From 72a2609f5d7421ab10d04b06f10e78814b0370cc Mon Sep 17 00:00:00 2001 From: Jakub Jelinek Date: Mon, 24 Nov 2008 13:57:37 +0100 Subject: [PATCH] re PR middle-end/37135 (code size increase for struct assignment) PR middle-end/37135 * dse.c (find_shift_sequence): Optimize extraction from a constant. From-SVN: r142157 --- gcc/ChangeLog | 5 +++++ gcc/dse.c | 23 +++++++++++++++++++++++ 2 files changed, 28 insertions(+) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 2f131afa8084..ecb4f628a50b 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,8 @@ +2008-11-24 Jakub Jelinek + + PR middle-end/37135 + * dse.c (find_shift_sequence): Optimize extraction from a constant. + 2008-11-23 John David Anglin * pa.c (function_arg): Revert 2008-10-26 change. diff --git a/gcc/dse.c b/gcc/dse.c index 0a3ebb40ffa4..d7fb2d8aa20c 100644 --- a/gcc/dse.c +++ b/gcc/dse.c @@ -1447,6 +1447,29 @@ find_shift_sequence (int access_size, rtx target, new_reg, shift_seq, insn, new_lhs; int cost; + /* If a constant was stored into memory, try to simplify it here, + otherwise the cost of the shift might preclude this optimization + e.g. at -Os, even when no actual shift will be needed. */ + if (CONSTANT_P (store_info->rhs)) + { + unsigned int byte = subreg_lowpart_offset (new_mode, store_mode); + rtx ret = simplify_subreg (new_mode, store_info->rhs, store_mode, + byte); + if (ret && CONSTANT_P (ret)) + { + ret = simplify_const_binary_operation (LSHIFTRT, new_mode, + ret, GEN_INT (shift)); + if (ret && CONSTANT_P (ret)) + { + byte = subreg_lowpart_offset (read_mode, new_mode); + ret = simplify_subreg (read_mode, ret, new_mode, byte); + if (ret && CONSTANT_P (ret) + && rtx_cost (ret, SET, speed) <= COSTS_N_INSNS (1)) + return ret; + } + } + } + /* Try a wider mode if truncating the store mode to NEW_MODE requires a real instruction. */ if (GET_MODE_BITSIZE (new_mode) < GET_MODE_BITSIZE (store_mode)