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[Qemu-devel] [PATCH 17/22] target-arm: Ignore most exceptions from scalb
From: |
Peter Maydell |
Subject: |
[Qemu-devel] [PATCH 17/22] target-arm: Ignore most exceptions from scalbn when doing fixpoint conversion |
Date: |
Tue, 31 Dec 2013 13:35:53 +0000 |
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 <address@hidden>
---
target-arm/helper.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/target-arm/helper.c b/target-arm/helper.c
index a9b0927..67dc212 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); \
}
--
1.8.5
- [Qemu-devel] [PATCH 16/22] target-arm: Rename A32 VFP conversion helpers, (continued)
- [Qemu-devel] [PATCH 16/22] target-arm: Rename A32 VFP conversion helpers, Peter Maydell, 2013/12/31
- [Qemu-devel] [PATCH 10/22] softfloat: Fix float64_to_uint32_round_to_zero, Peter Maydell, 2013/12/31
- [Qemu-devel] [PATCH 18/22] target-arm: A64: Add extra VFP fixed point conversion helpers, Peter Maydell, 2013/12/31
- [Qemu-devel] [PATCH 06/22] softfloat: Fix factor 2 error for scalbn on denormal inputs, Peter Maydell, 2013/12/31
- [Qemu-devel] [PATCH 05/22] softfloat: Only raise Invalid when conversions to int are out of range, Peter Maydell, 2013/12/31
- [Qemu-devel] [PATCH 09/22] softfloat: Fix float64_to_uint32, Peter Maydell, 2013/12/31
- [Qemu-devel] [PATCH 17/22] target-arm: Ignore most exceptions from scalbn when doing fixpoint conversion,
Peter Maydell <=
- [Qemu-devel] [PATCH 21/22] target-arm: A64: Add 1-source 32-to-32 and 64-to-64 FP instructions, Peter Maydell, 2013/12/31
- [Qemu-devel] [PATCH 04/22] softfloat: Fix float64_to_uint64, Peter Maydell, 2013/12/31
- [Qemu-devel] [PATCH 13/22] softfloat: Add float16 <=> float64 conversion functions, Peter Maydell, 2013/12/31
- [Qemu-devel] [PATCH 14/22] softfloat: Add support for ties-away rounding, Peter Maydell, 2013/12/31
- [Qemu-devel] [PATCH 12/22] softfloat: Factor out RoundAndPackFloat16 and NormalizeFloat16Subnormal, Peter Maydell, 2013/12/31