Revert "Roll clang n333938-3a6da112-1 : n340158-efb130fc-2."

This reverts commit 0aa05cca9db25a9fa8d18f77bf6b2452bc608ead.

Reason for revert:
This broke arm64-builder-rel and some other builders, see bug.

Original change's description:
> Roll clang n333938-3a6da112-1 : n340158-efb130fc-2.
> 
> Ran `tools/clang/scripts/upload_revision.py efb130fc93059bdf02d3a83950ddabc5d119f9de`.
> 
> This increases the clang version from 10 to 11.
> 
> It also disables the use of vector instructions in zlib to work around
> new false positives in msan (see crbug.com/1045291).
> 
> Bug: 1030664
> Change-Id: I5417d3063f0d67a61cdf31141b05a51a56e84482
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2014904
> Reviewed-by: Nico Weber <thakis@chromium.org>
> Commit-Queue: Hans Wennborg <hans@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#735080}

TBR=thakis@chromium.org,hans@chromium.org

Change-Id: I48754484c26ebf6b1f0b4a47c82fe3c74ee39837
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1030664,1045592
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2020785
Reviewed-by: Hans Wennborg <hans@chromium.org>
Commit-Queue: Hans Wennborg <hans@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#735124}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: ec2aab7d123590cfb332ba56d7faee2e1ff4a779

2 files changed, 12 insertions, 21 deletions

diff --git a/BUILD.gn b/BUILD.gn
index e57cbfb..9d0f021 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -23,14 +23,17 @@ if (current_cpu == "arm" || current_cpu == "arm64") {
   }
 }
 
-# TODO(https://crbug.com/1045291): Re-enable once msan bug is fixed, should
-# be set to:
-#    (current_cpu == "x86" || current_cpu == "x64") && !is_ios
-use_x86_x64_optimizations = false
+use_x86_x64_optimizations =
+    (current_cpu == "x86" || current_cpu == "x64") && !is_ios
 
 config("zlib_adler32_simd_config") {
   if (use_x86_x64_optimizations) {
     defines = [ "ADLER32_SIMD_SSSE3" ]
+    if (is_win) {
+      defines += [ "X86_WINDOWS" ]
+    } else {
+      defines += [ "X86_NOT_WINDOWS" ]
+    }
   } else if (use_arm_neon_optimizations) {
     defines = [ "ADLER32_SIMD_NEON" ]
   }
@@ -268,16 +271,6 @@ component("zlib") {
     defines += [ "CPU_NO_SIMD" ]
   }
 
-  # For cpu_features.c
-  # TODO(https://crbug.com/1045291): Check use_x86_x64_optimizations instead.
-  if ((current_cpu == "x86" || current_cpu == "x64") && !is_ios) {
-    if (is_win) {
-      defines += [ "X86_WINDOWS" ]
-    } else {
-      defines += [ "X86_NOT_WINDOWS" ]
-    }
-  }
-
   if (is_ios) {
     # iOS@ARM is a special case where we always have NEON but don't check
     # for crypto extensions.
diff --git a/cpu_features.c b/cpu_features.c
index 88f46bc..8a25dd2 100644
--- a/cpu_features.c
+++ b/cpu_features.c
@@ -35,10 +35,12 @@ int ZLIB_INTERNAL x86_cpu_enable_simd = 0;
 #include <zircon/features.h>
 #include <zircon/syscalls.h>
 #include <zircon/types.h>
-#elif defined(_MSC_VER)
+#elif defined(ARMV8_OS_WINDOWS) || defined(X86_WINDOWS)
 #include <windows.h>
-#else
+#elif !defined(_MSC_VER)
 #include <pthread.h>
+#else
+#error cpu_features.c CPU feature detection in not defined for your platform
 #endif
 
 #if !defined(CPU_NO_SIMD) && !defined(ARM_OS_IOS)
@@ -49,17 +51,13 @@ static void _cpu_check_features(void);
 static pthread_once_t cpu_check_inited_once = PTHREAD_ONCE_INIT;
 void ZLIB_INTERNAL cpu_check_features(void)
 {
-#if !defined(CPU_NO_SIMD) && !defined(ARM_OS_IOS)
     pthread_once(&cpu_check_inited_once, _cpu_check_features);
-#endif
 }
-#elif defined(_MSC_VER)
+#elif defined(ARMV8_OS_WINDOWS) || defined(X86_WINDOWS)
 static INIT_ONCE cpu_check_inited_once = INIT_ONCE_STATIC_INIT;
 static BOOL CALLBACK _cpu_check_features_forwarder(PINIT_ONCE once, PVOID param, PVOID* context)
 {
-#if !defined(CPU_NO_SIMD) && !defined(ARM_OS_IOS)
     _cpu_check_features();
-#endif
     return TRUE;
 }
 void ZLIB_INTERNAL cpu_check_features(void)