[ELF] --icf: don't fold a section without relocation and a section with relocations for SHT_CREL

Similar to commit 686cff1 for SHT_REL (#57693).
CREL hasn't been tested with ICF before.

And avoid a pitfall that eqClass[0] might interfere with ICF.

(cherry picked from commit e82f083)

Author: MaskRay

lld/ELF/ICF.cpp

@@ -324,7 +324,7 @@ bool ICF<ELFT>::equalsConstant(const InputSection *a, const InputSection *b) {
 
   const RelsOrRelas<ELFT> ra = a->template relsOrRelas<ELFT>();
   const RelsOrRelas<ELFT> rb = b->template relsOrRelas<ELFT>();
-  if (ra.areRelocsCrel())
+  if (ra.areRelocsCrel() || rb.areRelocsCrel())
     return constantEq(a, ra.crels, b, rb.crels);
   return ra.areRelocsRel() || rb.areRelocsRel()
              ? constantEq(a, ra.rels, b, rb.rels)
@@ -376,7 +376,7 @@ template <class ELFT>
 bool ICF<ELFT>::equalsVariable(const InputSection *a, const InputSection *b) {
   const RelsOrRelas<ELFT> ra = a->template relsOrRelas<ELFT>();
   const RelsOrRelas<ELFT> rb = b->template relsOrRelas<ELFT>();
-  if (ra.areRelocsCrel())
+  if (ra.areRelocsCrel() || rb.areRelocsCrel())
     return variableEq(a, ra.crels, b, rb.crels);
   return ra.areRelocsRel() || rb.areRelocsRel()
              ? variableEq(a, ra.rels, b, rb.rels)

lld/ELF/InputSection.cpp

@@ -150,12 +150,12 @@ RelsOrRelas<ELFT> InputSectionBase::relsOrRelas(bool supportsCrel) const {
     InputSectionBase *const &relSec = f->getSections()[relSecIdx];
     // Otherwise, allocate a buffer to hold the decoded RELA relocations. When
     // called for the first time, relSec is null (without --emit-relocs) or an
-    // InputSection with zero eqClass[0].
-    if (!relSec || !cast<InputSection>(relSec)->eqClass[0]) {
+    // InputSection with false decodedCrel.
+    if (!relSec || !cast<InputSection>(relSec)->decodedCrel) {
       auto *sec = makeThreadLocal<InputSection>(*f, shdr, name);
       f->cacheDecodedCrel(relSecIdx, sec);
       sec->type = SHT_RELA;
-      sec->eqClass[0] = SHT_RELA;
+      sec->decodedCrel = true;
 
       RelocsCrel<ELFT::Is64Bits> entries(sec->content_);
       sec->size = entries.size() * sizeof(typename ELFT::Rela);

lld/ELF/InputSection.h

@@ -176,6 +176,10 @@ class InputSectionBase : public SectionBase {
 
   mutable bool compressed = false;
 
+  // Whether this section is SHT_CREL and has been decoded to RELA by
+  // relsOrRelas.
+  bool decodedCrel = false;
+
   // Whether the section needs to be padded with a NOP filler due to
   // deleteFallThruJmpInsn.
   bool nopFiller = false;

lld/test/ELF/icf10.s

@@ -5,6 +5,9 @@
 # RUN: llvm-mc -filetype=obj -triple=x86_64-pc-freebsd %s -o %t.o
 # RUN: ld.lld --icf=all %t.o -o /dev/null --print-icf-sections 2>&1 | FileCheck %s
 
+# RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t.o --crel
+# RUN: ld.lld --icf=all %t.o -o /dev/null --print-icf-sections 2>&1 | FileCheck %s
+
 # Checks that ICF does not merge 2 sections the offset of
 # the relocations of which differ.