From 6686fc627ec2f805bc74599912c46d0ee1a4047c Mon Sep 17 00:00:00 2001
From: "H. Peter Anvin" <hpa@zytor.com>
Date: Thu, 22 Feb 2018 14:52:50 -0800
Subject: [PATCH] Introduce cold function attribute

Attribute to deemphasize certain code paths.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
---
 asm/error.c        |  8 ++++----
 configure.ac       |  1 +
 include/compiler.h | 16 ++++++++++++++++
 include/error.h    |  6 +++---
 include/nasmlib.h  |  2 +-
 5 files changed, 25 insertions(+), 8 deletions(-)

diff --git a/asm/error.c b/asm/error.c
index 45811a8d..1f91cd78 100644
--- a/asm/error.c
+++ b/asm/error.c
@@ -87,7 +87,7 @@ void nasm_error(int severity, const char *fmt, ...)
     va_end(ap);
 }
 
-no_return nasm_fatal(int flags, const char *fmt, ...)
+fatal_func nasm_fatal(int flags, const char *fmt, ...)
 {
     va_list ap;
 
@@ -96,7 +96,7 @@ no_return nasm_fatal(int flags, const char *fmt, ...)
     abort();			/* We should never get here */
 }
 
-no_return nasm_panic(int flags, const char *fmt, ...)
+fatal_func nasm_panic(int flags, const char *fmt, ...)
 {
     va_list ap;
 
@@ -105,12 +105,12 @@ no_return nasm_panic(int flags, const char *fmt, ...)
     abort();			/* We should never get here */
 }
 
-no_return nasm_panic_from_macro(const char *file, int line)
+fatal_func nasm_panic_from_macro(const char *file, int line)
 {
     nasm_panic(ERR_NOFILE, "Internal error at %s:%d\n", file, line);
 }
 
-no_return nasm_assert_failed(const char *file, int line, const char *msg)
+fatal_func nasm_assert_failed(const char *file, int line, const char *msg)
 {
     nasm_panic(0, "assertion %s failed at %s:%d", msg, file, line);
 }
diff --git a/configure.ac b/configure.ac
index 1f492103..4e27bb3e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -223,6 +223,7 @@ PA_FUNC_ATTRIBUTE(alloc_size, (1))
 PA_FUNC_ATTRIBUTE(format, [(printf,1,2)], int, [const char *, ...], ["%d",1])
 PA_FUNC_ATTRIBUTE(const)
 PA_FUNC_ATTRIBUTE(pure)
+PA_FUNC_ATTRIBUTE(cold)
 PA_FUNC_ATTRIBUTE_ERROR
 
 dnl
diff --git a/include/compiler.h b/include/compiler.h
index 6e919d3d..6c7e20c5 100644
--- a/include/compiler.h
+++ b/include/compiler.h
@@ -286,6 +286,22 @@ size_t strnlen(const char *s, size_t maxlen);
 #endif
 
 /*
+ * How to tell the compiler that a function is unlikely to be executed.
+ * This differs from unlikely() in that it is applied to a function call,
+ * not a boolean condition.
+ */
+#ifndef HAVE_FUNC_ATTRIBUTE_COLD
+# define unlikely_func __attribute__((cold))
+#else
+# define unlikely_func
+#endif
+
+/*
+ * A fatal function is both unlikely and no_return
+ */
+#define fatal_func no_return unlikely_func
+
+/*
  * How to tell the compiler that a function takes a printf-like string
  */
 #ifdef HAVE_FUNC_ATTRIBUTE_FORMAT
diff --git a/include/error.h b/include/error.h
index c49377eb..55cb1278 100644
--- a/include/error.h
+++ b/include/error.h
@@ -44,9 +44,9 @@
  * An error reporting function should look like this.
  */
 void printf_func(2, 3) nasm_error(int severity, const char *fmt, ...);
-no_return printf_func(2, 3) nasm_fatal(int flags, const char *fmt, ...);
-no_return printf_func(2, 3) nasm_panic(int flags, const char *fmt, ...);
-no_return nasm_panic_from_macro(const char *file, int line);
+fatal_func printf_func(2, 3) nasm_fatal(int flags, const char *fmt, ...);
+fatal_func printf_func(2, 3) nasm_panic(int flags, const char *fmt, ...);
+fatal_func nasm_panic_from_macro(const char *file, int line);
 #define panic() nasm_panic_from_macro(__FILE__, __LINE__);
 
 typedef void (*vefunc) (int severity, const char *fmt, va_list ap);
diff --git a/include/nasmlib.h b/include/nasmlib.h
index 78bb1e48..ae0473a1 100644
--- a/include/nasmlib.h
+++ b/include/nasmlib.h
@@ -111,7 +111,7 @@ void nasm_write(const void *, size_t, FILE *);
 /*
  * NASM assert failure
  */
-no_return nasm_assert_failed(const char *, int, const char *);
+fatal_func nasm_assert_failed(const char *, int, const char *);
 #define nasm_assert(x)                                          \
     do {                                                        \
         if (unlikely(!(x)))                                     \
-- 
2.11.4.GIT