Index: config/aarch64/aarch64-cost-tables.h =================================================================== --- config/aarch64/aarch64-cost-tables.h (revision 243974) +++ config/aarch64/aarch64-cost-tables.h (working copy) @@ -32,8 +32,8 @@ const struct cpu_cost_table thunderx_ext 0, /* Logical. */ 0, /* Shift. */ 0, /* Shift_reg. */ - COSTS_N_INSNS (1), /* Arith_shift. */ - COSTS_N_INSNS (1), /* Arith_shift_reg. */ + COSTS_N_INSNS (1)+1, /* Arith_shift. */ + COSTS_N_INSNS (1)+1, /* Arith_shift_reg. */ COSTS_N_INSNS (1), /* UNUSED: Log_shift. */ COSTS_N_INSNS (1), /* UNUSED: Log_shift_reg. */ 0, /* Extend. */ Index: config/aarch64/aarch64-tuning-flags.def =================================================================== --- config/aarch64/aarch64-tuning-flags.def (revision 243974) +++ config/aarch64/aarch64-tuning-flags.def (working copy) @@ -35,4 +35,8 @@ two load/stores are not at least 8 byte pairs. */ AARCH64_EXTRA_TUNING_OPTION ("slow_unaligned_ldpw", SLOW_UNALIGNED_LDPW) +/* Logical shift left <=4 with/without zero extend are considered easy + extended, also zero extends without the shift. */ +AARCH64_EXTRA_TUNING_OPTION ("easy_shift_extend", EASY_SHIFT_EXTEND) + #undef AARCH64_EXTRA_TUNING_OPTION Index: config/aarch64/aarch64.c =================================================================== --- config/aarch64/aarch64.c (revision 243974) +++ config/aarch64/aarch64.c (working copy) @@ -714,7 +714,8 @@ static const struct tune_params thunderx 0, /* max_case_values. */ 0, /* cache_line_size. */ tune_params::AUTOPREFETCHER_OFF, /* autoprefetcher_model. */ - (AARCH64_EXTRA_TUNE_SLOW_UNALIGNED_LDPW) /* tune_flags. */ + (AARCH64_EXTRA_TUNE_SLOW_UNALIGNED_LDPW + | AARCH64_EXTRA_TUNE_EASY_SHIFT_EXTEND) /* tune_flags. */ }; static const struct tune_params xgene1_tunings = @@ -5918,9 +5919,10 @@ aarch64_strip_shift (rtx x) /* Helper function for rtx cost calculation. Strip an extend expression from X. Returns the inner operand if successful, or the original expression on failure. We deal with a number of possible - canonicalization variations here. */ + canonicalization variations here. If STRIP_SHIFT is true, then + we can strip off a shift also. */ static rtx -aarch64_strip_extend (rtx x) +aarch64_strip_extend (rtx x, bool strip_shift) { rtx op = x; @@ -5944,7 +5946,8 @@ aarch64_strip_extend (rtx x) /* Now handle extended register, as this may also have an optional left shift by 1..4. */ - if (GET_CODE (op) == ASHIFT + if (strip_shift + && GET_CODE (op) == ASHIFT && CONST_INT_P (XEXP (op, 1)) && ((unsigned HOST_WIDE_INT) INTVAL (XEXP (op, 1))) <= 4) op = XEXP (op, 0); @@ -5968,6 +5971,39 @@ aarch64_shift_p (enum rtx_code code) return code == ASHIFT || code == ASHIFTRT || code == LSHIFTRT; } + +/* Return true iff X is an easy shift without a sign extend. */ + +static bool +aarch64_easy_mult_shift_p (rtx x) +{ + rtx op0, op1; + + op0 = XEXP (x, 0); + op1 = XEXP (x, 1); + + if (!(aarch64_tune_params.extra_tuning_flags + & AARCH64_EXTRA_TUNE_EASY_SHIFT_EXTEND)) + return false; + + if (GET_CODE (op0) == SIGN_EXTEND) + return false; + + if (GET_CODE (x) == ASHIFT && CONST_INT_P (op1) + && UINTVAL (op1) <= 4) + return true; + + if (GET_CODE (x) != MULT || !CONST_INT_P (op1)) + return false; + + HOST_WIDE_INT l2 = exact_log2 (INTVAL (op1)); + + if (l2 > 0 && l2 <= 4) + return true; + + return false; +} + /* Helper function for rtx cost calculation. Calculate the cost of a MULT or ASHIFT, which may be part of a compound PLUS/MINUS rtx. Return the calculated cost of the expression, recursing manually in to @@ -6005,7 +6041,11 @@ aarch64_rtx_mult_cost (rtx x, enum rtx_c { if (compound_p) { - if (REG_P (op1)) + /* If the shift is considered easy, + then don't add any cost. */ + if (aarch64_easy_mult_shift_p (x)) + ; + else if (REG_P (op1)) /* ARITH + shift-by-register. */ cost += extra_cost->alu.arith_shift_reg; else if (is_extend) @@ -6023,7 +6063,7 @@ aarch64_rtx_mult_cost (rtx x, enum rtx_c } /* Strip extends as we will have costed them in the case above. */ if (is_extend) - op0 = aarch64_strip_extend (op0); + op0 = aarch64_strip_extend (op0, true); cost += rtx_cost (op0, VOIDmode, code, 0, speed); @@ -6867,13 +6907,13 @@ cost_minus: if (speed) *cost += extra_cost->alu.extend_arith; - op1 = aarch64_strip_extend (op1); + op1 = aarch64_strip_extend (op1, true); *cost += rtx_cost (op1, VOIDmode, (enum rtx_code) GET_CODE (op1), 0, speed); return true; } - rtx new_op1 = aarch64_strip_extend (op1); + rtx new_op1 = aarch64_strip_extend (op1, false); /* Cost this as an FMA-alike operation. */ if ((GET_CODE (new_op1) == MULT @@ -6946,7 +6986,7 @@ cost_plus: if (speed) *cost += extra_cost->alu.extend_arith; - op0 = aarch64_strip_extend (op0); + op0 = aarch64_strip_extend (op0, true); *cost += rtx_cost (op0, VOIDmode, (enum rtx_code) GET_CODE (op0), 0, speed); return true; @@ -6954,7 +6994,7 @@ cost_plus: /* Strip any extend, leave shifts behind as we will cost them through mult_cost. */ - new_op0 = aarch64_strip_extend (op0); + new_op0 = aarch64_strip_extend (op0, false); if (GET_CODE (new_op0) == MULT || aarch64_shift_p (GET_CODE (new_op0)))