[PATCH] RISC-V: Increase mult/div cost if not implemented in hardware.
Jim Wilson
jimw@sifive.com
Tue Jan 16 03:05:00 GMT 2018
This increases the cost of multiply and divide when not present. This makes it
more likely that a multiply by constant gets replaced by a sequence of shift
and adds which is faster than a call to a libgcc routine. The divide cost
change doesn't do anything useful at present, but is added for consistency.
This was tested with a make check-gcc. There were no regressions.
Committed.
Jim
2018-01-15 Andrew Waterman <andrew@sifive.com>
gcc/
* config/riscv/riscv.c (riscv_rtx_costs) <MULT>: Increase cost if
!TARGET_MUL.
<UDIV>: Increase cost if !TARGET_DIV.
---
gcc/config/riscv/riscv.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/gcc/config/riscv/riscv.c b/gcc/config/riscv/riscv.c
index d260c0ebae1..19a01e0825a 100644
--- a/gcc/config/riscv/riscv.c
+++ b/gcc/config/riscv/riscv.c
@@ -1615,6 +1615,9 @@ riscv_rtx_costs (rtx x, machine_mode mode, int outer_code, int opno ATTRIBUTE_UN
case MULT:
if (float_mode_p)
*total = tune_info->fp_mul[mode == DFmode];
+ else if (!TARGET_MUL)
+ /* Estimate the cost of a library call. */
+ *total = COSTS_N_INSNS (speed ? 32 : 6);
else if (GET_MODE_SIZE (mode) > UNITS_PER_WORD)
*total = 3 * tune_info->int_mul[0] + COSTS_N_INSNS (2);
else if (!speed)
@@ -1635,7 +1638,10 @@ riscv_rtx_costs (rtx x, machine_mode mode, int outer_code, int opno ATTRIBUTE_UN
case UDIV:
case UMOD:
- if (speed)
+ if (!TARGET_DIV)
+ /* Estimate the cost of a library call. */
+ *total = COSTS_N_INSNS (speed ? 32 : 6);
+ else if (speed)
*total = tune_info->int_div[mode == DImode];
else
*total = COSTS_N_INSNS (1);
--
2.14.1
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