[tip:x86/asm] x86, asm: define CC_SET() and CC_OUT() macros

[tip-bot for H. Peter Anvin]

Commit-ID:  ff3554b409b82d349f71e9d7082648b7b0a1a5bb
Gitweb:     http://git.kernel.org/tip/ff3554b409b82d349f71e9d7082648b7b0a1a5bb
Author:     H. Peter Anvin <hpa@xxxxxxxxx>
AuthorDate: Wed, 8 Jun 2016 12:38:40 -0700
Committer:  H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
CommitDate: Wed, 8 Jun 2016 12:41:20 -0700

x86, asm: define CC_SET() and CC_OUT() macros

The CC_SET() and CC_OUT() macros can be used together to take
advantage of the new __GCC_ASM_FLAG_OUTPUTS__ feature in gcc 6+ while
remaining backwards compatible.  CC_SET() generates a SET instruction
on older compilers; CC_OUT() makes sure the output is received in the
correct variable.

Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxx>
Link: http://lkml.kernel.org/r/1465414726-197858-5-git-send-email-hpa@xxxxxxxxxxxxxxx
Reviewed-by: Andy Lutomirski <luto@xxxxxxxxxx>
Reviewed-by: Borislav Petkov <bp@xxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
 arch/x86/include/asm/asm.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h
index f5063b6..7acb51c 100644
--- a/arch/x86/include/asm/asm.h
+++ b/arch/x86/include/asm/asm.h
@@ -42,6 +42,18 @@
 #define _ASM_SI		__ASM_REG(si)
 #define _ASM_DI		__ASM_REG(di)
 
+/*
+ * Macros to generate condition code outputs from inline assembly,
+ * The output operand must be type "bool".
+ */
+#ifdef __GCC_ASM_FLAG_OUTPUTS__
+# define CC_SET(c) "\n\t/* output condition code " #c "*/\n"
+# define CC_OUT(c) "=@cc" #c
+#else
+# define CC_SET(c) "\n\tset" #c " %[_cc_" #c "]\n"
+# define CC_OUT(c) [_cc_ ## c] "=qm"
+#endif
+
 /* Exception table entry */
 #ifdef __ASSEMBLY__
 # define _ASM_EXTABLE_HANDLE(from, to, handler)			\