[PATCH] D30363: COFF ICF: Merge only functions. Do not merge read-only data.
Rui Ueyama via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Fri Feb 24 16:32:13 PST 2017
ruiu created this revision.
This seems to be the behavior of the MSVC linker. Previously, the
compatibility caused nasty issues in chromium build a few times.
https://reviews.llvm.org/D30363
Files:
lld/COFF/ICF.cpp
lld/test/COFF/icf-data.test
Index: lld/test/COFF/icf-data.test
===================================================================
--- /dev/null
+++ 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
+...
Index: lld/COFF/ICF.cpp
===================================================================
--- lld/COFF/ICF.cpp
+++ lld/COFF/ICF.cpp
@@ -71,10 +71,12 @@
}
// Returns true if section S is subject of ICF.
+// Essentially, we want to merge only functions.
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
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