Add tests for vectorized `index_*` procs

tests/core/normal.odin

@@ -34,6 +34,7 @@ download_assets :: proc() {
 @(require) import "path/filepath"
 @(require) import "reflect"
 @(require) import "runtime"
+@(require) import "simd/util"
 @(require) import "slice"
 @(require) import "strconv"
 @(require) import "strings"

tests/core/simd/util/test_core_simd_util.odin

@@ -0,0 +1,108 @@
+//+build i386, amd64
+package test_core_simd_util
+
+import simd_util "core:simd/util"
+import "core:testing"
+
+@test
+test_index_byte_sanity :: proc(t: ^testing.T) {
+	// We must be able to find the byte at the correct index.
+	for n in 1..<256 {
+		data := make([]u8, n)
+		defer delete(data)
+		for i in 0..<n-1 {
+			data[i] = '-'
+		}
+
+		// Find it at the end.
+		data[n-1] = 'o'
+		if !testing.expect_value(t, simd_util.index_byte(data, 'o'), n-1) {
+			return
+		}
+		if !testing.expect_value(t, simd_util.last_index_byte(data, 'o'), n-1) {
+			return
+		}
+		data[n-1] = '-'
+
+		// Find it in the middle.
+		data[n/2] = 'o'
+		if !testing.expect_value(t, simd_util.index_byte(data, 'o'), n/2) {
+			return
+		}
+		if !testing.expect_value(t, simd_util.last_index_byte(data, 'o'), n/2) {
+			return
+		}
+		data[n/2] = '-'
+
+		// Find it at the start.
+		data[0] = 'o'
+		if !testing.expect_value(t, simd_util.index_byte(data, 'o'), 0) {
+			return
+		}
+		if !testing.expect_value(t, simd_util.last_index_byte(data, 'o'), 0) {
+			return
+		}
+	}
+}
+
+@test
+test_index_byte_empty :: proc(t: ^testing.T) {
+	a: [1]u8
+	testing.expect_value(t, simd_util.index_byte(a[0:0], 'o'), -1)
+	testing.expect_value(t, simd_util.last_index_byte(a[0:0], 'o'), -1)
+}
+
+@test
+test_index_byte_multiple_hits :: proc(t: ^testing.T) {
+	for n in 5..<256 {
+		data := make([]u8, n)
+		defer delete(data)
+		for i in 0..<n-1 {
+			data[i] = '-'
+		}
+
+		data[n-1] = 'o'
+		data[n-3] = 'o'
+		data[n-5] = 'o'
+
+		// Find the first one.
+		if !testing.expect_value(t, simd_util.index_byte(data, 'o'), n-5) {
+			return
+		}
+
+		// Find the last one.
+		if !testing.expect_value(t, simd_util.last_index_byte(data, 'o'), n-1) {
+			return
+		}
+	}
+}
+
+@test
+test_index_byte_zero :: proc(t: ^testing.T) {
+	// This test protects against false positives in uninitialized memory.
+	for n in 1..<256 {
+		data := make([]u8, n + 64)
+		defer delete(data)
+		for i in 0..<n-1 {
+			data[i] = '-'
+		}
+
+		// Positive hit.
+		data[n-1] = 0
+		if !testing.expect_value(t, simd_util.index_byte(data[:n], 0), n-1) {
+			return
+		}
+		if !testing.expect_value(t, simd_util.last_index_byte(data[:n], 0), n-1) {
+			return
+		}
+
+		// Test for false positives.
+		data[n-1] = '-'
+		if !testing.expect_value(t, simd_util.index_byte(data[:n], 0), -1) {
+			return
+		}
+		if !testing.expect_value(t, simd_util.last_index_byte(data[:n], 0), -1) {
+			return
+		}
+	}
+}