I quite like this patch, it removes more code than it adds back. The results
should look clear
and if we end wishing optimizing a spot we can trade the loop for an inlined
function or macro. [1]
But there are a few things that I dislike about this patch.
--- a/mono/mini/cfold.c
+++ b/mono/mini/cfold.c
@@ -58,13 +58,18 @@ mono_is_power_of_two (guint32 val)
res = (cast)arg1-inst_c0 op (cast)arg2-inst_c0;\
break; \
+#define MONO_INST_NULLIFY_SREGS(dest) do {\
+(dest)-sreg1 = (dest)-sreg2 = (dest)-sreg3 = -1;\
+} while (0)
+
#undef MONO_INST_NEW
#define MONO_INST_NEW(cfg,dest,op) do {\
(dest) = mono_mempool_alloc ((cfg)-mempool, sizeof (MonoInst));
\
(dest)-inst_p0 = (dest)-inst_p1 = (dest)-next = NULL; \
(dest)-opcode = (op);\
(dest)-flags = 0; \
-(dest)-dreg = (dest)-sreg1 = (dest)-sreg2 = -1; \
+(dest)-dreg = -1;\
+MONO_INST_NULLIFY_SREGS ((dest));\
} while (0)
This is pure code duplication, kill it instead of patching.
@@ -138,6 +142,15 @@ ins_info[] = {
#include mini-ops.h
};
#undef MINI_OP
+#undef MINI_OP3
+
+#define MINI_OP(a,b,dest,src1,src2) -1,
+#define MINI_OP3(a,b,dest,src1,src2,src3) -1,
+gint8 ins_sreg_counts[] = {
+#include mini-ops.h
+};
+#undef MINI_OP
+#undef MINI_OP3
This information can be calculated at compile time. All we get from running
mini_init_op_sreg_counts
is an increased private RSS with no advantage. This information should be
packaged in the ins_info array.
@@ -437,7 +450,7 @@ struct MonoInst {
guint8 flags : 5;
/* used by the register allocator */
-gint32 dreg, sreg1, sreg2;
+gint32 dreg, sreg1, sreg2, sreg3;
This change increases the JIT working set significantly. Have you thought
about doing something like
struct MonoCallInst?
It would allow us to have 3 sregs and only pay the size price when needed.
It would be trivial to have
a function to detect such instructions by expanding mini-ops.h to avoid
hitting the ins_info array.
Besides that, I'm eager to have this patch in so I can exploit it on
Mono.Simd :)
[1] Doing something like like:
for (i = 0; i sreg_count (ins); ++i)
z
to
static inline foo() { z } //OR
#define FOO() do { z; } while (0)
if (has_sreg1)
foo ();
if (has_sreg2)
foo ();
if (unlikely (has_sreg3)
foo ();
2009/3/13 Mark Probst mark.pro...@gmail.com
On Mon, Feb 23, 2009 at 10:10 PM, Zoltan Varga var...@gmail.com wrote:
All this to add support for exactly one rarely used instruction, CAS.
As per Paolo's request I timed a --compile-all of
System.Windows.Forms.dll (which I chose instead of mscorlib.dll
because it's larger) with and without the patch. It turns out with
the patch we're about 10% slower. With the attached revised patch,
which uses macros for all the getter functions, the difference is
barely 3% (2.3166s vs 2.2522s, on x86).
Mark
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