[lld] 3fd1d69 - [ELF] relocateNonAlloc: clean up workaround code

[Fangrui Song via llvm-commits]

Author: Fangrui Song
Date: 2023-12-07T12:43:40-08:00
New Revision: 3fd1d6953d12e2fba6b5efae0a725500c963ce3a

URL: https://github.com/llvm/llvm-project/commit/3fd1d6953d12e2fba6b5efae0a725500c963ce3a
DIFF: https://github.com/llvm/llvm-project/commit/3fd1d6953d12e2fba6b5efae0a725500c963ce3a.diff

LOG: [ELF] relocateNonAlloc: clean up workaround code

relocateNonAlloc is costly for .debug_* section relocating. We don't
want to burn CPU cycles on other targets' workarounds.

Remove a temporary workaround for Linux objtool after a proper fix
https://git.kernel.org/linus/b8ec60e1186cdcfce41e7db4c827cb107e459002

Move the R_386_GOTPC workaround for GCC<8 beside the R_PC workaround.

Added: 
    

Modified: 
    lld/ELF/InputSection.cpp
    lld/test/ELF/i386-debug-noabs.test
    lld/test/ELF/non-abs-reloc.s

Removed: 
    


################################################################################
diff  --git a/lld/ELF/InputSection.cpp b/lld/ELF/InputSection.cpp
index 2c06bb594158c..81468a20dfb54 100644
--- a/lld/ELF/InputSection.cpp
+++ b/lld/ELF/InputSection.cpp
@@ -910,16 +910,8 @@ void InputSection::relocateNonAlloc(uint8_t *buf, ArrayRef<RelTy> rels) {
 
   for (size_t i = 0, relsSize = rels.size(); i != relsSize; ++i) {
     const RelTy &rel = rels[i];
-    RelType type = rel.getType(config->isMips64EL);
-
-    // GCC 8.0 or earlier have a bug that they emit R_386_GOTPC relocations
-    // against _GLOBAL_OFFSET_TABLE_ for .debug_info. The bug has been fixed
-    // in 2017 (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82630), but we
-    // need to keep this bug-compatible code for a while.
-    if (emachine == EM_386 && type == R_386_GOTPC)
-      continue;
-
-    uint64_t offset = rel.r_offset;
+    const RelType type = rel.getType(config->isMips64EL);
+    const uint64_t offset = rel.r_offset;
     uint8_t *bufLoc = buf + offset;
     int64_t addend = getAddend<ELFT>(rel);
     if (!RelTy::IsRela)
@@ -1016,8 +1008,8 @@ void InputSection::relocateNonAlloc(uint8_t *buf, ArrayRef<RelTy> rels) {
     std::string msg = getLocation(offset) + ": has non-ABS relocation " +
                       toString(type) + " against symbol '" + toString(sym) +
                       "'";
-    if (expr != R_PC) {
-      error(msg);
+    if (expr != R_PC && !(emachine == EM_386 && type == R_386_GOTPC)) {
+      errorOrWarn(msg);
       return;
     }
 
@@ -1029,11 +1021,11 @@ void InputSection::relocateNonAlloc(uint8_t *buf, ArrayRef<RelTy> rels) {
     // address 0. For bug-compatibility, we accept them with warnings. We
     // know Steel Bank Common Lisp as of 2018 have this bug.
     //
-    // RELA -r stopped earlier and does not get the warning. Suppress the
-    // warning for REL -r as well
-    // (https://github.com/ClangBuiltLinux/linux/issues/1937).
-    if (RelTy::IsRela || !config->relocatable)
-      warn(msg);
+    // GCC 8.0 or earlier have a bug that they emit R_386_GOTPC relocations
+    // against _GLOBAL_OFFSET_TABLE_ for .debug_info. The bug has been fixed in
+    // 2017 (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82630), but we need to
+    // keep this bug-compatible code for a while.
+    warn(msg);
     target.relocateNoSym(
         bufLoc, type,
         SignExtend64<bits>(sym.getVA(addend - offset - outSecOff)));

diff  --git a/lld/test/ELF/i386-debug-noabs.test b/lld/test/ELF/i386-debug-noabs.test
index 486cc8d9fbed8..02ef238dd1485 100644
--- a/lld/test/ELF/i386-debug-noabs.test
+++ b/lld/test/ELF/i386-debug-noabs.test
@@ -1,7 +1,8 @@
 # REQUIRES: x86
 
 # RUN: yaml2obj %s -o %t.o
-# RUN: ld.lld %t.o -o /dev/null --entry 0 --fatal-warnings
+# RUN: ld.lld %t.o -o /dev/null --entry 0 2>&1 | FileCheck %s
+# CHECK: warning: {{.*}}:(.debug_info+0x41f): has non-ABS relocation R_386_GOTPC against symbol '_GLOBAL_OFFSET_TABLE_'
 
 ## This is for https://bugs.llvm.org//show_bug.cgi?id=34852. GCC 8.0 or
 ## earlier have a bug which creates non-absolute R_386_GOTPC relocations

diff  --git a/lld/test/ELF/non-abs-reloc.s b/lld/test/ELF/non-abs-reloc.s
index 04f583ab25347..42b5f8fec1c43 100644
--- a/lld/test/ELF/non-abs-reloc.s
+++ b/lld/test/ELF/non-abs-reloc.s
@@ -15,7 +15,8 @@
 // DISASM-NEXT:   6: call{{.}} 0x5
 
 /// There is currently no error for -r. See also https://github.com/ClangBuiltLinux/linux/issues/1937
-// RUN: ld.lld -T lds -r a.o -o /dev/null --fatal-warnings
+// RUN: ld.lld -T lds -r a.o -o /dev/null 2>&1 | FileCheck %s --check-prefix=REL-R --implicit-check-not=warning:
+// REL-R: warning: {{.*}}:(.nonalloc1+0xa): has non-ABS relocation R_386_PC32 against symbol ''
 
 // RUN: llvm-mc -filetype=obj -triple=x86_64 asm -o b.o
 // RUN: ld.lld -T lds b.o -o b 2>&1 | FileCheck %s --check-prefix=CHECK2 --implicit-check-not=warning: