Integrate SIMD optimisations for zlib

third_party/zlib/BUILD.gn

Index: third_party/zlib/BUILD.gn
diff --git a/third_party/zlib/BUILD.gn b/third_party/zlib/BUILD.gn
index 9ac85a574fe53f7ef0e754d159909cdeb235b7f9..1bad4082bdda685470b43cac3de2389d30d13e1d 100644
--- a/third_party/zlib/BUILD.gn
+++ b/third_party/zlib/BUILD.gn
@@ -42,6 +42,18 @@ static_library("zlib") {
     "zutil.h",
   ]
 
+  if (is_linux && (cpu_arch == "x86" || cpu_arch == "x64")) {
+     sources += [ "crc_folding.c",
+                  "fill_window_sse.c",
+                  "x86.c",
+                  "x86.h" ]
+     defines = [ "HAVE_SSE2",
+                  "CHECK_SSE2",
+                  "USE_SSE4_2_CRC_HASH",
+                  "HAVE_PCLMULQDQ" ]
+     cflags = ["-msse2", "-msse4.2", "-mpclmul"]

[agl, 2014/09/23 21:41:39]

These compiler flags allow the compiler to use the given instructions anywhere
in the code, which isn't viable because we don't know if we'll have them at
runtime.

+  }
+
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]