gwj / at91sam9263 · Commits

Commit fe76d97653d6611df19dacc4e326fc7d3d057237

Authored by pbrook
1 parent 5c7908ed

Implement flush-to-zero mode (denormal results are replaced with zero). 

Signed-off-by: Paul Brook <paul@codesourcery.com>


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6107 c046a42c-6fe2-441c-8c8c-71466251a162
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Showing 3 changed files with 25 additions and 4 deletions
fpu/softfloat.c
  View file @fe76d97
... ... @@ -30,6 +30,8 @@ these four paragraphs for those parts of this code that are retained.
30 30  
31 31 =============================================================================*/
32 32  
  33 +/* FIXME: Flush-To-Zero only effects results. Denormal inputs should also
  34 + be flushed to zero. */
33 35 #include "softfloat.h"
34 36  
35 37 /*----------------------------------------------------------------------------
... ... @@ -294,6 +296,7 @@ static float32 roundAndPackFloat32( flag zSign, int16 zExp, bits32 zSig STATUS_P
294 296 return packFloat32( zSign, 0xFF, - ( roundIncrement == 0 ));
295 297 }
296 298 if ( zExp < 0 ) {
  299 + if ( STATUS(flush_to_zero) ) return packFloat32( zSign, 0, 0 );
297 300 isTiny =
298 301 ( STATUS(float_detect_tininess) == float_tininess_before_rounding )
299 302 || ( zExp < -1 )
... ... @@ -457,6 +460,7 @@ static float64 roundAndPackFloat64( flag zSign, int16 zExp, bits64 zSig STATUS_P
457 460 return packFloat64( zSign, 0x7FF, - ( roundIncrement == 0 ));
458 461 }
459 462 if ( zExp < 0 ) {
  463 + if ( STATUS(flush_to_zero) ) return packFloat64( zSign, 0, 0 );
460 464 isTiny =
461 465 ( STATUS(float_detect_tininess) == float_tininess_before_rounding )
462 466 || ( zExp < -1 )
... ... @@ -635,6 +639,7 @@ static floatx80
635 639 goto overflow;
636 640 }
637 641 if ( zExp <= 0 ) {
  642 + if ( STATUS(flush_to_zero) ) return packFloatx80( zSign, 0, 0 );
638 643 isTiny =
639 644 ( STATUS(float_detect_tininess) == float_tininess_before_rounding )
640 645 || ( zExp < 0 )
... ... @@ -965,6 +970,7 @@ static float128
965 970 return packFloat128( zSign, 0x7FFF, 0, 0 );
966 971 }
967 972 if ( zExp < 0 ) {
  973 + if ( STATUS(flush_to_zero) ) return packFloat128( zSign, 0, 0, 0 );
968 974 isTiny =
969 975 ( STATUS(float_detect_tininess) == float_tininess_before_rounding )
970 976 || ( zExp < -1 )
... ... @@ -1637,7 +1643,10 @@ static float32 addFloat32Sigs( float32 a, float32 b, flag zSign STATUS_PARAM)
1637 1643 if ( aSig | bSig ) return propagateFloat32NaN( a, b STATUS_VAR );
1638 1644 return a;
1639 1645 }
1640   - if ( aExp == 0 ) return packFloat32( zSign, 0, ( aSig + bSig )>>6 );
  1646 + if ( aExp == 0 ) {
  1647 + if ( STATUS(flush_to_zero) ) return packFloat32( zSign, 0, 0 );
  1648 + return packFloat32( zSign, 0, ( aSig + bSig )>>6 );
  1649 + }
1641 1650 zSig = 0x40000000 + aSig + bSig;
1642 1651 zExp = aExp;
1643 1652 goto roundAndPack;
... ... @@ -2595,7 +2604,10 @@ static float64 addFloat64Sigs( float64 a, float64 b, flag zSign STATUS_PARAM )
2595 2604 if ( aSig | bSig ) return propagateFloat64NaN( a, b STATUS_VAR );
2596 2605 return a;
2597 2606 }
2598   - if ( aExp == 0 ) return packFloat64( zSign, 0, ( aSig + bSig )>>9 );
  2607 + if ( aExp == 0 ) {
  2608 + if ( STATUS(flush_to_zero) ) return packFloat64( zSign, 0, 0 );
  2609 + return packFloat64( zSign, 0, ( aSig + bSig )>>9 );
  2610 + }
2599 2611 zSig = LIT64( 0x4000000000000000 ) + aSig + bSig;
2600 2612 zExp = aExp;
2601 2613 goto roundAndPack;
... ... @@ -4597,7 +4609,10 @@ static float128 addFloat128Sigs( float128 a, float128 b, flag zSign STATUS_PARAM
4597 4609 return a;
4598 4610 }
4599 4611 add128( aSig0, aSig1, bSig0, bSig1, &zSig0, &zSig1 );
4600   - if ( aExp == 0 ) return packFloat128( zSign, 0, zSig0, zSig1 );
  4612 + if ( aExp == 0 ) {
  4613 + if ( STATUS(flush_to_zero) ) return packFloat128( zSign, 0, 0, 0 );
  4614 + return packFloat128( zSign, 0, zSig0, zSig1 );
  4615 + }
4601 4616 zSig2 = 0;
4602 4617 zSig0 |= LIT64( 0x0002000000000000 );
4603 4618 zExp = aExp;
... ...
fpu/softfloat.h
  View file @fe76d97
... ... @@ -190,11 +190,16 @@ typedef struct float_status {
190 190 #ifdef FLOATX80
191 191 signed char floatx80_rounding_precision;
192 192 #endif
  193 + flag flush_to_zero;
193 194 flag default_nan_mode;
194 195 } float_status;
195 196  
196 197 void set_float_rounding_mode(int val STATUS_PARAM);
197 198 void set_float_exception_flags(int val STATUS_PARAM);
  199 +INLINE void set_flush_to_zero(flag val STATUS_PARAM)
  200 +{
  201 + STATUS(flush_to_zero) = val;
  202 +}
198 203 INLINE void set_default_nan_mode(flag val STATUS_PARAM)
199 204 {
200 205 STATUS(default_nan_mode) = val;
... ...
target-arm/helper.c
  View file @fe76d97
... ... @@ -2334,12 +2334,13 @@ void HELPER(vfp_set_fpscr)(CPUState *env, uint32_t val)
2334 2334 }
2335 2335 set_float_rounding_mode(i, &env->vfp.fp_status);
2336 2336 }
  2337 + if (changed & (1 << 24))
  2338 + set_flush_to_zero((val & (1 << 24)) != 0, &env->vfp.fp_status);
2337 2339 if (changed & (1 << 25))
2338 2340 set_default_nan_mode((val & (1 << 25)) != 0, &env->vfp.fp_status);
2339 2341  
2340 2342 i = vfp_exceptbits_to_host((val >> 8) & 0x1f);
2341 2343 set_float_exception_flags(i, &env->vfp.fp_status);
2342   - /* XXX: FZ and DN are not implemented. */
2343 2344 }
2344 2345  
2345 2346 #define VFP_HELPER(name, p) HELPER(glue(glue(vfp_,name),p))
... ...