[PATCH 02/25] tracing: Improve "if" macro code generation

[Peter Zijlstra]

With CONFIG_PROFILE_ALL_BRANCHES, the "if" macro converts the
conditional to an array index.  This can cause GCC to create horrible
code.  When there are nested ifs, the generated code uses register
values to encode branching decisions.

Make it easier for GCC to optimize by keeping the conditional as a
conditional rather than converting it to an integer.  This shrinks the
generated code quite a bit, and also makes the code sane enough for
objtool to understand.

Cc: rostedt@xxxxxxxxxxx
Cc: valentin.schneider@xxxxxxx
Cc: luto@xxxxxxxxxxxxxx
Cc: brgerst@xxxxxxxxx
Cc: catalin.marinas@xxxxxxx
Cc: mingo@xxxxxxxxxx
Cc: dvlasenk@xxxxxxxxxx
Cc: will.deacon@xxxxxxx
Cc: julien.thierry@xxxxxxx
Cc: torvalds@xxxxxxxxxxxxxxxxxxxx
Cc: dvyukov@xxxxxxxxxx
Cc: bp@xxxxxxxxx
Cc: tglx@xxxxxxxxxxxxx
Cc: james.morse@xxxxxxx
Cc: luto@xxxxxxxxxx
Cc: hpa@xxxxxxxxx
Reported-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20190307174802.46fmpysxyo35hh43@treble
---
 include/linux/compiler.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -67,7 +67,7 @@ void ftrace_likely_update(struct ftrace_
 				.line = __LINE__,			\
 			};						\
 		______r = !!(cond);					\
-		______f.miss_hit[______r]++;					\
+		______r ? ______f.miss_hit[1]++ : ______f.miss_hit[0]++;\
 		______r;						\
 	}))
 #endif /* CONFIG_PROFILE_ALL_BRANCHES */