From: Aurelien Jarno <aurelien@aurel32.net>
To: qemu-devel@nongnu.org
Subject: [Qemu-devel] [7008] tcg: add a CONST flag to TCG helpers
Date: Mon, 06 Apr 2009 12:34:00 +0000 [thread overview]
Message-ID: <E1Lqo1Y-0004XW-D4@cvs.savannah.gnu.org> (raw)
Revision: 7008
http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=7008
Author: aurel32
Date: 2009-04-06 12:33:59 +0000 (Mon, 06 Apr 2009)
Log Message:
-----------
tcg: add a CONST flag to TCG helpers
A const function only reads its arguments and does not use TCG
globals variables. Hence a call to such a function does not
save TCG globals variabes back to their canonical location.
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Modified Paths:
--------------
trunk/tcg/tcg.c
trunk/tcg/tcg.h
Modified: trunk/tcg/tcg.c
===================================================================
--- trunk/tcg/tcg.c 2009-04-06 12:33:51 UTC (rev 7007)
+++ trunk/tcg/tcg.c 2009-04-06 12:33:59 UTC (rev 7008)
@@ -1122,9 +1122,11 @@
dead_temps[arg] = 1;
}
- /* globals are live (they may be used by the call) */
- memset(dead_temps, 0, s->nb_globals);
-
+ if (!(call_flags & TCG_CALL_CONST)) {
+ /* globals are live (they may be used by the call) */
+ memset(dead_temps, 0, s->nb_globals);
+ }
+
/* input args are live */
dead_iargs = 0;
for(i = 0; i < nb_iargs; i++) {
@@ -1821,7 +1823,9 @@
/* store globals and free associated registers (we assume the call
can modify any global. */
- save_globals(s, allocated_regs);
+ if (!(flags & TCG_CALL_CONST)) {
+ save_globals(s, allocated_regs);
+ }
tcg_out_op(s, opc, &func_arg, &const_func_arg);
Modified: trunk/tcg/tcg.h
===================================================================
--- trunk/tcg/tcg.h 2009-04-06 12:33:51 UTC (rev 7007)
+++ trunk/tcg/tcg.h 2009-04-06 12:33:59 UTC (rev 7008)
@@ -178,6 +178,10 @@
and cannot raise exceptions. Hence a call to a pure function can be
safely suppressed if the return value is not used. */
#define TCG_CALL_PURE 0x0010
+/* A const function only reads its arguments and does not use TCG
+ globals variables. Hence a call to such a function does not
+ save TCG globals variabes back to their canonical location. */
+#define TCG_CALL_CONST 0x0020
/* used to align parameters */
#define TCG_CALL_DUMMY_TCGV MAKE_TCGV_I32(-1)
reply other threads:[~2009-04-06 12:34 UTC|newest]
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