Commit b9c18f56585ab146c6a25084bce00e4c52eefcc6
1 parent
34d5a9ff
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
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12 additions
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4 deletions
tcg/tcg.c
@@ -1122,9 +1122,11 @@ static void tcg_liveness_analysis(TCGContext *s) | @@ -1122,9 +1122,11 @@ static void tcg_liveness_analysis(TCGContext *s) | ||
1122 | dead_temps[arg] = 1; | 1122 | dead_temps[arg] = 1; |
1123 | } | 1123 | } |
1124 | 1124 | ||
1125 | - /* globals are live (they may be used by the call) */ | ||
1126 | - memset(dead_temps, 0, s->nb_globals); | ||
1127 | - | 1125 | + if (!(call_flags & TCG_CALL_CONST)) { |
1126 | + /* globals are live (they may be used by the call) */ | ||
1127 | + memset(dead_temps, 0, s->nb_globals); | ||
1128 | + } | ||
1129 | + | ||
1128 | /* input args are live */ | 1130 | /* input args are live */ |
1129 | dead_iargs = 0; | 1131 | dead_iargs = 0; |
1130 | for(i = 0; i < nb_iargs; i++) { | 1132 | for(i = 0; i < nb_iargs; i++) { |
@@ -1821,7 +1823,9 @@ static int tcg_reg_alloc_call(TCGContext *s, const TCGOpDef *def, | @@ -1821,7 +1823,9 @@ static int tcg_reg_alloc_call(TCGContext *s, const TCGOpDef *def, | ||
1821 | 1823 | ||
1822 | /* store globals and free associated registers (we assume the call | 1824 | /* store globals and free associated registers (we assume the call |
1823 | can modify any global. */ | 1825 | can modify any global. */ |
1824 | - save_globals(s, allocated_regs); | 1826 | + if (!(flags & TCG_CALL_CONST)) { |
1827 | + save_globals(s, allocated_regs); | ||
1828 | + } | ||
1825 | 1829 | ||
1826 | tcg_out_op(s, opc, &func_arg, &const_func_arg); | 1830 | tcg_out_op(s, opc, &func_arg, &const_func_arg); |
1827 | 1831 |
tcg/tcg.h
@@ -178,6 +178,10 @@ typedef int TCGv_i64; | @@ -178,6 +178,10 @@ typedef int TCGv_i64; | ||
178 | and cannot raise exceptions. Hence a call to a pure function can be | 178 | and cannot raise exceptions. Hence a call to a pure function can be |
179 | safely suppressed if the return value is not used. */ | 179 | safely suppressed if the return value is not used. */ |
180 | #define TCG_CALL_PURE 0x0010 | 180 | #define TCG_CALL_PURE 0x0010 |
181 | +/* A const function only reads its arguments and does not use TCG | ||
182 | + globals variables. Hence a call to such a function does not | ||
183 | + save TCG globals variabes back to their canonical location. */ | ||
184 | +#define TCG_CALL_CONST 0x0020 | ||
181 | 185 | ||
182 | /* used to align parameters */ | 186 | /* used to align parameters */ |
183 | #define TCG_CALL_DUMMY_TCGV MAKE_TCGV_I32(-1) | 187 | #define TCG_CALL_DUMMY_TCGV MAKE_TCGV_I32(-1) |