On Wed, 30 Jun 2010, Marcel Moolenaar wrote:
On Jun 30, 2010, at 2:40 AM, Bruce Evans wrote:
On Wed, 30 Jun 2010, Marcel Moolenaar wrote:
Log:
On powerpc, calculate s_scale using the non-FP version previously
specific to hp300. Since FreeBSD does not support hp300, hp300 has
been removed from the condition altogether.
Also, the style of the condition has been regressed from ifndef to
if !defined().
That's on purpose. Either we eliminate the whole conditional or we
end up adding other platforms to it.
Better to inhibit such mistakes. It's almost a sign of a mistake that
there is a long list of platforms in an ifdef.
...
Better still, rewrite the integer method using a C99 type, so that it
is as simple as the FP method:
s_scale = ((uintmax_t)p->kcountsize << SCALE_SHIFT) / o;
C99 uintmax_t now guarantees uintmax_t to have >= 64 bits, and practical
considerations guarantee p->kcountsize to fit in many fewer than 48 bits
even on 64-bit arches, so the shift cannot overflow.
I like this. What about the following (white-space corrupted)
simplification:
Almost OK. I orginally wrote it with a conditional operator, but decided
that that might be harder to understand.
Index: gmon.c
===================================================================
--- gmon.c (revision 209604)
+++ gmon.c (working copy)
@@ -110,24 +110,9 @@
p->tos[0].link = 0;
o = p->highpc - p->lowpc;
- if (p->kcountsize < o) {
-#if !defined(__powerpc__)
- s_scale = ((float)p->kcountsize / o ) * SCALE_1_TO_1;
-#else /* avoid floating point */
- int quot = o / p->kcountsize;
+ s_scale = (p->kcountsize < o) ?
+ ((uintmax_t)p->kcountsize << SCALE_1_TO_1) / o : SCALE_1_TO_1;
Shifting by 65536 is a bit much :-). Multiplication by 65536 might
give the same code as shifting by 16, but I think shifting is clearer.
The kernel uses shifting for the reverse conversion, with `16' hard-coded
in 2 statements and 2 comments, and with too much duplication in the
comments.
Remove this blank line too.
- if (quot >= 0x10000)
- s_scale = 1;
...
Bruce
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