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parisc: fix out-of-register compiler error in ldcw inline assembler function
The __ldcw macro has a problem when its argument needs to be reloaded from memory. The output memory operand and the input register operand both need to be reloaded using a register in class R1_REGS when generating 64-bit code. This fails because there's only a single register in the class. Instead, use a memory clobber. This also makes the __ldcw macro a compiler memory barrier. Signed-off-by: John David Anglin <dave.anglin@bell.net> Cc: <stable@vger.kernel.org> [3.13+] Signed-off-by: Helge Deller <deller@gmx.de>
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1 changed files with 10 additions and 3 deletions
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@ -33,11 +33,18 @@
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#endif /*!CONFIG_PA20*/
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/* LDCW, the only atomic read-write operation PA-RISC has. *sigh*. */
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/* LDCW, the only atomic read-write operation PA-RISC has. *sigh*.
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We don't explicitly expose that "*a" may be written as reload
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fails to find a register in class R1_REGS when "a" needs to be
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reloaded when generating 64-bit PIC code. Instead, we clobber
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memory to indicate to the compiler that the assembly code reads
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or writes to items other than those listed in the input and output
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operands. This may pessimize the code somewhat but __ldcw is
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usually used within code blocks surrounded by memory barriors. */
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#define __ldcw(a) ({ \
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unsigned __ret; \
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__asm__ __volatile__(__LDCW " 0(%2),%0" \
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: "=r" (__ret), "+m" (*(a)) : "r" (a)); \
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__asm__ __volatile__(__LDCW " 0(%1),%0" \
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: "=r" (__ret) : "r" (a) : "memory"); \
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__ret; \
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})
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