
~A() {}
@@ -96,12 +77,11 @@ namespace test4 {
// CHECK1: call i32 @__cxa_atexit{{.*}}_ZN5test41AD2Ev
// CHECK1: define linkonce_odr void @_ZN5test41AD2Ev({{.*}} comdat align
- // Test that we don't do this optimization at -O0 and call the complete
- // destructor for B instead. This enables the debugger to see both
- // destructors.
- // NOOPT2: define internal void @__cxx_global_var_init.2()
- // NOOPT2: call i32 @__cxa_atexit{{.*}}@_ZN5test41BD1Ev
- // NOOPT2: define linkonce_odr void @_ZN5test41BD1Ev({{.*}} comdat align
+ // test that we don't do this optimization at -O0 so that the debugger can
+ // see both destructors.
+ // NOOPT: define internal void @__cxx_global_var_init.2()
+ // NOOPT: call i32 @__cxa_atexit{{.*}}@_ZN5test41BD2Ev
+ // NOOPT: define linkonce_odr void @_ZN5test41BD2Ev({{.*}} comdat align
struct A {
virtual ~A() {}
};
@@ -149,11 +129,6 @@ namespace test7 {
// out if we should).
// pr17875.
// CHECK3: define void @_ZN5test71BD2Ev
-
- // At -O0, we should emit both destructors, the complete can be an alias to
- // the base one.
- // NOOPT3: @_ZN5test71BD1Ev = unnamed_addr alias void {{.*}} @_ZN5test71BD2Ev
- // NOOPT3: define void @_ZN5test71BD2Ev
template <typename> struct A {
~A() {}
};
Modified: cfe/trunk/test/CodeGenCXX/float16-declarations.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/float16-declarations.cpp?rev=338209&r1=338208&r2=338209&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/float16-declarations.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/float16-declarations.cpp Sat Jul 28 20:05:07 2018
@@ -103,7 +103,7 @@ int main(void) {
C1 c1(f1l);
// CHECK-DAG: [[F1L:%[a-z0-9]+]] = load half, half* %{{.*}}, align 2
-// CHECK-DAG: call void @_ZN2C1C1EDF16_(%class.C1* %{{.*}}, half %{{.*}})
+// CHECK-DAG: call void @_ZN2C1C2EDF16_(%class.C1* %{{.*}}, half %{{.*}})
S1<_Float16> s1 = { 132.f16 };
// CHECK-DAG: @_ZZ4mainE2s1 = private unnamed_addr constant %struct.S1 { half 0xH5820 }, align 2
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