[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Qemu-devel] [PATCH 2/2] target-alpha: Special case cmpbge with zero
From: |
Richard Henderson |
Subject: |
[Qemu-devel] [PATCH 2/2] target-alpha: Special case cmpbge with zero |
Date: |
Mon, 17 Aug 2015 15:03:35 -0700 |
Knowing the comparator is zero leads to a simpler operation.
Signed-off-by: Richard Henderson <address@hidden>
---
target-alpha/helper.h | 1 +
target-alpha/int_helper.c | 13 +++++++++++++
target-alpha/translate.c | 7 ++++++-
3 files changed, 20 insertions(+), 1 deletion(-)
diff --git a/target-alpha/helper.h b/target-alpha/helper.h
index d221f0d..83cbe2a 100644
--- a/target-alpha/helper.h
+++ b/target-alpha/helper.h
@@ -10,6 +10,7 @@ DEF_HELPER_FLAGS_1(cttz, TCG_CALL_NO_RWG_SE, i64, i64)
DEF_HELPER_FLAGS_2(zap, TCG_CALL_NO_RWG_SE, i64, i64, i64)
DEF_HELPER_FLAGS_2(zapnot, TCG_CALL_NO_RWG_SE, i64, i64, i64)
+DEF_HELPER_FLAGS_1(cmpbe0, TCG_CALL_NO_RWG_SE, i64, i64)
DEF_HELPER_FLAGS_2(cmpbge, TCG_CALL_NO_RWG_SE, i64, i64, i64)
DEF_HELPER_FLAGS_2(minub8, TCG_CALL_NO_RWG_SE, i64, i64, i64)
diff --git a/target-alpha/int_helper.c b/target-alpha/int_helper.c
index 4a6e955..900a7c6 100644
--- a/target-alpha/int_helper.c
+++ b/target-alpha/int_helper.c
@@ -58,6 +58,19 @@ uint64_t helper_zap(uint64_t val, uint64_t mask)
return helper_zapnot(val, ~mask);
}
+uint64_t helper_cmpbe0(uint64_t a)
+{
+ uint64_t c = (a - 0x0101010101010101ULL) & ~a & 0x8080808080808080ULL;
+ /* a.......b.......c.......d.......e.......f.......g.......h....... */
+ c |= c << 7;
+ /* ab......bc......cd......de......ef......fg......gh......h....... */
+ c |= c << 14;
+ /* abcd....bcde....cdef....defg....efgh....fgh.....gh......h....... */
+ c |= c << 28;
+ /* abcdefghbcdefgh.cdefgh..defgh...efgh....fgh.....gh......h....... */
+ return c >> 56;
+}
+
uint64_t helper_cmpbge(uint64_t a, uint64_t b)
{
uint64_t mask = 0x00ff00ff00ff00ffULL;
diff --git a/target-alpha/translate.c b/target-alpha/translate.c
index 81d4ff8..b766ae3 100644
--- a/target-alpha/translate.c
+++ b/target-alpha/translate.c
@@ -1507,7 +1507,12 @@ static ExitStatus translate_one(DisasContext *ctx,
uint32_t insn)
break;
case 0x0F:
/* CMPBGE */
- gen_helper_cmpbge(vc, va, vb);
+ if (ra == 31) {
+ /* Special case 0 >= X as X == 0. */
+ gen_helper_cmpbe0(vc, vb);
+ } else {
+ gen_helper_cmpbge(vc, va, vb);
+ }
break;
case 0x12:
/* S8ADDL */
--
2.4.3