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target-ppc: Introduce DFP Reround

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Add emulation of the PowerPC Decimal Floating Point Reround instructions
drrnd[q][.].

Signed-off-by: Tom Musta <tommusta@gmail.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
This commit is contained in:
Tom Musta 2014-04-21 15:55:11 -05:00 committed by Alexander Graf
parent 5826ebe27a
commit 512918aa79
3 changed files with 103 additions and 0 deletions
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97
target-ppc/dfp_helper.c
View file

@ -376,6 +376,23 @@ static inline void dfp_makeQNaN(decNumber *dn)
dn->bits |= DECNAN;
}
static inline int dfp_get_digit(decNumber *dn, int n)
{
assert(DECDPUN == 3);
int unit = n / DECDPUN;
int dig = n % DECDPUN;
switch (dig) {
case 0:
return dn->lsu[unit] % 10;
case 1:
return (dn->lsu[unit] / 10) % 10;
case 2:
return dn->lsu[unit] / 100;
default:
assert(0);
}
}
#define DFP_HELPER_TAB(op, dnop, postprocs, size) \
void helper_##op(CPUPPCState *env, uint64_t *t, uint64_t *a, uint64_t *b) \
{ \
@ -703,3 +720,83 @@ void helper_##op(CPUPPCState *env, uint64_t *t, uint64_t *a, \
DFP_HELPER_QUA(dqua, 64)
DFP_HELPER_QUA(dquaq, 128)
static void _dfp_reround(uint8_t rmc, int32_t ref_sig, int32_t xmax,
struct PPC_DFP *dfp)
{
int msd_orig, msd_rslt;
if (unlikely((ref_sig == 0) || (dfp->b.digits <= ref_sig))) {
dfp->t = dfp->b;
if (decNumberIsSNaN(&dfp->b)) {
dfp_makeQNaN(&dfp->t);
dfp_set_FPSCR_flag(dfp, FP_VX | FP_VXSNAN, FPSCR_VE);
}
return;
}
/* Reround is equivalent to quantizing b with 1**E(n) where */
/* n = exp(b) + numDigits(b) - reference_significance. */
decNumberFromUInt32(&dfp->a, 1);
dfp->a.exponent = dfp->b.exponent + dfp->b.digits - ref_sig;
if (unlikely(dfp->a.exponent > xmax)) {
dfp->t.digits = 0;
dfp->t.bits &= ~DECNEG;
dfp_makeQNaN(&dfp->t);
dfp_set_FPSCR_flag(dfp, FP_VX | FP_VXCVI, FPSCR_VE);
return;
}
dfp_quantize(rmc, dfp);
msd_orig = dfp_get_digit(&dfp->b, dfp->b.digits-1);
msd_rslt = dfp_get_digit(&dfp->t, dfp->t.digits-1);
/* If the quantization resulted in rounding up to the next magnitude, */
/* then we need to shift the significand and adjust the exponent. */
if (unlikely((msd_orig == 9) && (msd_rslt == 1))) {
decNumber negone;
decNumberFromInt32(&negone, -1);
decNumberShift(&dfp->t, &dfp->t, &negone, &dfp->context);
dfp->t.exponent++;
if (unlikely(dfp->t.exponent > xmax)) {
dfp_makeQNaN(&dfp->t);
dfp->t.digits = 0;
dfp_set_FPSCR_flag(dfp, FP_VX | FP_VXCVI, FP_VE);
/* Inhibit XX in this case */
decContextClearStatus(&dfp->context, DEC_Inexact);
}
}
}
#define DFP_HELPER_RRND(op, size) \
void helper_##op(CPUPPCState *env, uint64_t *t, uint64_t *a, \
uint64_t *b, uint32_t rmc) \
{ \
struct PPC_DFP dfp; \
int32_t ref_sig = *a & 0x3F; \
int32_t xmax = ((size) == 64) ? 369 : 6111; \
\
dfp_prepare_decimal##size(&dfp, 0, b, env); \
\
_dfp_reround(rmc, ref_sig, xmax, &dfp); \
decimal##size##FromNumber((decimal##size *)dfp.t64, &dfp.t, \
&dfp.context); \
QUA_PPs(&dfp); \
\
if (size == 64) { \
t[0] = dfp.t64[0]; \
} else if (size == 128) { \
t[0] = dfp.t64[HI_IDX]; \
t[1] = dfp.t64[LO_IDX]; \
} \
}
DFP_HELPER_RRND(drrnd, 64)
DFP_HELPER_RRND(drrndq, 128)

2
target-ppc/helper.h
View file

@ -640,3 +640,5 @@ DEF_HELPER_5(dquai, void, env, fprp, fprp, i32, i32)
DEF_HELPER_5(dquaiq, void, env, fprp, fprp, i32, i32)
DEF_HELPER_5(dqua, void, env, fprp, fprp, fprp, i32)
DEF_HELPER_5(dquaq, void, env, fprp, fprp, fprp, i32)
DEF_HELPER_5(drrnd, void, env, fprp, fprp, fprp, i32)
DEF_HELPER_5(drrndq, void, env, fprp, fprp, fprp, i32)

4
target-ppc/translate.c
View file

@ -8380,6 +8380,8 @@ GEN_DFP_T_B_U32_U32_Rc(dquai, SIMM5, RMC)
GEN_DFP_T_B_U32_U32_Rc(dquaiq, SIMM5, RMC)
GEN_DFP_T_A_B_I32_Rc(dqua, RMC)
GEN_DFP_T_A_B_I32_Rc(dquaq, RMC)
GEN_DFP_T_A_B_I32_Rc(drrnd, RMC)
GEN_DFP_T_A_B_I32_Rc(drrndq, RMC)
/*** SPE extension ***/
/* Register moves */
@ -11331,6 +11333,8 @@ GEN_DFP_TE_T_B_RMC_Rc(dquai, 0x03, 0x02),
GEN_DFP_TE_Tp_Bp_RMC_Rc(dquaiq, 0x03, 0x02),
GEN_DFP_T_A_B_RMC_Rc(dqua, 0x03, 0x00),
GEN_DFP_Tp_Ap_Bp_RMC_Rc(dquaq, 0x03, 0x00),
GEN_DFP_T_A_B_RMC_Rc(drrnd, 0x03, 0x01),
GEN_DFP_Tp_A_Bp_RMC_Rc(drrndq, 0x03, 0x01),
#undef GEN_SPE
#define GEN_SPE(name0, name1, opc2, opc3, inval0, inval1, type) \
GEN_OPCODE_DUAL(name0##_##name1, 0x04, opc2, opc3, inval0, inval1, type, PPC_NONE)