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power up skvx::map

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Rewrite map() to allow any number of arguments,
now also used for 2-argument (pow) and 3-argument (fma) operations.

I left a note about fma()... I can't understand why, but calling as
map(fmaf, x,y,z) ends up with scalar calls to fmaf(), but with the
lambda indirection we see perfect vector codegen.

I had to break map() back into two parts. I don't see any way to pass
both a variadic number of arguments and play our trick with the default
std::index_sequence parameter.  The lane lambda similarly exists only to
split up the expansion of the Rest... type pack from the I... index
pack; you can't use two pack expansions in the same expression.

Change-Id: Ia156a7fd846237f687d6018a7f95550c9fd4a56d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/325736
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Herb Derby <herb@google.com>
This commit is contained in:
Mike Klein 2020-10-12 12:38:10 -05:00 committed by Skia Commit-Bot
parent 21f8b51099
commit 840e8ea740
2 changed files with 37 additions and 60 deletions
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91
include/private/SkVx.h
View File

@ -314,8 +314,7 @@ SINT Vec<2*N,T> join(const Vec<N,T>& lo, const Vec<N,T>& hi) {
}
#endif
// Some operations we want are not expressible with Clang/GCC vector
// extensions, so we implement them using the recursive approach.
// Some operations we want are not expressible with Clang/GCC vector extensions.
// N == 1 scalar implementations.
SIT Vec<1,T> if_then_else(const Vec<1,M<T>>& cond, const Vec<1,T>& t, const Vec<1,T>& e) {
@ -324,8 +323,6 @@ SIT Vec<1,T> if_then_else(const Vec<1,M<T>>& cond, const Vec<1,T>& t, const Vec<
(~cond & bit_pun<Vec<1, M<T>>>(e)) );
}
SIT Vec<1,T> pow(const Vec<1,T>& x, const Vec<1,T>& y) { return std::pow(x.val, y.val); }
// All default N != 1 implementations just recurse on lo and hi halves.
// Clang can reason about naive_if_then_else() and optimize through it better
@ -403,9 +400,6 @@ SINT bool all(const Vec<N,T>& x) {
&& all(x.hi);
}
SINT Vec<N,T> pow(const Vec<N,T>& x, const Vec<N,T>& y) {
return join(pow(x.lo, y.lo), pow(x.hi, y.hi));
}
// Scalar/vector operations just splat the scalar to a vector...
SINTU Vec<N,T> operator+ (U x, const Vec<N,T>& y) { return Vec<N,T>(x) + y; }
@ -421,8 +415,6 @@ SINTU Vec<N,M<T>> operator<=(U x, const Vec<N,T>& y) { return Vec<N,T>(x) <= y;
SINTU Vec<N,M<T>> operator>=(U x, const Vec<N,T>& y) { return Vec<N,T>(x) >= y; }
SINTU Vec<N,M<T>> operator< (U x, const Vec<N,T>& y) { return Vec<N,T>(x) < y; }
SINTU Vec<N,M<T>> operator> (U x, const Vec<N,T>& y) { return Vec<N,T>(x) > y; }
SINTU Vec<N,T> pow(U x, const Vec<N,T>& y) { return pow(Vec<N,T>(x), y); }
// ... and same deal for vector/scalar operations.
SINTU Vec<N,T> operator+ (const Vec<N,T>& x, U y) { return x + Vec<N,T>(y); }
SINTU Vec<N,T> operator- (const Vec<N,T>& x, U y) { return x - Vec<N,T>(y); }
@ -437,7 +429,7 @@ SINTU Vec<N,M<T>> operator<=(const Vec<N,T>& x, U y) { return x <= Vec<N,T>(y);
SINTU Vec<N,M<T>> operator>=(const Vec<N,T>& x, U y) { return x >= Vec<N,T>(y); }
SINTU Vec<N,M<T>> operator< (const Vec<N,T>& x, U y) { return x < Vec<N,T>(y); }
SINTU Vec<N,M<T>> operator> (const Vec<N,T>& x, U y) { return x > Vec<N,T>(y); }
SINTU Vec<N,T> pow(const Vec<N,T>& x, U y) { return pow(x, Vec<N,T>(y)); }
// The various op= operators, for vectors...
SINT Vec<N,T>& operator+=(Vec<N,T>& x, const Vec<N,T>& y) { return (x = x + y); }
@ -505,16 +497,10 @@ SI Vec<sizeof...(Ix),T> shuffle(const Vec<N,T>& x) {
#endif
}
// fma() delivers a fused mul-add, even if that's really expensive.
SI Vec<1,float> fma(const Vec<1,float>& x, const Vec<1,float>& y, const Vec<1,float>& z) {
return std::fma(x.val, y.val, z.val);
}
SIN Vec<N,float> fma(const Vec<N,float>& x, const Vec<N,float>& y, const Vec<N,float>& z) {
return join(fma(x.lo, y.lo, z.lo),
fma(x.hi, y.hi, z.hi));
}
// Call map(fn, x) for a vector with fn() applied to each lane of x, { fn(x[0]), fn(x[1]), ... },
// or map(fn, x,y) for a vector of fn(x[i], y[i]), etc.
template <int N, typename T, typename Fn, std::size_t... I>
template <typename Fn, typename... Args, size_t... I>
#if defined(__clang__)
// CFI, specifically -fsanitize=cfi-icall, seems to give a false positive here,
// with errors like "control flow integrity check for type 'float (float)
@ -523,25 +509,37 @@ template <int N, typename T, typename Fn, std::size_t... I>
// So, stifle CFI in this function.
__attribute__((no_sanitize("cfi")))
#endif
SI auto map(const skvx::Vec<N,T>& x, Fn&& fn,
std::index_sequence<I...> ix = {}) -> skvx::Vec<N, decltype(fn(x[0]))> {
if /*constexpr*/ (sizeof...(I) == 0) {
// When called as map(x, fn), bootstrap the index_sequence we want: 0,1,...,N-1.
return map(x, fn, std::make_index_sequence<N>{});
}
return { fn(x[I])... };
SI auto map(std::index_sequence<I...>,
Fn&& fn, const Args&... args) -> skvx::Vec<sizeof...(I), decltype(fn(args[0]...))> {
auto lane = [&](size_t i) { return fn(args[i]...); };
return { lane(I)... };
}
SIN Vec<N,float> atan(const Vec<N,float>& x) { return map(x, atanf); }
SIN Vec<N,float> ceil(const Vec<N,float>& x) { return map(x, ceilf); }
SIN Vec<N,float> floor(const Vec<N,float>& x) { return map(x, floorf); }
SIN Vec<N,float> trunc(const Vec<N,float>& x) { return map(x, truncf); }
SIN Vec<N,float> round(const Vec<N,float>& x) { return map(x, roundf); }
SIN Vec<N,float> sqrt(const Vec<N,float>& x) { return map(x, sqrtf); }
SIN Vec<N,float> abs(const Vec<N,float>& x) { return map(x, fabsf); }
SIN Vec<N,float> sin(const Vec<N,float>& x) { return map(x, sinf); }
SIN Vec<N,float> cos(const Vec<N,float>& x) { return map(x, cosf); }
SIN Vec<N,float> tan(const Vec<N,float>& x) { return map(x, tanf); }
template <typename Fn, int N, typename T, typename... Rest>
auto map(Fn&& fn, const Vec<N,T>& first, const Rest&... rest) {
// Derive an {0...N-1} index_sequence from the size of the first arg: N lanes in, N lanes out.
return map(std::make_index_sequence<N>{}, fn, first,rest...);
}
SIN Vec<N,float> atan(const Vec<N,float>& x) { return map( atanf, x); }
SIN Vec<N,float> ceil(const Vec<N,float>& x) { return map( ceilf, x); }
SIN Vec<N,float> floor(const Vec<N,float>& x) { return map(floorf, x); }
SIN Vec<N,float> trunc(const Vec<N,float>& x) { return map(truncf, x); }
SIN Vec<N,float> round(const Vec<N,float>& x) { return map(roundf, x); }
SIN Vec<N,float> sqrt(const Vec<N,float>& x) { return map( sqrtf, x); }
SIN Vec<N,float> abs(const Vec<N,float>& x) { return map( fabsf, x); }
SIN Vec<N,float> sin(const Vec<N,float>& x) { return map( sinf, x); }
SIN Vec<N,float> cos(const Vec<N,float>& x) { return map( cosf, x); }
SIN Vec<N,float> tan(const Vec<N,float>& x) { return map( tanf, x); }
SIN Vec<N,float> pow(const Vec<N,float>& x,
const Vec<N,float>& y) { return map(powf, x,y); }
SIN Vec<N,float> fma(const Vec<N,float>& x,
const Vec<N,float>& y,
const Vec<N,float>& z) {
// I don't understand why Clang's codegen is terrible if we write map(fmaf, x,y,z) directly.
auto fn = [](float x, float y, float z) { return fmaf(x,y,z); };
return map(fn, x,y,z);
}
SI Vec<1,int> lrint(const Vec<1,float>& x) {
return (int)lrintf(x.val);
@ -704,27 +702,6 @@ SIN Vec<N,uint8_t> approx_scale(const Vec<N,uint8_t>& x, const Vec<N,uint8_t>& y
}
#endif
#if defined(__AVX2__)
SI Vec<4,float> fma(const Vec<4,float>& x, const Vec<4,float>& y, const Vec<4,float>& z) {
return bit_pun<Vec<4,float>>(_mm_fmadd_ps(bit_pun<__m128>(x),
bit_pun<__m128>(y),
bit_pun<__m128>(z)));
}
SI Vec<8,float> fma(const Vec<8,float>& x, const Vec<8,float>& y, const Vec<8,float>& z) {
return bit_pun<Vec<8,float>>(_mm256_fmadd_ps(bit_pun<__m256>(x),
bit_pun<__m256>(y),
bit_pun<__m256>(z)));
}
#elif defined(__aarch64__)
SI Vec<4,float> fma(const Vec<4,float>& x, const Vec<4,float>& y, const Vec<4,float>& z) {
// These instructions tend to work like z += xy, so the order here is z,x,y.
return bit_pun<Vec<4,float>>(vfmaq_f32(bit_pun<float32x4_t>(z),
bit_pun<float32x4_t>(x),
bit_pun<float32x4_t>(y)));
}
#endif
#endif // !defined(SKNX_NO_SIMD)
} // namespace skvx

6
src/opts/SkVM_opts.h
View File

@ -50,7 +50,7 @@ static inline skvx::Vec<N,int> gather32(const int* ptr, const skvx::Vec<N,int>&
return join(gather32(ptr, ix.lo),
gather32(ptr, ix.hi));
}
return map(ix, [&](int i) { return ptr[i]; });
return map([&](int i) { return ptr[i]; }, ix);
}
namespace SK_OPTS_NS {
@ -182,12 +182,12 @@ namespace SK_OPTS_NS {
STRIDE_K(Op::gather8): {
const uint8_t* ptr;
memcpy(&ptr, (const uint8_t*)args[immy] + immz, sizeof(ptr));
r[d].i32 = map(r[x].i32, [&](int ix) { return (int)ptr[ix]; });
r[d].i32 = map([&](int ix) { return (int)ptr[ix]; }, r[x].i32);
} break;
STRIDE_K(Op::gather16): {
const uint16_t* ptr;
memcpy(&ptr, (const uint8_t*)args[immy] + immz, sizeof(ptr));
r[d].i32 = map(r[x].i32, [&](int ix) { return (int)ptr[ix]; });
r[d].i32 = map([&](int ix) { return (int)ptr[ix]; }, r[x].i32);
} break;
STRIDE_K(Op::gather32): {
const int* ptr;