[ELF][PPC64] Improve "call lacks nop" diagnostic and make it compatible with GCC<5.5 and GCC<6.4

GCC before r245813 (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79439)
did not emit nop after b/bl. This can happen with recursive calls.
r245813 was back ported to GCC 5.5 and GCC 6.4.

This is common, for example, libstdc++.a(locale.o) shipped with GCC 4.9
and many objects in netlib lapack can cause lld to error.  gold allows
such calls to the same section. Our __plt_foo symbol's `section` field
is used for ThunkSection, so we can't implement a similar loosen rule
easily. But we can make use of its `file` field which is currently NULL.

Differential Revision: https://reviews.llvm.org/D71639

3 files changed, 9 insertions, 3 deletions

diff --git a/lld/test/ELF/ppc64-bsymbolic-toc-restore.s b/lld/test/ELF/ppc64-bsymbolic-toc-restore.s
index ff5eb148273..929c82cd24b 100644
--- a/lld/test/ELF/ppc64-bsymbolic-toc-restore.s
+++ b/lld/test/ELF/ppc64-bsymbolic-toc-restore.s
@@ -12,7 +12,7 @@
 # RUN: llvm-objdump -d -r %t | FileCheck %s
 # RUN: not ld.lld -shared %t1.o %t2.o -o %t 2>&1 | FileCheck --check-prefix=FAIL %s
 
-# FAIL: call lacks nop, can't restore toc
+# FAIL: call to def lacks nop, can't restore toc
 
 # Test to document the toc-restore behavior with -Bsymbolic option. Since
 # -Bsymbolic causes the call to bind to the internal defintion we know the
diff --git a/lld/test/ELF/ppc64-error-toc-restore.s b/lld/test/ELF/ppc64-error-toc-restore.s
index 19153b730ce..9700322a5e6 100644
--- a/lld/test/ELF/ppc64-error-toc-restore.s
+++ b/lld/test/ELF/ppc64-error-toc-restore.s
@@ -11,7 +11,7 @@
 // RUN: not ld.lld %t.o %t2.so -o %t 2>&1 | FileCheck %s
 
 # Calling external function bar needs a nop
-// CHECK: call lacks nop, can't restore toc
+// CHECK: call to foo lacks nop, can't restore toc
     .text
     .abiversion 2
 
diff --git a/lld/test/ELF/ppc64-error-toc-tail-call.s b/lld/test/ELF/ppc64-error-toc-tail-call.s
index da8fea26cc2..b303810b81d 100644
--- a/lld/test/ELF/ppc64-error-toc-tail-call.s
+++ b/lld/test/ELF/ppc64-error-toc-tail-call.s
@@ -11,10 +11,16 @@
 // 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 lacks nop, can't restore toc
+// CHECK: call to foo lacks nop, can't restore toc
+// CHECK-NOT: lacks nop
     .text
     .abiversion 2
 
 .global _start
 _start:
   b foo
+
+  // gcc/gfortran 5.4, 6.3 and earlier versions do not add nop for recursive
+  // calls.
+  b _start
+  b _start