Decode UTF-8 with PEXT when BMI2 is available

1 files changed, 57 insertions, 2 deletions

diff --git a/src/unicode.c b/src/unicode.c
index b32b413..6ad34a3 100644
--- a/src/unicode.c
+++ b/src/unicode.c
@@ -1,3 +1,7 @@
+#if ORYX_BMI2
+#	include <immintrin.h>
+#endif
+
 #include "common.h"
 #include "types.h"
 #include "unicode-data.h"
@@ -45,9 +49,19 @@ RUNE_IS_GEN(rune_is_xidc, xidc_stage1, xidc_stage2, 128)
 static const char lengths[] = {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
                                0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 2, 2, 3, 3, 4, 0};
 static const rune mins[] = {RUNE_C(4194304), 0, 128, 2048, RUNE_C(65536)};
+static const int shifte[] = {0, 6, 4, 2, 0};
+
+#if ORYX_BMI2
+static const uint32_t pextmsk[] = {
+	0x7F000000,
+	0x1F3F0000,
+	0x0F3F3F00,
+	0x073F3F3F,
+};
+#else
 static const int masks[] = {0x00, 0x7f, 0x1f, 0x0f, 0x07};
 static const int shiftc[] = {0, 18, 12, 6, 0};
-static const int shifte[] = {0, 6, 4, 2, 0};
+#endif
 
 rune
 utf8_decode(const uchar **buf)
@@ -55,12 +69,32 @@ utf8_decode(const uchar **buf)
 	const uchar *s = *buf;
 	int len = lengths[s[0] >> 3];
 	*buf = s + len + !len;
-
+#if ORYX_BMI2
+	rune c = 0;
+	switch (len) {
+	case 4:
+		c |= (rune)s[3] <<  0;
+		/* fallthrough */
+	case 3:
+		c |= (rune)s[2] <<  8;
+		/* fallthrough */
+	case 2:
+		c |= (rune)s[1] << 16;
+		/* fallthrough */
+	case 1:
+		c |= (rune)s[0] << 24;
+		break;
+	default:
+		__builtin_unreachable();
+	}
+	return _pext_u32(c, pextmsk[len - 1]);
+#else
 	rune c = (rune)(s[0] & masks[len]) << 18;
 	c |= (rune)(s[1] & 0x3f) << 12;
 	c |= (rune)(s[2] & 0x3f) << 6;
 	c |= (rune)(s[3] & 0x3f) << 0;
 	return c >> shiftc[len];
+#endif
 }
 
 size_t
@@ -72,11 +106,32 @@ utf8_validate_off(const uchar *s, size_t len)
 
 		const uchar *next = s + len + !len;
 
+#if ORYX_BMI2
+		rune c = 0;
+		switch (len) {
+		case 4:
+			c |= (rune)s[3] <<  0;
+			/* fallthrough */
+		case 3:
+			c |= (rune)s[2] <<  8;
+			/* fallthrough */
+		case 2:
+			c |= (rune)s[1] << 16;
+			/* fallthrough */
+		case 1:
+			c |= (rune)s[0] << 24;
+			break;
+		default:
+			__builtin_unreachable();
+		}
+		c = _pext_u32(c, pextmsk[len - 1]);
+#else
 		rune c = (rune)(s[0] & masks[len]) << 18;
 		c |= (rune)(s[1] & 0x3f) << 12;
 		c |= (rune)(s[2] & 0x3f) << 6;
 		c |= (rune)(s[3] & 0x3f) << 0;
 		c >>= shiftc[len];
+#endif
 
 		int e = (c < mins[len]) << 6;
 		e |= ((c >> 11) == 0x1B) << 7;