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Re: [PATCH] Prefer mempcpy to memcpy on x86_64 target (PR middle-end/81657).
On 03/14/2018 02:07 PM, Jakub Jelinek wrote:
> On Wed, Mar 14, 2018 at 01:54:39PM +0100, Martin Liška wrote:
>> --- a/gcc/builtins.c
>> +++ b/gcc/builtins.c
>> @@ -3651,13 +3651,24 @@ expand_builtin_memory_copy_args (tree dest, tree src, tree len,
>> src_mem = get_memory_rtx (src, len);
>> set_mem_align (src_mem, src_align);
>>
>> + bool is_move_done;
>> +
>> /* Copy word part most expediently. */
>
> This comment supposedly belongs right above the emit_block_move_hints call.
>
>> + bool bail_out_libcall = endp == 1
>> + && targetm.libc_func_speed ((int)BUILT_IN_MEMPCPY) == FAST_SPEED;
>
> Formatting. && belongs below endp. So either:
> bool bail_out_libcall
> = (endp == 1
> && ...);
> or
> bool bail_out_libcall = false;
> if (endp == 1
> && ...)
> bail_out_libcall = true;
> ?
> The variable is not named very well, shouldn't it be avoid_libcall or
> something similar? Perhaps the variable should have a comment describing
> what it is. Do you need separate argument for that bool and
> is_move_done, rather than just the flag being that some pointer to bool is
> non-NULL?
Can you please explain me how to replace the 2 new arguments?
>
>> dest_addr = emit_block_move_hints (dest_mem, src_mem, len_rtx,
>> CALL_EXPR_TAILCALL (exp)
>> && (endp == 0 || target == const0_rtx)
>> ? BLOCK_OP_TAILCALL : BLOCK_OP_NORMAL,
>> expected_align, expected_size,
>> - min_size, max_size, probable_max_size);
>> + min_size, max_size, probable_max_size,
>> + bail_out_libcall, &is_move_done);
>> +
>> + /* Bail out when a mempcpy call would be expanded as libcall and when
>> + we have a target that provides a fast implementation
>> + of mempcpy routine. */
>> + if (!is_move_done)
>> + return NULL_RTX;
>>
>> if (dest_addr == 0)
>> {
>> --- a/gcc/config/i386/i386.c
>> +++ b/gcc/config/i386/i386.c
>> @@ -2733,6 +2733,23 @@ ix86_using_red_zone (void)
>> && (!cfun->machine->has_local_indirect_jump
>> || cfun->machine->indirect_branch_type == indirect_branch_keep));
>> }
>> +
>
> Missing function comment here. For target hooks, usually there is a copy of
> the target.def comment, perhaps with further details on why it is overridden
> and what it does.
>> --- a/gcc/coretypes.h
>> +++ b/gcc/coretypes.h
>> @@ -384,6 +384,13 @@ enum excess_precision_type
>> EXCESS_PRECISION_TYPE_FAST
>> };
>>
>
> Missing comment describing what it is, plus it the enumerators are too
> generic, if it is libc_speed enum, perhaps LIBC_FAST_SPEED etc.?
>> --- a/gcc/targhooks.c
>> +++ b/gcc/targhooks.c
>> @@ -1642,6 +1642,12 @@ no_c99_libc_has_function (enum function_class fn_class ATTRIBUTE_UNUSED)
>> return false;
>> }
>>
>
> Again, missing function comment.
>
>> +enum libc_speed
>> +default_libc_func_speed (int)
>> +{
>> + return UNKNOWN_SPEED;
>> +}
>> +
>
>> --- a/gcc/testsuite/gcc.dg/string-opt-1.c
>> +++ b/gcc/testsuite/gcc.dg/string-opt-1.c
>> @@ -48,5 +48,5 @@ main (void)
>> return 0;
>> }
>>
>> -/* { dg-final { scan-assembler-not "\<mempcpy\>" } } */
>> -/* { dg-final { scan-assembler "memcpy" } } */
>> +/* { dg-final { scan-assembler-not "\<mempcpy\>" { target { i?86-*-* x86_64-*-* } } } } */
>> +/* { dg-final { scan-assembler "memcpy" { target { ! { i?86-*-* x86_64-*-* } } } } } */
>
> First of all, I don't really understand this, I'd expect both the
> two old dg-final lines to be used as is for non-x86 targets and another two
> for x86_64, and more importantly, the target hook is only for glibc, not for
> musl/bionic etc., nor for non-linux, so you probably need some effective
> target for it for whether it is glibc rather than musl/bionic, and use
> ...-*-linux* and ...-*-gnu* etc. rather than ...-*-*. Or tweak the dg-fianl
> patterns so that it succeeds on both variants of the target hook, but then
> does the test test anything at all?
I fixed that by preserving the old 2 old-finals and then I added a new for x86_64 target.
Apart from the comment above I've fixed all nits and mempcpy is not used when LHS == NULL.
Martin
>
> Jakub
>
>From 26979038ce9500015f957afd896146022a38490b Mon Sep 17 00:00:00 2001
From: marxin <mliska@suse.cz>
Date: Wed, 14 Mar 2018 09:44:18 +0100
Subject: [PATCH] Introduce new libc_func_speed target hook (PR
middle-end/81657).
gcc/ChangeLog:
2018-03-14 Martin Liska <mliska@suse.cz>
PR middle-end/81657
* builtins.c (expand_builtin_memory_copy_args): Handle situation
when libc library provides a fast mempcpy implementation/
* config/i386/i386-protos.h (gnu_libc_func_speed): New.
* config/i386/i386.c (enum libc_speed): Likewise.
(ix86_libc_func_speed): Likewise.
(TARGET_LIBC_FUNC_SPEED): Likewise.
* coretypes.h (enum libc_speed): Likewise.
* doc/tm.texi: Document new target hook.
* doc/tm.texi.in: Likewise.
* expr.c (emit_block_move_hints): Handle libc bail out argument.
* expr.h (emit_block_move_hints): Add new parameters.
* target.def: Add new hook.
* targhooks.c (enum libc_speed): New enum.
(default_libc_func_speed): Provide a default hook
implementation.
* targhooks.h (default_libc_func_speed): Likewise.
gcc/testsuite/ChangeLog:
2018-03-14 Martin Liska <mliska@suse.cz>
* gcc.dg/string-opt-1.c: Adjust scans for i386 and glibc target
and others.
---
gcc/builtins.c | 16 +++++++++++++++-
gcc/config/i386/i386-protos.h | 2 ++
gcc/config/i386/i386.c | 24 ++++++++++++++++++++++++
gcc/coretypes.h | 7 +++++++
gcc/doc/tm.texi | 4 ++++
gcc/doc/tm.texi.in | 1 +
gcc/expr.c | 16 +++++++++++++++-
gcc/expr.h | 4 +++-
gcc/target.def | 7 +++++++
gcc/targhooks.c | 9 +++++++++
gcc/targhooks.h | 1 +
gcc/testsuite/gcc.dg/string-opt-1.c | 5 +++--
12 files changed, 91 insertions(+), 5 deletions(-)
diff --git a/gcc/builtins.c b/gcc/builtins.c
index 85affa74510..b668045374c 100644
--- a/gcc/builtins.c
+++ b/gcc/builtins.c
@@ -3651,13 +3651,27 @@ expand_builtin_memory_copy_args (tree dest, tree src, tree len,
src_mem = get_memory_rtx (src, len);
set_mem_align (src_mem, src_align);
+ bool is_move_done;
+
+ /* emit_block_move_hints can generate a library call to memcpy function.
+ In situations when a libc library provides fast implementation
+ of mempcpy, then it's better to call mempcpy directly. */
+ bool avoid_libcall
+ = (endp == 1
+ && targetm.libc_func_speed ((int)BUILT_IN_MEMPCPY) == LIBC_FAST_SPEED
+ && target != const0_rtx);
+
/* Copy word part most expediently. */
dest_addr = emit_block_move_hints (dest_mem, src_mem, len_rtx,
CALL_EXPR_TAILCALL (exp)
&& (endp == 0 || target == const0_rtx)
? BLOCK_OP_TAILCALL : BLOCK_OP_NORMAL,
expected_align, expected_size,
- min_size, max_size, probable_max_size);
+ min_size, max_size, probable_max_size,
+ avoid_libcall, &is_move_done);
+
+ if (!is_move_done)
+ return NULL_RTX;
if (dest_addr == 0)
{
diff --git a/gcc/config/i386/i386-protos.h b/gcc/config/i386/i386-protos.h
index ef7c818986f..d3fc515845b 100644
--- a/gcc/config/i386/i386-protos.h
+++ b/gcc/config/i386/i386-protos.h
@@ -47,6 +47,8 @@ extern void ix86_reset_previous_fndecl (void);
extern bool ix86_using_red_zone (void);
+extern enum libc_speed gnu_libc_func_speed (int fn);
+
#ifdef RTX_CODE
extern int standard_80387_constant_p (rtx);
extern const char *standard_80387_constant_opcode (rtx);
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index af24c6ec5ba..f4cbecdf099 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -2733,6 +2733,27 @@ ix86_using_red_zone (void)
&& (!cfun->machine->has_local_indirect_jump
|| cfun->machine->indirect_branch_type == indirect_branch_keep));
}
+
+/* This hook determines whether a function from libc has a fast implementation
+ FN is present at the runtime. We override it for i386 and glibc C library
+ as this combination provides fast implementation of mempcpy function. */
+
+enum libc_speed
+ix86_libc_func_speed (int fn)
+{
+ enum built_in_function f = (built_in_function)fn;
+
+ if (!OPTION_GLIBC)
+ return LIBC_UNKNOWN_SPEED;
+
+ switch (f)
+ {
+ case BUILT_IN_MEMPCPY:
+ return LIBC_FAST_SPEED;
+ default:
+ return LIBC_UNKNOWN_SPEED;
+ }
+}
/* Return a string that documents the current -m options. The caller is
responsible for freeing the string. */
@@ -52061,6 +52082,9 @@ ix86_run_selftests (void)
#undef TARGET_WARN_PARAMETER_PASSING_ABI
#define TARGET_WARN_PARAMETER_PASSING_ABI ix86_warn_parameter_passing_abi
+#undef TARGET_LIBC_FUNC_SPEED
+#define TARGET_LIBC_FUNC_SPEED ix86_libc_func_speed
+
#if CHECKING_P
#undef TARGET_RUN_TARGET_SELFTESTS
#define TARGET_RUN_TARGET_SELFTESTS selftest::ix86_run_selftests
diff --git a/gcc/coretypes.h b/gcc/coretypes.h
index 283b4eb33fe..fe618f708f4 100644
--- a/gcc/coretypes.h
+++ b/gcc/coretypes.h
@@ -384,6 +384,13 @@ enum excess_precision_type
EXCESS_PRECISION_TYPE_FAST
};
+enum libc_speed
+{
+ LIBC_FAST_SPEED,
+ LIBC_SLOW_SPEED,
+ LIBC_UNKNOWN_SPEED
+};
+
/* Support for user-provided GGC and PCH markers. The first parameter
is a pointer to a pointer, the second a cookie. */
typedef void (*gt_pointer_operator) (void *, void *);
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index bd8b917ba82..0f7c91a22c4 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -5501,6 +5501,10 @@ macro, a reasonable default is used.
This hook determines whether a function from a class of functions
@var{fn_class} is present at the runtime.
@end deftypefn
+@deftypefn {Target Hook} libc_speed TARGET_LIBC_FUNC_SPEED (int @var{fn})
+This hook determines whether a function from libc has a fast implementation
+@var{fn} is present at the runtime.
+@end deftypefn
@defmac NEXT_OBJC_RUNTIME
Set this macro to 1 to use the "NeXT" Objective-C message sending conventions
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index b0207146e8c..4bb2998a8a1 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -3933,6 +3933,7 @@ macro, a reasonable default is used.
@end defmac
@hook TARGET_LIBC_HAS_FUNCTION
+@hook TARGET_LIBC_FUNC_SPEED
@defmac NEXT_OBJC_RUNTIME
Set this macro to 1 to use the "NeXT" Objective-C message sending conventions
diff --git a/gcc/expr.c b/gcc/expr.c
index 00660293f72..b6c13652d79 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -1554,6 +1554,8 @@ compare_by_pieces (rtx arg0, rtx arg1, unsigned HOST_WIDE_INT len,
MIN_SIZE is the minimal size of block to move
MAX_SIZE is the maximal size of block to move, if it can not be represented
in unsigned HOST_WIDE_INT, than it is mask of all ones.
+ If BAIL_OUT_LIBCALL is set true, do not emit library call and set
+ *IS_MOVE_DONE to false.
Return the address of the new block, if memcpy is called and returns it,
0 otherwise. */
@@ -1563,12 +1565,17 @@ emit_block_move_hints (rtx x, rtx y, rtx size, enum block_op_methods method,
unsigned int expected_align, HOST_WIDE_INT expected_size,
unsigned HOST_WIDE_INT min_size,
unsigned HOST_WIDE_INT max_size,
- unsigned HOST_WIDE_INT probable_max_size)
+ unsigned HOST_WIDE_INT probable_max_size,
+ bool bail_out_libcall, bool *is_move_done)
{
bool may_use_call;
rtx retval = 0;
unsigned int align;
+ /* When not doing a bail out, we always emit a memory move. */
+ if (is_move_done)
+ *is_move_done = true;
+
gcc_assert (size);
if (CONST_INT_P (size) && INTVAL (size) == 0)
return 0;
@@ -1625,6 +1632,13 @@ emit_block_move_hints (rtx x, rtx y, rtx size, enum block_op_methods method,
&& ADDR_SPACE_GENERIC_P (MEM_ADDR_SPACE (x))
&& ADDR_SPACE_GENERIC_P (MEM_ADDR_SPACE (y)))
{
+ if (bail_out_libcall)
+ {
+ if (is_move_done)
+ *is_move_done = false;
+ return retval;
+ }
+
/* Since x and y are passed to a libcall, mark the corresponding
tree EXPR as addressable. */
tree y_expr = MEM_EXPR (y);
diff --git a/gcc/expr.h b/gcc/expr.h
index b3d523bcb24..023bc5aec47 100644
--- a/gcc/expr.h
+++ b/gcc/expr.h
@@ -110,7 +110,9 @@ extern rtx emit_block_move_hints (rtx, rtx, rtx, enum block_op_methods,
unsigned int, HOST_WIDE_INT,
unsigned HOST_WIDE_INT,
unsigned HOST_WIDE_INT,
- unsigned HOST_WIDE_INT);
+ unsigned HOST_WIDE_INT,
+ bool bail_out_libcall = false,
+ bool *is_move_done = NULL);
extern rtx emit_block_cmp_hints (rtx, rtx, rtx, tree, rtx, bool,
by_pieces_constfn, void *);
extern bool emit_storent_insn (rtx to, rtx from);
diff --git a/gcc/target.def b/gcc/target.def
index c5b2a1e7e71..3bbddc82776 100644
--- a/gcc/target.def
+++ b/gcc/target.def
@@ -2639,6 +2639,13 @@ DEFHOOK
bool, (enum function_class fn_class),
default_libc_has_function)
+DEFHOOK
+(libc_func_speed,
+ "This hook determines whether a function from libc has a fast implementation\n\
+@var{fn} is present at the runtime.",
+ libc_speed, (int fn),
+ default_libc_func_speed)
+
/* True if new jumps cannot be created, to replace existing ones or
not, at the current point in the compilation. */
DEFHOOK
diff --git a/gcc/targhooks.c b/gcc/targhooks.c
index fafcc6c5196..6e44f6f79cf 100644
--- a/gcc/targhooks.c
+++ b/gcc/targhooks.c
@@ -1642,6 +1642,15 @@ no_c99_libc_has_function (enum function_class fn_class ATTRIBUTE_UNUSED)
return false;
}
+/* This hook determines whether a function from libc has a fast implementation
+ FN is present at the runtime. */
+
+enum libc_speed
+default_libc_func_speed (int)
+{
+ return LIBC_UNKNOWN_SPEED;
+}
+
tree
default_builtin_tm_load_store (tree ARG_UNUSED (type))
{
diff --git a/gcc/targhooks.h b/gcc/targhooks.h
index 8a4393f2ba4..7508673ad0a 100644
--- a/gcc/targhooks.h
+++ b/gcc/targhooks.h
@@ -205,6 +205,7 @@ extern bool default_have_conditional_execution (void);
extern bool default_libc_has_function (enum function_class);
extern bool no_c99_libc_has_function (enum function_class);
extern bool gnu_libc_has_function (enum function_class);
+extern enum libc_speed default_libc_func_speed (int);
extern tree default_builtin_tm_load_store (tree);
diff --git a/gcc/testsuite/gcc.dg/string-opt-1.c b/gcc/testsuite/gcc.dg/string-opt-1.c
index 2f060732bf0..7faaadcbb1f 100644
--- a/gcc/testsuite/gcc.dg/string-opt-1.c
+++ b/gcc/testsuite/gcc.dg/string-opt-1.c
@@ -48,5 +48,6 @@ main (void)
return 0;
}
-/* { dg-final { scan-assembler-not "\<mempcpy\>" } } */
-/* { dg-final { scan-assembler "memcpy" } } */
+/* { dg-final { scan-assembler-not "\<mempcpy\>" { target { ! { i?86-*-gnu* x86_64-*-gnu* i?86-*-linux* x86_64-*-linux* } } } } } */
+/* { dg-final { scan-assembler "memcpy" { target { ! { i?86-*-gnu* x86_64-*-gnu* i?86-*-linux* x86_64-*-linux* } } } } } */
+/* { dg-final { scan-assembler "mempcpy" { target { i?86-*-gnu* x86_64-*-gnu* i?86-*-linux* x86_64-*-linux* } } } } */
--
2.16.2