Rework the R_NEG support on both gas and ld for the PowerPC AIX targets, in order to manage C++ exceptions built with GCC.

bfd	PR binutils/21700
	* reloc.c (BFD_RELOC_PPC_NEG): New relocation.
	* bfd-in2.h: Regenerate.
	* libbfd.h: Regenerate.
	* coff-rs6000.c (_bfd_xcoff_reloc_type_lookup): Add
	BFD_RELOC_PPC_NEG handler.
	(xcoff_reloc_type_neg): Correctly substract addend.
	* coff64-rs6000.c (xcoff64_howto_table): Add R_NEG_32
	howto.
	(xcoff64_rtype2howto): Add handler for R_NEG_32.
	(xcoff64_reloc_type_lookup): Add BFD_RELOC_PPC_NEG handler.
	* xcofflink.c (xcoff_need_ldrel_p): Check output section
	for R_POS-like relocations. New argument added.
	(xcoff_mark): Adapt to new xcoff_need_ldrel_p argument.
	(xcoff_link_input_bfd): Likewise.

gas	* config/tc-ppc.c (ppc_get_csect_to_adjust): New function.
	(ppc_fix_adjustable): Manage fx_subsy part.
	(tc_gen_reloc): Create second relocation when both
	fx_addsy and fx_subsy are provided.
	* config/tc-ppc.h (RELOC_EXPANSION_POSSIBLE): New define.
	(MAX_RELOC_EXPANSION): Likewise.
	(TC_FORCE_RELOCATION_SUB_SAME): Likewise
	(UNDEFINED_DIFFERENCE_OK): Likewise
	* testsuite/gas/all/gas.exp: Skip difference between two
	undefined symbols test.

ld	* testsuite/ld-powerpc/aix52.exp: Add new test.
	* testsuite/ld-powerpc/aix-neg-reloc-32.d: New test.
	* testsuite/ld-powerpc/aix-neg-reloc-64.d: New test.
	* testsuite/ld-powerpc/aix-neg-reloc.ex: New test.
	* testsuite/ld-powerpc/aix-neg-reloc.s: New test.

3 files changed, 107 insertions, 28 deletions

diff --git a/gas/ChangeLog b/gas/ChangeLog
index 5111ace..c8ef5f3 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,17 @@
+2021-04-20  Clément Chigot  <clement.chigot@atos.net>
+
+	PR binutils/21700
+	* config/tc-ppc.c (ppc_get_csect_to_adjust): New function.
+	(ppc_fix_adjustable): Manage fx_subsy part.
+	(tc_gen_reloc): Create second relocation when both
+	fx_addsy and fx_subsy are provided.
+	* config/tc-ppc.h (RELOC_EXPANSION_POSSIBLE): New define.
+	(MAX_RELOC_EXPANSION): Likewise.
+	(TC_FORCE_RELOCATION_SUB_SAME): Likewise
+	(UNDEFINED_DIFFERENCE_OK): Likewise
+	* testsuite/gas/all/gas.exp: Skip difference between two
+	undefined symbols test.
+
 2021-04-19  Nick Clifton  <nickc@redhat.com>
 
 	* testsuite/gas/all/gas.exp: Add rs6000*-*-aix* to the list of
diff --git a/gas/config/tc-ppc.c b/gas/config/tc-ppc.c
index c719b40..7715fc5 100644
--- a/gas/config/tc-ppc.c
+++ b/gas/config/tc-ppc.c
@@ -6264,6 +6264,45 @@ md_pcrel_from_section (fixS *fixp, segT sec ATTRIBUTE_UNUSED)
 
 #ifdef OBJ_XCOFF
 
+/* Return the surrending csect for sym when possible.  */
+
+static symbolS*
+ppc_get_csect_to_adjust (symbolS *sym)
+{
+  if (sym == NULL)
+    return NULL;
+
+  valueT val = resolve_symbol_value (sym);
+  TC_SYMFIELD_TYPE *tc = symbol_get_tc (sym);
+  segT symseg = S_GET_SEGMENT (sym);
+
+  if (tc->subseg == 0
+      && tc->symbol_class != XMC_TC0
+      && tc->symbol_class != XMC_TC
+      && tc->symbol_class != XMC_TE
+      && symseg != bss_section
+      && symseg != ppc_xcoff_tbss_section.segment
+      /* Don't adjust if this is a reloc in the toc section.  */
+      && (symseg != data_section
+	  || ppc_toc_csect == NULL
+	  || val < ppc_toc_frag->fr_address
+	  || (ppc_after_toc_frag != NULL
+	      && val >= ppc_after_toc_frag->fr_address)))
+    {
+      symbolS* csect = tc->within;
+
+      /* If the symbol was not declared by a label (eg: a section symbol),
+         use the section instead of the csect.  This doesn't happen in
+         normal AIX assembly code.  */
+      if (csect == NULL)
+        csect = seg_info (symseg)->sym;
+
+      return csect;
+    }
+
+  return NULL;
+}
+
 /* This is called to see whether a fixup should be adjusted to use a
    section symbol.  We take the opportunity to change a fixup against
    a symbol in the TOC subsegment into a reloc against the
@@ -6274,7 +6313,7 @@ ppc_fix_adjustable (fixS *fix)
 {
   valueT val = resolve_symbol_value (fix->fx_addsy);
   segT symseg = S_GET_SEGMENT (fix->fx_addsy);
-  TC_SYMFIELD_TYPE *tc;
+  symbolS* csect;
 
   if (symseg == absolute_section)
     return 0;
@@ -6316,32 +6355,17 @@ ppc_fix_adjustable (fixS *fix)
     }
 
   /* Possibly adjust the reloc to be against the csect.  */
-  tc = symbol_get_tc (fix->fx_addsy);
-  if (tc->subseg == 0
-      && tc->symbol_class != XMC_TC0
-      && tc->symbol_class != XMC_TC
-      && tc->symbol_class != XMC_TE
-      && symseg != bss_section
-      && symseg != ppc_xcoff_tbss_section.segment
-      /* Don't adjust if this is a reloc in the toc section.  */
-      && (symseg != data_section
-	  || ppc_toc_csect == NULL
-	  || val < ppc_toc_frag->fr_address
-	  || (ppc_after_toc_frag != NULL
-	      && val >= ppc_after_toc_frag->fr_address)))
+  if ((csect = ppc_get_csect_to_adjust (fix->fx_addsy)) != NULL)
     {
-      symbolS *csect = tc->within;
-
-      /* If the symbol was not declared by a label (eg: a section symbol),
-         use the section instead of the csect.  This doesn't happen in
-         normal AIX assembly code.  */
-      if (csect == NULL)
-        csect = seg_info (symseg)->sym;
-
       fix->fx_offset += val - symbol_get_frag (csect)->fr_address;
       fix->fx_addsy = csect;
+    }
 
-      return 0;
+  if ((csect = ppc_get_csect_to_adjust (fix->fx_subsy)) != NULL)
+    {
+      fix->fx_offset -= resolve_symbol_value (fix->fx_subsy)
+	- symbol_get_frag (csect)->fr_address;
+      fix->fx_subsy = csect;
     }
 
   /* Adjust a reloc against a .lcomm symbol to be against the base
@@ -7367,12 +7391,14 @@ md_apply_fix (fixS *fixP, valueT *valP, segT seg)
 
 /* Generate a reloc for a fixup.  */
 
-arelent *
+arelent **
 tc_gen_reloc (asection *seg ATTRIBUTE_UNUSED, fixS *fixp)
 {
+  static arelent *relocs[3];
   arelent *reloc;
 
-  reloc = XNEW (arelent);
+  relocs[0] = reloc = XNEW (arelent);
+  relocs[1] = NULL;
 
   reloc->sym_ptr_ptr = XNEW (asymbol *);
   *reloc->sym_ptr_ptr = symbol_get_bfdsym (fixp->fx_addsy);
@@ -7386,11 +7412,33 @@ tc_gen_reloc (asection *seg ATTRIBUTE_UNUSED, fixS *fixp)
       as_bad_where (fixp->fx_file, fixp->fx_line,
 		    _("reloc %d not supported by object file format"),
 		    (int) fixp->fx_r_type);
-      return NULL;
+      relocs[0] = NULL;
     }
   reloc->addend = fixp->fx_addnumber;
 
-  return reloc;
+  if (fixp->fx_subsy && fixp->fx_addsy)
+    {
+      relocs[1] = reloc = XNEW (arelent);
+      relocs[2] = NULL;
+
+      reloc->sym_ptr_ptr = XNEW (asymbol *);
+      *reloc->sym_ptr_ptr = symbol_get_bfdsym (fixp->fx_subsy);
+      reloc->address = fixp->fx_frag->fr_address + fixp->fx_where;
+
+      reloc->howto = bfd_reloc_type_lookup (stdoutput, BFD_RELOC_PPC_NEG);
+      reloc->addend = fixp->fx_addnumber;
+
+      if (reloc->howto == (reloc_howto_type *) NULL)
+        {
+          as_bad_where (fixp->fx_file, fixp->fx_line,
+            _("reloc %d not supported by object file format"),
+            BFD_RELOC_PPC_NEG);
+	  relocs[0] = NULL;
+        }
+    }
+
+
+  return relocs;
 }
 
 void
diff --git a/gas/config/tc-ppc.h b/gas/config/tc-ppc.h
index d38c7d4..790994e 100644
--- a/gas/config/tc-ppc.h
+++ b/gas/config/tc-ppc.h
@@ -284,10 +284,27 @@ extern int ppc_force_relocation (struct fix *);
      || (FIX)->fx_r_type == BFD_RELOC_PPC_16DX_HA		\
      || (FIX)->fx_r_type == BFD_RELOC_PPC64_D34			\
      || (FIX)->fx_r_type == BFD_RELOC_PPC64_D28))
-#endif
 
 #define TC_VALIDATE_FIX_SUB(FIX, SEG) 0
 
+#endif /* OBJ_ELF */
+
+#define RELOC_EXPANSION_POSSIBLE
+#define MAX_RELOC_EXPANSION 2
+
+#if defined (OBJ_XCOFF)
+/* Force a relocation when the fix is negative. */
+#define TC_FORCE_RELOCATION_SUB_SAME(FIX, SEG)				\
+  (GENERIC_FORCE_RELOCATION_SUB_SAME(FIX, SEG)				\
+   || (((SEG)->flags & SEC_DEBUGGING) == 0				\
+	&& (FIX)->fx_addsy && (FIX)->fx_subsy				\
+	&& (S_GET_VALUE (fixP->fx_addsy) < S_GET_VALUE (fixP->fx_subsy))))
+
+/* XCOFF allows undefined differences which will be encoded with
+   R_NEG relocations.  */
+#define UNDEFINED_DIFFERENCE_OK
+#endif /* OBJ_XCOFF */
+
 /* Various frobbings of labels and their addresses.  */
 #define md_start_line_hook() ppc_start_line_hook ()
 extern void ppc_start_line_hook (void);