Use .text.unlikely and .text.eh prefixes for MachineBasicBlock sections.

Summary:
Instead of adding a ".unlikely" or ".eh" suffix for machine basic blocks,
this change updates the behaviour to use an appropriate prefix
instead. This allows lld to group basic block sections together
when -z,keep-text-section-prefix is specified and matches the behaviour
observed in gcc.

Reviewers: tmsriram, mtrofin, efriedma

Reviewed By: tmsriram, efriedma

Subscribers: eli.friedman, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D78742
This commit is contained in:
Snehasish Kumar 2020-04-24 14:35:19 -07:00 committed by Sriraman Tallam
parent 10bc12588d
commit 0cc063a8ff
5 changed files with 20 additions and 20 deletions

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@ -859,28 +859,28 @@ MCSection *TargetLoweringObjectFileELF::getSectionForMachineBasicBlock(
const Function &F, const MachineBasicBlock &MBB,
const TargetMachine &TM) const {
assert(MBB.isBeginSection() && "Basic block does not start a section!");
SmallString<128> Name;
Name =
(static_cast<MCSectionELF *>(MBB.getParent()->getSection()))->getName();
unsigned UniqueID = MCContext::GenericSectionID;
switch (MBB.getSectionID().Type) {
// Append suffixes to represent special cold and exception sections.
case MBBSectionID::SectionType::Exception:
Name += ".eh";
break;
case MBBSectionID::SectionType::Cold:
Name += ".unlikely";
break;
// For regular sections, either use a unique name, or a unique ID for the
// section.
default:
// For cold sections use the .text.unlikely prefix along with the parent
// function name. All cold blocks for the same function go to the same
// section. Similarly all exception blocks are grouped by symbol name
// under the .text.eh prefix. For regular sections, we either use a unique
// name, or a unique ID for the section.
SmallString<128> Name;
if (MBB.getSectionID() == MBBSectionID::ColdSectionID) {
Name += ".text.unlikely.";
Name += MBB.getParent()->getName();
} else if (MBB.getSectionID() == MBBSectionID::ExceptionSectionID) {
Name += ".text.eh.";
Name += MBB.getParent()->getName();
} else {
Name += MBB.getParent()->getSection()->getName();
if (TM.getUniqueBBSectionNames()) {
Name += ".";
Name += MBB.getSymbol()->getName();
} else
} else {
UniqueID = NextUniqueID++;
break;
}
}
unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_EXECINSTR;

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@ -50,7 +50,7 @@ declare i32 @baz() #1
; LINUX-SECTIONS1: .section .text.foo,"ax",@progbits,unique,1
; LINUX-SECTIONS1-LABEL: a.BB.foo:
; LINUX-SECTIONS1: jmp raa.BB.foo
; LINUX-SECTIONS1: .section .text.foo.unlikely,"ax",@progbits
; LINUX-SECTIONS1: .section .text.unlikely.foo,"ax",@progbits
; LINUX-SECTIONS1-LABEL: raa.BB.foo:
; LINUX-SECTIONS2: .section .text.foo,"ax",@progbits

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@ -62,7 +62,7 @@ declare i32 @__gxx_personality_v0(...)
; LINUX-SECTIONS1-LABEL: .LBB0_6:
; LINUX-SECTIONS1: .section .text.main,"ax",@progbits,unique,1
; LINUX-SECTIONS1-LABEL: al.BB.main:
; LINUX-SECTIONS1: .section .text.main.eh,"ax",@progbits
; LINUX-SECTIONS1: .section .text.eh.main,"ax",@progbits
; LINUX-SECTIONS1-LABEL: l.BB.main:
; LINUX-SECTIONS1-NOT: .section
; LINUX-SECTIONS1-LABEL: .LBB0_3:

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@ -48,7 +48,7 @@ declare i32 @baz() #1
; LINUX-SECTIONS1-LABEL: .Ltmp0:
; LINUX-SECTIONS1-NEXT: .size a.BB.foo, .Ltmp0-a.BB.foo
; LINUX-SECTIONS1-NOT: .section
; LINUX-SECTIONS1: .section .text.foo.unlikely,"ax",@progbits
; LINUX-SECTIONS1: .section .text.unlikely.foo,"ax",@progbits
; LINUX-SECTIONS1-LABEL: raa.BB.foo:
; LINUX-SECTIONS1: .section .text.foo,"ax",@progbits
; LINUX-SECTIONS1-LABEL: .Lfunc_end0:

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@ -34,7 +34,7 @@ declare i32 @_Z3foov() #1
; Check that the basic block with id 1 doesn't get a section.
; LINUX-SECTIONS-NOT: .section .text._Z3bazb.r.BB._Z3bazb,"ax",@progbits,unique
; Check that a single cold section is started here and id 1 and 2 blocks are placed here.
; LINUX-SECTIONS: .section .text._Z3bazb.unlikely,"ax",@progbits
; LINUX-SECTIONS: .section .text.unlikely._Z3bazb,"ax",@progbits
; LINUX-SECTIONS: r.BB._Z3bazb:
; LINUX-SECTIONS-NOT: .section .text._Z3bazb.rr.BB._Z3bazb,"ax",@progbits,unique
; LINUX-SECTIONS: .LBB0_2: