Re: [Qemu-devel] [PATCH 20/40] Add vs{l,r} instructions.

[Nathan Froyd]

On Mon, Jan 05, 2009 at 08:27:30PM +0100, Aurelien Jarno wrote:
> On Mon, Jan 05, 2009 at 10:29:56AM -0800, Nathan Froyd wrote:
> > FWIW, doing the check has the nice property of delivering the same
> > results as real hardware.  If you're using a comparison program like
> > ppctester, reducing those spurious failures is a win.  (There's already
> > spurious failures for div instructions in corner cases.)
> 
> Then I am fine with that. Could you please just add a comment that it is
> not necessary according to the spec, but done to match real hardware?

Done thusly.

-Nathan

>From aa19aa5e31aa9eec36a2cdfb2e1ed806555eda96 Mon Sep 17 00:00:00 2001
From: Nathan Froyd <address@hidden>
Date: Thu, 11 Dec 2008 12:02:03 -0800
Subject: [PATCH 4/5] Add vs{l,r} instructions.

Add explanatory comment about why we check equality of shift counts.

Signed-off-by: Nathan Froyd <address@hidden>
---
 target-ppc/helper.h    |    2 ++
 target-ppc/op_helper.c |   39 +++++++++++++++++++++++++++++++++++++++
 target-ppc/translate.c |    2 ++
 3 files changed, 43 insertions(+), 0 deletions(-)

diff --git a/target-ppc/helper.h b/target-ppc/helper.h
index 009f516..e15d6b0 100644
--- a/target-ppc/helper.h
+++ b/target-ppc/helper.h
@@ -185,6 +185,8 @@ DEF_HELPER_3(vsubuws, void, avr, avr, avr)
 DEF_HELPER_3(vrlb, void, avr, avr, avr)
 DEF_HELPER_3(vrlh, void, avr, avr, avr)
 DEF_HELPER_3(vrlw, void, avr, avr, avr)
+DEF_HELPER_3(vsl, void, avr, avr, avr)
+DEF_HELPER_3(vsr, void, avr, avr, avr)
 DEF_HELPER_4(vsldoi, void, avr, avr, avr, i32)
 DEF_HELPER_3(vspltb, void, avr, avr, i32)
 DEF_HELPER_3(vsplth, void, avr, avr, i32)
diff --git a/target-ppc/op_helper.c b/target-ppc/op_helper.c
index ef19bde..81abd63 100644
--- a/target-ppc/op_helper.c
+++ b/target-ppc/op_helper.c
@@ -2491,6 +2491,45 @@ void helper_vsel (ppc_avr_t *r, ppc_avr_t *a, ppc_avr_t 
*b, ppc_avr_t *c)
     r->u64[1] = (a->u64[1] & ~c->u64[1]) | (b->u64[1] & c->u64[1]);
 }
 
+#if defined(WORDS_BIGENDIAN)
+#define LEFT 0
+#define RIGHT 1
+#else
+#define LEFT 1
+#define RIGHT 0
+#endif
+/* The specification says that the results are undefined if all of the
+ * shift counts are not identical.  We check to make sure that they are
+ * to conform to what real hardware appears to do.  */
+#define VSHIFT(suffix, leftp)                                           \
+    void helper_vs##suffix (ppc_avr_t *r, ppc_avr_t *a, ppc_avr_t *b)   \
+    {                                                                   \
+        int shift = b->u8[LO_IDX*0x15] & 0x7;                           \
+        int doit = 1;                                                   \
+        int i;                                                          \
+        for (i = 0; i < ARRAY_SIZE(r->u8); i++) {                       \
+            doit = doit && ((b->u8[i] & 0x7) == shift);                 \
+        }                                                               \
+        if (doit) {                                                     \
+            if (shift == 0) {                                           \
+                *r = *a;                                                \
+            } else if (leftp) {                                         \
+                uint64_t carry = a->u64[LO_IDX] >> (64 - shift);        \
+                r->u64[HI_IDX] = (a->u64[HI_IDX] << shift) | carry;     \
+                r->u64[LO_IDX] = a->u64[LO_IDX] << shift;               \
+            } else {                                                    \
+                uint64_t carry = a->u64[HI_IDX] << (64 - shift);        \
+                r->u64[LO_IDX] = (a->u64[LO_IDX] >> shift) | carry;     \
+                r->u64[HI_IDX] = a->u64[HI_IDX] >> shift;               \
+            }                                                           \
+        }                                                               \
+    }
+VSHIFT(l, LEFT)
+VSHIFT(r, RIGHT)
+#undef VSHIFT
+#undef LEFT
+#undef RIGHT
+
 #define VSL(suffix, element)                                            \
     void helper_vsl##suffix (ppc_avr_t *r, ppc_avr_t *a, ppc_avr_t *b)  \
     {                                                                   \
diff --git a/target-ppc/translate.c b/target-ppc/translate.c
index e92156f..65a80f2 100644
--- a/target-ppc/translate.c
+++ b/target-ppc/translate.c
@@ -6356,6 +6356,8 @@ GEN_VXFORM(vsubsws, 0, 30);
 GEN_VXFORM(vrlb, 2, 0);
 GEN_VXFORM(vrlh, 2, 1);
 GEN_VXFORM(vrlw, 2, 2);
+GEN_VXFORM(vsl, 2, 7);
+GEN_VXFORM(vsr, 2, 11);
 GEN_VXFORM(vpkuhum, 7, 0);
 GEN_VXFORM(vpkuwum, 7, 1);
 GEN_VXFORM(vpkuhus, 7, 2);
-- 
1.6.0.5