[PATCH v2] microblaze: add BFD_RELOC_8 and BFD_RELOC_16 cases

[Sam Price]

From: Samuel Price <thesamprice@gmail.com>

md_apply_fix has cases for BFD_RELOC_32, BFD_RELOC_64 and for the
MicroBlaze-specific relocations, but none for BFD_RELOC_8 or BFD_RELOC_16.
Those fall through to the default and nothing is written, so a byte or
halfword datum whose value is only known at fixup time assembles to zero.
The fixup is then resolved and turned into BFD_RELOC_NONE, so no relocation
survives for the linker to correct it either, and the zero is permanent.

The two new cases replicate the BFD_RELOC_32 case immediately below them in
the same switch -- the same S_IS_DEFINED guard and the same target_big_endian
byte order -- narrowed to one and two bytes.

Fixes gas/all/simple-forward.  It also fixes gas/all/forward, which was
xfailed for microblaze-*-*, so drop it from that xfail list.  The gas
testsuite on microblaze-elf goes from 327 passes and 1 unexpected failure to
329 passes and 0 failures.

gas/
	* config/tc-microblaze.c (md_apply_fix): Handle BFD_RELOC_8 and
	BFD_RELOC_16.
	* testsuite/gas/all/forward.d: Remove the microblaze-*-* xfail.

Signed-off-by: Sam Price <thesamprice@gmail.com>
Reviewed-by: Neal Frager <neal.frager@amd.com>
Assisted-by: Claude (Anthropic)
---

Changes since v1:

  - forward.d: also update the comment above the #xfail line, which still
    read "mep and microblaze use complex relocs and don't resolve the
    relocs" after microblaze was dropped from the xfail list.  Caught by
    Neal Frager.  Reworded for the now-single target: "mep uses ...
    doesn't".

No change to gas/config/tc-microblaze.c.  The testsuite result is unchanged
and was re-measured on f621e384d9c with the new comment in place: 327 passes
and 1 unexpected failure -> 329 passes and 0, no unexpected successes.  The
comment is inert to DejaGnu.

v1: https://inbox.sourceware.org/binutils/20260920235724.37190-1-thesamprice@gmail.com/

I considered writing the two new cases the way aarch64 and mips do instead --

  case BFD_RELOC_16:
  case BFD_RELOC_8:
    if (fixP->fx_done)
      md_number_to_chars (buf, *valP, fixP->fx_size);
    break;

-- which is shorter, drops the endianness branch, and guards on fx_done
rather than S_IS_DEFINED, which is arguably what is really meant here.  The
comment on that case in tc-mips.c describes this exact failure mode: "If we
are deleting this reloc entry, we must fill in the value now."

I kept the local form so the patch stays minimal and consistent with its
neighbour, but I am happy to send the md_number_to_chars version instead if
you would rather have it.  Or if you want the neighbors converted to
aarch64 / mips and tested I can do that also.

 gas/config/tc-microblaze.c      | 23 +++++++++++++++++++++++
 gas/testsuite/gas/all/forward.d |  4 ++--
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/gas/config/tc-microblaze.c b/gas/config/tc-microblaze.c
index 3e3dca81921..36b98bbd8fc 100644
--- a/gas/config/tc-microblaze.c
+++ b/gas/config/tc-microblaze.c
@@ -2145,6 +2145,29 @@ md_apply_fix (fixS *   fixP,
 	    }
 	}
       break;
+    case BFD_RELOC_8:
+      /* Don't do anything if the symbol is not defined.  */
+      if (fixP->fx_addsy == NULL || S_IS_DEFINED (fixP->fx_addsy))
+	buf[0] |= (val & 0xff);
+      break;
+
+    case BFD_RELOC_16:
+      /* Don't do anything if the symbol is not defined.  */
+      if (fixP->fx_addsy == NULL || S_IS_DEFINED (fixP->fx_addsy))
+	{
+	  if (target_big_endian)
+	    {
+	      buf[0] |= ((val >> 8) & 0xff);
+	      buf[1] |= (val & 0xff);
+	    }
+	  else
+	    {
+	      buf[1] |= ((val >> 8) & 0xff);
+	      buf[0] |= (val & 0xff);
+	    }
+	}
+      break;
+
     case BFD_RELOC_32:
     case BFD_RELOC_RVA:
     case BFD_RELOC_32_PCREL:
diff --git a/gas/testsuite/gas/all/forward.d b/gas/testsuite/gas/all/forward.d
index d921ec517be..39f7b2941e8 100644
--- a/gas/testsuite/gas/all/forward.d
+++ b/gas/testsuite/gas/all/forward.d
@@ -8,10 +8,10 @@
 # choose to emit them even though the relocs are in .data, leading to
 # "redefined symbol cannot be used on reloc".
 #xfail: am33*-*-* crx*-*-* h8300*-*-* mn10200*-*-* mn10300*-*-*
-# mep and microblaze use complex relocs and don't resolve the relocs.
+# mep uses complex relocs and doesn't resolve the relocs.
 # one of the relocs references minus_one, which is a bug, but no one
 # seems bothered enough to fix this.
-#xfail: mep-*-* microblaze-*-*
+#xfail: mep-*-*
 
 .*: .*
 
-- 
2.39.5 (Apple Git-154)