target-sh4: improve TLB
SH4 is using 16-bit instructions which means most of the constants are
loaded through a constant pool at the end of the subroutine. The same
memory page is therefore accessed in exec and read mode.
With the current implementation, a QEMU TLB entry is set to read or
read/write mode after an UTLB search and to exec mode after an ITLB
search, which causes a lot of TLB exceptions to switch from read or
read/write to exec and vice versa.
This patch optimizes that by already setting the QEMU TLB entry in read
or read/write mode when an UTLB entry is copied into ITLB (during an
ITLB miss). This improve the emulation speed by about 14%.
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
diff --git a/target-sh4/helper.c b/target-sh4/helper.c
index 863886b..2343366 100644
--- a/target-sh4/helper.c
+++ b/target-sh4/helper.c
@@ -280,35 +280,40 @@
env->mmucr = (env->mmucr & 0xffff03ff) | (urc << 10);
}
-/* Find itlb entry - update itlb from utlb if necessary and asked for
+/* Copy and utlb entry into itlb
+ Return entry
+*/
+static int copy_utlb_entry_itlb(CPUState *env, int utlb)
+{
+ int itlb;
+
+ tlb_t * ientry;
+ itlb = itlb_replacement(env);
+ ientry = &env->itlb[itlb];
+ if (ientry->v) {
+ tlb_flush_page(env, ientry->vpn << 10);
+ }
+ *ientry = env->utlb[utlb];
+ update_itlb_use(env, itlb);
+ return itlb;
+}
+
+/* Find itlb entry
Return entry, MMU_ITLB_MISS, MMU_ITLB_MULTIPLE or MMU_DTLB_MULTIPLE
- Update the itlb from utlb if update is not 0
*/
static int find_itlb_entry(CPUState * env, target_ulong address,
- int use_asid, int update)
+ int use_asid)
{
- int e, n;
+ int e;
e = find_tlb_entry(env, address, env->itlb, ITLB_SIZE, use_asid);
- if (e == MMU_DTLB_MULTIPLE)
+ if (e == MMU_DTLB_MULTIPLE) {
e = MMU_ITLB_MULTIPLE;
- else if (e == MMU_DTLB_MISS && update) {
- e = find_tlb_entry(env, address, env->utlb, UTLB_SIZE, use_asid);
- if (e >= 0) {
- tlb_t * ientry;
- n = itlb_replacement(env);
- ientry = &env->itlb[n];
- if (ientry->v) {
- tlb_flush_page(env, ientry->vpn << 10);
- }
- *ientry = env->utlb[e];
- e = n;
- } else if (e == MMU_DTLB_MISS)
- e = MMU_ITLB_MISS;
- } else if (e == MMU_DTLB_MISS)
+ } else if (e == MMU_DTLB_MISS) {
e = MMU_ITLB_MISS;
- if (e >= 0)
+ } else if (e >= 0) {
update_itlb_use(env, e);
+ }
return e;
}
@@ -340,13 +345,31 @@
use_asid = (env->mmucr & MMUCR_SV) == 0 || (env->sr & SR_MD) == 0;
if (rw == 2) {
- n = find_itlb_entry(env, address, use_asid, 1);
+ n = find_itlb_entry(env, address, use_asid);
if (n >= 0) {
matching = &env->itlb[n];
if (!(env->sr & SR_MD) && !(matching->pr & 2))
n = MMU_ITLB_VIOLATION;
else
*prot = PAGE_EXEC;
+ } else {
+ n = find_utlb_entry(env, address, use_asid);
+ if (n >= 0) {
+ n = copy_utlb_entry_itlb(env, n);
+ matching = &env->itlb[n];
+ if (!(env->sr & SR_MD) && !(matching->pr & 2)) {
+ n = MMU_ITLB_VIOLATION;
+ } else {
+ *prot = PAGE_READ | PAGE_EXEC;
+ if ((matching->pr & 1) && matching->d) {
+ *prot |= PAGE_WRITE;
+ }
+ }
+ } else if (n == MMU_DTLB_MULTIPLE) {
+ n = MMU_ITLB_MULTIPLE;
+ } else if (n == MMU_DTLB_MISS) {
+ n = MMU_ITLB_MISS;
+ }
}
} else {
n = find_utlb_entry(env, address, use_asid);
