Some uses of ALTERNATIVE() may depend on a feature that is disabled at
compile time by a Kconfig option. In this case the unused alternative
instructions waste space, and if the original instruction is a nop, it
wastes time and space.
This patch adds an optional 'config' option to ALTERNATIVE() and
alternative_insn that allows the compiler to remove both the original
and alternative instructions if the config option is not defined.
Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
+#include <linux/kconfig.h>
#include <linux/types.h>
#include <linux/stddef.h>
#include <linux/stringify.h>
#include <linux/types.h>
#include <linux/stddef.h>
#include <linux/stringify.h>
* be fixed in a binutils release posterior to 2.25.51.0.2 (anything
* containing commit 4e4d08cf7399b606 or c1baaddf8861).
*/
* be fixed in a binutils release posterior to 2.25.51.0.2 (anything
* containing commit 4e4d08cf7399b606 or c1baaddf8861).
*/
-#define ALTERNATIVE(oldinstr, newinstr, feature) \
+#define __ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg_enabled) \
+ ".if "__stringify(cfg_enabled)" == 1\n" \
"661:\n\t" \
oldinstr "\n" \
"662:\n" \
"661:\n\t" \
oldinstr "\n" \
"662:\n" \
"664:\n\t" \
".popsection\n\t" \
".org . - (664b-663b) + (662b-661b)\n\t" \
"664:\n\t" \
".popsection\n\t" \
".org . - (664b-663b) + (662b-661b)\n\t" \
- ".org . - (662b-661b) + (664b-663b)\n"
+ ".org . - (662b-661b) + (664b-663b)\n" \
+ ".endif\n"
+
+#define _ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg, ...) \
+ __ALTERNATIVE_CFG(oldinstr, newinstr, feature, IS_ENABLED(cfg))
-.macro alternative_insn insn1 insn2 cap
+.macro alternative_insn insn1, insn2, cap, enable = 1
+ .if \enable
661: \insn1
662: .pushsection .altinstructions, "a"
altinstruction_entry 661b, 663f, \cap, 662b-661b, 664f-663f
661: \insn1
662: .pushsection .altinstructions, "a"
altinstruction_entry 661b, 663f, \cap, 662b-661b, 664f-663f
664: .popsection
.org . - (664b-663b) + (662b-661b)
.org . - (662b-661b) + (664b-663b)
664: .popsection
.org . - (664b-663b) + (662b-661b)
.org . - (662b-661b) + (664b-663b)
.org . - (662b-661b) + (664b-663b)
.endm
.org . - (662b-661b) + (664b-663b)
.endm
+#define _ALTERNATIVE_CFG(insn1, insn2, cap, cfg, ...) \
+ alternative_insn insn1, insn2, cap, IS_ENABLED(cfg)
+
+
#endif /* __ASSEMBLY__ */
#endif /* __ASSEMBLY__ */
+/*
+ * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature));
+ *
+ * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature, CONFIG_FOO));
+ * N.B. If CONFIG_FOO is specified, but not selected, the whole block
+ * will be omitted, including oldinstr.
+ */
+#define ALTERNATIVE(oldinstr, newinstr, ...) \
+ _ALTERNATIVE_CFG(oldinstr, newinstr, __VA_ARGS__, 1)
+
#endif /* __ASM_ALTERNATIVE_H */
#endif /* __ASM_ALTERNATIVE_H */