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| author | Richard Earnshaw <rearnsha@arm.com> | 2019-10-18 19:02:50 +0000 |
|---|---|---|
| committer | Richard Earnshaw <rearnsha@gcc.gnu.org> | 2019-10-18 19:02:50 +0000 |
| commit | bbead5babc046279d886b059e68e613b0185b2ff (patch) | |
| tree | 124a99d80876a893377cb89eb847f09c6eca55f6 /gcc/config | |
| parent | 0a67306e3cc2adfe0ef2fe313a86f57141ab57b2 (diff) | |
| download | gcc-bbead5babc046279d886b059e68e613b0185b2ff.zip gcc-bbead5babc046279d886b059e68e613b0185b2ff.tar.gz gcc-bbead5babc046279d886b059e68e613b0185b2ff.tar.bz2 | |
[arm] Correct cost calculations involving borrow for subtracts.
The rtx_cost calculations when a borrow operation was being performed were
not being calculated correctly. The borrow is free as part of the
subtract-with-carry instructions. This patch recognizes the various
idioms that can describe this and returns the correct costs.
* config/arm/arm.c (arm_rtx_costs_internal, case MINUS): Handle
borrow operations.
From-SVN: r277173
Diffstat (limited to 'gcc/config')
| -rw-r--r-- | gcc/config/arm/arm.c | 49 |
1 files changed, 42 insertions, 7 deletions
diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c index 820a41f..fd74222 100644 --- a/gcc/config/arm/arm.c +++ b/gcc/config/arm/arm.c @@ -10049,15 +10049,46 @@ arm_rtx_costs_internal (rtx x, enum rtx_code code, enum rtx_code outer_code, rtx shift_by_reg = NULL; rtx shift_op; rtx non_shift_op; + rtx op0 = XEXP (x, 0); + rtx op1 = XEXP (x, 1); - shift_op = shifter_op_p (XEXP (x, 0), &shift_by_reg); + /* Factor out any borrow operation. There's more than one way + of expressing this; try to recognize them all. */ + if (GET_CODE (op0) == MINUS) + { + if (arm_borrow_operation (op1, SImode)) + { + op1 = XEXP (op0, 1); + op0 = XEXP (op0, 0); + } + else if (arm_borrow_operation (XEXP (op0, 1), SImode)) + op0 = XEXP (op0, 0); + } + else if (GET_CODE (op1) == PLUS + && arm_borrow_operation (XEXP (op1, 0), SImode)) + op1 = XEXP (op1, 0); + else if (GET_CODE (op0) == NEG + && arm_borrow_operation (op1, SImode)) + { + /* Negate with carry-in. For Thumb2 this is done with + SBC R, X, X lsl #1 (ie X - 2X - C) as Thumb lacks the + RSC instruction that exists in Arm mode. */ + if (speed_p) + *cost += (TARGET_THUMB2 + ? extra_cost->alu.arith_shift + : extra_cost->alu.arith); + *cost += rtx_cost (XEXP (op0, 0), mode, MINUS, 0, speed_p); + return true; + } + + shift_op = shifter_op_p (op0, &shift_by_reg); if (shift_op == NULL) { - shift_op = shifter_op_p (XEXP (x, 1), &shift_by_reg); - non_shift_op = XEXP (x, 0); + shift_op = shifter_op_p (op1, &shift_by_reg); + non_shift_op = op0; } else - non_shift_op = XEXP (x, 1); + non_shift_op = op1; if (shift_op != NULL) { @@ -10087,10 +10118,10 @@ arm_rtx_costs_internal (rtx x, enum rtx_code code, enum rtx_code outer_code, return true; } - if (CONST_INT_P (XEXP (x, 0))) + if (CONST_INT_P (op0)) { int insns = arm_gen_constant (MINUS, SImode, NULL_RTX, - INTVAL (XEXP (x, 0)), NULL_RTX, + INTVAL (op0), NULL_RTX, NULL_RTX, 1, 0); *cost = COSTS_N_INSNS (insns); if (speed_p) @@ -10101,7 +10132,11 @@ arm_rtx_costs_internal (rtx x, enum rtx_code code, enum rtx_code outer_code, else if (speed_p) *cost += extra_cost->alu.arith; - return false; + /* Don't recurse as we don't want to cost any borrow that + we've stripped. */ + *cost += rtx_cost (op0, mode, MINUS, 0, speed_p); + *cost += rtx_cost (op1, mode, MINUS, 1, speed_p); + return true; } if (GET_MODE_CLASS (mode) == MODE_INT |