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authorChris Demetriou <cgd@google.com>2004-01-20 07:06:14 +0000
committerChris Demetriou <cgd@google.com>2004-01-20 07:06:14 +0000
commitb3208fb8f774204d28a0a6830b398c61ffb805a7 (patch)
tree13acd1af307b86d15242118bbd42778d1865bdf1
parent4fcef00ad0f7de5a38ce1431e9db564aa3508871 (diff)
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2004-01-19 Chris Demetriou <cgd@broadcom.com>
* mips.igen (check_mf_cycles, check_mt_hilo, check_mf_hilo) (check_mult_hilo): Improve comments. (check_div_hilo): Likewise. Also, fork off a new version to handle mips32/mips64 (since there are no hazards to check in MIPS32/MIPS64).
-rw-r--r--sim/mips/ChangeLog8
-rw-r--r--sim/mips/mips.igen72
2 files changed, 69 insertions, 11 deletions
diff --git a/sim/mips/ChangeLog b/sim/mips/ChangeLog
index e5b5216..fab4c6e 100644
--- a/sim/mips/ChangeLog
+++ b/sim/mips/ChangeLog
@@ -1,3 +1,11 @@
+2004-01-19 Chris Demetriou <cgd@broadcom.com>
+
+ * mips.igen (check_mf_cycles, check_mt_hilo, check_mf_hilo)
+ (check_mult_hilo): Improve comments.
+ (check_div_hilo): Likewise. Also, fork off a new version
+ to handle mips32/mips64 (since there are no hazards to check
+ in MIPS32/MIPS64).
+
2003-06-17 Richard Sandiford <rsandifo@redhat.com>
* mips.igen (do_dmultx): Fix check for negative operands.
diff --git a/sim/mips/mips.igen b/sim/mips/mips.igen
index 358c8ab..cfc2d6d 100644
--- a/sim/mips/mips.igen
+++ b/sim/mips/mips.igen
@@ -218,18 +218,39 @@
}
-// Helper:
+// Helpers:
//
// Check that an access to a HI/LO register meets timing requirements
//
-// The following requirements exist:
+// In all MIPS ISAs,
//
-// - A MT {HI,LO} update was not immediatly preceeded by a MF {HI,LO} read
-// - A OP {HI,LO} update was not immediatly preceeded by a MF {HI,LO} read
-// - A MF {HI,LO} read was not corrupted by a preceeding MT{LO,HI} update
-// corruption occures when MT{LO,HI} is preceeded by a OP {HI,LO}.
+// OP {HI and LO} followed by MT{LO or HI} (and not MT{HI or LO})
+// makes subsequent MF{HI or LO} UNPREDICTABLE. (1)
+//
+// The following restrictions exist for MIPS I - MIPS III:
+//
+// MF{HI or LO} followed by MT{HI or LO} w/ less than 2 instructions
+// in between makes MF UNPREDICTABLE. (2)
+//
+// MF{HI or LO} followed by OP {HI and LO} w/ less than 2 instructions
+// in between makes MF UNPREDICTABLE. (3)
+//
+// On the r3900, restriction (2) is not present, and restriction (3) is not
+// present for multiplication.
+//
+// For now this code is paranoid. Historically the simulator
+// enforced restrictions (2) and (3) for more ISAs and CPU types than
+// necessary. Unfortunately, at least some MIPS IV and later parts'
+// documentation describes them as having these hazards (e.g. vr5000),
+// so they can't be removed for at leats MIPS IV. MIPS V hasn't been
+// checked (since there are no known hardware implementations).
+//
+
+// check_mf_cycles:
+//
+// Helper used by check_mt_hilo, check_mult_hilo, and check_div_hilo
+// to check for restrictions (2) and (3) above.
//
-
:function:::int:check_mf_cycles:hilo_history *history, signed64 time, const char *new
{
if (history->mf.timestamp + 3 > time)
@@ -243,6 +264,12 @@
return 1;
}
+
+// check_mt_hilo:
+//
+// Check for restriction (2) above (for ISAs/processors that have it),
+// and record timestamps for restriction (1) above.
+//
:function:::int:check_mt_hilo:hilo_history *history
*mipsI:
*mipsII:
@@ -271,6 +298,11 @@
}
+// check_mf_hilo:
+//
+// Check for restriction (1) above, and record timestamps for
+// restriction (2) and (3) above.
+//
:function:::int:check_mf_hilo:hilo_history *history, hilo_history *peer
*mipsI:
*mipsII:
@@ -309,6 +341,11 @@
+// check_mult_hilo:
+//
+// Check for restriction (3) above (for ISAs/processors that have it)
+// for MULT ops, and record timestamps for restriction (1) above.
+//
:function:::int:check_mult_hilo:hilo_history *hi, hilo_history *lo
*mipsI:
*mipsII:
@@ -328,8 +365,6 @@
return ok;
}
-// The r3900 mult and multu insns _can_ be exectuted immediatly after
-// a mf{hi,lo}
:function:::int:check_mult_hilo:hilo_history *hi, hilo_history *lo
*mips32:
*mips64:
@@ -345,14 +380,17 @@
}
+// check_div_hilo:
+//
+// Check for restriction (3) above (for ISAs/processors that have it)
+// for DIV ops, and record timestamps for restriction (1) above.
+//
:function:::int:check_div_hilo:hilo_history *hi, hilo_history *lo
*mipsI:
*mipsII:
*mipsIII:
*mipsIV:
*mipsV:
-*mips32:
-*mips64:
*vr4100:
*vr5000:
*r3900:
@@ -367,6 +405,18 @@
return ok;
}
+:function:::int:check_div_hilo:hilo_history *hi, hilo_history *lo
+*mips32:
+*mips64:
+{
+ signed64 time = sim_events_time (SD);
+ hi->op.timestamp = time;
+ lo->op.timestamp = time;
+ hi->op.cia = CIA;
+ lo->op.cia = CIA;
+ return 1;
+}
+
// Helper:
//