Improve how our printk calls do_div by using constants.
The do_div code has a nice optimization in it when it is called with
constants. The current highly generalized use of it defeats those
optimizations and causes trouble on ARM, resulting in a complex and
buggy code path.
Since we only need to print in bases 8, 10, and 16, do a minor
restructuring of the code so that we call do_div with constants.
If you need base 2, print in base 16 and do it in your head. :-)
This fixes an ongoing problem with ARM, will not harm X86, and will
help PPC should we ever want to support it again.
Plus, I don't have to ever try to understand the div64 assembly and where
it's going wrong :-)
Change-Id: I6a480011916eb0834e05c5bb10909d83330fe797
Signed-off-by: Ronald G. Minnich <rminnich@gmail.com>
Reviewed-on: http://review.coreboot.org/2235
Tested-by: build bot (Jenkins)
Reviewed-by: David Hendricks <dhendrix@chromium.org>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
diff --git a/src/console/vtxprintf.c b/src/console/vtxprintf.c
index 28c5a60..9de2584 100644
--- a/src/console/vtxprintf.c
+++ b/src/console/vtxprintf.c
@@ -69,8 +69,22 @@
i = 0;
if (num == 0)
tmp[i++]='0';
- else while (num != 0)
- tmp[i++] = digits[do_div(num,base)];
+ else while (num != 0){
+ /* there are some nice optimizations in the
+ * Macros-From-Hell that form the div64 code
+ * *IF* you call it with a constant.
+ * We're firmware, we only do bases
+ * 8, 10, and 16. Let's be smart.
+ * This greatly helps ARM, reduces the
+ * code footprint at compile time, and does not hurt x86.
+ */
+ if (base == 10)
+ tmp[i++] = digits[do_div(num,10)];
+ else if (base == 8)
+ tmp[i++] = digits[do_div(num,8)];
+ else /* sorry, you're out of choices */
+ tmp[i++] = digits[do_div(num,16)];
+ }
if (i > precision)
precision = i;
size -= precision;