diff options
Diffstat (limited to 'gcc/expr.c')
| -rw-r--r-- | gcc/expr.c | 74 |
1 files changed, 74 insertions, 0 deletions
@@ -3814,6 +3814,80 @@ emit_move_insn (rtx x, rtx y) gcc_assert (mode != BLKmode && (GET_MODE (y) == mode || GET_MODE (y) == VOIDmode)); + /* If we have a copy that looks like one of the following patterns: + (set (subreg:M1 (reg:M2 ...)) (subreg:M1 (reg:M2 ...))) + (set (subreg:M1 (reg:M2 ...)) (mem:M1 ADDR)) + (set (mem:M1 ADDR) (subreg:M1 (reg:M2 ...))) + (set (subreg:M1 (reg:M2 ...)) (constant C)) + where mode M1 is equal in size to M2, try to detect whether the + mode change involves an implicit round trip through memory. + If so, see if we can avoid that by removing the subregs and + doing the move in mode M2 instead. */ + + rtx x_inner = NULL_RTX; + rtx y_inner = NULL_RTX; + + auto candidate_subreg_p = [&](rtx subreg) { + return (REG_P (SUBREG_REG (subreg)) + && known_eq (GET_MODE_SIZE (GET_MODE (SUBREG_REG (subreg))), + GET_MODE_SIZE (GET_MODE (subreg))) + && optab_handler (mov_optab, GET_MODE (SUBREG_REG (subreg))) + != CODE_FOR_nothing); + }; + + auto candidate_mem_p = [&](machine_mode innermode, rtx mem) { + return (!targetm.can_change_mode_class (innermode, GET_MODE (mem), ALL_REGS) + && !push_operand (mem, GET_MODE (mem)) + /* Not a candiate if innermode requires too much alignment. */ + && (MEM_ALIGN (mem) >= GET_MODE_ALIGNMENT (innermode) + || targetm.slow_unaligned_access (GET_MODE (mem), + MEM_ALIGN (mem)) + || !targetm.slow_unaligned_access (innermode, + MEM_ALIGN (mem)))); + }; + + if (SUBREG_P (x) && candidate_subreg_p (x)) + x_inner = SUBREG_REG (x); + + if (SUBREG_P (y) && candidate_subreg_p (y)) + y_inner = SUBREG_REG (y); + + if (x_inner != NULL_RTX + && y_inner != NULL_RTX + && GET_MODE (x_inner) == GET_MODE (y_inner) + && !targetm.can_change_mode_class (GET_MODE (x_inner), mode, ALL_REGS)) + { + x = x_inner; + y = y_inner; + mode = GET_MODE (x_inner); + } + else if (x_inner != NULL_RTX + && MEM_P (y) + && candidate_mem_p (GET_MODE (x_inner), y)) + { + x = x_inner; + y = adjust_address (y, GET_MODE (x_inner), 0); + mode = GET_MODE (x_inner); + } + else if (y_inner != NULL_RTX + && MEM_P (x) + && candidate_mem_p (GET_MODE (y_inner), x)) + { + x = adjust_address (x, GET_MODE (y_inner), 0); + y = y_inner; + mode = GET_MODE (y_inner); + } + else if (x_inner != NULL_RTX + && CONSTANT_P (y) + && !targetm.can_change_mode_class (GET_MODE (x_inner), + mode, ALL_REGS) + && (y_inner = simplify_subreg (GET_MODE (x_inner), y, mode, 0))) + { + x = x_inner; + y = y_inner; + mode = GET_MODE (x_inner); + } + if (CONSTANT_P (y)) { if (optimize |