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Basic block sections should enable not function sections implicitly. 

Basic block sections enables function sections implicitly, this is not needed
and is inefficient with "=list" option.

We had basic block sections enable function sections implicitly in clang. This
is particularly inefficient with "=list" option as it places functions that do
not have any basic block sections in separate sections. This causes unnecessary
object file overhead for large applications.

This patch disables this implicit behavior. It only creates function sections
for those functions that require basic block sections.

This patch is the second of two patches and this patch removes the implicit
enabling of function sections with basic block sections in clang.

Differential Revision: https://reviews.llvm.org/D93876
This commit is contained in:
Sriraman Tallam 2021-02-17 12:34:37 -08:00
parent 279c5dc2f3
commit e741916330
2 changed files with 4 additions and 8 deletions
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7
clang/lib/Frontend/CompilerInvocation.cpp
View File

@ -1383,8 +1383,7 @@ void CompilerInvocation::GenerateCodeGenArgs(
GenerateArg(Args, OPT_ftime_report, SA);
}
if (Opts.FunctionSections &&
(Opts.BBSections == "none" || Opts.BBSections == "labels"))
if (Opts.FunctionSections)
GenerateArg(Args, OPT_ffunction_sections, SA);
if (Opts.PrepareForLTO && !Opts.PrepareForThinLTO)
@ -1678,9 +1677,7 @@ bool CompilerInvocation::ParseCodeGenArgsImpl(CodeGenOptions &Opts,
}
// Basic Block Sections implies Function Sections.
Opts.FunctionSections =
Args.hasArg(OPT_ffunction_sections) ||
(Opts.BBSections != "none" && Opts.BBSections != "labels");
Opts.FunctionSections = Args.hasArg(OPT_ffunction_sections);
Opts.PrepareForLTO = Args.hasArg(OPT_flto, OPT_flto_EQ);
Opts.PrepareForThinLTO = false;

5
clang/test/CodeGen/basic-block-sections.c
View File

@ -32,10 +32,9 @@ int another(int a) {
// BB_WORLD: world:
// BB_WORLD: .section .text.world,"ax",@progbits,unique
// BB_WORLD: world.__part.1:
// BB_WORLD: .section .text.another,"ax",@progbits
// BB_ALL: .section .text.another,"ax",@progbits,unique
// BB_ALL: .section .text.another,"ax",@progbits
// BB_ALL: another.__part.1:
// BB_LIST-NOT: .section .text.another,"ax",@progbits,unique
// BB_LIST-NOT: .section .text.another,"ax",@progbits
// BB_LIST: another:
// BB_LIST-NOT: another.__part.1:
//