intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 77 insertions, 0 deletions

diff --git a/contrib/libs/base64/neon64/dec_neon.c b/contrib/libs/base64/neon64/dec_neon.c
new file mode 100644
index 0000000000..713d8ca9a4
--- /dev/null
+++ b/contrib/libs/base64/neon64/dec_neon.c
@@ -0,0 +1,77 @@
+// If we have NEON support, pick off 64 bytes at a time for as long as we can.
+// Unlike the SSE codecs, we don't write trailing zero bytes to output, so we
+// don't need to check if we have enough remaining input to cover them:
+while (srclen >= 64)
+{
+	uint8x16x4_t set1, set2, set3, set4, set5, set6, set7, delta;
+	uint8x16x3_t dec;
+
+	// Load 64 bytes and deinterleave:
+	uint8x16x4_t str = vld4q_u8((uint8_t *)c);
+
+	// The input consists of six character sets in the Base64 alphabet,
+	// which we need to map back to the 6-bit values they represent.
+	// There are three ranges, two singles, and then there's the rest.
+	//
+	//  #  From       To        Add  Characters
+	//  1  [43]       [62]      +19  +
+	//  2  [47]       [63]      +16  /
+	//  3  [48..57]   [52..61]   +4  0..9
+	//  4  [65..90]   [0..25]   -65  A..Z
+	//  5  [97..122]  [26..51]  -71  a..z
+	// (6) Everything else => invalid input
+
+	// Benchmarking on the Raspberry Pi 2B and Clang shows that looping
+	// generates slightly faster code than explicit unrolling:
+	for (int i = 0; i < 4; i++) {
+		set1.val[i] = CMPEQ(str.val[i], '+');
+		set2.val[i] = CMPEQ(str.val[i], '/');
+		set3.val[i] = RANGE(str.val[i], '0', '9');
+		set4.val[i] = RANGE(str.val[i], 'A', 'Z');
+		set5.val[i] = RANGE(str.val[i], 'a', 'z');
+		set6.val[i] = CMPEQ(str.val[i], '-');
+		set7.val[i] = CMPEQ(str.val[i], '_');
+
+		delta.val[i] = REPLACE(set1.val[i], 19);
+		delta.val[i] = vorrq_u8(delta.val[i], REPLACE(set2.val[i],  16));
+		delta.val[i] = vorrq_u8(delta.val[i], REPLACE(set3.val[i],   4));
+		delta.val[i] = vorrq_u8(delta.val[i], REPLACE(set4.val[i], -65));
+		delta.val[i] = vorrq_u8(delta.val[i], REPLACE(set5.val[i], -71));
+		delta.val[i] = vorrq_u8(delta.val[i], REPLACE(set6.val[i], 17));
+		delta.val[i] = vorrq_u8(delta.val[i], REPLACE(set7.val[i], -32));
+	}
+
+	// Check for invalid input: if any of the delta values are zero,
+	// fall back on bytewise code to do error checking and reporting:
+	uint8x16_t classified = CMPEQ(delta.val[0], 0);
+	classified = vorrq_u8(classified, CMPEQ(delta.val[1], 0));
+	classified = vorrq_u8(classified, CMPEQ(delta.val[2], 0));
+	classified = vorrq_u8(classified, CMPEQ(delta.val[3], 0));
+
+	// Extract both 32-bit halves; check that all bits are zero:
+	if (vgetq_lane_u32((uint32x4_t)classified, 0) != 0
+	 || vgetq_lane_u32((uint32x4_t)classified, 1) != 0
+	 || vgetq_lane_u32((uint32x4_t)classified, 2) != 0
+	 || vgetq_lane_u32((uint32x4_t)classified, 3) != 0) {
+		break;
+	}
+
+	// Now simply add the delta values to the input:
+	str.val[0] = vaddq_u8(str.val[0], delta.val[0]);
+	str.val[1] = vaddq_u8(str.val[1], delta.val[1]);
+	str.val[2] = vaddq_u8(str.val[2], delta.val[2]);
+	str.val[3] = vaddq_u8(str.val[3], delta.val[3]);
+
+	// Compress four bytes into three:
+	dec.val[0] = vshlq_n_u8(str.val[0], 2) | vshrq_n_u8(str.val[1], 4);
+	dec.val[1] = vshlq_n_u8(str.val[1], 4) | vshrq_n_u8(str.val[2], 2);
+	dec.val[2] = vshlq_n_u8(str.val[2], 6) | str.val[3];
+
+	// Interleave and store decoded result:
+	vst3q_u8((uint8_t *)o, dec);
+
+	c += 64;
+	o += 48;
+	outl += 48;
+	srclen -= 64;
+}