[lld] r248581 - COFF: ICF should not merge sectinos if their alignments are not the same.

[Rui Ueyama via llvm-commits]

Author: ruiu
Date: Fri Sep 25 11:50:12 2015
New Revision: 248581

URL: http://llvm.org/viewvc/llvm-project?rev=248581&view=rev
Log:
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.

Added:
    lld/trunk/test/COFF/icf-different-align.test
Modified:
    lld/trunk/COFF/Chunks.h
    lld/trunk/COFF/ICF.cpp

Modified: lld/trunk/COFF/Chunks.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/Chunks.h?rev=248581&r1=248580&r2=248581&view=diff
==============================================================================
--- lld/trunk/COFF/Chunks.h (original)
+++ lld/trunk/COFF/Chunks.h Fri Sep 25 11:50:12 2015
@@ -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; }
 

Modified: lld/trunk/COFF/ICF.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/ICF.cpp?rev=248581&r1=248580&r2=248581&view=diff
==============================================================================
--- lld/trunk/COFF/ICF.cpp (original)
+++ lld/trunk/COFF/ICF.cpp Fri Sep 25 11:50:12 2015
@@ -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 SectionCh
   // 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();

Added: lld/trunk/test/COFF/icf-different-align.test
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/COFF/icf-different-align.test?rev=248581&view=auto
==============================================================================
--- lld/trunk/test/COFF/icf-different-align.test (added)
+++ lld/trunk/test/COFF/icf-different-align.test Fri Sep 25 11:50:12 2015
@@ -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
+...