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COFF: ICF should not merge sectinos if their alignments are not the same. 

There's actually a room to improve this patch. Instead of not merging
sections that have different alignements, we can choose the section that
has the largest alignment requirement among all sections that are otherwise
considered the same. Then all section alignments are satisfied, so we can
merge them.

I don't know if that improvement could make any difference for real-world
input, so I'll leave it alone. Would be interesting to revisit later.

llvm-svn: 248581
This commit is contained in:
Rui Ueyama 2015-09-25 16:50:12 +00:00
parent c9e746b9e6
commit 548d22c073
3 changed files with 65 additions and 2 deletions
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4
lld/COFF/Chunks.h
View File

@ -62,8 +62,8 @@ public:
virtual void writeTo(uint8_t *Buf) const {}
// The writer sets and uses the addresses.
uint64_t getRVA() { return RVA; }
uint32_t getAlign() { return Align; }
uint64_t getRVA() const { return RVA; }
uint32_t getAlign() const { return Align; }
void setRVA(uint64_t V) { RVA = V; }
void setOutputSectionOff(uint64_t V) { OutputSectionOff = V; }

2
lld/COFF/ICF.cpp
View File

@ -85,6 +85,7 @@ uint64_t ICF::getHash(SectionChunk *C) {
return hash_combine(C->getPermissions(),
hash_value(C->SectionName),
C->NumRelocs,
C->getAlign(),
uint32_t(C->Header->SizeOfRawData),
C->Checksum);
}
@ -122,6 +123,7 @@ bool ICF::equalsConstant(const SectionChunk *A, const SectionChunk *B) {
// Compare section attributes and contents.
return A->getPermissions() == B->getPermissions() &&
A->SectionName == B->SectionName &&
A->getAlign() == B->getAlign() &&
A->Header->SizeOfRawData == B->Header->SizeOfRawData &&
A->Checksum == B->Checksum &&
A->getContents() == B->getContents();

61
lld/test/COFF/icf-different-align.test Normal file
View File

@ -0,0 +1,61 @@
# RUN: yaml2obj < %s > %t.obj
# RUN: lld-link /entry:foo /out:%t.exe /subsystem:console /include:bar \
# RUN: /verbose %t.obj > %t.log 2>&1
# RUN: FileCheck %s < %t.log
# CHECK-NOT: Selected foo
# CHECK-NOT: Removed bar
---
header:
Machine: IMAGE_FILE_MACHINE_AMD64
Characteristics: []
sections:
- Name: '.text$mn'
Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_LNK_COMDAT, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
Alignment: 8
SectionData: 4883EC28E8000000004883C428C3
- Name: '.text$mn'
Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_LNK_COMDAT, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
Alignment: 16
SectionData: 4883EC28E8000000004883C428C3
symbols:
- Name: '.text$mn'
Value: 0
SectionNumber: 1
SimpleType: IMAGE_SYM_TYPE_NULL
ComplexType: IMAGE_SYM_DTYPE_NULL
StorageClass: IMAGE_SYM_CLASS_STATIC
SectionDefinition:
Length: 14
NumberOfRelocations: 0
NumberOfLinenumbers: 0
CheckSum: 1682752513
Number: 0
Selection: IMAGE_COMDAT_SELECT_NODUPLICATES
- Name: '.text$mn'
Value: 0
SectionNumber: 2
SimpleType: IMAGE_SYM_TYPE_NULL
ComplexType: IMAGE_SYM_DTYPE_NULL
StorageClass: IMAGE_SYM_CLASS_STATIC
SectionDefinition:
Length: 14
NumberOfRelocations: 0
NumberOfLinenumbers: 0
CheckSum: 1682752513
Number: 0
Selection: IMAGE_COMDAT_SELECT_NODUPLICATES
- Name: foo
Value: 0
SectionNumber: 1
SimpleType: IMAGE_SYM_TYPE_NULL
ComplexType: IMAGE_SYM_DTYPE_FUNCTION
StorageClass: IMAGE_SYM_CLASS_EXTERNAL
- Name: bar
Value: 0
SectionNumber: 2
SimpleType: IMAGE_SYM_TYPE_NULL
ComplexType: IMAGE_SYM_DTYPE_FUNCTION
StorageClass: IMAGE_SYM_CLASS_EXTERNAL
...