From 19eb459da38318eb238560ca6087a46fe5c5bbd0 Mon Sep 17 00:00:00 2001
From: Nick Terrell <terrelln@fb.com>
Date: Mon, 15 Nov 2021 16:57:00 -0800
Subject: [PATCH] [linux-kernel] Don't inline function in zstd_opt.c

The optimal parser is unlikely to be used in the linux kernel in
practice. There is no reason these functions should be force inlined,
since we aren't gaining anything, and are losing build size.

| Compiler | Before (Bytes) | After (Bytes) | Delta (Bytes) |
|----------|----------------|---------------|---------------|
| gcc-11   |        1142090 |        952754 |       -189336 |
| clang-12 |        1228402 |        976290 |       -252112 |

This is a temporary solution pending the resolution of PR #2862 in the
`dev` branch.
---
 contrib/linux-kernel/Makefile           |  4 ++--
 contrib/linux-kernel/test/macro-test.sh |  1 -
 lib/compress/zstd_opt.c                 | 14 ++++++++++++++
 3 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/contrib/linux-kernel/Makefile b/contrib/linux-kernel/Makefile
index f79de6792..47a431740 100644
--- a/contrib/linux-kernel/Makefile
+++ b/contrib/linux-kernel/Makefile
@@ -41,7 +41,6 @@ libzstd:
 		-DZSTD_MEMORY_SANITIZER=0 \
 		-DZSTD_DATAFLOW_SANITIZER=0 \
 		-DZSTD_COMPRESS_HEAPMODE=1 \
-		-UZSTD_NO_INLINE \
 		-UNO_PREFETCH \
 		-U__cplusplus \
 		-UZSTD_DLL_EXPORT \
@@ -55,7 +54,8 @@ libzstd:
 		-RZSTD_FALLTHROUGH=fallthrough \
 		-DZSTD_HAVE_WEAK_SYMBOLS=0 \
 		-DZSTD_TRACE=0 \
-		-DZSTD_NO_TRACE
+		-DZSTD_NO_TRACE \
+		-DZSTD_LINUX_KERNEL
 	mv linux/lib/zstd/zstd.h linux/include/linux/zstd_lib.h
 	mv linux/lib/zstd/zstd_errors.h linux/include/linux/
 	cp linux_zstd.h linux/include/linux/zstd.h
diff --git a/contrib/linux-kernel/test/macro-test.sh b/contrib/linux-kernel/test/macro-test.sh
index bde6cbb56..9ea84aa66 100755
--- a/contrib/linux-kernel/test/macro-test.sh
+++ b/contrib/linux-kernel/test/macro-test.sh
@@ -36,7 +36,6 @@ test_not_present "ZSTD_NO_INTRINSICS"
 test_not_present "ZSTD_NO_UNUSED_FUNCTIONS"
 test_not_present "ZSTD_LEGACY_SUPPORT"
 test_not_present "STATIC_BMI2"
-test_not_present "ZSTD_NO_INLINE"
 test_not_present "ZSTD_DLL_EXPORT"
 test_not_present "ZSTD_DLL_IMPORT"
 test_not_present "__ICCARM__"
diff --git a/lib/compress/zstd_opt.c b/lib/compress/zstd_opt.c
index 909e06d05..0488589ff 100644
--- a/lib/compress/zstd_opt.c
+++ b/lib/compress/zstd_opt.c
@@ -8,6 +8,20 @@
  * You may select, at your option, one of the above-listed licenses.
  */
 
+/**
+ * Disable inlining for the optimal parser for the kernel build.
+ * It is unlikely to be used in the kernel, and where it is used
+ * latency shouldn't matter because it is very slow to begin with.
+ * We prefer a ~180KB binary size win over faster optimal parsing.
+ *
+ * TODO(https://github.com/facebook/zstd/issues/2862):
+ * Improve the code size of the optimal parser in general, so we
+ * don't need this hack for the kernel build.
+ */
+#ifdef ZSTD_LINUX_KERNEL
+#define ZSTD_NO_INLINE 1
+#endif
+
 #include "zstd_compress_internal.h"
 #include "hist.h"
 #include "zstd_opt.h"