Hi all,
There are other places besides expand where we might want to synthesize an
integer
multiplication by a constant. Thankfully the algorithm selection code in
expmed.c
is already quite well separated from the RTL implementation, so if we can just
factor
out the prototype of choose_mult_variant and some enums and structs that it
needs into
a separate header file we can reuse them from other parts of the compiler.
I need this for patch 2/2 which hooks up the vectorizer to synthesize vector
multiplications using sequences of shifts and other arithmetic ops when
appropriate.
The new header is called mult-synthesis.h. Should I add it to some makefile?
grepping around for a bit I'm not sure what to do about it.
Bootstrapped and tested on arm, aarch64, x86_64.
Thanks,
Kyrill
2016-06-13 Kyrylo Tkachov <kyrylo.tkac...@arm.com>
* mult-synthesis.h: New file. Add choose_mult_variant prototype.
* expmed.h: Include mult-synthesis.h
(enum alg_code): Move to mult-synthesis.h
(struct mult_cost): Likewise.
(struct algorithm): Likewise.
* expmed.c (enum mult_variant): Move to mult-synthesis.h
(choose_mult_variant): Delete prototype. Remove static qualifier.
diff --git a/gcc/expmed.h b/gcc/expmed.h
index 1a32e9f1b664f250c5092022eb965237ed0342fc..304ce02d78a9e3e024c13caee7869d67dfdab65c 100644
--- a/gcc/expmed.h
+++ b/gcc/expmed.h
@@ -21,35 +21,7 @@ along with GCC; see the file COPYING3. If not see
#define EXPMED_H 1
#include "insn-codes.h"
-
-enum alg_code {
- alg_unknown,
- alg_zero,
- alg_m, alg_shift,
- alg_add_t_m2,
- alg_sub_t_m2,
- alg_add_factor,
- alg_sub_factor,
- alg_add_t2_m,
- alg_sub_t2_m,
- alg_impossible
-};
-
-/* This structure holds the "cost" of a multiply sequence. The
- "cost" field holds the total rtx_cost of every operator in the
- synthetic multiplication sequence, hence cost(a op b) is defined
- as rtx_cost(op) + cost(a) + cost(b), where cost(leaf) is zero.
- The "latency" field holds the minimum possible latency of the
- synthetic multiply, on a hypothetical infinitely parallel CPU.
- This is the critical path, or the maximum height, of the expression
- tree which is the sum of rtx_costs on the most expensive path from
- any leaf to the root. Hence latency(a op b) is defined as zero for
- leaves and rtx_cost(op) + max(latency(a), latency(b)) otherwise. */
-
-struct mult_cost {
- short cost; /* Total rtx_cost of the multiplication sequence. */
- short latency; /* The latency of the multiplication sequence. */
-};
+#include "mult-synthesis.h"
/* This macro is used to compare a pointer to a mult_cost against an
single integer "rtx_cost" value. This is equivalent to the macro
@@ -65,38 +37,6 @@ struct mult_cost {
|| ((X)->cost == (Y)->cost \
&& (X)->latency < (Y)->latency))
-/* This structure records a sequence of operations.
- `ops' is the number of operations recorded.
- `cost' is their total cost.
- The operations are stored in `op' and the corresponding
- logarithms of the integer coefficients in `log'.
-
- These are the operations:
- alg_zero total := 0;
- alg_m total := multiplicand;
- alg_shift total := total * coeff
- alg_add_t_m2 total := total + multiplicand * coeff;
- alg_sub_t_m2 total := total - multiplicand * coeff;
- alg_add_factor total := total * coeff + total;
- alg_sub_factor total := total * coeff - total;
- alg_add_t2_m total := total * coeff + multiplicand;
- alg_sub_t2_m total := total * coeff - multiplicand;
-
- The first operand must be either alg_zero or alg_m. */
-
-struct algorithm
-{
- struct mult_cost cost;
- short ops;
- /* The size of the OP and LOG fields are not directly related to the
- word size, but the worst-case algorithms will be if we have few
- consecutive ones or zeros, i.e., a multiplicand like 10101010101...
- In that case we will generate shift-by-2, add, shift-by-2, add,...,
- in total wordsize operations. */
- enum alg_code op[MAX_BITS_PER_WORD];
- char log[MAX_BITS_PER_WORD];
-};
-
/* The entry for our multiplication cache/hash table. */
struct alg_hash_entry {
/* The number we are multiplying by. */
diff --git a/gcc/expmed.c b/gcc/expmed.c
index 6645a535b3eef9624e6f3ce61d2fcf864d1cf574..22564fa423aec52febef6220d3f59a82e09b118a 100644
--- a/gcc/expmed.c
+++ b/gcc/expmed.c
@@ -2482,16 +2482,9 @@ expand_variable_shift (enum tree_code code, machine_mode mode, rtx shifted,
}
-/* Indicates the type of fixup needed after a constant multiplication.
- BASIC_VARIANT means no fixup is needed, NEGATE_VARIANT means that
- the result should be negated, and ADD_VARIANT means that the
- multiplicand should be added to the result. */
-enum mult_variant {basic_variant, negate_variant, add_variant};
static void synth_mult (struct algorithm *, unsigned HOST_WIDE_INT,
const struct mult_cost *, machine_mode mode);
-static bool choose_mult_variant (machine_mode, HOST_WIDE_INT,
- struct algorithm *, enum mult_variant *, int);
static rtx expand_mult_const (machine_mode, rtx, HOST_WIDE_INT, rtx,
const struct algorithm *, enum mult_variant);
static unsigned HOST_WIDE_INT invert_mod2n (unsigned HOST_WIDE_INT, int);
@@ -2981,7 +2974,7 @@ synth_mult (struct algorithm *alg_out, unsigned HOST_WIDE_INT t,
Return true if the cheapest of these cost less than MULT_COST,
describing the algorithm in *ALG and final fixup in *VARIANT. */
-static bool
+bool
choose_mult_variant (machine_mode mode, HOST_WIDE_INT val,
struct algorithm *alg, enum mult_variant *variant,
int mult_cost)
diff --git a/gcc/mult-synthesis.h b/gcc/mult-synthesis.h
new file mode 100644
index 0000000000000000000000000000000000000000..cd0e46176805dabeac0c71c5a16f9bfb8ee1356e
--- /dev/null
+++ b/gcc/mult-synthesis.h
@@ -0,0 +1,94 @@
+/* Multiplication synthesis utilities.
+ Copyright (C) 1987-2016 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3. If not see
+<http://www.gnu.org/licenses/>. */
+
+#ifndef GCC_MULT_SYNTHESIS_H
+#define GCC_MULT_SYNTHESIS_H 1
+
+enum alg_code {
+ alg_unknown,
+ alg_zero,
+ alg_m, alg_shift,
+ alg_add_t_m2,
+ alg_sub_t_m2,
+ alg_add_factor,
+ alg_sub_factor,
+ alg_add_t2_m,
+ alg_sub_t2_m,
+ alg_impossible
+};
+
+/* Indicates the type of fixup needed after a constant multiplication.
+ BASIC_VARIANT means no fixup is needed, NEGATE_VARIANT means that
+ the result should be negated, and ADD_VARIANT means that the
+ multiplicand should be added to the result. */
+enum mult_variant {basic_variant, negate_variant, add_variant};
+
+/* This structure holds the "cost" of a multiply sequence. The
+ "cost" field holds the total rtx_cost of every operator in the
+ synthetic multiplication sequence, hence cost (a op b) is defined
+ as rtx_cost (op) + cost (a) + cost (b), where cost (leaf) is zero.
+ The "latency" field holds the minimum possible latency of the
+ synthetic multiply, on a hypothetical infinitely parallel CPU.
+ This is the critical path, or the maximum height, of the expression
+ tree which is the sum of rtx_costs on the most expensive path from
+ any leaf to the root. Hence latency (a op b) is defined as zero for
+ leaves and rtx_cost (op) + max (latency (a), latency (b)) otherwise. */
+
+struct mult_cost {
+ short cost; /* Total rtx_cost of the multiplication sequence. */
+ short latency; /* The latency of the multiplication sequence. */
+};
+
+/* This structure records a sequence of operations.
+ `ops' is the number of operations recorded.
+ `cost' is their total cost.
+ The operations are stored in `op' and the corresponding
+ logarithms of the integer coefficients in `log'.
+
+ These are the operations:
+ alg_zero total := 0;
+ alg_m total := multiplicand;
+ alg_shift total := total * coeff
+ alg_add_t_m2 total := total + multiplicand * coeff;
+ alg_sub_t_m2 total := total - multiplicand * coeff;
+ alg_add_factor total := total * coeff + total;
+ alg_sub_factor total := total * coeff - total;
+ alg_add_t2_m total := total * coeff + multiplicand;
+ alg_sub_t2_m total := total * coeff - multiplicand;
+
+ The first operand must be either alg_zero or alg_m. */
+
+struct algorithm
+{
+ struct mult_cost cost;
+ short ops;
+ /* The size of the OP and LOG fields are not directly related to the
+ word size, but the worst-case algorithms will be if we have few
+ consecutive ones or zeros, i.e., a multiplicand like 10101010101...
+ In that case we will generate shift-by-2, add, shift-by-2, add,...,
+ in total wordsize operations. */
+ enum alg_code op[MAX_BITS_PER_WORD];
+ char log[MAX_BITS_PER_WORD];
+};
+
+/* Defined in expmed.c. */
+bool choose_mult_variant (machine_mode, HOST_WIDE_INT, struct algorithm *,
+ mult_variant *, int);
+
+#endif /* ifdef GCC_MULT_SYNTHESIS_H. */
