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Committed, CRIS: helper functionality to avoid hw multiplication/cache bug
- From: Hans-Peter Nilsson <hans-peter dot nilsson at axis dot com>
- To: binutils at sources dot redhat dot com
- Date: Mon, 22 Mar 2004 00:51:54 +0100
- Subject: Committed, CRIS: helper functionality to avoid hw multiplication/cache bug
See <URL:http://developer.axis.com/doc/hardware/etrax100lx/des_ref/errata_etrax_100lx.html>
"Multiply operations and cache behavior" and <URL:http://gcc.gnu.org/PR14471>.
Will commit to 2.15 too.
gas/ChangeLog:
* doc/c-cris.texi (CRIS-Opts): Document --no-mul-bug-abort,
--mul-bug-abort and the default behavior.
* config/tc-cris.c (cris_insn_kind): New member CRIS_INSN_MUL.
(err_for_dangerous_mul_placement): New variable.
(STATE_MUL, OPTION_MULBUG_ABORT_ON, OPTION_MULBUG_ABORT_OFF): New
macros.
(md_cris_relax_table): Have placeholder for STATE_MUL.
(md_longopts): New options --mul-bug-abort and --no-mul-bug-abort.
(cris_relax_frag) <case ENCODE_RELAX (STATE_MUL, STATE_BYTE)>: New
case doing nothing.
(md_estimate_size_before_relax) <case ENCODE_RELAX (STATE_MUL,
STATE_BYTE)>: Ditto.
(md_convert_frag) <ENCODE_RELAX (STATE_MUL, STATE_BYTE)>: Check
alignment and position of this frag, emit error message if
suspicious.
(md_assemble): For a multiply insn and when checking it,
transform the current frag into a special frag for that purpose.
(md_parse_option) <case OPTION_MULBUG_ABORT_OFF, case
OPTION_MULBUG_ABORT_ON>: Handle new options.
gas/testsuite/ChangeLog:
* gas/cris/regreg.d: Assemble with --no-mul-bug-abort.
* gas/cris/mulbug-err-1.s, gas/cris/rd-mulbug-1.d: New tests.
gas/testsuite/gas/cris/mulbug-err-1.s::
--- /dev/null Tue Oct 29 15:57:07 2002
+++ gas/testsuite/gas/cris/mulbug-err-1.s Thu Feb 26 16:43:37 2004
@@ -0,0 +1,55 @@
+; Test error message for mul insns at locations likely to trig
+; a hardware bug.
+
+; { dg-do assemble { target cris-*-* } }
+
+ ; First, .text isn't dword-aligned by default.
+ .text
+ muls.w $r1,$r4 ; { dg-error "align" }
+ nop
+ muls.b $r1,$r4 ; { dg-error "align" }
+ mulu.d $r1,$r4 ; { dg-error "align" }
+
+; Neither are other code sections, aligned to word.
+ .section .text.1,"ax",@progbits
+ .p2align 1
+ muls.w $r1,$r4 ; { dg-error "align" }
+ nop
+ mulu.b $r1,$r4 ; { dg-error "align" }
+ muls.d $r1,$r4 ; { dg-error "align" }
+
+; Now, a section aligned to dword. Errors for certain relative
+; positions only.
+ .section .text.2,"ax",@progbits
+ .p2align 2
+ mulu.w $r1,$r4
+ nop
+ muls.d $r1,$r4
+ mulu.w $r1,$r4 ; { dg-error "align" }
+
+; For good measure, a cache-line-aligned section.
+ .section .text.3,"ax",@progbits
+ .p2align 5
+ muls.w $r1,$r4
+ mulu.d $r4,$r1
+ mulu.b $r1,$r4
+ .rept 12
+ nop
+ .endr
+ mulu.b $r1,$r4 ; { dg-error "align" }
+ mulu.b $r1,$r4
+
+; Last, make sure typical alignment use by a fixed gcc passes.
+ .section .text.4,"ax",@progbits
+ .align 1
+ moveq 0,$r13
+ moveq 1,$r13
+ .p2alignw 5,0x050f,2
+ muls.d $r1,$r4
+ .rept 12
+ moveq 2,$r13
+ .endr
+ .p2alignw 5,0x050f,2
+ muls.w $r1,$r4
+ .p2alignw 5,0x050f,2
+ muls.b $r4,$r1
gas/testsuite/gas/cris/rd-mulbug-1.d::
--- /dev/null Tue Oct 29 15:57:07 2002
+++ gas/testsuite/gas/cris/rd-mulbug-1.d Thu Feb 26 16:50:52 2004
@@ -0,0 +1,24 @@
+#objdump: -s
+#source: mulbug-err-1.s
+#as: --em=criself --no-mul-bug-abort
+
+# Check that we don't get any errors or messages with
+# "--no-mul-bug-abort". No checking for "--mul-bug-abort",
+# though.
+
+.*: file format .*-cris
+
+Contents of section \.text:
+ 0+ 114d0f05 014d2149 .*
+Contents of section \.text\.1:
+ 0+ 114d0f05 0149214d .*
+Contents of section \.text\.2:
+ 0+ 11490f05 214d1149 .*
+Contents of section \.text\.3:
+ 0+ 114d2419 01490f05 0f050f05 0f050f05 .*
+ 0+10 0f050f05 0f050f05 0f050f05 0f050149 .*
+ 0+20 0149 .*
+Contents of section \.text\.4:
+ 0+ 40d241d2 214d42d2 42d242d2 42d242d2 .*
+ 0+10 42d242d2 42d242d2 42d242d2 42d20f05 .*
+ 0+20 114d041d .*
Index: gas/config/tc-cris.c
===================================================================
RCS file: /cvs/src/src/gas/config/tc-cris.c,v
retrieving revision 1.28
diff -c -p -r1.28 tc-cris.c
*** gas/config/tc-cris.c 21 Nov 2003 00:24:40 -0000 1.28
--- gas/config/tc-cris.c 21 Mar 2004 22:59:00 -0000
***************
*** 58,64 ****
Note that some prefix-insns might be assembled as CRIS_INSN_NORMAL. */
enum cris_insn_kind
{
! CRIS_INSN_NORMAL, CRIS_INSN_NONE, CRIS_INSN_BRANCH
};
/* An instruction will have one of these prefixes.
--- 58,64 ----
Note that some prefix-insns might be assembled as CRIS_INSN_NORMAL. */
enum cris_insn_kind
{
! CRIS_INSN_NORMAL, CRIS_INSN_NONE, CRIS_INSN_BRANCH, CRIS_INSN_MUL
};
/* An instruction will have one of these prefixes.
*************** const pseudo_typeS md_pseudo_table[] =
*** 187,192 ****
--- 187,196 ----
static int warn_for_branch_expansion = 0;
+ /* Whether to emit error when a MULS/MULU could be located last on a
+ cache-line. */
+ static int err_for_dangerous_mul_placement = 1;
+
const char cris_comment_chars[] = ";";
/* This array holds the chars that only start a comment at the beginning of
*************** const char FLT_CHARS[] = "";
*** 219,228 ****
length: byte, word, 10-byte expansion
2. BDAP
! length: byte, word, dword */
#define STATE_CONDITIONAL_BRANCH (1)
#define STATE_BASE_PLUS_DISP_PREFIX (2)
#define STATE_LENGTH_MASK (3)
#define STATE_BYTE (0)
--- 223,238 ----
length: byte, word, 10-byte expansion
2. BDAP
! length: byte, word, dword
!
! 3. MULS/MULU
! Not really a relaxation (no infrastructure to get delay-slots
! right), just an alignment and placement checker for the v10
! multiply/cache-bug. */
#define STATE_CONDITIONAL_BRANCH (1)
#define STATE_BASE_PLUS_DISP_PREFIX (2)
+ #define STATE_MUL (3)
#define STATE_LENGTH_MASK (3)
#define STATE_BYTE (0)
*************** const relax_typeS md_cris_relax_table[]
*** 282,288 ****
{BDAP_WF, BDAP_WB, 2, ENCODE_RELAX (2, 2)},
/* BDAP.d [PC+] (2, 2). */
! {0, 0, 4, 0}
};
#undef BRANCH_BF
--- 292,304 ----
{BDAP_WF, BDAP_WB, 2, ENCODE_RELAX (2, 2)},
/* BDAP.d [PC+] (2, 2). */
! {0, 0, 4, 0},
!
! /* Unused (2, 3). */
! {0, 0, 0, 0},
!
! /* MULS/MULU (3, 0). Positions (3, 1..3) are unused. */
! {0, 0, 0, 0}, {0, 0, 0, 0}, {0, 0, 0, 0}, {0, 0, 0, 0}
};
#undef BRANCH_BF
*************** struct option md_longopts[] =
*** 304,309 ****
--- 320,329 ----
{"underscore", no_argument, NULL, OPTION_US},
#define OPTION_PIC (OPTION_MD_BASE + 2)
{"pic", no_argument, NULL, OPTION_PIC},
+ #define OPTION_MULBUG_ABORT_ON (OPTION_MD_BASE + 3)
+ {"mul-bug-abort", no_argument, NULL, OPTION_MULBUG_ABORT_ON},
+ #define OPTION_MULBUG_ABORT_OFF (OPTION_MD_BASE + 4)
+ {"no-mul-bug-abort", no_argument, NULL, OPTION_MULBUG_ABORT_OFF},
{NULL, no_argument, NULL, 0}
};
*************** cris_relax_frag (seg, fragP, stretch)
*** 392,397 ****
--- 412,421 ----
aim = S_GET_VALUE (symbolP);
break;
+ case ENCODE_RELAX (STATE_MUL, STATE_BYTE):
+ /* Nothing to do here. */
+ return 0;
+
default:
as_fatal (_("internal inconsistency problem in %s: fr_subtype %d"),
__FUNCTION__, fragP->fr_subtype);
*************** md_estimate_size_before_relax (fragP, se
*** 558,563 ****
--- 582,591 ----
fragP->fr_var = md_cris_relax_table[fragP->fr_subtype].rlx_length;
break;
+ case ENCODE_RELAX (STATE_MUL, STATE_BYTE):
+ /* Nothing to do here. */
+ break;
+
default:
BAD_CASE (fragP->fr_subtype);
}
*************** md_convert_frag (abfd, sec, fragP)
*** 679,684 ****
--- 707,730 ----
var_part_size = 4;
break;
+ case ENCODE_RELAX (STATE_MUL, STATE_BYTE):
+ /* This is the only time we check position and aligmnent of the
+ placement-tracking frag. */
+ if (sec->alignment_power < 2)
+ as_bad_where (fragP->fr_file, fragP->fr_line,
+ _("section alignment must be >= 4 bytes to check MULS/MULU safeness"));
+ else
+ {
+ /* If the address after the MULS/MULU has alignment which is
+ that of the section and may be that of a cache-size of the
+ buggy versions, then the MULS/MULU can be placed badly. */
+ if ((address_of_var_part
+ & ((1 << sec->alignment_power) - 1) & 31) == 0)
+ as_bad_where (fragP->fr_file, fragP->fr_line,
+ _("dangerous MULS/MULU location; give it higher alignment"));
+ }
+ break;
+
default:
BAD_CASE (fragP->fr_subtype);
break;
*************** md_assemble (str)
*** 967,972 ****
--- 1013,1025 ----
output_instruction.expr.X_add_number);
}
}
+ else if (output_instruction.insn_type == CRIS_INSN_MUL
+ && err_for_dangerous_mul_placement)
+ /* Create a frag which which we track the location of the mul insn
+ (in the last two bytes before the mul-frag). */
+ frag_variant (rs_machine_dependent, 0, 0,
+ ENCODE_RELAX (STATE_MUL, STATE_BYTE),
+ NULL, 0, opcodep);
else
{
if (output_instruction.imm_oprnd_size > 0)
*************** cris_process_instruction (insn_text, out
*** 1572,1577 ****
--- 1625,1633 ----
!= (unsigned int) out_insnp->imm_oprnd_size))
as_bad (_("PIC relocation size does not match operand size"));
}
+ else if (instruction->op == cris_muls_op
+ || instruction->op == cris_mulu_op)
+ out_insnp->insn_type = CRIS_INSN_MUL;
}
break;
}
*************** md_parse_option (arg, argp)
*** 2945,2950 ****
--- 3001,3014 ----
case OPTION_PIC:
pic = TRUE;
+ return 1;
+
+ case OPTION_MULBUG_ABORT_OFF:
+ err_for_dangerous_mul_placement = 0;
+ return 1;
+
+ case OPTION_MULBUG_ABORT_ON:
+ err_for_dangerous_mul_placement = 1;
return 1;
default:
Index: gas/doc/c-cris.texi
===================================================================
RCS file: /cvs/src/src/gas/doc/c-cris.texi,v
retrieving revision 1.1
diff -c -p -r1.1 c-cris.texi
*** gas/doc/c-cris.texi 9 Feb 2002 03:12:24 -0000 1.1
--- gas/doc/c-cris.texi 21 Mar 2004 22:59:00 -0000
*************** When @option{-N} is specified, @code{@va
*** 74,79 ****
--- 74,98 ----
warning when a 16-bit branch instruction is expanded into a
32-bit multiple-instruction construct (@pxref{CRIS-Expand}).
+ @cindex @option{--no-mul-bug-abort} command line option, CRIS
+ @cindex @option{--mul-bug-abort} command line option, CRIS
+ @cindex CRIS @option{--no-mul-bug-abort} command line option
+ @cindex CRIS @option{--mul-bug-abort} command line option
+
+ Some versions of the CRIS v10, for example in the Etrax 100 LX,
+ contain a bug that causes destabilizing memory accesses when a
+ multiply instruction is executed with certain values in the
+ first operand just before a cache-miss. When the
+ @option{--mul-bug-abort} command line option is active (the
+ default value), @code{@value{AS}} will refuse to assemble a file
+ containing a multiply instruction at a dangerous offset, one
+ that could be the last on a cache-line, or is in a section with
+ insufficient alignment. This placement checking does not catch
+ any case where the multiply instruction is dangerously placed
+ because it is located in a delay-slot. The
+ @option{--mul-bug-abort} command line option turns off the
+ checking.
+
@node CRIS-Expand
@section Instruction expansion
Index: gas/testsuite/gas/cris/regreg.d
===================================================================
RCS file: /cvs/src/src/gas/testsuite/gas/cris/regreg.d,v
retrieving revision 1.3
diff -c -p -r1.3 regreg.d
*** gas/testsuite/gas/cris/regreg.d 15 Jun 2003 23:46:37 -0000 1.3
--- gas/testsuite/gas/cris/regreg.d 21 Mar 2004 22:59:00 -0000
***************
*** 1,4 ****
--- 1,5 ----
#objdump: -dr
+ #as: --no-mul-bug-abort
#name: @OC@
# Test the @OC@ insn.
brgds, H-P