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target/ppc: Use non-arithmetic conversions for fp load/store 

Memory operations have no side effects on fp state.
The use of a "real" conversions between float64 and float32
would raise exceptions for SNaN and out-of-range inputs.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
Richard Henderson 2018-07-03 08:17:32 -07:00 committed by David Gibson
parent 3843471755
commit 86c0cab11a
3 changed files with 62 additions and 31 deletions
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63
target/ppc/fpu_helper.c
View File

@ -47,24 +47,61 @@ static inline bool fp_exceptions_enabled(CPUPPCState *env)
/*****************************************************************************/
/* Floating point operations helpers */
uint64_t helper_float32_to_float64(CPUPPCState *env, uint32_t arg)
{
CPU_FloatU f;
CPU_DoubleU d;
f.l = arg;
d.d = float32_to_float64(f.f, &env->fp_status);
return d.ll;
/*
* This is the non-arithmatic conversion that happens e.g. on loads.
* In the Power ISA pseudocode, this is called DOUBLE.
*/
uint64_t helper_todouble(uint32_t arg)
{
uint32_t abs_arg = arg & 0x7fffffff;
uint64_t ret;
if (likely(abs_arg >= 0x00800000)) {
/* Normalized operand, or Inf, or NaN. */
ret = (uint64_t)extract32(arg, 30, 2) << 62;
ret |= ((extract32(arg, 30, 1) ^ 1) * (uint64_t)7) << 59;
ret |= (uint64_t)extract32(arg, 0, 30) << 29;
} else {
/* Zero or Denormalized operand. */
ret = (uint64_t)extract32(arg, 31, 1) << 63;
if (unlikely(abs_arg != 0)) {
/* Denormalized operand. */
int shift = clz32(abs_arg) - 9;
int exp = -126 - shift + 1023;
ret |= (uint64_t)exp << 52;
ret |= abs_arg << (shift + 29);
}
}
return ret;
}
uint32_t helper_float64_to_float32(CPUPPCState *env, uint64_t arg)
/*
* This is the non-arithmatic conversion that happens e.g. on stores.
* In the Power ISA pseudocode, this is called SINGLE.
*/
uint32_t helper_tosingle(uint64_t arg)
{
CPU_FloatU f;
CPU_DoubleU d;
int exp = extract64(arg, 52, 11);
uint32_t ret;
d.ll = arg;
f.f = float64_to_float32(d.d, &env->fp_status);
return f.l;
if (likely(exp > 896)) {
/* No denormalization required (includes Inf, NaN). */
ret = extract64(arg, 62, 2) << 30;
ret |= extract64(arg, 29, 30);
} else {
/* Zero or Denormal result. If the exponent is in bounds for
* a single-precision denormal result, extract the proper bits.
* If the input is not zero, and the exponent is out of bounds,
* then the result is undefined; this underflows to zero.
*/
ret = extract64(arg, 63, 1) << 31;
if (unlikely(exp >= 874)) {
/* Denormal result. */
ret |= ((1ULL << 52) | extract64(arg, 0, 52)) >> (896 + 30 - exp);
}
}
return ret;
}
static inline int ppc_float32_get_unbiased_exp(float32 f)

4
target/ppc/helper.h
View File

@ -61,8 +61,8 @@ DEF_HELPER_2(compute_fprf_float64, void, env, i64)
DEF_HELPER_3(store_fpscr, void, env, i64, i32)
DEF_HELPER_2(fpscr_clrbit, void, env, i32)
DEF_HELPER_2(fpscr_setbit, void, env, i32)
DEF_HELPER_2(float64_to_float32, i32, env, i64)
DEF_HELPER_2(float32_to_float64, i64, env, i32)
DEF_HELPER_FLAGS_1(todouble, TCG_CALL_NO_RWG_SE, i64, i32)
DEF_HELPER_FLAGS_1(tosingle, TCG_CALL_NO_RWG_SE, i32, i64)
DEF_HELPER_4(fcmpo, void, env, i64, i64, i32)
DEF_HELPER_4(fcmpu, void, env, i64, i64, i32)

26
target/ppc/translate/fp-impl.inc.c
View File

@ -660,15 +660,12 @@ GEN_LDUF(name, ldop, op | 0x21, type); \
GEN_LDUXF(name, ldop, op | 0x01, type); \
GEN_LDXF(name, ldop, 0x17, op | 0x00, type)
static inline void gen_qemu_ld32fs(DisasContext *ctx, TCGv_i64 arg1, TCGv arg2)
static void gen_qemu_ld32fs(DisasContext *ctx, TCGv_i64 dest, TCGv addr)
{
TCGv t0 = tcg_temp_new();
TCGv_i32 t1 = tcg_temp_new_i32();
gen_qemu_ld32u(ctx, t0, arg2);
tcg_gen_trunc_tl_i32(t1, t0);
tcg_temp_free(t0);
gen_helper_float32_to_float64(arg1, cpu_env, t1);
tcg_temp_free_i32(t1);
TCGv_i32 tmp = tcg_temp_new_i32();
tcg_gen_qemu_ld_i32(tmp, addr, ctx->mem_idx, DEF_MEMOP(MO_UL));
gen_helper_todouble(dest, tmp);
tcg_temp_free_i32(tmp);
}
/* lfd lfdu lfdux lfdx */
@ -836,15 +833,12 @@ GEN_STUF(name, stop, op | 0x21, type); \
GEN_STUXF(name, stop, op | 0x01, type); \
GEN_STXF(name, stop, 0x17, op | 0x00, type)
static inline void gen_qemu_st32fs(DisasContext *ctx, TCGv_i64 arg1, TCGv arg2)
static void gen_qemu_st32fs(DisasContext *ctx, TCGv_i64 src, TCGv addr)
{
TCGv_i32 t0 = tcg_temp_new_i32();
TCGv t1 = tcg_temp_new();
gen_helper_float64_to_float32(t0, cpu_env, arg1);
tcg_gen_extu_i32_tl(t1, t0);
tcg_temp_free_i32(t0);
gen_qemu_st32(ctx, t1, arg2);
tcg_temp_free(t1);
TCGv_i32 tmp = tcg_temp_new_i32();
gen_helper_tosingle(tmp, src);
tcg_gen_qemu_st_i32(tmp, addr, ctx->mem_idx, DEF_MEMOP(MO_UL));
tcg_temp_free_i32(tmp);
}
/* stfd stfdu stfdux stfdx */