diff options
| -rw-r--r-- | tcg/README | 19 | ||||
| -rw-r--r-- | tcg/optimize.c | 3 | ||||
| -rw-r--r-- | tcg/tcg-op.h | 18 | ||||
| -rw-r--r-- | tcg/tcg.c | 24 | ||||
| -rw-r--r-- | tcg/tcg.h | 26 |
5 files changed, 60 insertions, 30 deletions
diff --git a/tcg/README b/tcg/README index 9d1b100613..ec1ac79375 100644 --- a/tcg/README +++ b/tcg/README @@ -77,11 +77,20 @@ destroyed, but local temporaries and globals are preserved. Using the tcg_gen_helper_x_y it is possible to call any function taking i32, i64 or pointer types. By default, before calling a helper, all globals are stored at their canonical location and it is assumed -that the function can modify them. This can be overridden by the -TCG_CALL_CONST function modifier. By default, the helper is allowed to -modify the CPU state or raise an exception. This can be overridden by -the TCG_CALL_PURE function modifier, in which case the call to the -function is removed if the return value is not used. +that the function can modify them. By default, the helper is allowed to +modify the CPU state or raise an exception. + +This can be overridden using the following function modifiers: +- TCG_CALL_NO_READ_GLOBALS means that the helper does not read globals, + either directly or via an exception. They will not be saved to their + canonical locations before calling the helper. +- TCG_CALL_NO_WRITE_GLOBALS means that the helper does not modify any globals. + They will only be saved to their canonical location before calling helpers, + but they won't be reloaded afterwise. +- TCG_CALL_NO_SIDE_EFFECTS means that the call to the function is removed if + the return value is not used. + +Note that TCG_CALL_NO_READ_GLOBALS implies TCG_CALL_NO_WRITE_GLOBALS. On some TCG targets (e.g. x86), several calling conventions are supported. diff --git a/tcg/optimize.c b/tcg/optimize.c index a06c8eb43e..8e5d918030 100644 --- a/tcg/optimize.c +++ b/tcg/optimize.c @@ -915,7 +915,8 @@ static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t *tcg_opc_ptr, case INDEX_op_call: nb_call_args = (args[0] >> 16) + (args[0] & 0xffff); - if (!(args[nb_call_args + 1] & (TCG_CALL_CONST | TCG_CALL_PURE))) { + if (!(args[nb_call_args + 1] & (TCG_CALL_NO_READ_GLOBALS | + TCG_CALL_NO_WRITE_GLOBALS))) { for (i = 0; i < nb_globals; i++) { reset_temp(i); } diff --git a/tcg/tcg-op.h b/tcg/tcg-op.h index 8100a5a2e0..8d1da2b670 100644 --- a/tcg/tcg-op.h +++ b/tcg/tcg-op.h @@ -401,10 +401,10 @@ static inline void tcg_gen_helperN(void *func, int flags, int sizemask, } /* Note: Both tcg_gen_helper32() and tcg_gen_helper64() are currently - reserved for helpers in tcg-runtime.c. These helpers are all const - and pure, hence the call to tcg_gen_callN() with TCG_CALL_CONST | - TCG_CALL_PURE. This may need to be adjusted if these functions - start to be used with other helpers. */ + reserved for helpers in tcg-runtime.c. These helpers all do not read + globals and do not have side effects, hence the call to tcg_gen_callN() + with TCG_CALL_NO_READ_GLOBALS | TCG_CALL_NO_SIDE_EFFECTS. This may need + to be adjusted if these functions start to be used with other helpers. */ static inline void tcg_gen_helper32(void *func, int sizemask, TCGv_i32 ret, TCGv_i32 a, TCGv_i32 b) { @@ -413,8 +413,9 @@ static inline void tcg_gen_helper32(void *func, int sizemask, TCGv_i32 ret, fn = tcg_const_ptr(func); args[0] = GET_TCGV_I32(a); args[1] = GET_TCGV_I32(b); - tcg_gen_callN(&tcg_ctx, fn, TCG_CALL_CONST | TCG_CALL_PURE, sizemask, - GET_TCGV_I32(ret), 2, args); + tcg_gen_callN(&tcg_ctx, fn, + TCG_CALL_NO_READ_GLOBALS | TCG_CALL_NO_SIDE_EFFECTS, + sizemask, GET_TCGV_I32(ret), 2, args); tcg_temp_free_ptr(fn); } @@ -426,8 +427,9 @@ static inline void tcg_gen_helper64(void *func, int sizemask, TCGv_i64 ret, fn = tcg_const_ptr(func); args[0] = GET_TCGV_I64(a); args[1] = GET_TCGV_I64(b); - tcg_gen_callN(&tcg_ctx, fn, TCG_CALL_CONST | TCG_CALL_PURE, sizemask, - GET_TCGV_I64(ret), 2, args); + tcg_gen_callN(&tcg_ctx, fn, + TCG_CALL_NO_READ_GLOBALS | TCG_CALL_NO_SIDE_EFFECTS, + sizemask, GET_TCGV_I64(ret), 2, args); tcg_temp_free_ptr(fn); } @@ -1251,7 +1251,7 @@ static void tcg_liveness_analysis(TCGContext *s) /* pure functions can be removed if their result is not used */ - if (call_flags & TCG_CALL_PURE) { + if (call_flags & TCG_CALL_NO_SIDE_EFFECTS) { for(i = 0; i < nb_oargs; i++) { arg = args[i]; if (!dead_temps[arg] || mem_temps[arg]) { @@ -1277,11 +1277,15 @@ static void tcg_liveness_analysis(TCGContext *s) dead_temps[arg] = 1; mem_temps[arg] = 0; } - - if (!(call_flags & TCG_CALL_CONST)) { + + if (!(call_flags & TCG_CALL_NO_READ_GLOBALS)) { + /* globals should be synced to memory */ + memset(mem_temps, 1, s->nb_globals); + } + if (!(call_flags & (TCG_CALL_NO_WRITE_GLOBALS | + TCG_CALL_NO_READ_GLOBALS))) { /* globals should go back to memory */ memset(dead_temps, 1, s->nb_globals); - memset(mem_temps, 1, s->nb_globals); } /* input args are live */ @@ -2128,10 +2132,14 @@ static int tcg_reg_alloc_call(TCGContext *s, const TCGOpDef *def, tcg_reg_free(s, reg); } } - - /* store globals and free associated registers (we assume the call - can modify any global. */ - if (!(flags & TCG_CALL_CONST)) { + + /* Save globals if they might be written by the helper, sync them if + they might be read. */ + if (flags & TCG_CALL_NO_READ_GLOBALS) { + /* Nothing to do */ + } else if (flags & TCG_CALL_NO_WRITE_GLOBALS) { + sync_globals(s, allocated_regs); + } else { save_globals(s, allocated_regs); } @@ -253,14 +253,24 @@ typedef int TCGv_i64; #define TCGV_UNUSED_I64(x) x = MAKE_TCGV_I64(-1) /* call flags */ -/* A pure function only reads its arguments and TCG global variables - 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 - global variables. Hence a call to such a function does not - save TCG global variables back to their canonical location. */ -#define TCG_CALL_CONST 0x0020 +/* Helper does not read globals (either directly or through an exception). It + implies TCG_CALL_NO_WRITE_GLOBALS. */ +#define TCG_CALL_NO_READ_GLOBALS 0x0010 +/* Helper does not write globals */ +#define TCG_CALL_NO_WRITE_GLOBALS 0x0020 +/* Helper can be safely suppressed if the return value is not used. */ +#define TCG_CALL_NO_SIDE_EFFECTS 0x0040 + +/* convenience version of most used call flags */ +#define TCG_CALL_NO_RWG TCG_CALL_NO_READ_GLOBALS +#define TCG_CALL_NO_WG TCG_CALL_NO_WRITE_GLOBALS +#define TCG_CALL_NO_SE TCG_CALL_NO_SIDE_EFFECTS +#define TCG_CALL_NO_RWG_SE (TCG_CALL_NO_RWG | TCG_CALL_NO_SE) +#define TCG_CALL_NO_WG_SE (TCG_CALL_NO_WG | TCG_CALL_NO_SE) + +/* compatibility call flags, they should be eventually be removed */ +#define TCG_CALL_PURE TCG_CALL_NO_SIDE_EFFECTS +#define TCG_CALL_CONST TCG_CALL_NO_READ_GLOBALS /* used to align parameters */ #define TCG_CALL_DUMMY_TCGV MAKE_TCGV_I32(-1) |