On Fri, 11 Jun 2004 cgd@xxxxxxxxxxxx wrote:
> in retrospect, the 'B' variation probably wasn't the greatest idea.
>
> If it were removed (leaving 'c' and 'c','q' variations), I don't know
> that any real harm would occur.
>
> It may be very confusing to people who expect that the break code will
> translate into the instruction in an obvious way, and obviously it
> would mess up use of 20-bit codes, but i don't know how prevalent that
> is.
>
> Unfortunately, at this point, Linux should probably accept the
> divide-by-zero code in both locations.
>
>
> (Really, from day one, assemblers probably should have accepted a
> 20-bit code. I just checked my copy of the Kane r2000/r3000 book, and
> it was 20-bit all the way back then. If i had to guess, i'd guess
> that gas was copying a non-gnu assembler's behaviour. In any case,
> water under the bridge.)
As it's at least annoying to have different break codes for divisions
expanded by gcc explicitly and ones created implicitly by gas, here's the
most reasonable (IMO) approach to fix that. I think it should have been
implemented this way originally (if at all).
gas/testsuite/:
2004-06-22 Maciej W. Rozycki <macro@xxxxxxxxxxxxx>
* gas/mips/break20.s: Test the "break20" alias.
* gas/mips/break20.d: Results for the test.
* gas/mips/mips32.s: Replace "break" with "break20".
* gas/mips/set-arch.s: Likewise.
* gas/mips/mips32.d: Adjust for the new output.
* gas/mips/set-arch.d: Likewise.
opcodes/:
2004-06-22 Maciej W. Rozycki <macro@xxxxxxxxxxxxx>
* mips-opc.c (mips_builtin_opcodes): Replace the MIPS32 ISA
specific "break" encoding with a "break20" alias accepted for any
ISA.
I decided to give a precedence to "break x,y" over "break20 z" to avoid
perhaps a bit surprising output in `objdump'.
The question is: does anyone know of possible troubles with this change?
Chances are someone depends on the current semantics for
-march=mips32/mips64, but that's fragile anyway as building with a
different setting results in different code.
Or should we get rid of the 20-bit "break" completely? The two-argument
version provides the same functionality, although the 10-bit codes to be
used do not map to the 20-bit equivalent "optically" very well.
Especially if decimal notation is used.
Note the same problem appears to be the case with "sdbbp". It could be
handled similarly, but given the limited use of "sdbbp" for
non-MIPS32/MIPS64 ISAs it may not be worth the hassle. I see no problem
writing a similar fix if desired, though.
Maciej
--
+ Maciej W. Rozycki, Technical University of Gdansk, Poland +
+--------------------------------------------------------------+
+ e-mail: macro@xxxxxxxxxxxxx, PGP key available +
binutils-2.15.91-20040615-mips-break20.patch
diff -up --recursive --new-file binutils-2.15.91-20040615.macro/gas/testsuite/gas/mips/break20.d binutils-2.15.91-20040615/gas/testsuite/gas/mips/break20.d
--- binutils-2.15.91-20040615.macro/gas/testsuite/gas/mips/break20.d 2003-05-08 03:25:31.000000000 +0000
+++ binutils-2.15.91-20040615/gas/testsuite/gas/mips/break20.d 2004-06-17 21:03:30.000000000 +0000
@@ -10,9 +10,13 @@ Disassembly of section .text:
0+0008 <[^>]*> break 0x14
0+000c <[^>]*> break 0x14,0x28
0+0010 <[^>]*> break 0x3ff,0x3ff
-0+0014 <[^>]*> sdbbp
-0+0018 <[^>]*> sdbbp
-0+001c <[^>]*> sdbbp 0x14
-0+0020 <[^>]*> sdbbp 0x14,0x28
-0+0024 <[^>]*> sdbbp 0x3ff,0x3ff
+0+0014 <[^>]*> break
+0+0018 <[^>]*> break 0x0,0x14
+0+001c <[^>]*> break 0x14,0x28
+0+0020 <[^>]*> break 0x3ff,0x3ff
+0+0024 <[^>]*> sdbbp
+0+0028 <[^>]*> sdbbp
+0+002c <[^>]*> sdbbp 0x14
+0+0030 <[^>]*> sdbbp 0x14,0x28
+0+0034 <[^>]*> sdbbp 0x3ff,0x3ff
...
diff -up --recursive --new-file binutils-2.15.91-20040615.macro/gas/testsuite/gas/mips/break20.s binutils-2.15.91-20040615/gas/testsuite/gas/mips/break20.s
--- binutils-2.15.91-20040615.macro/gas/testsuite/gas/mips/break20.s 1999-08-10 14:24:45.000000000 +0000
+++ binutils-2.15.91-20040615/gas/testsuite/gas/mips/break20.s 2004-06-17 19:57:51.000000000 +0000
@@ -6,6 +6,11 @@ foo:
break 20,40
break 1023,1023
+ break20 0
+ break20 20
+ break20 20520
+ break20 1048575
+
sdbbp
sdbbp 0
sdbbp 20
diff -up --recursive --new-file binutils-2.15.91-20040615.macro/gas/testsuite/gas/mips/mips32.d binutils-2.15.91-20040615/gas/testsuite/gas/mips/mips32.d
--- binutils-2.15.91-20040615.macro/gas/testsuite/gas/mips/mips32.d 2003-05-08 03:25:35.000000000 +0000
+++ binutils-2.15.91-20040615/gas/testsuite/gas/mips/mips32.d 2004-06-17 21:15:04.000000000 +0000
@@ -48,7 +48,7 @@ Disassembly of section .text:
0+0098 <[^>]*> 4359e260 wait 0x56789
0+009c <[^>]*> 0000000d break
0+00a0 <[^>]*> 0000000d break
-0+00a4 <[^>]*> 0048d14d break 0x12345
+0+00a4 <[^>]*> 0048d14d break 0x48,0x345
0+00a8 <[^>]*> 7000003f sdbbp
0+00ac <[^>]*> 7000003f sdbbp
0+00b0 <[^>]*> 7159e27f sdbbp 0x56789
diff -up --recursive --new-file binutils-2.15.91-20040615.macro/gas/testsuite/gas/mips/mips32.s binutils-2.15.91-20040615/gas/testsuite/gas/mips/mips32.s
--- binutils-2.15.91-20040615.macro/gas/testsuite/gas/mips/mips32.s 2002-09-05 03:25:40.000000000 +0000
+++ binutils-2.15.91-20040615/gas/testsuite/gas/mips/mips32.s 2004-06-17 21:13:22.000000000 +0000
@@ -62,7 +62,7 @@ text_label:
# different.
break
break 0 # disassembles without code
- break 0x12345
+ break20 0x12345
sdbbp
sdbbp 0 # disassembles without code
sdbbp 0x56789
diff -up --recursive --new-file binutils-2.15.91-20040615.macro/gas/testsuite/gas/mips/set-arch.d binutils-2.15.91-20040615/gas/testsuite/gas/mips/set-arch.d
--- binutils-2.15.91-20040615.macro/gas/testsuite/gas/mips/set-arch.d 2003-10-01 03:25:36.000000000 +0000
+++ binutils-2.15.91-20040615/gas/testsuite/gas/mips/set-arch.d 2004-06-17 21:17:46.000000000 +0000
@@ -160,7 +160,7 @@ Disassembly of section \.text:
00000260 <[^>]*> 4359e260 wait 0x56789
00000264 <[^>]*> 0000000d break
00000268 <[^>]*> 0000000d break
-0000026c <[^>]*> 0048d14d break 0x12345
+0000026c <[^>]*> 0048d14d break 0x48,0x345
00000270 <[^>]*> 7000003f sdbbp
00000274 <[^>]*> 7000003f sdbbp
00000278 <[^>]*> 7159e27f sdbbp 0x56789
diff -up --recursive --new-file binutils-2.15.91-20040615.macro/gas/testsuite/gas/mips/set-arch.s binutils-2.15.91-20040615/gas/testsuite/gas/mips/set-arch.s
--- binutils-2.15.91-20040615.macro/gas/testsuite/gas/mips/set-arch.s 2003-06-29 19:41:33.000000000 +0000
+++ binutils-2.15.91-20040615/gas/testsuite/gas/mips/set-arch.s 2004-06-17 21:18:01.000000000 +0000
@@ -204,7 +204,7 @@ text_label:
# different.
break
break 0 # disassembles without code
- break 0x12345
+ break20 0x12345
sdbbp
sdbbp 0 # disassembles without code
sdbbp 0x56789
diff -up --recursive --new-file binutils-2.15.91-20040615.macro/opcodes/mips-opc.c binutils-2.15.91-20040615/opcodes/mips-opc.c
--- binutils-2.15.91-20040615.macro/opcodes/mips-opc.c 2003-11-19 04:25:23.000000000 +0000
+++ binutils-2.15.91-20040615/opcodes/mips-opc.c 2004-06-17 19:46:23.000000000 +0000
@@ -274,9 +274,9 @@ const struct mips_opcode mips_builtin_op
{"bnel", "s,t,p", 0x54000000, 0xfc000000, CBL|RD_s|RD_t, I2|T3 },
{"bnel", "s,I,p", 0, (int) M_BNEL_I, INSN_MACRO, I2|T3 },
{"break", "", 0x0000000d, 0xffffffff, TRAP, I1 },
-{"break", "B", 0x0000000d, 0xfc00003f, TRAP, I32 },
{"break", "c", 0x0000000d, 0xfc00ffff, TRAP, I1 },
{"break", "c,q", 0x0000000d, 0xfc00003f, TRAP, I1 },
+{"break20", "B", 0x0000000d, 0xfc00003f, TRAP, I1 },
{"c.f.d", "S,T", 0x46200030, 0xffe007ff, RD_S|RD_T|WR_CC|FP_D, I1 },
{"c.f.d", "M,S,T", 0x46200030, 0xffe000ff, RD_S|RD_T|WR_CC|FP_D, I4|I32 },
{"c.f.s", "S,T", 0x46000030, 0xffe007ff, RD_S|RD_T|WR_CC|FP_S, I1 },
