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authorPeter Maydell <peter.maydell@linaro.org>2013-12-20 11:15:52 +0000
committerPeter Maydell <peter.maydell@linaro.org>2013-12-31 01:08:57 +0000
commit145bcb64e4bcc4189a4f705a47a13e49c2d985ac (patch)
treefd6f2383e61804b8010741627b6f93cc9f4e19e2
parent65d89aab85b29184bbe46929c02b33c66285fd03 (diff)
downloadqemu-arm-145bcb64e4bcc4189a4f705a47a13e49c2d985ac.tar.gz
target-arm: Ignore most exceptions from scalbn when doing fixpoint conversion
The VFP fixed point conversion helpers first call float_scalbn and then convert the result to an integer. This scalbn operation may set floating point exception flags for: * overflow & inexact (if it overflows to infinity) * input denormal squashed to zero * output denormal squashed to zero Of these, we only care about the input-denormal flag, since the output of the whole scale-and-convert operation will be an integer (so squashed-output-denormal and overflow don't apply). Suppress the others by saving the pre-scalb exception flags and only copying across a potential input-denormal flag. Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
-rw-r--r--target-arm/helper.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/target-arm/helper.c b/target-arm/helper.c
index a9b092746c..67dc212603 100644
--- a/target-arm/helper.c
+++ b/target-arm/helper.c
@@ -3994,18 +3994,27 @@ float##fsz HELPER(vfp_##name##to##p)(uint##isz##_t x, uint32_t shift, \
return float##fsz##_scalbn(tmp, -(int)shift, fpst); \
}
+/* Notice that we want only input-denormal exception flags from the
+ * scalbn operation: the other possible flags (overflow+inexact if
+ * we overflow to infinity, output-denormal) aren't correct for the
+ * complete scale-and-convert operation.
+ */
#define VFP_CONV_FLOAT_FIX_ROUND(name, p, fsz, isz, itype, round) \
uint##isz##_t HELPER(vfp_to##name##p##round)(float##fsz x, \
uint32_t shift, \
void *fpstp) \
{ \
float_status *fpst = fpstp; \
+ int old_exc_flags = get_float_exception_flags(fpst); \
float##fsz tmp; \
if (float##fsz##_is_any_nan(x)) { \
float_raise(float_flag_invalid, fpst); \
return 0; \
} \
tmp = float##fsz##_scalbn(x, shift, fpst); \
+ old_exc_flags |= get_float_exception_flags(fpst) \
+ & float_flag_input_denormal; \
+ set_float_exception_flags(old_exc_flags, fpst); \
return float##fsz##_to_##itype##round(tmp, fpst); \
}