ELF: Do not ICF two sections with different output sections.

pcc · pcc · commit 11dc7fcae2d1 · 2018-05-23T01:58:43.000Z
Note that this doesn't do the right thing in the case where there is a linker script. We probably need to move output section assignment before ICF to get the correct behaviour here. Differential Revision: https://reviews.llvm.org/D47241 llvm-svn: 333052
diff --git a/lld/ELF/ICF.cpp b/lld/ELF/ICF.cpp
@@ -78,6 +78,7 @@
 #include "SymbolTable.h"
 #include "Symbols.h"
 #include "SyntheticSections.h"
+#include "Writer.h"
 #include "lld/Common/Threads.h"
 #include "llvm/ADT/Hashing.h"
 #include "llvm/BinaryFormat/ELF.h"
@@ -302,6 +303,13 @@ bool ICF<ELFT>::equalsConstant(const InputSection *A, const InputSection *B) {
       A->getSize() != B->getSize() || A->Data != B->Data)
     return false;
 
+  // If two sections have different output sections, we cannot merge them.
+  // FIXME: This doesn't do the right thing in the case where there is a linker
+  // script. We probably need to move output section assignment before ICF to
+  // get the correct behaviour here.
+  if (getOutputSectionName(A) != getOutputSectionName(B))
+    return false;
+
   if (A->AreRelocsRela)
     return constantEq(A, A->template relas<ELFT>(), B,
                       B->template relas<ELFT>());
diff --git a/lld/ELF/InputSection.cpp b/lld/ELF/InputSection.cpp
@@ -325,7 +325,7 @@ template <class ELFT> void InputSection::copyShtGroup(uint8_t *Buf) {
     *To++ = Sections[Idx]->getOutputSection()->SectionIndex;
 }
 
-InputSectionBase *InputSection::getRelocatedSection() {
+InputSectionBase *InputSection::getRelocatedSection() const {
   if (!File || (Type != SHT_RELA && Type != SHT_REL))
     return nullptr;
   ArrayRef<InputSectionBase *> Sections = File->getSections();
diff --git a/lld/ELF/InputSection.h b/lld/ELF/InputSection.h
@@ -317,7 +317,7 @@ class InputSection : public InputSectionBase {
 
   static bool classof(const SectionBase *S);
 
-  InputSectionBase *getRelocatedSection();
+  InputSectionBase *getRelocatedSection() const;
 
   template <class ELFT, class RelTy>
   void relocateNonAlloc(uint8_t *Buf, llvm::ArrayRef<RelTy> Rels);
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
@@ -92,7 +92,7 @@ static bool isSectionPrefix(StringRef Prefix, StringRef Name) {
   return Name.startswith(Prefix) || Name == Prefix.drop_back();
 }
 
-StringRef elf::getOutputSectionName(InputSectionBase *S) {
+StringRef elf::getOutputSectionName(const InputSectionBase *S) {
   if (Config->Relocatable)
     return S->Name;
 
diff --git a/lld/ELF/Writer.h b/lld/ELF/Writer.h
@@ -48,7 +48,7 @@ struct PhdrEntry {
 };
 
 void addReservedSymbols();
-llvm::StringRef getOutputSectionName(InputSectionBase *S);
+llvm::StringRef getOutputSectionName(const InputSectionBase *S);
 
 template <class ELFT> uint32_t calcMipsEFlags();
 
diff --git a/lld/test/ELF/icf-different-output-sections.s b/lld/test/ELF/icf-different-output-sections.s
@@ -0,0 +1,9 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
+# RUN: ld.lld %t -o %t2 --icf=all --print-icf-sections | count 0
+
+.section foo,"ax"
+.byte 42
+
+.section bar,"ax"
+.byte 42

Original file line number	Diff line number	Diff line change
`@@ -325,7 +325,7 @@ template <class ELFT> void InputSection::copyShtGroup(uint8_t *Buf) {`
`325`	`325`	`*To++ = Sections[Idx]->getOutputSection()->SectionIndex;`
`326`	`326`	`}`
`327`	`327`
`328`		`-InputSectionBase *InputSection::getRelocatedSection() {`
	`328`	`+InputSectionBase *InputSection::getRelocatedSection() const {`
`329`	`329`	`if (!File \|\| (Type != SHT_RELA && Type != SHT_REL))`
`330`	`330`	`return nullptr;`
`331`	`331`	`ArrayRef<InputSectionBase *> Sections = File->getSections();`
Original file line number	Diff line number	Diff line change
`@@ -92,7 +92,7 @@ static bool isSectionPrefix(StringRef Prefix, StringRef Name) {`
`92`	`92`	`return Name.startswith(Prefix) \|\| Name == Prefix.drop_back();`
`93`	`93`	`}`
`94`	`94`
`95`		`-StringRef elf::getOutputSectionName(InputSectionBase *S) {`
	`95`	`+StringRef elf::getOutputSectionName(const InputSectionBase *S) {`
`96`	`96`	`if (Config->Relocatable)`
`97`	`97`	`return S->Name;`
`98`	`98`