Kconfig: add config option for asm goto w/ outputs

This allows C code to make use of compilers with support for output
variables along the fallthrough path via preprocessor define:

  CONFIG_CC_HAS_ASM_GOTO_OUTPUT

[ This is not used anywhere yet, and currently released compilers don't
  support this yet, but it's coming, and I have some local experimental
  patches to take advantage of it when it does   - Linus ]

Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/init/Kconfig b/init/Kconfig
index 2d12d38cdd88a4f66ead444754fe67d704a604b5..b5294bcba61d341dbe86f0b07f225de39b53271c 100644 (file)
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -36,6 +36,10 @@ config CC_CAN_LINK
 config CC_HAS_ASM_GOTO
        def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
 
+config CC_HAS_ASM_GOTO_OUTPUT
+       depends on CC_HAS_ASM_GOTO
+       def_bool $(success,echo 'int foo(int x) { asm goto ("": "=r"(x) ::: bar); return x; bar: return 0; }' | $(CC) -x c - -c -o /dev/null)
+
 config TOOLS_SUPPORT_RELR
        def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)