Discussion:
[PATCH v3] GAS/MIPS: Add `-mfix-r5900' option for the R5900 short loop erratum
(too old to reply)
Fredrik Noring
2018-11-27 19:32:54 UTC
Permalink
`-march=r5900' already enables the R5900 short loop workaround.
However, the R5900 ISA and most other MIPS ISAs are mutually
exclusive since R5900-specific instructions are generated as well.

The `-mfix-r5900' option can be used in combination with e.g.
`-mips2' or `-mips3' to generate generic MIPS binaries that also
work with the R5900 target.

This change has been tested with `make RUNTESTFLAGS=mips.exp
check-gas' for the targets `mipsr5900el-unknown-linux-gnu',
`mipsr5900el-elf' and `mips3-unknown-linux-gnu'.

gas/
* config/tc-mips.c (options, md_longopts, can_swap_branch_p)
(md_parse_option, mips_after_parse_args, md_show_usage): New
`-mfix-r5900' option to fix the R5900 short loop erratum.
* doc/as.texi: Document the `-mfix-r5900' option.
* doc/c-mips.texi: Likewise.
* testsuite/gas/mips/mips.exp: Run R5900 dump tests.
* testsuite/gas/mips/r5900-fix.d: Test `-mfix-r5900' option.
* testsuite/gas/mips/r5900-fix.s: Likewise.
* testsuite/gas/mips/r5900-no-fix.d: Test `-mno-fix-r5900'.
* testsuite/gas/mips/r5900-no-fix.s: Likewise.
---
Changes in v3:
- ChangeLog entry
- Handle mips_fix_r5900_explicit in mips_after_parse_args

Changes in v2:
- Discard `-mfix-r5900' option localisation
- Discard `.set reorder' from r5900-fix.s
- Swap `.ent' and label in r5900-fix.s
- Test `-mfix-r5900' border cases
- Honor and test `-mno-fix-r5900'
- Improve documentation wording
---
gas/config/tc-mips.c | 24 +++++++++++++++-
gas/doc/as.texi | 9 ++++++
gas/doc/c-mips.texi | 8 ++++++
gas/testsuite/gas/mips/mips.exp | 2 ++
gas/testsuite/gas/mips/r5900-fix.d | 30 ++++++++++++++++++++
gas/testsuite/gas/mips/r5900-fix.s | 40 +++++++++++++++++++++++++++
gas/testsuite/gas/mips/r5900-no-fix.d | 13 +++++++++
gas/testsuite/gas/mips/r5900-no-fix.s | 17 ++++++++++++
8 files changed, 142 insertions(+), 1 deletion(-)
create mode 100644 gas/testsuite/gas/mips/r5900-fix.d
create mode 100644 gas/testsuite/gas/mips/r5900-fix.s
create mode 100644 gas/testsuite/gas/mips/r5900-no-fix.d
create mode 100644 gas/testsuite/gas/mips/r5900-no-fix.s

diff --git a/gas/config/tc-mips.c b/gas/config/tc-mips.c
index 918525b4e9..fcb230b226 100644
--- a/gas/config/tc-mips.c
+++ b/gas/config/tc-mips.c
@@ -939,6 +939,10 @@ static int mips_fix_rm7000;
/* ...likewise -mfix-cn63xxp1 */
static bfd_boolean mips_fix_cn63xxp1;

+/* ...likewise -mfix-r5900 */
+static bfd_boolean mips_fix_r5900;
+static bfd_boolean mips_fix_r5900_explicit;
+
/* We don't relax branches by default, since this causes us to expand
`la .l2 - .l1' if there's a branch between .l1 and .l2, because we
fail to compute the offset before expanding the macro to the most
@@ -1488,6 +1492,8 @@ enum options
OPTION_NO_FIX_VR4130,
OPTION_FIX_CN63XXP1,
OPTION_NO_FIX_CN63XXP1,
+ OPTION_FIX_R5900,
+ OPTION_NO_FIX_R5900,
OPTION_TRAP,
OPTION_BREAK,
OPTION_EB,
@@ -1636,6 +1642,8 @@ struct option md_longopts[] =
{"mno-fix-rm7000", no_argument, NULL, OPTION_NO_FIX_RM7000},
{"mfix-cn63xxp1", no_argument, NULL, OPTION_FIX_CN63XXP1},
{"mno-fix-cn63xxp1", no_argument, NULL, OPTION_NO_FIX_CN63XXP1},
+ {"mfix-r5900", no_argument, NULL, OPTION_FIX_R5900},
+ {"mno-fix-r5900", no_argument, NULL, OPTION_NO_FIX_R5900},

/* Miscellaneous options. */
{"trap", no_argument, NULL, OPTION_TRAP},
@@ -6997,7 +7005,7 @@ can_swap_branch_p (struct mips_cl_insn *ip, expressionS *address_expr,
- a branch delay slot of the loop is not NOP (EE 2.9 or later).

We need to do this because of a hardware bug in the R5900 chip. */
- if (mips_opts.arch == CPU_R5900
+ if (mips_fix_r5900
/* Check if instruction has a parameter, ignore "j $31". */
&& (address_expr != NULL)
/* Parameter must be 16 bit. */
@@ -14763,6 +14771,16 @@ md_parse_option (int c, const char *arg)
mips_fix_cn63xxp1 = FALSE;
break;

+ case OPTION_FIX_R5900:
+ mips_fix_r5900 = TRUE;
+ mips_fix_r5900_explicit = TRUE;
+ break;
+
+ case OPTION_NO_FIX_R5900:
+ mips_fix_r5900 = FALSE;
+ mips_fix_r5900_explicit = TRUE;
+ break;
+
case OPTION_RELAX_BRANCH:
mips_relax_branch = 1;
break;
@@ -15051,6 +15069,9 @@ mips_after_parse_args (void)

if (mips_flag_mdebug < 0)
mips_flag_mdebug = 0;
+
+ if (!mips_fix_r5900_explicit)
+ mips_fix_r5900 = file_mips_opts.arch == CPU_R5900;
}

void
@@ -20125,6 +20146,7 @@ MIPS options:\n\
-mfix-vr4130 work around VR4130 mflo/mfhi errata\n\
-mfix-24k insert a nop after ERET and DERET instructions\n\
-mfix-cn63xxp1 work around CN63XXP1 PREF errata\n\
+-mfix-r5900 work around R5900 short loop errata\n\
-mgp32 use 32-bit GPRs, regardless of the chosen ISA\n\
-mfp32 use 32-bit FPRs, regardless of the chosen ISA\n\
-msym32 assume all symbols have 32-bit values\n\
diff --git a/gas/doc/as.texi b/gas/doc/as.texi
index acecd35225..1e00e7811b 100644
--- a/gas/doc/as.texi
+++ b/gas/doc/as.texi
@@ -453,6 +453,7 @@ gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
[@b{-mfix-rm7000}] [@b{-mno-fix-rm7000}]
[@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
[@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
+ [@b{-mfix-r5900}] [@b{-mno-fix-r5900}]
[@b{-mdebug}] [@b{-no-mdebug}]
[@b{-mpdr}] [@b{-mno-pdr}]
@end ifset
@@ -1444,6 +1445,14 @@ of an mfhi or mflo instruction occurs in the following two instructions.
Cause nops to be inserted if a dmult or dmultu instruction is
followed by a load instruction.

+@item -mfix-r5900
+@itemx -mno-fix-r5900
+Do not attempt to schedule the preceding instruction into the delay slot
+of a branch instruction placed at the end of a short loop of six
+instructions or fewer and always schedule a @code{nop} instruction there
+instead. The short loop bug under certain conditions causes loops to
+execute only once or twice, due to a hardware bug in the R5900 chip.
+
@item -mdebug
@itemx -no-mdebug
Cause stabs-style debugging output to go into an ECOFF-style .mdebug
diff --git a/gas/doc/c-mips.texi b/gas/doc/c-mips.texi
index 7751ce01d6..76dfb10794 100644
--- a/gas/doc/c-mips.texi
+++ b/gas/doc/c-mips.texi
@@ -327,6 +327,14 @@ Insert nops to work around the 24K @samp{eret}/@samp{deret} errata.
Replace @code{pref} hints 0 - 4 and 6 - 24 with hint 28 to work around
certain CN63XXP1 errata.

+@item -mfix-r5900
+@itemx -mno-fix-r5900
+Do not attempt to schedule the preceding instruction into the delay slot
+of a branch instruction placed at the end of a short loop of six
+instructions or fewer and always schedule a @code{nop} instruction there
+instead. The short loop bug under certain conditions causes loops to
+execute only once or twice, due to a hardware bug in the R5900 chip.
+
@item -m4010
@itemx -no-m4010
Generate code for the LSI R4010 chip. This tells the assembler to
diff --git a/gas/testsuite/gas/mips/mips.exp b/gas/testsuite/gas/mips/mips.exp
index 0da442c1d5..bc65917ffd 100644
--- a/gas/testsuite/gas/mips/mips.exp
+++ b/gas/testsuite/gas/mips/mips.exp
@@ -1560,6 +1560,8 @@ if { [istarget mips*-*-vxworks*] } {
run_dump_test_arches "break-error" [mips_arch_list_all]

run_dump_test "r5900"
+ run_dump_test "r5900-fix"
+ run_dump_test "r5900-no-fix"
run_dump_test "r5900-full"
run_list_test "r5900-nollsc" "-mabi=o64 -march=r5900"
run_dump_test "r5900-vu0"
diff --git a/gas/testsuite/gas/mips/r5900-fix.d b/gas/testsuite/gas/mips/r5900-fix.d
new file mode 100644
index 0000000000..faf482022a
--- /dev/null
+++ b/gas/testsuite/gas/mips/r5900-fix.d
@@ -0,0 +1,30 @@
+#objdump: -dr --prefix-addresses --show-raw-insn -M gpr-names=numeric -mmips:5900
+#name: MIPS R5900 workarounds (-mips3 -mfix-r5900)
+#as: -mips3 -mfix-r5900
+
+.*: +file format .*mips.*
+
+Disassembly of section \.text:
+[0-9a-f]+ <[^>]*> 2403012c li \$3,300
+[0-9a-f]+ <[^>]*> 2063ffff addi \$3,\$3,-1
+[0-9a-f]+ <[^>]*> 2084ffff addi \$4,\$4,-1
+[0-9a-f]+ <[^>]*> 1460fffd bnez \$3,[0-9a-f]+ <short_loop3>
+[0-9a-f]+ <[^>]*> 00000000 nop
+[0-9a-f]+ <[^>]*> 2403012c li \$3,300
+[0-9a-f]+ <[^>]*> 2063ffff addi \$3,\$3,-1
+[0-9a-f]+ <[^>]*> 2084ffff addi \$4,\$4,-1
+[0-9a-f]+ <[^>]*> 20a5ffff addi \$5,\$5,-1
+[0-9a-f]+ <[^>]*> 20c6ffff addi \$6,\$6,-1
+[0-9a-f]+ <[^>]*> 20e7ffff addi \$7,\$7,-1
+[0-9a-f]+ <[^>]*> 1460fffa bnez \$3,[0-9a-f]+ <short_loop6>
+[0-9a-f]+ <[^>]*> 00000000 nop
+[0-9a-f]+ <[^>]*> 2403012c li \$3,300
+[0-9a-f]+ <[^>]*> 2063ffff addi \$3,\$3,-1
+[0-9a-f]+ <[^>]*> 2084ffff addi \$4,\$4,-1
+[0-9a-f]+ <[^>]*> 20a5ffff addi \$5,\$5,-1
+[0-9a-f]+ <[^>]*> 20c6ffff addi \$6,\$6,-1
+[0-9a-f]+ <[^>]*> 20e7ffff addi \$7,\$7,-1
+[0-9a-f]+ <[^>]*> 1460fffa bnez \$3,[0-9a-f]+ <short_loop7>
+[0-9a-f]+ <[^>]*> 2108ffff addi \$8,\$8,-1
+[0-9a-f]+ <[^>]*> 24040003 li \$4,3
+ \.\.\.
diff --git a/gas/testsuite/gas/mips/r5900-fix.s b/gas/testsuite/gas/mips/r5900-fix.s
new file mode 100644
index 0000000000..97ab76cf1b
--- /dev/null
+++ b/gas/testsuite/gas/mips/r5900-fix.s
@@ -0,0 +1,40 @@
+ .text
+
+ .ent test_mfix_r5900
+test_mfix_r5900:
+ # Test the short loop fix with 3 loop instructions.
+ li $3, 300
+short_loop3:
+ addi $3, -1
+ addi $4, -1
+ # A NOP will be inserted in the branch delay slot.
+ bne $3, $0, short_loop3
+
+ # Test the short loop fix with 6 loop instructions.
+ li $3, 300
+short_loop6:
+ addi $3, -1
+ addi $4, -1
+ addi $5, -1
+ addi $6, -1
+ addi $7, -1
+ # A NOP will be inserted in the branch delay slot.
+ bne $3, $0, short_loop6
+
+ # Test the short loop fix with 7 loop instructions.
+ li $3, 300
+short_loop7:
+ addi $3, -1
+ addi $4, -1
+ addi $5, -1
+ addi $6, -1
+ addi $7, -1
+ addi $8, -1
+ # The short loop fix does not apply for loops with
+ # more than 6 instructions.
+ bne $3, $0, short_loop7
+
+ li $4, 3
+
+ .space 8
+ .end test_mfix_r5900
diff --git a/gas/testsuite/gas/mips/r5900-no-fix.d b/gas/testsuite/gas/mips/r5900-no-fix.d
new file mode 100644
index 0000000000..2ac60c9147
--- /dev/null
+++ b/gas/testsuite/gas/mips/r5900-no-fix.d
@@ -0,0 +1,13 @@
+#objdump: -dr --prefix-addresses --show-raw-insn -M gpr-names=numeric -mmips:5900
+#name: MIPS R5900 workarounds disabled (-mno-fix-r5900)
+#as: -march=r5900 -mtune=r5900 -mno-fix-r5900
+
+.*: +file format .*mips.*
+
+Disassembly of section \.text:
+[0-9a-f]+ <[^>]*> 2403012c li \$3,300
+[0-9a-f]+ <[^>]*> 2063ffff addi \$3,\$3,-1
+[0-9a-f]+ <[^>]*> 1460fffe bnez \$3,[0-9a-f]+ <short_loop_no_mfix_r5900>
+[0-9a-f]+ <[^>]*> 2084ffff addi \$4,\$4,-1
+[0-9a-f]+ <[^>]*> 24040003 li \$4,3
+ \.\.\.
diff --git a/gas/testsuite/gas/mips/r5900-no-fix.s b/gas/testsuite/gas/mips/r5900-no-fix.s
new file mode 100644
index 0000000000..723288976b
--- /dev/null
+++ b/gas/testsuite/gas/mips/r5900-no-fix.s
@@ -0,0 +1,17 @@
+ .text
+
+ .ent test_no_mfix_r5900
+test_no_mfix_r5900:
+ # Test that the short loop fix with 3 loop instructions
+ # is not applied with `-mno-fix-r5900'.
+ li $3, 300
+short_loop_no_mfix_r5900:
+ addi $3, -1
+ addi $4, -1
+ # A NOP will not be inserted in the branch delay slot.
+ bne $3, $0, short_loop_no_mfix_r5900
+
+ li $4, 3
+
+ .space 8
+ .end test_no_mfix_r5900
--
2.18.1
Maciej W. Rozycki
2018-11-30 18:42:21 UTC
Permalink
From: Fredrik Noring <***@nocrew.org>

`-march=r5900' already enables the R5900 short loop workaround.
However, the R5900 ISA and most other MIPS ISAs are mutually
exclusive since R5900-specific instructions are generated as well.

The `-mfix-r5900' option can be used in combination with e.g.
`-mips2' or `-mips3' to generate generic MIPS binaries that also
work with the R5900 target.

This change has been tested with `make RUNTESTFLAGS=mips.exp
check-gas' for the targets `mipsr5900el-unknown-linux-gnu',
`mipsr5900el-elf' and `mips3-unknown-linux-gnu'.

gas/
* config/tc-mips.c (mips_fix_r5900, mips_fix_r5900_explicit):
New variables.
(options): Add OPTION_FIX_R5900 and OPTION_NO_FIX_R5900
enumeration constants.
(md_longopts): Add "mfix-r5900" and "mno-fix-r5900" options.
(can_swap_branch_p, md_parse_option, mips_after_parse_args):
Handle the new options.
(md_show_usage): Document the `-mfix-r5900' option.
* doc/as.texi: Likewise.
* doc/c-mips.texi: Likewise.
* testsuite/gas/mips/mips.exp: Run R5900 dump tests.
* testsuite/gas/mips/r5900-fix.d: Test `-mfix-r5900' option.
* testsuite/gas/mips/r5900-fix.s: Likewise.
* testsuite/gas/mips/r5900-no-fix.d: Test `-mno-fix-r5900'.
* testsuite/gas/mips/r5900-no-fix.s: Likewise.
---
Hi Fredrik,

I have moved and commented code in `mips_after_parse_args' and updated
your ChangeLog entry with `mips_fix_r5900' and `mips_fix_r5900_explicit'
references, also making the remaining config/tc-mips.c references more
specific. This is the resulting version I have committed.

Thank you for your contribution to the GNU project!

Maciej
---
diff --git a/gas/config/tc-mips.c b/gas/config/tc-mips.c
index 918525b..2942036 100644
--- a/gas/config/tc-mips.c
+++ b/gas/config/tc-mips.c
@@ -939,6 +939,10 @@ static int mips_fix_rm7000;
/* ...likewise -mfix-cn63xxp1 */
static bfd_boolean mips_fix_cn63xxp1;

+/* ...likewise -mfix-r5900 */
+static bfd_boolean mips_fix_r5900;
+static bfd_boolean mips_fix_r5900_explicit;
+
/* We don't relax branches by default, since this causes us to expand
`la .l2 - .l1' if there's a branch between .l1 and .l2, because we
fail to compute the offset before expanding the macro to the most
@@ -1488,6 +1492,8 @@ enum options
OPTION_NO_FIX_VR4130,
OPTION_FIX_CN63XXP1,
OPTION_NO_FIX_CN63XXP1,
+ OPTION_FIX_R5900,
+ OPTION_NO_FIX_R5900,
OPTION_TRAP,
OPTION_BREAK,
OPTION_EB,
@@ -1636,6 +1642,8 @@ struct option md_longopts[] =
{"mno-fix-rm7000", no_argument, NULL, OPTION_NO_FIX_RM7000},
{"mfix-cn63xxp1", no_argument, NULL, OPTION_FIX_CN63XXP1},
{"mno-fix-cn63xxp1", no_argument, NULL, OPTION_NO_FIX_CN63XXP1},
+ {"mfix-r5900", no_argument, NULL, OPTION_FIX_R5900},
+ {"mno-fix-r5900", no_argument, NULL, OPTION_NO_FIX_R5900},

/* Miscellaneous options. */
{"trap", no_argument, NULL, OPTION_TRAP},
@@ -6997,7 +7005,7 @@ can_swap_branch_p (struct mips_cl_insn *ip, expressionS *address_expr,
- a branch delay slot of the loop is not NOP (EE 2.9 or later).

We need to do this because of a hardware bug in the R5900 chip. */
- if (mips_opts.arch == CPU_R5900
+ if (mips_fix_r5900
/* Check if instruction has a parameter, ignore "j $31". */
&& (address_expr != NULL)
/* Parameter must be 16 bit. */
@@ -14763,6 +14771,16 @@ md_parse_option (int c, const char *arg)
mips_fix_cn63xxp1 = FALSE;
break;

+ case OPTION_FIX_R5900:
+ mips_fix_r5900 = TRUE;
+ mips_fix_r5900_explicit = TRUE;
+ break;
+
+ case OPTION_NO_FIX_R5900:
+ mips_fix_r5900 = FALSE;
+ mips_fix_r5900_explicit = TRUE;
+ break;
+
case OPTION_RELAX_BRANCH:
mips_relax_branch = 1;
break;
@@ -15036,6 +15054,10 @@ mips_after_parse_args (void)
/* Set up initial mips_opts state. */
mips_opts = file_mips_opts;

+ /* For the R5900 default to `-mfix-r5900' unless the user told otherwise. */
+ if (!mips_fix_r5900_explicit)
+ mips_fix_r5900 = file_mips_opts.arch == CPU_R5900;
+
/* The register size inference code is now placed in
file_mips_check_options. */

@@ -20125,6 +20147,7 @@ MIPS options:\n\
-mfix-vr4130 work around VR4130 mflo/mfhi errata\n\
-mfix-24k insert a nop after ERET and DERET instructions\n\
-mfix-cn63xxp1 work around CN63XXP1 PREF errata\n\
+-mfix-r5900 work around R5900 short loop errata\n\
-mgp32 use 32-bit GPRs, regardless of the chosen ISA\n\
-mfp32 use 32-bit FPRs, regardless of the chosen ISA\n\
-msym32 assume all symbols have 32-bit values\n\
diff --git a/gas/doc/as.texi b/gas/doc/as.texi
index acecd35..1e00e78 100644
--- a/gas/doc/as.texi
+++ b/gas/doc/as.texi
@@ -453,6 +453,7 @@ gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
[@b{-mfix-rm7000}] [@b{-mno-fix-rm7000}]
[@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
[@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
+ [@b{-mfix-r5900}] [@b{-mno-fix-r5900}]
[@b{-mdebug}] [@b{-no-mdebug}]
[@b{-mpdr}] [@b{-mno-pdr}]
@end ifset
@@ -1444,6 +1445,14 @@ of an mfhi or mflo instruction occurs in the following two instructions.
Cause nops to be inserted if a dmult or dmultu instruction is
followed by a load instruction.

+@item -mfix-r5900
+@itemx -mno-fix-r5900
+Do not attempt to schedule the preceding instruction into the delay slot
+of a branch instruction placed at the end of a short loop of six
+instructions or fewer and always schedule a @code{nop} instruction there
+instead. The short loop bug under certain conditions causes loops to
+execute only once or twice, due to a hardware bug in the R5900 chip.
+
@item -mdebug
@itemx -no-mdebug
Cause stabs-style debugging output to go into an ECOFF-style .mdebug
diff --git a/gas/doc/c-mips.texi b/gas/doc/c-mips.texi
index 7751ce0..76dfb10 100644
--- a/gas/doc/c-mips.texi
+++ b/gas/doc/c-mips.texi
@@ -327,6 +327,14 @@ Insert nops to work around the 24K @samp{eret}/@samp{deret} errata.
Replace @code{pref} hints 0 - 4 and 6 - 24 with hint 28 to work around
certain CN63XXP1 errata.

+@item -mfix-r5900
+@itemx -mno-fix-r5900
+Do not attempt to schedule the preceding instruction into the delay slot
+of a branch instruction placed at the end of a short loop of six
+instructions or fewer and always schedule a @code{nop} instruction there
+instead. The short loop bug under certain conditions causes loops to
+execute only once or twice, due to a hardware bug in the R5900 chip.
+
@item -m4010
@itemx -no-m4010
Generate code for the LSI R4010 chip. This tells the assembler to
diff --git a/gas/testsuite/gas/mips/mips.exp b/gas/testsuite/gas/mips/mips.exp
index 0da442c..bc65917 100644
--- a/gas/testsuite/gas/mips/mips.exp
+++ b/gas/testsuite/gas/mips/mips.exp
@@ -1560,6 +1560,8 @@ if { [istarget mips*-*-vxworks*] } {
run_dump_test_arches "break-error" [mips_arch_list_all]

run_dump_test "r5900"
+ run_dump_test "r5900-fix"
+ run_dump_test "r5900-no-fix"
run_dump_test "r5900-full"
run_list_test "r5900-nollsc" "-mabi=o64 -march=r5900"
run_dump_test "r5900-vu0"
diff --git a/gas/testsuite/gas/mips/r5900-fix.d b/gas/testsuite/gas/mips/r5900-fix.d
new file mode 100644
index 0000000..faf4820
--- /dev/null
+++ b/gas/testsuite/gas/mips/r5900-fix.d
@@ -0,0 +1,30 @@
+#objdump: -dr --prefix-addresses --show-raw-insn -M gpr-names=numeric -mmips:5900
+#name: MIPS R5900 workarounds (-mips3 -mfix-r5900)
+#as: -mips3 -mfix-r5900
+
+.*: +file format .*mips.*
+
+Disassembly of section \.text:
+[0-9a-f]+ <[^>]*> 2403012c li \$3,300
+[0-9a-f]+ <[^>]*> 2063ffff addi \$3,\$3,-1
+[0-9a-f]+ <[^>]*> 2084ffff addi \$4,\$4,-1
+[0-9a-f]+ <[^>]*> 1460fffd bnez \$3,[0-9a-f]+ <short_loop3>
+[0-9a-f]+ <[^>]*> 00000000 nop
+[0-9a-f]+ <[^>]*> 2403012c li \$3,300
+[0-9a-f]+ <[^>]*> 2063ffff addi \$3,\$3,-1
+[0-9a-f]+ <[^>]*> 2084ffff addi \$4,\$4,-1
+[0-9a-f]+ <[^>]*> 20a5ffff addi \$5,\$5,-1
+[0-9a-f]+ <[^>]*> 20c6ffff addi \$6,\$6,-1
+[0-9a-f]+ <[^>]*> 20e7ffff addi \$7,\$7,-1
+[0-9a-f]+ <[^>]*> 1460fffa bnez \$3,[0-9a-f]+ <short_loop6>
+[0-9a-f]+ <[^>]*> 00000000 nop
+[0-9a-f]+ <[^>]*> 2403012c li \$3,300
+[0-9a-f]+ <[^>]*> 2063ffff addi \$3,\$3,-1
+[0-9a-f]+ <[^>]*> 2084ffff addi \$4,\$4,-1
+[0-9a-f]+ <[^>]*> 20a5ffff addi \$5,\$5,-1
+[0-9a-f]+ <[^>]*> 20c6ffff addi \$6,\$6,-1
+[0-9a-f]+ <[^>]*> 20e7ffff addi \$7,\$7,-1
+[0-9a-f]+ <[^>]*> 1460fffa bnez \$3,[0-9a-f]+ <short_loop7>
+[0-9a-f]+ <[^>]*> 2108ffff addi \$8,\$8,-1
+[0-9a-f]+ <[^>]*> 24040003 li \$4,3
+ \.\.\.
diff --git a/gas/testsuite/gas/mips/r5900-fix.s b/gas/testsuite/gas/mips/r5900-fix.s
new file mode 100644
index 0000000..97ab76c
--- /dev/null
+++ b/gas/testsuite/gas/mips/r5900-fix.s
@@ -0,0 +1,40 @@
+ .text
+
+ .ent test_mfix_r5900
+test_mfix_r5900:
+ # Test the short loop fix with 3 loop instructions.
+ li $3, 300
+short_loop3:
+ addi $3, -1
+ addi $4, -1
+ # A NOP will be inserted in the branch delay slot.
+ bne $3, $0, short_loop3
+
+ # Test the short loop fix with 6 loop instructions.
+ li $3, 300
+short_loop6:
+ addi $3, -1
+ addi $4, -1
+ addi $5, -1
+ addi $6, -1
+ addi $7, -1
+ # A NOP will be inserted in the branch delay slot.
+ bne $3, $0, short_loop6
+
+ # Test the short loop fix with 7 loop instructions.
+ li $3, 300
+short_loop7:
+ addi $3, -1
+ addi $4, -1
+ addi $5, -1
+ addi $6, -1
+ addi $7, -1
+ addi $8, -1
+ # The short loop fix does not apply for loops with
+ # more than 6 instructions.
+ bne $3, $0, short_loop7
+
+ li $4, 3
+
+ .space 8
+ .end test_mfix_r5900
diff --git a/gas/testsuite/gas/mips/r5900-no-fix.d b/gas/testsuite/gas/mips/r5900-no-fix.d
new file mode 100644
index 0000000..2ac60c9
--- /dev/null
+++ b/gas/testsuite/gas/mips/r5900-no-fix.d
@@ -0,0 +1,13 @@
+#objdump: -dr --prefix-addresses --show-raw-insn -M gpr-names=numeric -mmips:5900
+#name: MIPS R5900 workarounds disabled (-mno-fix-r5900)
+#as: -march=r5900 -mtune=r5900 -mno-fix-r5900
+
+.*: +file format .*mips.*
+
+Disassembly of section \.text:
+[0-9a-f]+ <[^>]*> 2403012c li \$3,300
+[0-9a-f]+ <[^>]*> 2063ffff addi \$3,\$3,-1
+[0-9a-f]+ <[^>]*> 1460fffe bnez \$3,[0-9a-f]+ <short_loop_no_mfix_r5900>
+[0-9a-f]+ <[^>]*> 2084ffff addi \$4,\$4,-1
+[0-9a-f]+ <[^>]*> 24040003 li \$4,3
+ \.\.\.
diff --git a/gas/testsuite/gas/mips/r5900-no-fix.s b/gas/testsuite/gas/mips/r5900-no-fix.s
new file mode 100644
index 0000000..7232889
--- /dev/null
+++ b/gas/testsuite/gas/mips/r5900-no-fix.s
@@ -0,0 +1,17 @@
+ .text
+
+ .ent test_no_mfix_r5900
+test_no_mfix_r5900:
+ # Test that the short loop fix with 3 loop instructions
+ # is not applied with `-mno-fix-r5900'.
+ li $3, 300
+short_loop_no_mfix_r5900:
+ addi $3, -1
+ addi $4, -1
+ # A NOP will not be inserted in the branch delay slot.
+ bne $3, $0, short_loop_no_mfix_r5900
+
+ li $4, 3
+
+ .space 8
+ .end test_no_mfix_r5900

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