[llvm-branch-commits] [lld] release/19.x: [ELF] --icf: don't fold a section without relocation and a section with relocations for SHT_CREL (PR #109309)

[via llvm-branch-commits]

https://github.com/llvmbot created https://github.com/llvm/llvm-project/pull/109309

Backport e82f0838ae88ad69515ebec234765e3e2607bebf

Requested by: @MaskRay

>From 119843a88fc06832df46a423d0d0de6e28a60b43 Mon Sep 17 00:00:00 2001
From: Fangrui Song <i at maskray.me>
Date: Wed, 18 Sep 2024 23:06:12 -0700
Subject: [PATCH] [ELF] --icf: don't fold a section without relocation and a
 section with relocations for SHT_CREL

Similar to commit 686cff17cc310884e48ae963bf7507f96950cc90 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 e82f0838ae88ad69515ebec234765e3e2607bebf)
---
 lld/ELF/ICF.cpp          | 4 ++--
 lld/ELF/InputSection.cpp | 6 +++---
 lld/ELF/InputSection.h   | 4 ++++
 lld/test/ELF/icf10.s     | 3 +++
 4 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/lld/ELF/ICF.cpp b/lld/ELF/ICF.cpp
index 44e8a71cc62869..5591c5e71e0b1a 100644
--- a/lld/ELF/ICF.cpp
+++ b/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)
diff --git a/lld/ELF/InputSection.cpp b/lld/ELF/InputSection.cpp
index 570e485455bade..a165c813d4259c 100644
--- a/lld/ELF/InputSection.cpp
+++ b/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);
diff --git a/lld/ELF/InputSection.h b/lld/ELF/InputSection.h
index 6659530a9c9c26..afa6ee5bd0826f 100644
--- a/lld/ELF/InputSection.h
+++ b/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;
diff --git a/lld/test/ELF/icf10.s b/lld/test/ELF/icf10.s
index 3c18c431c3b9da..ff926d0e16b103 100644
--- a/lld/test/ELF/icf10.s
+++ b/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.