From 3e26513656bff4e70ab14b9a3913b98068950d9a Mon Sep 17 00:00:00 2001
From: Clement Courbet <courbet@google.com>
Date: Fri, 18 Jun 2021 13:21:37 +0000
Subject: [PATCH] Add WEBP_RESTRICT & use it in VP8BitReader

Marking the `VP8BitReader` as `__restrict__` helps the compiler generate
better code avoiding issues related to aliasing (re-loads/stores).

Change-Id: Ib7178f57e27e5f40572efc3e567cdf994ea6d928
---
 src/utils/bit_reader_inl_utils.h |  2 +-
 src/utils/utils.h                | 10 ++++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/utils/bit_reader_inl_utils.h b/src/utils/bit_reader_inl_utils.h
index 46b38807..c5f9ae5c 100644
--- a/src/utils/bit_reader_inl_utils.h
+++ b/src/utils/bit_reader_inl_utils.h
@@ -104,7 +104,7 @@ void VP8LoadNewBytes(VP8BitReader* const br) {
 }
 
 // Read a bit with proba 'prob'. Speed-critical function!
-static WEBP_INLINE int VP8GetBit(VP8BitReader* const br,
+static WEBP_INLINE int VP8GetBit(VP8BitReader* WEBP_RESTRICT const br,
                                  int prob, const char label[]) {
   // Don't move this declaration! It makes a big speed difference to store
   // 'range' *before* calling VP8LoadNewBytes(), even if this function doesn't
diff --git a/src/utils/utils.h b/src/utils/utils.h
index ef04f108..0026a747 100644
--- a/src/utils/utils.h
+++ b/src/utils/utils.h
@@ -25,6 +25,16 @@
 #include "src/dsp/dsp.h"
 #include "src/webp/types.h"
 
+//------------------------------------------------------------------------------
+// restrict
+
+#if defined(__GNUC__) || defined(__clang__)
+#define WEBP_RESTRICT __restrict
+#else
+#define WEBP_RESTRICT
+#endif
+
+
 #ifdef __cplusplus
 extern "C" {
 #endif