aboutsummaryrefslogtreecommitdiff
path: root/opcodes
diff options
context:
space:
mode:
authorMaciej W. Rozycki <macro@imgtec.com>2016-07-08 16:07:39 +0100
committerMaciej W. Rozycki <macro@imgtec.com>2016-07-13 17:42:43 +0100
commit92281a5b06dd83a2a7d96ab8d83ae40b4e519acd (patch)
tree64dfb1df6965f4739048e2aac84567d8c96f0ec7 /opcodes
parentd9dcf8c6ef6e9b5e987ffcc6ba012623564d6986 (diff)
downloadgdb-92281a5b06dd83a2a7d96ab8d83ae40b4e519acd.zip
gdb-92281a5b06dd83a2a7d96ab8d83ae40b4e519acd.tar.gz
gdb-92281a5b06dd83a2a7d96ab8d83ae40b4e519acd.tar.bz2
MIPS/opcodes: Address issues with NAL disassembly
Address issues with the disassembly of the NAL assembly idiom and R6 instruction introduced with commit 7361da2c952e ("Add support for MIPS R6.") and then further tweaked with commit b9121b573e2e ("Add in a JALRC alias and fix the NAL instruction."). As from R6 this instruction has replaced the encoding of `bltzal $0, . + 4' as the solely supported form of the former BLTZAL instruction for the regular MIPS ISA. The instruction is marked as an alias only in our regular MIPS opcode table, making it fail to disassemble in R6 code if the `no-aliases' machine option has been passed to `objdump': $ cat test.s .text foo: nal $ as -mips64r6 -o test.o test.s $ objdump -dr --prefix-addresses --show-raw-insn -M no-aliases test.o nal.o: file format elf32-tradbigmips Disassembly of section .text: 00000000 <foo> 04100000 0x4100000 ... $ This is because the `bltzal' entry has been marked as pre-R6 only in the opcode table and there is no other opcode pattern to match. Additionally the changes referred made NAL replace the equivalent `bltzal $0, . + 4' instruction in disassembly, unless the `no-aliases' machine option has been used, in legacy code. Seeing NAL, especially in its updated form lacking the branch target argument, in the disassembly of such code may be confusing to people. This is because unlike with EHB only used in R2 and newer code -- the machine encoding of which we anyway always disassemble to its corresponding current architecture's mnemonic rather than its legacy meaning of `sll $0, $0, 3' -- BLTZAL has been indeed used in legacy code. Even though `bltzal $0, . + 8' and its machine code encoding (0x04100001) -- which is not equivalent to NAL and still disassembles as BLTZAL -- has been the predominant form as opposed to NAL's `bltzal $0, . + 4' (0x04100000), it makes sense to always keep the old form in disassembly, while still accepting `nal' in assembly. Remove the alias marking then from the the `nal' instruction pattern, making it always match for R6 code, even with the `no-aliases' option. And move the entry beyond the `bltzal' entry, making the latter one take precedence for legacy binary code, while letting the former still match any `nal' mnemonic in source code assembled for a legacy target. Add a suitable test case to the GAS test suite. While the change affects the disassembler more than the assembler, so placing the test case in the binutils test suite might be more appropriate, the intent is also to verify that `nal' is still accepted by GAS for legacy targets, plus we have test infrastructure available in the GAS test suite for automatic multiple ISA level testing, which we lack from the binutils framework. opcodes/ * mips-opc.c (mips_builtin_opcodes): Remove the INSN2_ALIAS annotation from the "nal" entry and reorder it beyond "bltzal". gas/ * testsuite/gas/mips/nal-1.d: New test. * testsuite/gas/mips/mipsr6@nal-1.d: New test. * testsuite/gas/mips/nal-2.d: New test. * testsuite/gas/mips/mipsr6@nal-2.d: New test. * testsuite/gas/mips/nal.s: New test source. * testsuite/gas/mips/mips.exp: Run the new tests.
Diffstat (limited to 'opcodes')
-rw-r--r--opcodes/ChangeLog5
-rw-r--r--opcodes/mips-opc.c2
2 files changed, 6 insertions, 1 deletions
diff --git a/opcodes/ChangeLog b/opcodes/ChangeLog
index 091d8d4..20bcdde 100644
--- a/opcodes/ChangeLog
+++ b/opcodes/ChangeLog
@@ -1,3 +1,8 @@
+2016-07-13 Maciej W. Rozycki <macro@imgtec.com>
+
+ * mips-opc.c (mips_builtin_opcodes): Remove the INSN2_ALIAS
+ annotation from the "nal" entry and reorder it beyond "bltzal".
+
2016-07-12 Jose E. Marchesi <jose.marchesi@oracle.com>
* sparc-opc.c (ldtxa): New macro.
diff --git a/opcodes/mips-opc.c b/opcodes/mips-opc.c
index a95eff1..3dcec76 100644
--- a/opcodes/mips-opc.c
+++ b/opcodes/mips-opc.c
@@ -431,7 +431,6 @@ const struct mips_opcode mips_builtin_opcodes[] =
{"move", "d,s", 0x00000021, 0xfc1f07ff, WR_1|RD_2, INSN2_ALIAS, I1, 0, 0 },/* addu */
{"b", "p", 0x10000000, 0xffff0000, UBD, INSN2_ALIAS, I1, 0, 0 },/* beq 0,0 */
{"b", "p", 0x04010000, 0xffff0000, UBD, INSN2_ALIAS, I1, 0, 0 },/* bgez 0 */
-{"nal", "", 0x04100000, 0xffffffff, WR_31|CBD, INSN2_ALIAS, I1, 0, 0 },/* bltzal 0 */
{"bal", "p", 0x04110000, 0xffff0000, WR_31|UBD, INSN2_ALIAS, I1, 0, 0 },/* bgezal 0*/
{"bc", "+'", 0xc8000000, 0xfc000000, NODS, 0, I37, 0, 0 },
{"balc", "+'", 0xe8000000, 0xfc000000, WR_31|NODS, 0, I37, 0, 0 },
@@ -750,6 +749,7 @@ const struct mips_opcode mips_builtin_opcodes[] =
{"bltz", "s,p", 0x04000000, 0xfc1f0000, RD_1|CBD, 0, I1, 0, 0 },
{"bltzl", "s,p", 0x04020000, 0xfc1f0000, RD_1|CBL, 0, I2|T3, 0, I37 },
{"bltzal", "s,p", 0x04100000, 0xfc1f0000, RD_1|WR_31|CBD, 0, I1, 0, I37 },
+{"nal", "", 0x04100000, 0xffffffff, WR_31|CBD, 0, I1, 0, 0 }, /* bltzal 0,.+4 */
{"bltzall", "s,p", 0x04120000, 0xfc1f0000, RD_1|WR_31|CBL, 0, I2|T3, 0, I37 },
{"bnez", "s,p", 0x14000000, 0xfc1f0000, RD_1|CBD, 0, I1, 0, 0 },
{"bnezl", "s,p", 0x54000000, 0xfc1f0000, RD_1|CBL, 0, I2|T3, 0, I37 },