[PATCH] D72183: [ELF][PPC64] Add --lax-call-lacks-nop

[Fangrui Song via Phabricator via llvm-commits]

MaskRay updated this revision to Diff 236145.
MaskRay added a comment.
Herald added subscribers: kbarton, nemanjai.

Add a hint. Add a test (we have to work around a MC deficiency)


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D72183/new/

https://reviews.llvm.org/D72183

Files:
  lld/ELF/Config.h
  lld/ELF/Driver.cpp
  lld/ELF/InputSection.cpp
  lld/ELF/Options.td
  lld/test/ELF/ppc64-error-toc-tail-call.s


Index: lld/test/ELF/ppc64-error-toc-tail-call.s
===================================================================
--- lld/test/ELF/ppc64-error-toc-tail-call.s
+++ lld/test/ELF/ppc64-error-toc-tail-call.s
@@ -11,8 +11,7 @@
 // RUN: not ld.lld %t.o %t2.so -o %t 2>&1 | FileCheck %s
 
 # A tail call to an external function without a nop should issue an error.
-// CHECK: call to foo lacks nop, can't restore toc
-// CHECK-NOT: lacks nop
+// CHECK: call to foo lacks nop, can't restore toc{{$}}
     .text
     .abiversion 2
 
Index: lld/ELF/Options.td
===================================================================
--- lld/ELF/Options.td
+++ lld/ELF/Options.td
@@ -220,6 +220,10 @@
 
 defm keep_unique: Eq<"keep-unique", "Do not fold this symbol during ICF">;
 
+def lax_call_lacks_nop : F<"lax-call-lacks-nop">,
+    HelpText<"(PowerPC64) Don't error on b/bl not followed by nop, if the target is "
+             "defined in the same file. This is for compatibility with GCC<5.4 and GCC<6.4">;
+
 defm library: Eq<"library", "Root name of library to use">,
   MetaVarName<"<libName>">;
 
Index: lld/ELF/InputSection.cpp
===================================================================
--- lld/ELF/InputSection.cpp
+++ lld/ELF/InputSection.cpp
@@ -975,13 +975,16 @@
         // gcc/gfortran 5.4, 6.3 and earlier versions do not add nop for
         // recursive calls even if the function is preemptible. This is not
         // wrong in the common case where the function is not preempted at
-        // runtime. Just ignore.
+        // runtime. Just ignore if --lax-call-lacks-nop is specified.
         if ((bufLoc + 8 > bufEnd || read32(bufLoc + 4) != 0x60000000) &&
-            rel.sym->file != file) {
+            !(config->laxCallLacksNop && rel.sym->file == file)) {
+          std::string hint;
+          if (rel.sym->file == file)
+            hint = "; pass -Wl,--lax-call-lacks-nop to ignore the error";
           // Use substr(6) to remove the "__plt_" prefix.
           errorOrWarn(getErrorLocation(bufLoc) + "call to " +
                       lld::toString(*rel.sym).substr(6) +
-                      " lacks nop, can't restore toc");
+                      " lacks nop, can't restore toc" + hint);
           break;
         }
         write32(bufLoc + 4, 0xe8410018); // ld %r2, 24(%r1)
Index: lld/ELF/Driver.cpp
===================================================================
--- lld/ELF/Driver.cpp
+++ lld/ELF/Driver.cpp
@@ -887,6 +887,7 @@
   config->ignoreFunctionAddressEquality =
       args.hasArg(OPT_ignore_function_address_equality);
   config->init = args.getLastArgValue(OPT_init, "_init");
+  config->laxCallLacksNop = args.hasArg(OPT_lax_call_lacks_nop);
   config->ltoAAPipeline = args.getLastArgValue(OPT_lto_aa_pipeline);
   config->ltoCSProfileGenerate = args.hasArg(OPT_lto_cs_profile_generate);
   config->ltoCSProfileFile = args.getLastArgValue(OPT_lto_cs_profile_file);
Index: lld/ELF/Config.h
===================================================================
--- lld/ELF/Config.h
+++ lld/ELF/Config.h
@@ -148,6 +148,7 @@
   bool emitLLVM;
   bool emitRelocs;
   bool enableNewDtags;
+  bool errorCallLacksNop;
   bool executeOnly;
   bool exportDynamic;
   bool fixCortexA53Errata843419;
@@ -163,6 +164,7 @@
   bool hasDynSymTab;
   bool ignoreDataAddressEquality;
   bool ignoreFunctionAddressEquality;
+  bool laxCallLacksNop;
   bool ltoCSProfileGenerate;
   bool ltoDebugPassManager;
   bool ltoNewPassManager;


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