On 11/02/2015 04:13 PM, Peter Maydell wrote:
On 2 November 2015 at 14:48, Paolo Bonzini <pbonz...@redhat.com> wrote:
On 02/11/2015 15:09, Peter Maydell wrote:
diff --git a/target-sparc/vis_helper.c b/target-sparc/vis_helper.c
index 383cc8b..45fc7db 100644
--- a/target-sparc/vis_helper.c
+++ b/target-sparc/vis_helper.c
@@ -447,7 +447,7 @@ uint32_t helper_fpackfix(uint64_t gsr, uint64_t rs2)
for (word = 0; word < 2; word++) {
uint32_t val;
int32_t src = rs2 >> (word * 32);
- int64_t scaled = src << scale;
+ int64_t scaled = (int64_t)src << scale;
int64_t from_fixed = scaled >> 16;
This will now shift left into the sign bit of a signed integer,
which is undefined behaviour.
Why "now"? It would have done the same before.
True, but I was reviewing the new code rather than the
code you were taking away :-)
Incidentally, that manual says the fpackfix and fpack32 insns
use a 4 bit GSR.scale_factor value, but our code is masking
by 0x1f in helper_fpack32 and helper_fpackfix. Which is right?
The 2011 manual has 5 bits for fpack32 and fpackfix; fpack16 uses only 4 bits.
I do think we'd be better served by casting to uint64_t on that line. Note
that fpackfix requires the same correction. And it wouldn't hurt to cast to
uint32_t in fpack16, lest we anger the self-same shifting gods.
r~
