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added support for fast approximate rsqrt(double). Provide 16 digit accurancy but is over 3x faster than 1/sqrt(double)

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Evghenii
2014-02-04 14:44:54 +01:00
parent b0753dc93d
commit eb1a495a7a
5 changed files with 48 additions and 24 deletions
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2
builtins/target-avx1-i64x4base.ll
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@@ -511,3 +511,5 @@ define <4 x double> @__max_varying_double(<4 x double>, <4 x double>) nounwind r
ret <4 x double> %call
}
rsqrt_double()
rcp_double()

9
builtins/target-generic-common.ll
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@@ -191,13 +191,14 @@ declare <WIDTH x double> @__max_varying_double(<WIDTH x double>,
declare float @__rsqrt_uniform_float(float) nounwind readnone
declare float @__rcp_uniform_float(float) nounwind readnone
declare double @__rsqrt_uniform_double(double) nounwind readnone
declare double @__rcp_uniform_double(double) nounwind readnone
declare double @__rsqrt_uniform_double(double, <WIDTH x MASK>) nounwind readnone
declare double @__rcp_uniform_double(double, <WIDTH x MASK>) nounwind readnone
declare float @__sqrt_uniform_float(float) nounwind readnone
declare <WIDTH x float> @__rcp_varying_float(<WIDTH x float>) nounwind readnone
declare <WIDTH x float> @__rsqrt_varying_float(<WIDTH x float>) nounwind readnone
declare <WIDTH x double> @__rcp_varying_double(<WIDTH x double>) nounwind readnone
declare <WIDTH x double> @__rsqrt_varying_double(<WIDTH x double>) nounwind readnone
declare <WIDTH x double> @__rcp_varying_double(<WIDTH x double>, <WIDTH x MASK>) nounwind readnone
declare <WIDTH x double> @__rsqrt_varying_double(<WIDTH x double>, <WIDTH x MASK>) nounwind readnone
declare <WIDTH x float> @__sqrt_varying_float(<WIDTH x float>) nounwind readnone
declare double @__sqrt_uniform_double(double) nounwind readnone

22
builtins/util.m4
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@@ -4533,31 +4533,29 @@ define_down_avgs()
')
define(`rsqrt_double', `
define double @__rsqrt_uniform_double(double) nounwind alwaysinline readnone
declare double @__rsqrt_safe_uniform_double___und(double, <WIDTH x MASK>)
define double @__rsqrt_uniform_double(double, <WIDTH x MASK>) nounwind alwaysinline readnone
{
%flt = fptrunc double %0 to float
%res = call float @__rsqrt_uniform_float(float %flt)
%dres = fpext float %res to double
ret double %dres
%res = call double @__rsqrt_safe_uniform_double___und(double %0, <WIDTH x MASK> %1)
ret double %res
}
define <WIDTH x double> @__rsqrt_varying_double(<WIDTH x double>) nounwind alwaysinline readnone
declare <WIDTH x double> @__rsqrt_safe_varying_double___vyd(<WIDTH x double>, <WIDTH x MASK>)
define <WIDTH x double> @__rsqrt_varying_double(<WIDTH x double>, <WIDTH x MASK>) nounwind alwaysinline readnone
{
%flt = fptrunc <WIDTH x double> %0 to <WIDTH x float>
%res = call <WIDTH x float> @__rsqrt_varying_float(<WIDTH x float> %flt)
%dres = fpext <WIDTH x float> %res to <WIDTH x double>
ret <WIDTH x double> %dres
%res = call <WIDTH x double> @__rsqrt_safe_varying_double___vyd(<WIDTH x double> %0, <WIDTH x MASK> %1)
ret <WIDTH x double> %res
}
')
define(`rcp_double', `
define double @__rcp_uniform_double(double) nounwind alwaysinline readnone
define double @__rcp_uniform_double(double, <WIDTH x MASK>) nounwind alwaysinline readnone
{
%flt = fptrunc double %0 to float
%res = call float @__rcp_uniform_float(float %flt)
%dres = fpext float %res to double
ret double %dres
}
define <WIDTH x double> @__rcp_varying_double(<WIDTH x double>) nounwind alwaysinline readnone
define <WIDTH x double> @__rcp_varying_double(<WIDTH x double>, <WIDTH x MASK>) nounwind alwaysinline readnone
{
%flt = fptrunc <WIDTH x double> %0 to <WIDTH x float>
%res = call <WIDTH x float> @__rcp_varying_float(<WIDTH x float> %flt)

35
stdlib.ispc
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@@ -1393,12 +1393,12 @@ static inline uniform float rcp(uniform float v) {
__declspec(safe)
static inline double rcp(double v) {
return __rcp_varying_double(v);
return __rcp_varying_double(v, (IntMaskType)__mask);
}
__declspec(safe)
static inline uniform double rcp(uniform double v) {
return __rcp_uniform_double(v);
return __rcp_uniform_double(v, (IntMaskType)__mask);
}
///////////////////////////////////////////////////////////////////////////
@@ -3527,14 +3527,37 @@ static inline uniform double sqrt(uniform double v) {
return __sqrt_uniform_double(v);
}
__declspec(safe)
static inline double rsqrt(double v) {
return __rsqrt_varying_double(v);
#define RSQRTD(QUAL) \
__declspec(safe) \
static inline QUAL double __rsqrt_iterate_double(QUAL double x, QUAL double y) \
{ \
QUAL double xh = x*0.5d; \
y += y*(0.5d0 - xh*y*y); \
y += y*(0.5d0 - xh*y*y); \
return y; \
} \
__declspec(safe) \
static inline QUAL double __rsqrt_safe_##QUAL##_double (QUAL double x) \
{ \
if (x <= 1.0d+33 && x >= 1.0d-33) \
return __rsqrt_iterate_double(x, rsqrt((QUAL float)x)); \
QUAL int64 ex = intbits(x) & 0x7fe0000000000000; \
QUAL double exp = doublebits( 0x7fd0000000000000 - ex ); /* 1.0d/exponent */ \
QUAL double exph = doublebits( 0x5fe0000000000000 - (ex >> 1)); /* 1.0d/sqrt(exponent) */ \
QUAL double y = rsqrt((QUAL float)(x*exp)); \
return __rsqrt_iterate_double(x, y*exph); \
}
RSQRTD(varying)
__declspec(safe)
static inline double rsqrt(double v) {
return __rsqrt_varying_double(v, (IntMaskType)__mask);
}
RSQRTD(uniform)
__declspec(safe)
static inline uniform double rsqrt(uniform double v) {
return __rsqrt_uniform_double(v);
return __rsqrt_uniform_double(v, (IntMaskType)__mask);
}
__declspec(safe)
static inline double ldexp(double x, int n) {

4
tests/test-148.ispc
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@@ -3,11 +3,11 @@ export uniform int width() { return programCount; }
export void f_f(uniform float RET[], uniform float aFOO[]) {
double x = aFOO[programIndex];
double x = aFOO[programIndex]*1d100;
double d, invsqrt = rsqrt(x);
d = (x * (invsqrt * invsqrt)) - 1.0d0;
if (d < 0.0d0) d = -d;
RET[programIndex] = d > 1d-5;
RET[programIndex] = d > 1d-15;
}