diff options
| author | Peter Maydell <peter.maydell@linaro.org> | 2014-02-20 10:35:50 +0000 |
|---|---|---|
| committer | Peter Maydell <peter.maydell@linaro.org> | 2014-02-20 10:35:50 +0000 |
| commit | 67d43538aee10b6cfe8f3606c69187a3e142a2ba (patch) | |
| tree | 4eb0637464a3011cc1ecc91b4e4ae9e6867d8445 /include/fpu | |
| parent | bc242f9bb6324a50e7572c0997904b66b630f73a (diff) | |
softfloat: Support halving the result of muladd operation
The ARMv8 instruction set includes a fused floating point
reciprocal square root step instruction which demands an
"(x * y + z) / 2" fused operation. Support this by adding
a flag to the softfloat muladd operations which requests
that the result is halved before rounding.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Diffstat (limited to 'include/fpu')
| -rw-r--r-- | include/fpu/softfloat.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/include/fpu/softfloat.h b/include/fpu/softfloat.h index 806ae13780..4b4df88527 100644 --- a/include/fpu/softfloat.h +++ b/include/fpu/softfloat.h @@ -249,11 +249,14 @@ void float_raise( int8 flags STATUS_PARAM); | Using these differs from negating an input or output before calling | the muladd function in that this means that a NaN doesn't have its | sign bit inverted before it is propagated. +| We also support halving the result before rounding, as a special +| case to support the ARM fused-sqrt-step instruction FRSQRTS. *----------------------------------------------------------------------------*/ enum { float_muladd_negate_c = 1, float_muladd_negate_product = 2, float_muladd_negate_result = 4, + float_muladd_halve_result = 8, }; /*---------------------------------------------------------------------------- |