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-rw-r--r--include/linux/compiler-gcc.h16
-rw-r--r--include/linux/compiler-intel.h3
-rw-r--r--include/linux/compiler.h4
3 files changed, 22 insertions, 1 deletions
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index cdf13ca7cac3..371e560d13cf 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -9,10 +9,24 @@
+ __GNUC_MINOR__ * 100 \
+ __GNUC_PATCHLEVEL__)
-
/* Optimization barrier */
+
/* The "volatile" is due to gcc bugs */
#define barrier() __asm__ __volatile__("": : :"memory")
+/*
+ * This version is i.e. to prevent dead stores elimination on @ptr
+ * where gcc and llvm may behave differently when otherwise using
+ * normal barrier(): while gcc behavior gets along with a normal
+ * barrier(), llvm needs an explicit input variable to be assumed
+ * clobbered. The issue is as follows: while the inline asm might
+ * access any memory it wants, the compiler could have fit all of
+ * @ptr into memory registers instead, and since @ptr never escaped
+ * from that, it proofed that the inline asm wasn't touching any of
+ * it. This version works well with both compilers, i.e. we're telling
+ * the compiler that the inline asm absolutely may see the contents
+ * of @ptr. See also: https://llvm.org/bugs/show_bug.cgi?id=15495
+ */
+#define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory")
/*
* This macro obfuscates arithmetic on a variable address so that gcc
diff --git a/include/linux/compiler-intel.h b/include/linux/compiler-intel.h
index ba147a1727e6..0c9a2f2c2802 100644
--- a/include/linux/compiler-intel.h
+++ b/include/linux/compiler-intel.h
@@ -13,9 +13,12 @@
/* Intel ECC compiler doesn't support gcc specific asm stmts.
* It uses intrinsics to do the equivalent things.
*/
+#undef barrier_data
#undef RELOC_HIDE
#undef OPTIMIZER_HIDE_VAR
+#define barrier_data(ptr) barrier()
+
#define RELOC_HIDE(ptr, off) \
({ unsigned long __ptr; \
__ptr = (unsigned long) (ptr); \
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 0e41ca0e5927..867722591be2 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -169,6 +169,10 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
# define barrier() __memory_barrier()
#endif
+#ifndef barrier_data
+# define barrier_data(ptr) barrier()
+#endif
+
/* Unreachable code */
#ifndef unreachable
# define unreachable() do { } while (1)