Add contrib intdiv: fast integer division by invariant scalars using multiplication

BUILD

@@ -503,6 +503,22 @@ cc_library(
     local_defines = ["HWY_HEADER_ONLY"],
 )
 
+cc_library(
+    name = "intdiv",
+    compatible_with = [],
+    copts = COPTS,
+    hdrs = [
+        "hwy/contrib/intdiv/intdiv.h",
+    ],
+    textual_hdrs = [
+        "hwy/contrib/intdiv/intdiv-inl.h",
+    ],
+    deps = [
+        ":hwy",
+    ],
+)
+
+
 cc_test(
     name = "list_targets",
     size = "small",
@@ -592,6 +608,17 @@ HWY_TEST_DEPS = [
     for subdir, test, extra_deps in HWY_TESTS
 ]
 
+cc_test(
+    name = "intdiv_test",
+    size = "medium",
+    timeout = "long",
+    srcs = ["hwy/contrib/intdiv/intdiv_test.cc"],
+    copts = COPTS + HWY_TEST_COPTS,
+    local_defines = ["HWY_IS_TEST"],
+    tags = ["hwy_ops_test"],
+    deps = HWY_TEST_DEPS + [":intdiv"],
+)
+
 # For manually building the tests we define here (:all does not work in --config=msvc)
 test_suite(
     name = "hwy_ops_tests",

CMakeLists.txt

@@ -222,6 +222,8 @@ list(APPEND HWY_CONTRIB_SOURCES
     hwy/contrib/image/image.cc
     hwy/contrib/image/image.h
     hwy/contrib/math/fast_math-inl.h
+    hwy/contrib/intdiv/intdiv.h
+    hwy/contrib/intdiv/intdiv-inl.h
     hwy/contrib/math/math-inl.h
     hwy/contrib/matvec/matvec-inl.h
     hwy/contrib/random/random-inl.h
@@ -881,6 +883,7 @@ list(APPEND HWY_TEST_FILES
   hwy/contrib/bit_pack/bit_pack_test.cc
   hwy/contrib/dot/dot_test.cc
   hwy/contrib/matvec/matvec_test.cc
+  hwy/contrib/intdiv/intdiv_test.cc
   hwy/contrib/image/image_test.cc
   # Disabled due to SIGILL in clang7 debug build during gtest discovery phase,
   # not reproducible locally. Still tested via bazel build.

hwy.gni

@@ -50,6 +50,8 @@ hwy_contrib_public = [
   "$_hwy/contrib/dot/dot-inl.h",
   "$_hwy/contrib/image/image.h",
   "$_hwy/contrib/math/fast_math-inl.h",
+  "$_hwy/contrib/intdiv/intdiv.h",
+  "$_hwy/contrib/intdiv/intdiv-inl.h",
   "$_hwy/contrib/math/math-inl.h",
 ]