* [PATCH v3 1/2] Temporary remove "at least 8 byte alignment" code from x86
@ 2016-08-30 16:34 Denys Vlasenko
2016-08-30 16:35 ` [PATCH v3 2/2] Extend -falign-FOO=N to N[,M[,N2[,M2]]] Denys Vlasenko
0 siblings, 1 reply; 2+ messages in thread
From: Denys Vlasenko @ 2016-08-30 16:34 UTC (permalink / raw)
To: gcc-patches; +Cc: Denys Vlasenko, Andrew Pinski
This change drops forced alignment to 8 if requested alignment is higher
than 8: before the patch, -falign-functions=9 was generating
.p2align 4,,8
.p2align 3
which means: "align to 16 if the skip is 8 bytes or less; else align to 8".
After this change, ".p2align 3" is not emitted.
This behavior will be implemented differently by the next patch.
2016-08-30 Denys Vlasenko <dvlasenk@redhat.com>
* config/i386/freebsd.h (ASM_OUTPUT_MAX_SKIP_ALIGN): Remove "If N
is large, do at least 8 byte alignment" code.
* config/i386/gnu-user.h (ASM_OUTPUT_MAX_SKIP_ALIGN): Likewise.
* config/i386/iamcu.h (ASM_OUTPUT_MAX_SKIP_ALIGN): Likewise.
* config/i386/openbsdelf.h (ASM_OUTPUT_MAX_SKIP_ALIGN): Likewise.
* config/i386/x86-64.h (ASM_OUTPUT_MAX_SKIP_ALIGN): Likewise.
Index: gcc/config/i386/freebsd.h
===================================================================
--- gcc/config/i386/freebsd.h (revision 239390)
+++ gcc/config/i386/freebsd.h (working copy)
@@ -92,25 +92,17 @@ along with GCC; see the file COPYING3. If not see
/* A C statement to output to the stdio stream FILE an assembler
command to advance the location counter to a multiple of 1<<LOG
- bytes if it is within MAX_SKIP bytes.
+ bytes if it is within MAX_SKIP bytes. */
- This is used to align code labels according to Intel recommendations. */
-
#ifdef HAVE_GAS_MAX_SKIP_P2ALIGN
#undef ASM_OUTPUT_MAX_SKIP_ALIGN
#define ASM_OUTPUT_MAX_SKIP_ALIGN(FILE,LOG,MAX_SKIP) \
do { \
if ((LOG) != 0) { \
- if ((MAX_SKIP) == 0) fprintf ((FILE), "\t.p2align %d\n", (LOG)); \
- else { \
+ if ((MAX_SKIP) == 0 || (MAX_SKIP) >= (1<<(LOG))) \
+ fprintf ((FILE), "\t.p2align %d\n", (LOG)); \
+ else \
fprintf ((FILE), "\t.p2align %d,,%d\n", (LOG), (MAX_SKIP)); \
- /* Make sure that we have at least 8 byte alignment if > 8 byte \
- alignment is preferred. */ \
- if ((LOG) > 3 \
- && (1 << (LOG)) > ((MAX_SKIP) + 1) \
- && (MAX_SKIP) >= 7) \
- fputs ("\t.p2align 3\n", (FILE)); \
- } \
} \
} while (0)
#endif
Index: gcc/config/i386/gnu-user.h
===================================================================
--- gcc/config/i386/gnu-user.h (revision 239390)
+++ gcc/config/i386/gnu-user.h (working copy)
@@ -94,24 +94,16 @@ along with GCC; see the file COPYING3. If not see
/* A C statement to output to the stdio stream FILE an assembler
command to advance the location counter to a multiple of 1<<LOG
- bytes if it is within MAX_SKIP bytes.
+ bytes if it is within MAX_SKIP bytes. */
- This is used to align code labels according to Intel recommendations. */
-
#ifdef HAVE_GAS_MAX_SKIP_P2ALIGN
#define ASM_OUTPUT_MAX_SKIP_ALIGN(FILE,LOG,MAX_SKIP) \
do { \
if ((LOG) != 0) { \
- if ((MAX_SKIP) == 0) fprintf ((FILE), "\t.p2align %d\n", (LOG)); \
- else { \
+ if ((MAX_SKIP) == 0 || (MAX_SKIP) >= (1<<(LOG))) \
+ fprintf ((FILE), "\t.p2align %d\n", (LOG)); \
+ else \
fprintf ((FILE), "\t.p2align %d,,%d\n", (LOG), (MAX_SKIP)); \
- /* Make sure that we have at least 8 byte alignment if > 8 byte \
- alignment is preferred. */ \
- if ((LOG) > 3 \
- && (1 << (LOG)) > ((MAX_SKIP) + 1) \
- && (MAX_SKIP) >= 7) \
- fputs ("\t.p2align 3\n", (FILE)); \
- } \
} \
} while (0)
#endif
Index: gcc/config/i386/iamcu.h
===================================================================
--- gcc/config/i386/iamcu.h (revision 239390)
+++ gcc/config/i386/iamcu.h (working copy)
@@ -62,23 +62,15 @@ see the files COPYING3 and COPYING.RUNTIME respect
/* A C statement to output to the stdio stream FILE an assembler
command to advance the location counter to a multiple of 1<<LOG
- bytes if it is within MAX_SKIP bytes.
+ bytes if it is within MAX_SKIP bytes. */
- This is used to align code labels according to Intel recommendations. */
-
#define ASM_OUTPUT_MAX_SKIP_ALIGN(FILE,LOG,MAX_SKIP) \
do { \
if ((LOG) != 0) { \
- if ((MAX_SKIP) == 0) fprintf ((FILE), "\t.p2align %d\n", (LOG)); \
- else { \
+ if ((MAX_SKIP) == 0 || (MAX_SKIP) >= (1<<(LOG))) \
+ fprintf ((FILE), "\t.p2align %d\n", (LOG)); \
+ else \
fprintf ((FILE), "\t.p2align %d,,%d\n", (LOG), (MAX_SKIP)); \
- /* Make sure that we have at least 8 byte alignment if > 8 byte \
- alignment is preferred. */ \
- if ((LOG) > 3 \
- && (1 << (LOG)) > ((MAX_SKIP) + 1) \
- && (MAX_SKIP) >= 7) \
- fputs ("\t.p2align 3\n", (FILE)); \
- } \
} \
} while (0)
Index: gcc/config/i386/openbsdelf.h
===================================================================
--- gcc/config/i386/openbsdelf.h (revision 239390)
+++ gcc/config/i386/openbsdelf.h (working copy)
@@ -63,24 +63,16 @@ along with GCC; see the file COPYING3. If not see
/* A C statement to output to the stdio stream FILE an assembler
command to advance the location counter to a multiple of 1<<LOG
- bytes if it is within MAX_SKIP bytes.
+ bytes if it is within MAX_SKIP bytes. */
- This is used to align code labels according to Intel recommendations. */
-
#ifdef HAVE_GAS_MAX_SKIP_P2ALIGN
#define ASM_OUTPUT_MAX_SKIP_ALIGN(FILE,LOG,MAX_SKIP) \
do { \
if ((LOG) != 0) { \
- if ((MAX_SKIP) == 0) fprintf ((FILE), "\t.p2align %d\n", (LOG)); \
- else { \
+ if ((MAX_SKIP) == 0 || (MAX_SKIP) >= (1<<(LOG))) \
+ fprintf ((FILE), "\t.p2align %d\n", (LOG)); \
+ else \
fprintf ((FILE), "\t.p2align %d,,%d\n", (LOG), (MAX_SKIP)); \
- /* Make sure that we have at least 8 byte alignment if > 8 byte \
- alignment is preferred. */ \
- if ((LOG) > 3 \
- && (1 << (LOG)) > ((MAX_SKIP) + 1) \
- && (MAX_SKIP) >= 7) \
- fputs ("\t.p2align 3\n", (FILE)); \
- } \
} \
} while (0)
#endif
Index: gcc/config/i386/x86-64.h
===================================================================
--- gcc/config/i386/x86-64.h (revision 239390)
+++ gcc/config/i386/x86-64.h (working copy)
@@ -65,16 +65,10 @@ see the files COPYING3 and COPYING.RUNTIME respect
#define ASM_OUTPUT_MAX_SKIP_ALIGN(FILE,LOG,MAX_SKIP) \
do { \
if ((LOG) != 0) { \
- if ((MAX_SKIP) == 0) fprintf ((FILE), "\t.p2align %d\n", (LOG)); \
- else { \
+ if ((MAX_SKIP) == 0 || (MAX_SKIP) >= (1<<(LOG))) \
+ fprintf ((FILE), "\t.p2align %d\n", (LOG)); \
+ else \
fprintf ((FILE), "\t.p2align %d,,%d\n", (LOG), (MAX_SKIP)); \
- /* Make sure that we have at least 8 byte alignment if > 8 byte \
- alignment is preferred. */ \
- if ((LOG) > 3 \
- && (1 << (LOG)) > ((MAX_SKIP) + 1) \
- && (MAX_SKIP) >= 7) \
- fputs ("\t.p2align 3\n", (FILE)); \
- } \
} \
} while (0)
#undef ASM_OUTPUT_MAX_SKIP_PAD
^ permalink raw reply [flat|nested] 2+ messages in thread
* [PATCH v3 2/2] Extend -falign-FOO=N to N[,M[,N2[,M2]]]
2016-08-30 16:34 [PATCH v3 1/2] Temporary remove "at least 8 byte alignment" code from x86 Denys Vlasenko
@ 2016-08-30 16:35 ` Denys Vlasenko
0 siblings, 0 replies; 2+ messages in thread
From: Denys Vlasenko @ 2016-08-30 16:35 UTC (permalink / raw)
To: gcc-patches; +Cc: Denys Vlasenko, Andrew Pinski
falign-functions=N is too simplistic.
Ingo Molnar ran some tests and it seems that on latest x86 CPUs, 64-byte alignment
of functions runs fastest (he tried many other possibilites):
this way, after a call CPU can fetch a lot of insns in the first cacheline fill.
However, developers are less than thrilled by the idea of a slam-dunk 64-byte
aligning everything. Too much waste:
On 05/20/2015 02:47 AM, Linus Torvalds wrote:
> At the same time, I have to admit that I abhor a 64-byte function
> alignment, when we have a fair number of functions that are (much)
> smaller than that.
>
> Is there some way to get gcc to take the size of the function into
> account? Because aligning a 16-byte or 32-byte function on a 64-byte
> alignment is just criminally nasty and wasteful.
This change makes it possible to align functions to 64-byte boundaries *if*
this does not introduce huge amount of padding.
Example syntax is -falign-functions=64,9: "align to 64 by skipping up to
9 bytes (not inclusive)". IOW: "after a call insn, CPU will always be able
to fetch at least 9 bytes of insns".
x86 had a tweak: -falign-functions=N with N > 8 was adding secondary alignment.
For example, falign-functions=10 was emitting this before every function:
.p2align 4,,9
.p2align 3
This tweak was removed by the previous patch. Now it is reinstated
by the logic that if falign-functions=N[,M] is specified and N > 8,
then default value of N2 is 8, not 0. But now this can be suppressed by
falign-functions=N,M,0 - which wasn't possible before.
In general, optional N2,M2 pair can be used to generate any secondary
alignment user wants.
Testing:
Tested that with -falign-functions=N (tried 8, 15, 16, 17...) the alignment
directives are the same before and after the patch.
Tested that -falign-functions=N,N (two equal parameters) works exactly
like -falign-functions=N.
No change from past behavior:
Tested that "-falign-functions" uses an arch-dependent alignment.
Tested that "-O2" uses an arch-dependent alignment.
Tested that "-O2 -falign-functions=N" uses explicitly given alignment.
2016-08-30 Denys Vlasenko <dvlasenk@redhat.com>
* common.opt (-falign-functions=): Accept a string instead of integer.
(-falign-jumps=): Likewise.
(-falign-labels=): Likewise.
(-falign-loops=): Likewise.
* flags.h (struct target_flag_state): Revamp how alignment data is stored:
for each of four alignment types, store two pairs of log/maxskip values.
* toplev.c (read_uint): New function.
(read_log_maxskip): New function.
(parse_N_M): New function.
(init_alignments): Set align_FOO[0/1].log/maxskip from
specified falign-FOO=N[,M[,N[,M]]] options.
* varasm.c (assemble_start_function): Call two ASM_OUTPUT_MAX_SKIP_ALIGN
macros, first for N,M and second time for N2,M2 from
falign-functions=N,M,N2,M2. This generates 0, 1, or 2 align directives.
* config/aarch64/aarch64-protos.h (struct tune_params):
Change foo_align members from integers to strings.
* config/i386/i386.c (struct ptt): Likewise.
* config/aarch64/aarch64.c (<cpu>_tunings):
Change foo_align field values from integers to strings.
* config/i386/i386.c (processor_target_table): Likewise.
* config/arm/arm.c (arm_override_options_after_change_1):
Fix if() condition to detect that -falign-functions is specified.
* config/i386/i386.c (ix86_default_align): Likewise.
* common/config/i386/i386-common.c (ix86_handle_option):
Remove conversion of malign_foo's to falign_foo's.
The warning is still emitted.
* doc/invoke.texi: Update option documentation.
* testsuite/gcc.target/i386/falign-functions.c: New file.
Index: gcc/common/config/i386/i386-common.c
===================================================================
--- gcc/common/config/i386/i386-common.c (revision 239860)
+++ gcc/common/config/i386/i386-common.c (working copy)
@@ -998,36 +998,17 @@ ix86_handle_option (struct gcc_options *opts,
}
return true;
-
- /* Comes from final.c -- no real reason to change it. */
-#define MAX_CODE_ALIGN 16
-
case OPT_malign_loops_:
warning_at (loc, 0, "-malign-loops is obsolete, use -falign-loops");
- if (value > MAX_CODE_ALIGN)
- error_at (loc, "-malign-loops=%d is not between 0 and %d",
- value, MAX_CODE_ALIGN);
- else
- opts->x_align_loops = 1 << value;
return true;
case OPT_malign_jumps_:
warning_at (loc, 0, "-malign-jumps is obsolete, use -falign-jumps");
- if (value > MAX_CODE_ALIGN)
- error_at (loc, "-malign-jumps=%d is not between 0 and %d",
- value, MAX_CODE_ALIGN);
- else
- opts->x_align_jumps = 1 << value;
return true;
case OPT_malign_functions_:
warning_at (loc, 0,
"-malign-functions is obsolete, use -falign-functions");
- if (value > MAX_CODE_ALIGN)
- error_at (loc, "-malign-functions=%d is not between 0 and %d",
- value, MAX_CODE_ALIGN);
- else
- opts->x_align_functions = 1 << value;
return true;
case OPT_mbranch_cost_:
Index: gcc/common.opt
===================================================================
--- gcc/common.opt (revision 239860)
+++ gcc/common.opt (working copy)
@@ -896,32 +896,32 @@ Common Report Var(flag_aggressive_loop_optimizatio
Aggressively optimize loops using language constraints.
falign-functions
-Common Report Var(align_functions,0) Optimization UInteger
+Common Report Var(flag_align_functions) Optimization
Align the start of functions.
falign-functions=
-Common RejectNegative Joined UInteger Var(align_functions)
+Common RejectNegative Joined Var(str_align_functions)
falign-jumps
-Common Report Var(align_jumps,0) Optimization UInteger
+Common Report Var(flag_align_jumps) Optimization
Align labels which are only reached by jumping.
falign-jumps=
-Common RejectNegative Joined UInteger Var(align_jumps)
+Common RejectNegative Joined Var(str_align_jumps)
falign-labels
-Common Report Var(align_labels,0) Optimization UInteger
+Common Report Var(flag_align_labels) Optimization
Align all labels.
falign-labels=
-Common RejectNegative Joined UInteger Var(align_labels)
+Common RejectNegative Joined Var(str_align_labels)
falign-loops
-Common Report Var(align_loops,0) Optimization UInteger
+Common Report Var(flag_align_loops) Optimization
Align the start of loops.
falign-loops=
-Common RejectNegative Joined UInteger Var(align_loops)
+Common RejectNegative Joined Var(str_align_loops)
fargument-alias
Common Ignore
Index: gcc/config/aarch64/aarch64-protos.h
===================================================================
--- gcc/config/aarch64/aarch64-protos.h (revision 239860)
+++ gcc/config/aarch64/aarch64-protos.h (working copy)
@@ -208,9 +208,9 @@ struct tune_params
int memmov_cost;
int issue_rate;
unsigned int fusible_ops;
- int function_align;
- int jump_align;
- int loop_align;
+ const char *function_align;
+ const char *jump_align;
+ const char *loop_align;
int int_reassoc_width;
int fp_reassoc_width;
int vec_reassoc_width;
Index: gcc/config/aarch64/aarch64.c
===================================================================
--- gcc/config/aarch64/aarch64.c (revision 239860)
+++ gcc/config/aarch64/aarch64.c (working copy)
@@ -521,9 +521,9 @@ static const struct tune_params generic_tunings =
4, /* memmov_cost */
2, /* issue_rate */
AARCH64_FUSE_NOTHING, /* fusible_ops */
- 8, /* function_align. */
- 8, /* jump_align. */
- 4, /* loop_align. */
+ "8", /* function_align. */
+ "8", /* jump_align. */
+ "4", /* loop_align. */
2, /* int_reassoc_width. */
4, /* fp_reassoc_width. */
1, /* vec_reassoc_width. */
@@ -547,9 +547,9 @@ static const struct tune_params cortexa35_tunings
1, /* issue_rate */
(AARCH64_FUSE_AES_AESMC | AARCH64_FUSE_MOV_MOVK | AARCH64_FUSE_ADRP_ADD
| AARCH64_FUSE_MOVK_MOVK | AARCH64_FUSE_ADRP_LDR), /* fusible_ops */
- 16, /* function_align. */
- 8, /* jump_align. */
- 8, /* loop_align. */
+ "16", /* function_align. */
+ "8", /* jump_align. */
+ "8", /* loop_align. */
2, /* int_reassoc_width. */
4, /* fp_reassoc_width. */
1, /* vec_reassoc_width. */
@@ -573,9 +573,9 @@ static const struct tune_params cortexa53_tunings
2, /* issue_rate */
(AARCH64_FUSE_AES_AESMC | AARCH64_FUSE_MOV_MOVK | AARCH64_FUSE_ADRP_ADD
| AARCH64_FUSE_MOVK_MOVK | AARCH64_FUSE_ADRP_LDR), /* fusible_ops */
- 16, /* function_align. */
- 8, /* jump_align. */
- 8, /* loop_align. */
+ "16", /* function_align. */
+ "8", /* jump_align. */
+ "8", /* loop_align. */
2, /* int_reassoc_width. */
4, /* fp_reassoc_width. */
1, /* vec_reassoc_width. */
@@ -599,9 +599,9 @@ static const struct tune_params cortexa57_tunings
3, /* issue_rate */
(AARCH64_FUSE_AES_AESMC | AARCH64_FUSE_MOV_MOVK | AARCH64_FUSE_ADRP_ADD
| AARCH64_FUSE_MOVK_MOVK), /* fusible_ops */
- 16, /* function_align. */
- 8, /* jump_align. */
- 8, /* loop_align. */
+ "16", /* function_align. */
+ "8", /* jump_align. */
+ "8", /* loop_align. */
2, /* int_reassoc_width. */
4, /* fp_reassoc_width. */
1, /* vec_reassoc_width. */
@@ -625,9 +625,9 @@ static const struct tune_params cortexa72_tunings
3, /* issue_rate */
(AARCH64_FUSE_AES_AESMC | AARCH64_FUSE_MOV_MOVK | AARCH64_FUSE_ADRP_ADD
| AARCH64_FUSE_MOVK_MOVK), /* fusible_ops */
- 16, /* function_align. */
- 8, /* jump_align. */
- 8, /* loop_align. */
+ "16", /* function_align. */
+ "8", /* jump_align. */
+ "8", /* loop_align. */
2, /* int_reassoc_width. */
4, /* fp_reassoc_width. */
1, /* vec_reassoc_width. */
@@ -651,9 +651,9 @@ static const struct tune_params cortexa73_tunings
2, /* issue_rate. */
(AARCH64_FUSE_AES_AESMC | AARCH64_FUSE_MOV_MOVK | AARCH64_FUSE_ADRP_ADD
| AARCH64_FUSE_MOVK_MOVK | AARCH64_FUSE_ADRP_LDR), /* fusible_ops */
- 16, /* function_align. */
- 8, /* jump_align. */
- 8, /* loop_align. */
+ "16", /* function_align. */
+ "8", /* jump_align. */
+ "8", /* loop_align. */
2, /* int_reassoc_width. */
4, /* fp_reassoc_width. */
1, /* vec_reassoc_width. */
@@ -676,9 +676,9 @@ static const struct tune_params exynosm1_tunings =
4, /* memmov_cost */
3, /* issue_rate */
(AARCH64_FUSE_AES_AESMC), /* fusible_ops */
- 4, /* function_align. */
- 4, /* jump_align. */
- 4, /* loop_align. */
+ "4", /* function_align. */
+ "4", /* jump_align. */
+ "4", /* loop_align. */
2, /* int_reassoc_width. */
4, /* fp_reassoc_width. */
1, /* vec_reassoc_width. */
@@ -701,9 +701,9 @@ static const struct tune_params thunderx_tunings =
6, /* memmov_cost */
2, /* issue_rate */
AARCH64_FUSE_CMP_BRANCH, /* fusible_ops */
- 8, /* function_align. */
- 8, /* jump_align. */
- 8, /* loop_align. */
+ "8", /* function_align. */
+ "8", /* jump_align. */
+ "8", /* loop_align. */
2, /* int_reassoc_width. */
4, /* fp_reassoc_width. */
1, /* vec_reassoc_width. */
@@ -726,9 +726,9 @@ static const struct tune_params xgene1_tunings =
6, /* memmov_cost */
4, /* issue_rate */
AARCH64_FUSE_NOTHING, /* fusible_ops */
- 16, /* function_align. */
- 8, /* jump_align. */
- 16, /* loop_align. */
+ "16", /* function_align. */
+ "8", /* jump_align. */
+ "16", /* loop_align. */
2, /* int_reassoc_width. */
4, /* fp_reassoc_width. */
1, /* vec_reassoc_width. */
@@ -752,9 +752,9 @@ static const struct tune_params qdf24xx_tunings =
4, /* issue_rate */
(AARCH64_FUSE_MOV_MOVK | AARCH64_FUSE_ADRP_ADD
| AARCH64_FUSE_MOVK_MOVK), /* fuseable_ops */
- 16, /* function_align. */
- 8, /* jump_align. */
- 16, /* loop_align. */
+ "16", /* function_align. */
+ "8", /* jump_align. */
+ "16", /* loop_align. */
2, /* int_reassoc_width. */
4, /* fp_reassoc_width. */
1, /* vec_reassoc_width. */
@@ -777,9 +777,9 @@ static const struct tune_params vulcan_tunings =
4, /* memmov_cost. */
4, /* issue_rate. */
AARCH64_FUSE_NOTHING, /* fuseable_ops. */
- 16, /* function_align. */
- 8, /* jump_align. */
- 16, /* loop_align. */
+ "16", /* function_align. */
+ "8", /* jump_align. */
+ "16", /* loop_align. */
3, /* int_reassoc_width. */
2, /* fp_reassoc_width. */
2, /* vec_reassoc_width. */
Index: gcc/config/arm/arm.c
===================================================================
--- gcc/config/arm/arm.c (revision 239860)
+++ gcc/config/arm/arm.c (working copy)
@@ -2899,9 +2899,10 @@ static GTY(()) tree init_optimize;
static void
arm_override_options_after_change_1 (struct gcc_options *opts)
{
- if (opts->x_align_functions <= 0)
- opts->x_align_functions = TARGET_THUMB_P (opts->x_target_flags)
- && opts->x_optimize_size ? 2 : 4;
+ /* -falign-functions without argument: supply one */
+ if (opts->x_flag_align_functions && !opts->x_str_align_functions)
+ opts->x_str_align_functions = TARGET_THUMB_P (opts->x_target_flags)
+ && opts->x_optimize_size ? "2" : "4";
}
/* Implement targetm.override_options_after_change. */
Index: gcc/config/i386/i386.c
===================================================================
--- gcc/config/i386/i386.c (revision 239860)
+++ gcc/config/i386/i386.c (working copy)
@@ -2626,45 +2626,43 @@ struct ptt
{
const char *const name; /* processor name */
const struct processor_costs *cost; /* Processor costs */
- const int align_loop; /* Default alignments. */
- const int align_loop_max_skip;
- const int align_jump;
- const int align_jump_max_skip;
- const int align_func;
+ const char *const align_loop; /* Default alignments. */
+ const char *const align_jump;
+ const char *const align_func;
};
/* This table must be in sync with enum processor_type in i386.h. */
static const struct ptt processor_target_table[PROCESSOR_max] =
{
- {"generic", &generic_cost, 16, 10, 16, 10, 16},
- {"i386", &i386_cost, 4, 3, 4, 3, 4},
- {"i486", &i486_cost, 16, 15, 16, 15, 16},
- {"pentium", &pentium_cost, 16, 7, 16, 7, 16},
- {"lakemont", &lakemont_cost, 16, 7, 16, 7, 16},
- {"pentiumpro", &pentiumpro_cost, 16, 15, 16, 10, 16},
- {"pentium4", &pentium4_cost, 0, 0, 0, 0, 0},
- {"nocona", &nocona_cost, 0, 0, 0, 0, 0},
- {"core2", &core_cost, 16, 10, 16, 10, 16},
- {"nehalem", &core_cost, 16, 10, 16, 10, 16},
- {"sandybridge", &core_cost, 16, 10, 16, 10, 16},
- {"haswell", &core_cost, 16, 10, 16, 10, 16},
- {"bonnell", &atom_cost, 16, 15, 16, 7, 16},
- {"silvermont", &slm_cost, 16, 15, 16, 7, 16},
- {"knl", &slm_cost, 16, 15, 16, 7, 16},
- {"skylake-avx512", &core_cost, 16, 10, 16, 10, 16},
- {"intel", &intel_cost, 16, 15, 16, 7, 16},
- {"geode", &geode_cost, 0, 0, 0, 0, 0},
- {"k6", &k6_cost, 32, 7, 32, 7, 32},
- {"athlon", &athlon_cost, 16, 7, 16, 7, 16},
- {"k8", &k8_cost, 16, 7, 16, 7, 16},
- {"amdfam10", &amdfam10_cost, 32, 24, 32, 7, 32},
- {"bdver1", &bdver1_cost, 16, 10, 16, 7, 11},
- {"bdver2", &bdver2_cost, 16, 10, 16, 7, 11},
- {"bdver3", &bdver3_cost, 16, 10, 16, 7, 11},
- {"bdver4", &bdver4_cost, 16, 10, 16, 7, 11},
- {"btver1", &btver1_cost, 16, 10, 16, 7, 11},
- {"btver2", &btver2_cost, 16, 10, 16, 7, 11},
- {"znver1", &znver1_cost, 16, 10, 16, 7, 11}
+ {"generic", &generic_cost, "16,11", "16,11","16"},
+ {"i386", &i386_cost, "4", "4", "4"},
+ {"i486", &i486_cost, "16", "16", "16"},
+ {"pentium", &pentium_cost, "16,8", "16,8", "16"},
+ {"lakemont", &lakemont_cost,"16,8", "16,8", "16"},
+ {"pentiumpro", &pentiumpro_cost,"16", "16,11","16"},
+ {"pentium4", &pentium4_cost,NULL, NULL, NULL},
+ {"nocona", &nocona_cost, NULL, NULL, NULL},
+ {"core2", &core_cost, "16,11", "16,11","16"},
+ {"nehalem", &core_cost, "16,11", "16,11","16"},
+ {"sandybridge",&core_cost, "16,11", "16,11","16"},
+ {"haswell", &core_cost, "16,11", "16,11","16"},
+ {"bonnell", &atom_cost, "16", "16,8", "16"},
+ {"silvermont", &slm_cost, "16", "16,8", "16"},
+ {"knl", &slm_cost, "16", "16,8", "16"},
+ {"skylake-avx512", &core_cost,"16,11", "16,11","16"},
+ {"intel", &intel_cost, "16", "16,8", "16"},
+ {"geode", &geode_cost, NULL, NULL, NULL},
+ {"k6", &k6_cost, "32,8", "32,8", "32"},
+ {"athlon", &athlon_cost, "16,8", "16,8", "16"},
+ {"k8", &k8_cost, "16,8", "16,8", "16"},
+ {"amdfam10", &amdfam10_cost,"32,25", "32,8", "32"},
+ {"bdver1", &bdver1_cost, "16,11", "16,8", "11"},
+ {"bdver2", &bdver2_cost, "16,11", "16,8", "11"},
+ {"bdver3", &bdver3_cost, "16,11", "16,8", "11"},
+ {"bdver4", &bdver4_cost, "16,11", "16,8", "11"},
+ {"btver1", &btver1_cost, "16,11", "16,8", "11"},
+ {"btver2", &btver2_cost, "16,11", "16,8", "11"},
+ {"znver1", &znver1_cost, "16,11", "16,8", "11"}
};
\f
static unsigned int
@@ -4695,19 +4693,18 @@ set_ix86_tune_features (enum processor_type ix86_t
static void
ix86_default_align (struct gcc_options *opts)
{
- if (opts->x_align_loops == 0)
+ /* -falign-foo without argument: supply one */
+ if (opts->x_flag_align_loops && !opts->x_str_align_loops)
{
- opts->x_align_loops = processor_target_table[ix86_tune].align_loop;
- align_loops_max_skip = processor_target_table[ix86_tune].align_loop_max_skip;
+ opts->x_str_align_loops = processor_target_table[ix86_tune].align_loop;
}
- if (opts->x_align_jumps == 0)
+ if (opts->x_flag_align_jumps && !opts->x_str_align_jumps)
{
- opts->x_align_jumps = processor_target_table[ix86_tune].align_jump;
- align_jumps_max_skip = processor_target_table[ix86_tune].align_jump_max_skip;
+ opts->x_str_align_jumps = processor_target_table[ix86_tune].align_jump;
}
- if (opts->x_align_functions == 0)
+ if (opts->x_flag_align_functions && !opts->x_str_align_functions)
{
- opts->x_align_functions = processor_target_table[ix86_tune].align_func;
+ opts->x_str_align_functions = processor_target_table[ix86_tune].align_func;
}
}
Index: gcc/doc/invoke.texi
===================================================================
--- gcc/doc/invoke.texi (revision 239860)
+++ gcc/doc/invoke.texi (working copy)
@@ -337,9 +337,10 @@ Objective-C and Objective-C++ Dialects}.
@item Optimization Options
@xref{Optimize Options,,Options that Control Optimization}.
-@gccoptlist{-faggressive-loop-optimizations -falign-functions[=@var{n}] @gol
--falign-jumps[=@var{n}] @gol
--falign-labels[=@var{n}] -falign-loops[=@var{n}] @gol
+@gccoptlist{-faggressive-loop-optimizations @gol
+-falign-functions[=@var{n}[,@var{m},[@var{n}[,@var{m}]]]] @gol
+-falign-jumps[=@var{n}[,@var{m}]] @gol
+-falign-labels[=@var{n}[,@var{m}]] -falign-loops[=@var{n}[,@var{m}]] @gol
-fassociative-math -fauto-profile -fauto-profile[=@var{path}] @gol
-fauto-inc-dec -fbranch-probabilities @gol
-fbranch-target-load-optimize -fbranch-target-load-optimize2 @gol
@@ -7952,9 +7953,11 @@ The @option{-fstrict-overflow} option is enabled a
@item -falign-functions
@itemx -falign-functions=@var{n}
+@itemx -falign-functions=@var{n},@var{m}
@opindex falign-functions
+If @var{m} is not specified, it defaults to @var{n}.
Align the start of functions to the next power-of-two greater than
-@var{n}, skipping up to @var{n} bytes. For instance,
+@var{n}, skipping up to @var{m}-1 bytes. For instance,
@option{-falign-functions=32} aligns functions to the next 32-byte
boundary, but @option{-falign-functions=24} aligns to the next
32-byte boundary only if this can be done by skipping 23 bytes or less.
@@ -7971,9 +7974,11 @@ Enabled at levels @option{-O2}, @option{-O3}.
@item -falign-labels
@itemx -falign-labels=@var{n}
+@itemx -falign-labels=@var{n},@var{m}
@opindex falign-labels
+If @var{m} is not specified, it defaults to @var{n}.
Align all branch targets to a power-of-two boundary, skipping up to
-@var{n} bytes like @option{-falign-functions}. This option can easily
+@var{m}-1 bytes like @option{-falign-functions}. This option can easily
make code slower, because it must insert dummy operations for when the
branch target is reached in the usual flow of the code.
@@ -7990,8 +7995,10 @@ Enabled at levels @option{-O2}, @option{-O3}.
@item -falign-loops
@itemx -falign-loops=@var{n}
+@itemx -falign-loops=@var{n},@var{m}
@opindex falign-loops
-Align loops to a power-of-two boundary, skipping up to @var{n} bytes
+If @var{m} is not specified, it defaults to @var{n}.
+Align loops to a power-of-two boundary, skipping up to @var{m}-1 bytes
like @option{-falign-functions}. If the loops are
executed many times, this makes up for any execution of the dummy
operations.
@@ -8005,9 +8012,11 @@ Enabled at levels @option{-O2}, @option{-O3}.
@item -falign-jumps
@itemx -falign-jumps=@var{n}
+@itemx -falign-jumps=@var{n},@var{m}
@opindex falign-jumps
+If @var{m} is not specified, it defaults to @var{n}.
Align branch targets to a power-of-two boundary, for branch targets
-where the targets can only be reached by jumping, skipping up to @var{n}
+where the targets can only be reached by jumping, skipping up to @var{m}-1
bytes like @option{-falign-functions}. In this case, no dummy operations
need be executed.
Index: gcc/flags.h
===================================================================
--- gcc/flags.h (revision 239860)
+++ gcc/flags.h (working copy)
@@ -43,19 +43,22 @@ extern bool final_insns_dump_p;
/* Other basic status info about current function. */
/* Target-dependent global state. */
-struct target_flag_state {
+struct align_flags {
/* Values of the -falign-* flags: how much to align labels in code.
- 0 means `use default', 1 means `don't align'.
- For each variable, there is an _log variant which is the power
- of two not less than the variable, for .align output. */
- int x_align_loops_log;
- int x_align_loops_max_skip;
- int x_align_jumps_log;
- int x_align_jumps_max_skip;
- int x_align_labels_log;
- int x_align_labels_max_skip;
- int x_align_functions_log;
+ log is "align to 2^log" (so 0 means no alignment).
+ maxskip is the maximum allowed amount of padding to insert. */
+ int log;
+ int maxskip;
+};
+struct target_flag_state {
+ /* Each falign-foo can generate up to two levels of alignment:
+ -falign-foo=N,M[,N2,M2] */
+ struct align_flags x_align_loops[2];
+ struct align_flags x_align_jumps[2];
+ struct align_flags x_align_labels[2];
+ struct align_flags x_align_functions[2];
+
/* The excess precision currently in effect. */
enum excess_precision x_flag_excess_precision;
};
@@ -67,20 +70,21 @@ extern struct target_flag_state *this_target_flag_
#define this_target_flag_state (&default_target_flag_state)
#endif
-#define align_loops_log \
- (this_target_flag_state->x_align_loops_log)
-#define align_loops_max_skip \
- (this_target_flag_state->x_align_loops_max_skip)
-#define align_jumps_log \
- (this_target_flag_state->x_align_jumps_log)
-#define align_jumps_max_skip \
- (this_target_flag_state->x_align_jumps_max_skip)
-#define align_labels_log \
- (this_target_flag_state->x_align_labels_log)
-#define align_labels_max_skip \
- (this_target_flag_state->x_align_labels_max_skip)
-#define align_functions_log \
- (this_target_flag_state->x_align_functions_log)
+#define align_loops (this_target_flag_state->x_align_loops)
+#define align_jumps (this_target_flag_state->x_align_jumps)
+#define align_labels (this_target_flag_state->x_align_labels)
+#define align_functions (this_target_flag_state->x_align_functions)
+#define align_loops_log (align_loops[0].log)
+#define align_jumps_log (align_jumps[0].log)
+#define align_labels_log (align_labels[0].log)
+#define align_functions_log (align_functions[0].log)
+#define align_loops_max_skip (align_loops[0].maxskip)
+#define align_jumps_max_skip (align_jumps[0].maxskip)
+#define align_labels_max_skip (align_labels[0].maxskip)
+#define align_functions_max_skip (align_functions[0].maxskip)
+/* String representaions of the above options are available in
+ const char *str_align_foo. NULL if not set. */
+
#define flag_excess_precision \
(this_target_flag_state->x_flag_excess_precision)
Index: gcc/testsuite/gcc.target/i386/falign-functions.c
===================================================================
--- gcc/testsuite/gcc.target/i386/falign-functions.c (nonexistent)
+++ gcc/testsuite/gcc.target/i386/falign-functions.c (working copy)
@@ -0,0 +1,8 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -falign-functions=64,8" } */
+/* { dg-final { scan-assembler ".p2align 6,,7" } } */
+
+void
+test_func (void)
+{
+}
Index: gcc/toplev.c
===================================================================
--- gcc/toplev.c (revision 239860)
+++ gcc/toplev.c (working copy)
@@ -1177,29 +1177,78 @@ target_supports_section_anchors_p (void)
return true;
}
-/* Default the align_* variables to 1 if they're still unset, and
- set up the align_*_log variables. */
+static const char *
+read_uint (const char *flag, const char *name, int *np)
+{
+ const char *flag_start = flag;
+ int n = 0;
+ char c;
+
+ while ((c = *flag++) >= '0' && c <= '9')
+ n = n*10 + (c-'0');
+ *np = n & 0x3fffffff; /* avoid accidentally negative numbers */
+ if (c == '\0')
+ return NULL;
+ if (c == ',')
+ return flag;
+
+ error_at (UNKNOWN_LOCATION, "-falign-%s parameter is bad at '%s'",
+ name, flag_start);
+ return NULL;
+}
+
+static const char *
+read_log_maxskip (const char *flag, const char *name, struct align_flags *a)
+{
+ int n, m;
+ flag = read_uint (flag, name, &a->log);
+ n = a->log;
+ if (n != 0)
+ a->log = floor_log2 (n * 2 - 1);
+ if (!flag)
+ {
+ a->maxskip = n ? n - 1 : 0;
+ return flag;
+ }
+ flag = read_uint (flag, name, &a->maxskip);
+ m = a->maxskip;
+ if (m > n) m = n;
+ if (m > 0) m--; /* -falign-foo=N,M means M-1 max bytes of padding, not M */
+ a->maxskip = m;
+ return flag;
+}
+
static void
+parse_N_M (const char *flag, const char *name, struct align_flags a[2])
+{
+ if (flag)
+ {
+ flag = read_log_maxskip (flag, name, &a[0]);
+ if (flag)
+ flag = read_log_maxskip (flag, name, &a[1]);
+#if defined (__i386__) || defined (__x86_64__)
+ /* Before -falign-foo=N,M,N2,M2 was introduced, x86 had a tweak.
+ -falign-functions=N with N > 8 was adding secondary alignment.
+ -falign-functions=10 was emitting this before every function:
+ .p2align 4,,9
+ .p2align 3
+ Now this behavior (and more) can be explicitly requested:
+ -falign-functions=16,10,8
+ Retain old behavior if N2 is missing: */
+ else if (a[0].log > 3)
+ a[1].log = 3;
+#endif
+ }
+}
+
+/* Process -falign-foo=N[,M[,N2[,M2]]] options. */
+static void
init_alignments (void)
{
- if (align_loops <= 0)
- align_loops = 1;
- if (align_loops_max_skip > align_loops)
- align_loops_max_skip = align_loops - 1;
- align_loops_log = floor_log2 (align_loops * 2 - 1);
- if (align_jumps <= 0)
- align_jumps = 1;
- if (align_jumps_max_skip > align_jumps)
- align_jumps_max_skip = align_jumps - 1;
- align_jumps_log = floor_log2 (align_jumps * 2 - 1);
- if (align_labels <= 0)
- align_labels = 1;
- align_labels_log = floor_log2 (align_labels * 2 - 1);
- if (align_labels_max_skip > align_labels)
- align_labels_max_skip = align_labels - 1;
- if (align_functions <= 0)
- align_functions = 1;
- align_functions_log = floor_log2 (align_functions * 2 - 1);
+ parse_N_M (str_align_loops, "loops", align_loops);
+ parse_N_M (str_align_jumps, "jumps", align_jumps);
+ parse_N_M (str_align_labels, "labels", align_labels);
+ parse_N_M (str_align_functions, "functions", align_functions);
}
/* Process the options that have been parsed. */
Index: gcc/varasm.c
===================================================================
--- gcc/varasm.c (revision 239860)
+++ gcc/varasm.c (working copy)
@@ -1791,7 +1791,9 @@ assemble_start_function (tree decl, const char *fn
{
#ifdef ASM_OUTPUT_MAX_SKIP_ALIGN
ASM_OUTPUT_MAX_SKIP_ALIGN (asm_out_file,
- align_functions_log, align_functions - 1);
+ align_functions[0].log, align_functions[0].maxskip);
+ ASM_OUTPUT_MAX_SKIP_ALIGN (asm_out_file,
+ align_functions[1].log, align_functions[1].maxskip);
#else
ASM_OUTPUT_ALIGN (asm_out_file, align_functions_log);
#endif
^ permalink raw reply [flat|nested] 2+ messages in thread
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2016-08-30 16:34 [PATCH v3 1/2] Temporary remove "at least 8 byte alignment" code from x86 Denys Vlasenko
2016-08-30 16:35 ` [PATCH v3 2/2] Extend -falign-FOO=N to N[,M[,N2[,M2]]] Denys Vlasenko
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