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Re: [Qemu-devel] [PATCH 4/6] target-arm: fix saturated values for Neon r
From: |
Peter Maydell |
Subject: |
Re: [Qemu-devel] [PATCH 4/6] target-arm: fix saturated values for Neon right shifts. |
Date: |
Mon, 14 Feb 2011 17:49:07 +0000 |
On 14 February 2011 17:46, Peter Maydell <address@hidden> wrote:
> On 11 February 2011 15:11, <address@hidden> wrote:
>> NEON_VOP_ENV(qrshl_s8, neon_s8, 4)
>> @@ -924,7 +924,11 @@ uint32_t HELPER(neon_qrshl_s32)(CPUState *env, uint32_t
>> valop, uint32_t shiftop)
>> dest = val << shift;
>> if ((dest >> shift) != val) {
>> SET_QC();
>> - dest = (uint32_t)(1 << (sizeof(val) * 8 - 1)) - (val > 0 ? 1 :
>> 0);
>> + if (val < 0) {
>> + dest = INT32_MIN;
>> + } else {
>> + dest = INT32_MAX;
>> + }
>
> Again, right answers but the way most of the rest of the code
> forces a 32 bit value to signed saturation is
> dest = (val >> 31) ^ ~SIGNBIT;
...and also this is patching a function newly introduced in
patch 1/6 -- better to just have 1/6 have the correct code.
-- PMM
- [Qemu-devel] [PATCH v3 0/6] target-arm: Fix Neon shift instructions., christophe.lyon, 2011/02/11
- [Qemu-devel] [PATCH 6/6] target-arm: fix decoding of Neon 64 bit shifts., christophe.lyon, 2011/02/11
- [Qemu-devel] [PATCH 4/6] target-arm: fix saturated values for Neon right shifts., christophe.lyon, 2011/02/11
- [Qemu-devel] [PATCH 1/6] target-arm: Fix rounding constant addition for Neon shift instructions., christophe.lyon, 2011/02/11
- [Qemu-devel] [PATCH 2/6] target-arm: fix Neon right shifts with shift amount == input width., christophe.lyon, 2011/02/11
- [Qemu-devel] [PATCH 5/6] target-arm: fix Neon VQSHRN and VSHRN., christophe.lyon, 2011/02/11
- [Qemu-devel] [PATCH 3/6] target-arm: fix unsigned 64 bit right shifts., christophe.lyon, 2011/02/11