parisc: fix out-of-register compiler error in ldcw inline assembler function

[cascardo/linux.git] / arch / parisc / include / asm / ldcw.h

diff --git a/arch/parisc/include/asm/ldcw.h b/arch/parisc/include/asm/ldcw.h
index d2d11b7..8121aa6 100644 (file)
--- a/arch/parisc/include/asm/ldcw.h
+++ b/arch/parisc/include/asm/ldcw.h
@@ -33,11 +33,18 @@
 
 #endif /*!CONFIG_PA20*/
 
-/* LDCW, the only atomic read-write operation PA-RISC has. *sigh*.  */
+/* LDCW, the only atomic read-write operation PA-RISC has. *sigh*.
+   We don't explicitly expose that "*a" may be written as reload
+   fails to find a register in class R1_REGS when "a" needs to be
+   reloaded when generating 64-bit PIC code.  Instead, we clobber
+   memory to indicate to the compiler that the assembly code reads
+   or writes to items other than those listed in the input and output
+   operands.  This may pessimize the code somewhat but __ldcw is
+   usually used within code blocks surrounded by memory barriors.  */
 #define __ldcw(a) ({                                           \
        unsigned __ret;                                         \
-       __asm__ __volatile__(__LDCW " 0(%2),%0"                 \
-               : "=r" (__ret), "+m" (*(a)) : "r" (a));         \
+       __asm__ __volatile__(__LDCW " 0(%1),%0"                 \
+               : "=r" (__ret) : "r" (a) : "memory");           \
        __ret;                                                  \
 })