Fix a bug in ICF involving COFF associative sections.

Associative sections are sections that need to be linked if their associated
sections are linked. Associative sections are used to append auxiliary data
such as debug info.

Previously, we compared all associative sections when comparing two comdat
sections. Because usually assocative sections are not mergeable sections,
we missed a lot of mergeable sections. MSVC linker doesn't seem to check
the identity of associative sections.

This patch makes LLD to ignore associative sections when doing ICF.

llvm-svn: 288483

diff --git a/lld/COFF/ICF.cpp b/lld/COFF/ICF.cpp
index a2c5a90..4d4d2f3 100644 (file)
--- a/lld/COFF/ICF.cpp
+++ b/lld/COFF/ICF.cpp
@@ -95,11 +95,6 @@ bool ICF::equalsConstant(const SectionChunk *A, const SectionChunk *B) {
     return false;
   }
 
-  // Compare associative sections.
-  for (size_t I = 0, E = A->AssocChildren.size(); I != E; ++I)
-    if (A->AssocChildren[I]->GroupID != B->AssocChildren[I]->GroupID)
-      return false;
-
   // Compare relocations.
   auto Eq = [&](const coff_relocation &R1, const coff_relocation &R2) {
     if (R1.Type != R2.Type ||
@@ -129,11 +124,6 @@ bool ICF::equalsConstant(const SectionChunk *A, const SectionChunk *B) {
 }
 
 bool ICF::equalsVariable(const SectionChunk *A, const SectionChunk *B) {
-  // Compare associative sections.
-  for (size_t I = 0, E = A->AssocChildren.size(); I != E; ++I)
-    if (A->AssocChildren[I]->GroupID != B->AssocChildren[I]->GroupID)
-      return false;
-
   // Compare relocations.
   auto Eq = [&](const coff_relocation &R1, const coff_relocation &R2) {
     SymbolBody *B1 = A->File->getSymbolBody(R1.SymbolTableIndex)->repl();

diff --git a/lld/test/COFF/icf-associative.test b/lld/test/COFF/icf-associative.test
new file mode 100644 (file)
index 0000000..1c63b05
--- /dev/null
+++ b/lld/test/COFF/icf-associative.test
@@ -0,0 +1,104 @@
+# RUN: yaml2obj < %s > %t.obj
+# RUN: lld-link /entry:foo /out:%t.exe /subsystem:console /include:bar \
+# RUN:   /debug /verbose %t.obj > %t.log 2>&1
+# RUN: FileCheck %s < %t.log
+
+# CHECK: Selected foo
+# CHECK:   Removed bar
+
+--- !COFF
+header:
+  Machine:         IMAGE_FILE_MACHINE_AMD64
+  Characteristics: []
+sections:
+  - Name:            '.text$mn'
+    Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_LNK_COMDAT, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
+    Alignment:       16
+    SectionData:     4883EC28E8000000004883C428C3
+
+  - Name:            '.debug$S'
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_LNK_COMDAT, IMAGE_SCN_MEM_DISCARDABLE, IMAGE_SCN_MEM_READ ]
+    Alignment:       1
+    SectionData:     0000000000000000000000000000
+
+  - Name:            '.text$mn'
+    Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_LNK_COMDAT, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
+    Alignment:       16
+    SectionData:     4883EC28E8000000004883C428C3
+
+  - Name:            '.debug$S'
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_LNK_COMDAT, IMAGE_SCN_MEM_DISCARDABLE, IMAGE_SCN_MEM_READ ]
+    Alignment:       1
+    SectionData:     FFFFFFFFFFFFFFFFFFFFFFFFFFFF
+
+symbols:
+  - Name:            '.text$mn'
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          14
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        1682752513
+      Number:          0
+      Selection:       IMAGE_COMDAT_SELECT_ANY
+
+  - Name:            '.debug$S'
+    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:        0
+      Number:          1
+      Selection:       IMAGE_COMDAT_SELECT_ASSOCIATIVE
+
+  - Name:            '.text$mn'
+    Value:           0
+    SectionNumber:   3
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          14
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        1682752513
+      Number:          0
+      Selection:       IMAGE_COMDAT_SELECT_ANY
+
+  - Name:            '.debug$S'
+    Value:           0
+    SectionNumber:   4
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          14
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        0
+      Number:          3
+      Selection:       IMAGE_COMDAT_SELECT_ASSOCIATIVE
+
+  - 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:   3
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_FUNCTION
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+...