[PATCH v2] gas: Enable PC-relative diff relocations on sparc64

[James Clarke <jrtc27 at jrtc27 dot com>]

gas/
	* config/tc-sparc.c (tc_gen_reloc): Convert BFD_RELOC_8/16/32/64
	into the corresponding BFD_RELOC_8/16/32/64_PCREL relocation
	when requested.
	* config/tc-sparc.h (DIFF_EXPR_OK): Define to enable PC-relative
	diff relocations.
	(TC_FORCE_RELOCATION_SUB_LOCAL): Define to ensure only supported
	relocations are made PC-relative.
	(CFI_DIFF_EXPR_OK): Define to 0 to force BFD_RELOC_32_PCREL to
	be used directly, since otherwise BFD_RELOC_SPARC_UA32 will be
	used for .eh_frame which cannot in general be converted to a
	BFD_RELOC_32_PCREL due to alignment requirements.
---

Changes in v2:

	* Fix issues with CFI causing testsuite regressions
	* Ensure only supported relocations are made PC-relative (otherwise
	fixup_segment can try to make anything PC-relative, and tc_gen_reloc will
	still use the old non-PC-relative relocation code, leading to bogus
	relocations)

 gas/config/tc-sparc.c | 26 +++++++++++++++++++++++++-
 gas/config/tc-sparc.h | 17 +++++++++++++++++
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/gas/config/tc-sparc.c b/gas/config/tc-sparc.c
index 692a1873f4..6d1b038daa 100644
--- a/gas/config/tc-sparc.c
+++ b/gas/config/tc-sparc.c
@@ -3946,8 +3946,33 @@ tc_gen_reloc (asection *section, fixS *fixp)
 
   switch (fixp->fx_r_type)
     {
+    case BFD_RELOC_8:
     case BFD_RELOC_16:
     case BFD_RELOC_32:
+    case BFD_RELOC_64:
+      if (fixp->fx_pcrel)
+	{
+	  switch (fixp->fx_size)
+	    {
+	    default:
+	      as_bad_where (fixp->fx_file, fixp->fx_line,
+			    _("can not do %d byte pc-relative relocation"),
+			    fixp->fx_size);
+	      code = fixp->fx_r_type;
+	      fixp->fx_pcrel = 0;
+	      break;
+	    case 1: code = BFD_RELOC_8_PCREL;  break;
+	    case 2: code = BFD_RELOC_16_PCREL; break;
+	    case 4: code = BFD_RELOC_32_PCREL; break;
+#ifdef BFD64
+	    case 8: code = BFD_RELOC_64_PCREL; break;
+#endif
+	    }
+	  if (fixp->fx_pcrel)
+	    fixp->fx_addnumber = fixp->fx_offset;
+	  break;
+	}
+      /* Fall through.  */
     case BFD_RELOC_HI22:
     case BFD_RELOC_LO10:
     case BFD_RELOC_32_PCREL_S2:
@@ -3960,7 +3985,6 @@ tc_gen_reloc (asection *section, fixS *fixp)
     case BFD_RELOC_SPARC_WDISP16:
     case BFD_RELOC_SPARC_WDISP19:
     case BFD_RELOC_SPARC_WDISP22:
-    case BFD_RELOC_64:
     case BFD_RELOC_SPARC_5:
     case BFD_RELOC_SPARC_6:
     case BFD_RELOC_SPARC_7:
diff --git a/gas/config/tc-sparc.h b/gas/config/tc-sparc.h
index 3dd2483cd7..f24460cefd 100644
--- a/gas/config/tc-sparc.h
+++ b/gas/config/tc-sparc.h
@@ -77,6 +77,8 @@ extern void sparc_handle_align (struct frag *);
 
 #define MAX_MEM_FOR_RS_ALIGN_CODE  (3 + 4 + 4)
 
+#define DIFF_EXPR_OK    /* foo-. gets turned into PC relative relocs */
+
 /* I know that "call 0" fails in sparc-coff if this doesn't return 1.  I
    don't know about other relocation types, or other formats, yet.  */
 #ifdef OBJ_COFF
@@ -128,6 +130,15 @@ extern void sparc_handle_align (struct frag *);
 /* Finish up the entire symtab.  */
 #define tc_adjust_symtab() sparc_adjust_symtab ()
 extern void sparc_adjust_symtab (void);
+
+/* Don't allow the generic code to convert fixups involving the
+   subtraction of a label in the current section to pc-relative if we
+   don't have the necessary pc-relative relocation.  */
+#define TC_FORCE_RELOCATION_SUB_LOCAL(FIX, SEG)		\
+  (!((FIX)->fx_r_type == BFD_RELOC_64			\
+     || (FIX)->fx_r_type == BFD_RELOC_32		\
+     || (FIX)->fx_r_type == BFD_RELOC_16		\
+     || (FIX)->fx_r_type == BFD_RELOC_8))
 #endif
 
 #ifdef OBJ_AOUT
@@ -200,4 +211,10 @@ extern int sparc_cie_data_alignment;
 #define DWARF2_DEFAULT_RETURN_COLUMN    15
 #define DWARF2_CIE_DATA_ALIGNMENT       sparc_cie_data_alignment
 
+/* cons_fix_new_sparc will chooose BFD_RELOC_SPARC_UA32 for the difference
+   expressions, but there is no corresponding PC-relative relocation; as this
+   is for debugging info though, alignment does not matter, so by disabling
+   this, BFD_RELOC_32_PCREL will be emitted directly instead.  */
+#define CFI_DIFF_EXPR_OK 0
+
 /* end of tc-sparc.h */
-- 
2.11.0