Skip to content

R
riscv-gcc-1
Commit 9acc9cbe by Evandro Menezes
Options

[AArch64] Add more choices for the reciprocal square root approximation 

Allow a target to prefer such operation depending on the operation mode.

gcc/
	* config/aarch64/aarch64-protos.h
	(AARCH64_APPROX_MODE): New macro.
	(AARCH64_APPROX_{NONE,ALL}): Likewise.
	(cpu_approx_modes): New structure.
	(tune_params): New member "approx_modes".
	* config/aarch64/aarch64-tuning-flags.def
	(AARCH64_EXTRA_TUNE_APPROX_RSQRT): Remove macro.
	* config/aarch64/aarch64.c
	({generic,exynosm1,xgene1}_approx_modes): New core
	"cpu_approx_modes" structures.
	(generic_tunings): New member "approx_modes".
	(cortexa35_tunings): Likewise.
	(cortexa53_tunings): Likewise.
	(cortexa57_tunings): Likewise.
	(cortexa72_tunings): Likewise.
	(exynosm1_tunings): Likewise.
	(thunderx_tunings): Likewise.
	(xgene1_tunings): Likewise.
	(use_rsqrt_p): New argument for the mode and use new member from
	"tune_params".
	(aarch64_builtin_reciprocal): Devise mode from builtin.
	(aarch64_optab_supported_p): New argument for the mode.
	* doc/invoke.texi (-mlow-precision-recip-sqrt): Reword description.

From-SVN: r237395
parent d4f076c9
Showing with 55 additions and 11 deletions
gcc/config/aarch64/aarch64-protos.h
......@@ -178,6 +178,23 @@ struct cpu_branch_cost
const int unpredictable; /* Unpredictable branch or optimizing for speed. */
};
/* Control approximate alternatives to certain FP operators. */
#define AARCH64_APPROX_MODE(MODE) \
((MIN_MODE_FLOAT <= (MODE) && (MODE) <= MAX_MODE_FLOAT) \
? (1 << ((MODE) - MIN_MODE_FLOAT)) \
: (MIN_MODE_VECTOR_FLOAT <= (MODE) && (MODE) <= MAX_MODE_VECTOR_FLOAT) \
? (1 << ((MODE) - MIN_MODE_VECTOR_FLOAT \
+ MAX_MODE_FLOAT - MIN_MODE_FLOAT + 1)) \
: (0))
#define AARCH64_APPROX_NONE (0)
#define AARCH64_APPROX_ALL (-1)
/* Allowed modes for approximations. */
struct cpu_approx_modes
{
const unsigned int recip_sqrt; /* Reciprocal square root. */
};
struct tune_params
{
const struct cpu_cost_table *insn_extra_cost;
......@@ -185,6 +202,7 @@ struct tune_params
const struct cpu_regmove_cost *regmove_cost;
const struct cpu_vector_cost *vec_costs;
const struct cpu_branch_cost *branch_costs;
const struct cpu_approx_modes *approx_modes;
int memmov_cost;
int issue_rate;
unsigned int fusible_ops;
......
gcc/config/aarch64/aarch64-tuning-flags.def
......@@ -29,5 +29,3 @@
AARCH64_TUNE_ to give an enum name. */
AARCH64_EXTRA_TUNING_OPTION ("rename_fma_regs", RENAME_FMA_REGS)
AARCH64_EXTRA_TUNING_OPTION ("approx_rsqrt", APPROX_RSQRT)
gcc/config/aarch64/aarch64.c
......@@ -393,6 +393,24 @@ static const struct cpu_branch_cost cortexa57_branch_cost =
3 /* Unpredictable. */
};
/* Generic approximation modes. */
static const cpu_approx_modes generic_approx_modes =
{
AARCH64_APPROX_NONE /* recip_sqrt */
};
/* Approximation modes for Exynos M1. */
static const cpu_approx_modes exynosm1_approx_modes =
{
AARCH64_APPROX_ALL /* recip_sqrt */
};
/* Approximation modes for X-Gene 1. */
static const cpu_approx_modes xgene1_approx_modes =
{
AARCH64_APPROX_ALL /* recip_sqrt */
};
static const struct tune_params generic_tunings =
{
&cortexa57_extra_costs,
......@@ -400,6 +418,7 @@ static const struct tune_params generic_tunings =
&generic_regmove_cost,
&generic_vector_cost,
&generic_branch_cost,
&generic_approx_modes,
4, /* memmov_cost */
2, /* issue_rate */
AARCH64_FUSE_NOTHING, /* fusible_ops */
......@@ -424,6 +443,7 @@ static const struct tune_params cortexa35_tunings =
&cortexa53_regmove_cost,
&generic_vector_cost,
&generic_branch_cost,
&generic_approx_modes,
4, /* memmov_cost */
1, /* issue_rate */
(AARCH64_FUSE_MOV_MOVK | AARCH64_FUSE_ADRP_ADD
......@@ -449,6 +469,7 @@ static const struct tune_params cortexa53_tunings =
&cortexa53_regmove_cost,
&generic_vector_cost,
&generic_branch_cost,
&generic_approx_modes,
4, /* memmov_cost */
2, /* issue_rate */
(AARCH64_FUSE_AES_AESMC | AARCH64_FUSE_MOV_MOVK | AARCH64_FUSE_ADRP_ADD
......@@ -474,6 +495,7 @@ static const struct tune_params cortexa57_tunings =
&cortexa57_regmove_cost,
&cortexa57_vector_cost,
&cortexa57_branch_cost,
&generic_approx_modes,
4, /* memmov_cost */
3, /* issue_rate */
(AARCH64_FUSE_AES_AESMC | AARCH64_FUSE_MOV_MOVK | AARCH64_FUSE_ADRP_ADD
......@@ -499,6 +521,7 @@ static const struct tune_params cortexa72_tunings =
&cortexa57_regmove_cost,
&cortexa57_vector_cost,
&generic_branch_cost,
&generic_approx_modes,
4, /* memmov_cost */
3, /* issue_rate */
(AARCH64_FUSE_AES_AESMC | AARCH64_FUSE_MOV_MOVK | AARCH64_FUSE_ADRP_ADD
......@@ -524,6 +547,7 @@ static const struct tune_params exynosm1_tunings =
&exynosm1_regmove_cost,
&exynosm1_vector_cost,
&generic_branch_cost,
&exynosm1_approx_modes,
4, /* memmov_cost */
3, /* issue_rate */
(AARCH64_FUSE_AES_AESMC), /* fusible_ops */
......@@ -538,7 +562,7 @@ static const struct tune_params exynosm1_tunings =
48, /* max_case_values. */
64, /* cache_line_size. */
tune_params::AUTOPREFETCHER_WEAK, /* autoprefetcher_model. */
(AARCH64_EXTRA_TUNE_APPROX_RSQRT) /* tune_flags. */
(AARCH64_EXTRA_TUNE_NONE) /* tune_flags. */
};
static const struct tune_params thunderx_tunings =
......@@ -548,6 +572,7 @@ static const struct tune_params thunderx_tunings =
&thunderx_regmove_cost,
&generic_vector_cost,
&generic_branch_cost,
&generic_approx_modes,
6, /* memmov_cost */
2, /* issue_rate */
AARCH64_FUSE_CMP_BRANCH, /* fusible_ops */
......@@ -572,6 +597,7 @@ static const struct tune_params xgene1_tunings =
&xgene1_regmove_cost,
&xgene1_vector_cost,
&generic_branch_cost,
&xgene1_approx_modes,
6, /* memmov_cost */
4, /* issue_rate */
AARCH64_FUSE_NOTHING, /* fusible_ops */
......@@ -586,7 +612,7 @@ static const struct tune_params xgene1_tunings =
0, /* max_case_values. */
0, /* cache_line_size. */
tune_params::AUTOPREFETCHER_OFF, /* autoprefetcher_model. */
(AARCH64_EXTRA_TUNE_APPROX_RSQRT) /* tune_flags. */
(AARCH64_EXTRA_TUNE_NONE) /* tune_flags. */
};
/* Support for fine-grained override of the tuning structures. */
......@@ -7320,12 +7346,12 @@ aarch64_memory_move_cost (machine_mode mode ATTRIBUTE_UNUSED,
to optimize 1.0/sqrt. */
static bool
use_rsqrt_p (void)
use_rsqrt_p (machine_mode mode)
{
return (!flag_trapping_math
&& flag_unsafe_math_optimizations
&& ((aarch64_tune_params.extra_tuning_flags
& AARCH64_EXTRA_TUNE_APPROX_RSQRT)
&& ((aarch64_tune_params.approx_modes->recip_sqrt
& AARCH64_APPROX_MODE (mode))
|| flag_mrecip_low_precision_sqrt));
}
......@@ -7335,7 +7361,9 @@ use_rsqrt_p (void)
static tree
aarch64_builtin_reciprocal (tree fndecl)
{
if (!use_rsqrt_p ())
machine_mode mode = TYPE_MODE (TREE_TYPE (fndecl));
if (!use_rsqrt_p (mode))
return NULL_TREE;
return aarch64_builtin_rsqrt (DECL_FUNCTION_CODE (fndecl));
}
......@@ -13731,13 +13759,13 @@ aarch64_promoted_type (const_tree t)
/* Implement the TARGET_OPTAB_SUPPORTED_P hook. */
static bool
aarch64_optab_supported_p (int op, machine_mode, machine_mode,
aarch64_optab_supported_p (int op, machine_mode mode1, machine_mode,
optimization_type opt_type)
{
switch (op)
{
case rsqrt_optab:
return opt_type == OPTIMIZE_FOR_SPEED && use_rsqrt_p ();
return opt_type == OPTIMIZE_FOR_SPEED && use_rsqrt_p (mode1);
default:
return true;
......
gcc/doc/invoke.texi
......@@ -13022,7 +13022,7 @@ corresponding flag to the linker.
@item -mno-low-precision-recip-sqrt
@opindex mlow-precision-recip-sqrt
@opindex mno-low-precision-recip-sqrt
Enable or disable reciprocal square root approximation.
Enable or disable the reciprocal square root approximation.
This option only has an effect if @option{-ffast-math} or
@option{-funsafe-math-optimizations} is used as well. Enabling this reduces
precision of reciprocal square root results to about 16 bits for
......
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment