diff options
| author | Rui Ueyama <ruiu@google.com> | 2017-04-27 23:03:22 +0000 |
|---|---|---|
| committer | Rui Ueyama <ruiu@google.com> | 2017-04-27 23:03:22 +0000 |
| commit | a85572ebf0421f3cb0bacb0b1ad4321ff955ee52 (patch) | |
| tree | 4f87510315ea48d7ebfb8beff8ee7dd6ab1ae100 | |
| parent | b907563fbcd71abcf6600688942c710468d43168 (diff) | |
| download | bcm5719-llvm-a85572ebf0421f3cb0bacb0b1ad4321ff955ee52.tar.gz bcm5719-llvm-a85572ebf0421f3cb0bacb0b1ad4321ff955ee52.zip | |
COFF ICF: Merge only functions. Do not merge read-only data.
This seems to be the behavior of the MSVC linker. Previously, this
incompatibility caused nasty issues in chromium build a few times.
Differential Revision: https://reviews.llvm.org/D30363
llvm-svn: 301598
| -rw-r--r-- | lld/COFF/ICF.cpp | 10 | ||||
| -rw-r--r-- | lld/test/COFF/icf-data.test | 61 |
2 files changed, 70 insertions, 1 deletions
diff --git a/lld/COFF/ICF.cpp b/lld/COFF/ICF.cpp index 19468c0fac5..fe59de6efa5 100644 --- a/lld/COFF/ICF.cpp +++ b/lld/COFF/ICF.cpp @@ -71,10 +71,18 @@ uint32_t ICF::getHash(SectionChunk *C) { } // Returns true if section S is subject of ICF. +// +// Microsoft's documentation +// (https://msdn.microsoft.com/en-us/library/bxwfs976.aspx; visited April +// 2017) says that /opt:icf folds both functions and read-only data. +// Despite that, the MSVC linker folds only functions. We found +// a few instances of programs that are not safe for data merging. +// Therefore, we merge only functions just like the MSVC tool. bool ICF::isEligible(SectionChunk *C) { bool Global = C->Sym && C->Sym->isExternal(); + bool Executable = C->getPermissions() & llvm::COFF::IMAGE_SCN_MEM_EXECUTE; bool Writable = C->getPermissions() & llvm::COFF::IMAGE_SCN_MEM_WRITE; - return C->isCOMDAT() && C->isLive() && Global && !Writable; + return C->isCOMDAT() && C->isLive() && Global && Executable && !Writable; } // Split a range into smaller ranges by recoloring sections diff --git a/lld/test/COFF/icf-data.test b/lld/test/COFF/icf-data.test new file mode 100644 index 00000000000..20bdecaf3cf --- /dev/null +++ b/lld/test/COFF/icf-data.test @@ -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: Removed foo +# CHECK-NOT: Removed bar + +--- !COFF +header: + Machine: IMAGE_FILE_MACHINE_AMD64 + Characteristics: [] +sections: + - Name: '.text$mn' + Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_LNK_COMDAT, IMAGE_SCN_MEM_READ ] + Alignment: 16 + SectionData: 4883EC28E8000000004883C428C3 + - Name: '.text$mn' + Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_LNK_COMDAT, 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 +... |
