From 39cab01994f20e38587d0ef91c9c87f2ef537078 Mon Sep 17 00:00:00 2001 From: Roger Sayle Date: Wed, 14 Jul 2004 13:50:39 +0000 Subject: [PATCH] expmed.c (expand_sdiv_pow2): New function to expand signed division by a positive power of two... * expmed.c (expand_sdiv_pow2): New function to expand signed division by a positive power of two, split out from expand_divmod. Provide an alternate implementation when shifts are expensive. Lower the threshold for using a branchless implementation to BRANCH_COST >= 2. (expand_divmod): Call expand_sdiv_pow2 for suitable divisions. From-SVN: r84686 --- gcc/ChangeLog | 8 ++++++ gcc/expmed.c | 81 ++++++++++++++++++++++++++++++++++++----------------------- 2 files changed, 57 insertions(+), 32 deletions(-) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 6ad49a1..c3fe6c0 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,11 @@ +2004-07-14 Roger Sayle + + * expmed.c (expand_sdiv_pow2): New function to expand signed division + by a positive power of two, split out from expand_divmod. Provide + an alternate implementation when shifts are expensive. Lower the + threshold for using a branchless implementation to BRANCH_COST >= 2. + (expand_divmod): Call expand_sdiv_pow2 for suitable divisions. + 2004-07-14 Paolo Bonzini * tree-dfa.c (make_rename_temp): *Really* work just diff --git a/gcc/expmed.c b/gcc/expmed.c index 45d87f6..d93351d 100644 --- a/gcc/expmed.c +++ b/gcc/expmed.c @@ -52,6 +52,7 @@ static rtx extract_split_bit_field (rtx, unsigned HOST_WIDE_INT, unsigned HOST_WIDE_INT, int); static void do_cmp_and_jump (rtx, rtx, enum rtx_code, enum machine_mode, rtx); static rtx expand_smod_pow2 (enum machine_mode, rtx, HOST_WIDE_INT); +static rtx expand_sdiv_pow2 (enum machine_mode, rtx, HOST_WIDE_INT); /* Nonzero means divides or modulus operations are relatively cheap for powers of two, so don't use branches; emit the operation instead. @@ -3170,6 +3171,53 @@ expand_smod_pow2 (enum machine_mode mode, rtx op0, HOST_WIDE_INT d) emit_label (label); return result; } + +/* Expand signed division of OP0 by a power of two D in mode MODE. + This routine is only called for positive values of D. */ + +static rtx +expand_sdiv_pow2 (enum machine_mode mode, rtx op0, HOST_WIDE_INT d) +{ + rtx temp, label; + tree shift; + int logd; + + logd = floor_log2 (d); + shift = build_int_2 (logd, 0); + + if (d == 2 && BRANCH_COST >= 1) + { + temp = gen_reg_rtx (mode); + temp = emit_store_flag (temp, LT, op0, const0_rtx, mode, 0, 1); + temp = expand_binop (mode, add_optab, temp, op0, NULL_RTX, + 0, OPTAB_LIB_WIDEN); + return expand_shift (RSHIFT_EXPR, mode, temp, shift, NULL_RTX, 0); + } + + if (BRANCH_COST >= 2) + { + int ushift = GET_MODE_BITSIZE (mode) - logd; + + temp = gen_reg_rtx (mode); + temp = emit_store_flag (temp, LT, op0, const0_rtx, mode, 0, -1); + if (shift_cost[mode][ushift] > COSTS_N_INSNS (1)) + temp = expand_binop (mode, and_optab, temp, GEN_INT (d - 1), + NULL_RTX, 0, OPTAB_LIB_WIDEN); + else + temp = expand_shift (RSHIFT_EXPR, mode, temp, + build_int_2 (ushift, 0), NULL_RTX, 1); + temp = expand_binop (mode, add_optab, temp, op0, NULL_RTX, + 0, OPTAB_LIB_WIDEN); + return expand_shift (RSHIFT_EXPR, mode, temp, shift, NULL_RTX, 0); + } + + label = gen_label_rtx (); + temp = copy_to_mode_reg (mode, op0); + do_cmp_and_jump (temp, const0_rtx, GE, mode, label); + expand_inc (temp, GEN_INT (d - 1)); + emit_label (label); + return expand_shift (RSHIFT_EXPR, mode, temp, shift, NULL_RTX, 0); +} /* Emit the code to divide OP0 by OP1, putting the result in TARGET if that is convenient, and returning where the result is. @@ -3582,38 +3630,7 @@ expand_divmod (int rem_flag, enum tree_code code, enum machine_mode mode, if (remainder) return gen_lowpart (mode, remainder); } - lgup = floor_log2 (abs_d); - if (BRANCH_COST < 1 || (abs_d != 2 && BRANCH_COST < 3)) - { - rtx label = gen_label_rtx (); - rtx t1; - - t1 = copy_to_mode_reg (compute_mode, op0); - do_cmp_and_jump (t1, const0_rtx, GE, - compute_mode, label); - expand_inc (t1, gen_int_mode (abs_d - 1, - compute_mode)); - emit_label (label); - quotient = expand_shift (RSHIFT_EXPR, compute_mode, t1, - build_int_2 (lgup, 0), - tquotient, 0); - } - else - { - rtx t1, t2, t3; - t1 = expand_shift (RSHIFT_EXPR, compute_mode, op0, - build_int_2 (size - 1, 0), - NULL_RTX, 0); - t2 = expand_shift (RSHIFT_EXPR, compute_mode, t1, - build_int_2 (size - lgup, 0), - NULL_RTX, 1); - t3 = force_operand (gen_rtx_PLUS (compute_mode, - op0, t2), - NULL_RTX); - quotient = expand_shift (RSHIFT_EXPR, compute_mode, t3, - build_int_2 (lgup, 0), - tquotient, 0); - } + quotient = expand_sdiv_pow2 (compute_mode, op0, abs_d); /* We have computed OP0 / abs(OP1). If OP1 is negative, negate the quotient. */ -- 2.7.4