Re: [PATCH 1/2] opcodes/mips: use .word/.short for undefined instructions

[Andrew Burgess <aburgess@redhat.com>]

"Maciej W. Rozycki" <macro@orcam.me.uk> writes:

> Andrew,
>
>> I've updated the patch.  Let me know what you think.
>
>  I'd say it's OK, except that I put your change through my MIPS regression 
> tester and that revealed failures from your new case for numerous targets, 
> e.g.:
>
> mips-elf  +FAIL: microMIPS source file contains reserved encoding (o32)
> mips-img-elf  +FAIL: microMIPS source file contains reserved encoding (o32)
> mips-img-elf  +FAIL: microMIPS source file contains reserved encoding (n32)
>
> etc.  The usual suspect is section padding owing to different alignments 
> used with individual MIPS targets, e.g.:
>
> extra regexps in 
> .../binutils/testsuite/binutils-all/mips/micromips-reserved-enc-o32.d starting with "^
> \.\.\.$"
> EOF from tmpdir/dump.out
> FAIL: microMIPS source file contains reserved encoding (o32)
>
> See e.g. binutils/testsuite/binutils-all/mips/micromips-branch-alias.s for 
> how to add suitable padding at the end.
>
>  And then:
>
> mipsisa32r6-elf  +FAIL: microMIPS source file contains reserved encoding (o32)
> mipsisa32r6-linux  +FAIL: microMIPS source file contains reserved encoding (o32)
> mipsisa32r6el-elf  +FAIL: microMIPS source file contains reserved encoding (o32)
>
> etc., due to:
>
> .../binutils/testsuite/binutils-all/mips/micromips-reserved-enc.s: Assembler messages:
> .../binutils/testsuite/binutils-all/mips/micromips-reserved-enc.s:3: Fatal error: `micromips' cannot be used with `mips32r6'
>
> We don't care about different ISA levels here, so let's set a reasonable 
> one, as in binutils/testsuite/binutils-all/mips/micromips-branch-alias.s 
> again:
>
> 	.module	mips64r3
>
> (it could be `.set' too, but let's be consistent, and it has to be a 
> 64-bit one for the n32/n64 ABIs).
>
>  OK with these updates, thank you for your contribution.

Right, I think I've got it this time :)

Updated patch is below.  Given the updates are minor, if I don't hear
back from you I'll push this sometime next week.

I tested this against all the targets you listed, the only place this
test still fails is for `mipsisa64sr71k-elf`, but that build looks
pretty broken anyway.  The failure is in gas, during argument parsing,
and I see the same failure for many of the tests, so I don't think I
need to worry about that.  Everything else looks like a PASS or
UNSUPPORTED, which I think is fine.

Thanks for all your feedback on this one.

Andrew

---

commit c84e242a7a45787c9ff60a3cf06b3b7f30d85970
Author: Andrew Burgess <aburgess@redhat.com>
Date:   Fri Jan 6 16:42:23 2023 +0000

    opcodes/mips: disassemble unknown micromips instructions as two shorts
    
    Before commit:
    
      commit 2438b771ee07be19d5b01ea55e077dd8b7cef445
      Date:   Wed Nov 2 15:53:43 2022 +0000
    
          opcodes/mips: use .word/.short for undefined instructions
    
    unknown 32-bit microMIPS instructions were disassembled as a raw
    32-bit number with no '.word' directive.  The above commit changed
    this and added a '.word' directive before the 32-bit number.
    
    It was pointed out on the mailing list, that for microMIPS it would be
    better to display such 32-bit instructions using a '.short' directive
    followed by two 16-bit values.
    
    This commit updates the mips disassembler to do this, and adds a new
    test that validates this output.

diff --git a/binutils/testsuite/binutils-all/mips/micromips-reserved-enc-n32.d b/binutils/testsuite/binutils-all/mips/micromips-reserved-enc-n32.d
new file mode 100644
index 00000000000..e6608f30265
--- /dev/null
+++ b/binutils/testsuite/binutils-all/mips/micromips-reserved-enc-n32.d
@@ -0,0 +1,5 @@
+#PROG: objcopy
+#objdump: -d --prefix-addresses --show-raw-insn
+#name: microMIPS source file contains reserved encoding (n32)
+#source: micromips-reserved-enc.s
+#dump: micromips-reserved-enc-o32.d
diff --git a/binutils/testsuite/binutils-all/mips/micromips-reserved-enc-n64.d b/binutils/testsuite/binutils-all/mips/micromips-reserved-enc-n64.d
new file mode 100644
index 00000000000..f892bfabbe7
--- /dev/null
+++ b/binutils/testsuite/binutils-all/mips/micromips-reserved-enc-n64.d
@@ -0,0 +1,5 @@
+#PROG: objcopy
+#objdump: -d --prefix-addresses --show-raw-insn
+#name: microMIPS source file contains reserved encoding (n64)
+#source: micromips-reserved-enc.s
+#dump: micromips-reserved-enc-o32.d
diff --git a/binutils/testsuite/binutils-all/mips/micromips-reserved-enc-o32.d b/binutils/testsuite/binutils-all/mips/micromips-reserved-enc-o32.d
new file mode 100644
index 00000000000..3de3989b37a
--- /dev/null
+++ b/binutils/testsuite/binutils-all/mips/micromips-reserved-enc-o32.d
@@ -0,0 +1,10 @@
+#PROG: objcopy
+#objdump: -d --prefix-addresses --show-raw-insn
+#name: microMIPS source file contains reserved encoding (o32)
+#source: micromips-reserved-enc.s
+
+.*: +file format .*mips.*
+
+Disassembly of section \.text:
+[0-9a-f]+ <[^>]*> 7f6e 5d4c 	\.short	0x7f6e, 0x5d4c
+	\.\.\.
diff --git a/binutils/testsuite/binutils-all/mips/micromips-reserved-enc.s b/binutils/testsuite/binutils-all/mips/micromips-reserved-enc.s
new file mode 100644
index 00000000000..d4918f36857
--- /dev/null
+++ b/binutils/testsuite/binutils-all/mips/micromips-reserved-enc.s
@@ -0,0 +1,9 @@
+	.module mips64r3
+	.module	micromips
+foo:
+	.insn
+	.short	0x7f6e, 0x5d4c
+
+# Force some (non-delay-slot) zero bytes, to make 'objdump' print ...
+	.align	4, 0
+	.space	16
diff --git a/binutils/testsuite/binutils-all/mips/mips.exp b/binutils/testsuite/binutils-all/mips/mips.exp
index 6a0ec25a06f..91bf3274592 100644
--- a/binutils/testsuite/binutils-all/mips/mips.exp
+++ b/binutils/testsuite/binutils-all/mips/mips.exp
@@ -266,3 +266,7 @@ run_dump_test_n64 "global-local-symtab-sort-n64${tmips}"
 run_dump_test_o32 "global-local-symtab-final-o32" useld
 run_dump_test_n32 "global-local-symtab-final-n32" useld
 run_dump_test_n64 "global-local-symtab-final-n64" useld
+
+run_dump_test_o32 "micromips-reserved-enc-o32"
+run_dump_test_n32 "micromips-reserved-enc-n32"
+run_dump_test_n64 "micromips-reserved-enc-n64"
diff --git a/opcodes/mips-dis.c b/opcodes/mips-dis.c
index 6a513cd8946..859d4e3806f 100644
--- a/opcodes/mips-dis.c
+++ b/opcodes/mips-dis.c
@@ -2600,12 +2600,15 @@ print_insn_micromips (bfd_vma memaddr, struct disassemble_info *info)
 	}
     }
 
-  if (length == 2)
-    infprintf (is, dis_style_assembler_directive, ".short");
-  else
-    infprintf (is, dis_style_assembler_directive, ".word");
+  infprintf (is, dis_style_assembler_directive, ".short");
   infprintf (is, dis_style_text, "\t");
-  infprintf (is, dis_style_immediate, "0x%x", insn);
+  if (length != 2)
+    {
+      infprintf (is, dis_style_immediate, "0x%x", (insn >> 16) & 0xffff);
+      infprintf (is, dis_style_text, ", ");
+    }
+  infprintf (is, dis_style_immediate, "0x%x", (insn & 0xffff));
+
   info->insn_type = dis_noninsn;
 
   return length;