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>
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@7008 c046a42c-6fe2-441c-8c8c-71466251a162
diff --git a/tcg/tcg.c b/tcg/tcg.c
index e550850..c64043f 100644
--- a/tcg/tcg.c
+++ b/tcg/tcg.c
@@ -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);
diff --git a/tcg/tcg.h b/tcg/tcg.h
index cb4911c..c9b001e 100644
--- a/tcg/tcg.h
+++ b/tcg/tcg.h
@@ -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)
