From 2d53967b486fa213613f4ced6b3087050997b82b Mon Sep 17 00:00:00 2001
From: George Rimar <grimar@accesssoftek.com>
Date: Fri, 23 Feb 2018 10:37:33 +0000
Subject: [PATCH] Recommit "[ELF] - Do not crash with --emit-relocs and
 --icf=all together."

Latest patch version now.

Original commit message:

[ELF] - Do not crash with --emit-relocs and --icf=all together.

Previously we would crash because did not mark .rel[a] sections
as dead and they tried to access parent which was not live
after ICF and therefore was null.

Differential revision: https://reviews.llvm.org/D43241

llvm-svn: 325879
---
 lld/ELF/ICF.cpp                | 15 ++++++---------
 lld/test/ELF/emit-relocs-icf.s | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+), 9 deletions(-)
 create mode 100644 lld/test/ELF/emit-relocs-icf.s

diff --git a/lld/ELF/ICF.cpp b/lld/ELF/ICF.cpp
index c3b96bd..8b58c99 100644
--- a/lld/ELF/ICF.cpp
+++ b/lld/ELF/ICF.cpp
@@ -437,17 +437,14 @@ template <class ELFT> void ICF<ELFT>::run() {
     for (size_t I = Begin + 1; I < End; ++I) {
       print("  removing identical section " + toString(Sections[I]));
       Sections[Begin]->replace(Sections[I]);
+
+      // At this point we know sections merged are fully identical and hence
+      // we want to remove duplicate implicit dependencies such as link order
+      // and relocation sections.
+      for (InputSection *IS : Sections[I]->DependentSections)
+        IS->Live = false;
     }
   });
-
-  // Mark ARM Exception Index table sections that refer to folded code
-  // sections as not live. These sections have an implict dependency
-  // via the link order dependency.
-  if (Config->EMachine == EM_ARM)
-    for (InputSectionBase *Sec : InputSections)
-      if (auto *S = dyn_cast<InputSection>(Sec))
-        if (S->Flags & SHF_LINK_ORDER)
-          S->Live = S->getLinkOrderDep()->Live;
 }
 
 // ICF entry point function.
diff --git a/lld/test/ELF/emit-relocs-icf.s b/lld/test/ELF/emit-relocs-icf.s
new file mode 100644
index 0000000..59e003f
--- /dev/null
+++ b/lld/test/ELF/emit-relocs-icf.s
@@ -0,0 +1,33 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t1.o
+# RUN: ld.lld --emit-relocs --icf=all %t1.o -o %t
+# RUN: llvm-readobj -r %t | FileCheck %s
+
+# CHECK:      Relocations [
+# CHECK-NEXT:   Section {{.*}} .rela.text {
+# CHECK-NEXT:     R_X86_64_32 .text 0x1
+# CHECK-NEXT:     R_X86_64_PLT32 fn 0xFFFFFFFFFFFFFFFC
+# CHECK-NEXT:   }
+# CHECK-NEXT: ]
+
+.section .text.fn,"ax",@progbits,unique,0
+.globl fn
+.type fn,@function
+fn:
+ nop
+
+bar:
+  movl $bar, %edx
+  callq fn@PLT
+  nop
+
+.section .text.fn2,"ax",@progbits,unique,1
+.globl fn2
+.type fn2,@function
+fn2:
+ nop
+
+foo:
+  movl $foo, %edx
+  callq fn2@PLT
+  nop
-- 
2.7.4