On 30/10/18 17:25, Peter Maydell wrote:
In handle_vec_simd_shli() we have a check:
if (size > 3 && !is_q) {
unallocated_encoding(s);
return;
}
However this can never be true, because we calculate
int size = 32 - clz32(immh) - 1;
where immh is a 4 bit field which we know cannot be all-zeroes.
So the clz32() return must be in {28,29,30,31} and the resulting
size is in {0,1,2,3}, and "size > 3" is never true.
This unnecessary code confuses Coverity's analysis:
in CID 1396476 it thinks we might later index off the
end of an array because the condition implies that we
might have a size > 3.
Remove the code, and instead assert that the size is in [0..3],
since the decode that enforces that is somewhat distant from
this function.
Signed-off-by: Peter Maydell <peter.mayd...@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <phi...@redhat.com>
---
Alex, if you could run this through the risu testset just as
a sanity check that would be very helpful.
target/arm/translate-a64.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)
diff --git a/target/arm/translate-a64.c b/target/arm/translate-a64.c
index 88195ab9490..fd36425f1ae 100644
--- a/target/arm/translate-a64.c
+++ b/target/arm/translate-a64.c
@@ -9483,12 +9483,10 @@ static void handle_vec_simd_shli(DisasContext *s, bool
is_q, bool insert,
int immhb = immh << 3 | immb;
int shift = immhb - (8 << size);
- if (extract32(immh, 3, 1) && !is_q) {
- unallocated_encoding(s);
- return;
- }
+ /* Range of size is limited by decode: immh is a non-zero 4 bit field */
+ assert(size >= 0 && size <= 3);
- if (size > 3 && !is_q) {
+ if (extract32(immh, 3, 1) && !is_q) {
unallocated_encoding(s);
return;
}
