[PATCH] Prefer mempcpy to memcpy on x86_64 target (PR middle-end/81657).

[Martin Liška <mliska at suse dot cz>]

Hi.

This is fix for the PR that introduces a new target macro. Using the macro
one can say that a target has a fast mempcpy and thus it's preferred to be used
if possible.

Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.
I also tested on x86_64-linux-gnu.

Ready to be installed?
Martin

gcc/ChangeLog:

2018-03-08  Martin Liska  <mliska@suse.cz>

	PR middle-end/81657
	* builtins.c (expand_builtin_memory_copy_args): Add new
	arguments.
	* config/i386/i386.h (TARGET_HAS_FAST_MEMPCPY_ROUTINE):
	New macro.
	* defaults.h (TARGET_HAS_FAST_MEMPCPY_ROUTINE): Likewise.
	* doc/tm.texi: Likewise.
	* doc/tm.texi.in: Likewise.
	* expr.c (compare_by_pieces): Add support for bail out.
	(emit_block_move_hints): Likewise.
	* expr.h (emit_block_move_hints): Add new arguments.

gcc/testsuite/ChangeLog:

2018-03-09  Martin Liska  <mliska@suse.cz>

	PR middle-end/81657
	* gcc.dg/string-opt-1.c: Adjust test to run only on non-x86
	target.
---
 gcc/builtins.c                      | 13 ++++++++++++-
 gcc/config/i386/i386.h              |  3 +++
 gcc/defaults.h                      |  7 +++++++
 gcc/doc/tm.texi                     |  5 +++++
 gcc/doc/tm.texi.in                  |  5 +++++
 gcc/expr.c                          | 16 +++++++++++++++-
 gcc/expr.h                          |  4 +++-
 gcc/testsuite/gcc.dg/string-opt-1.c |  4 ++--
 8 files changed, 52 insertions(+), 5 deletions(-)


diff --git a/gcc/builtins.c b/gcc/builtins.c
index 85affa74510..c2ca36934f7 100644
--- 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.  */
   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,
+				     TARGET_HAS_FAST_MEMPCPY_ROUTINE
+				     && endp == 1,
+				     &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)
     {
diff --git a/gcc/config/i386/i386.h b/gcc/config/i386/i386.h
index e43edd77b56..8744d706fd7 100644
--- a/gcc/config/i386/i386.h
+++ b/gcc/config/i386/i386.h
@@ -1914,6 +1914,9 @@ typedef struct ix86_args {
 
 #define CLEAR_RATIO(speed) ((speed) ? MIN (6, ix86_cost->move_ratio) : 2)
 
+/* C library provides fast implementation of mempcpy function.  */
+#define TARGET_HAS_FAST_MEMPCPY_ROUTINE 1
+
 /* Define if shifts truncate the shift count which implies one can
    omit a sign-extension or zero-extension of a shift count.
 
diff --git a/gcc/defaults.h b/gcc/defaults.h
index 78a08a33f12..2e5caac8dcd 100644
--- a/gcc/defaults.h
+++ b/gcc/defaults.h
@@ -1340,6 +1340,13 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #define SET_RATIO(speed) MOVE_RATIO (speed)
 #endif
 
+/* By default do not generate libcall to mempcpy and rather use
+   libcall to memcpy and adjustment of return value.  */
+
+#ifndef TARGET_HAS_FAST_MEMPCPY_ROUTINE
+#define TARGET_HAS_FAST_MEMPCPY_ROUTINE 0
+#endif
+
 /* Supply a default definition of STACK_SAVEAREA_MODE for emit_stack_save.
    Normally move_insn, so Pmode stack pointer.  */
 
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index bd8b917ba82..0c8a3f3298c 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -6627,6 +6627,11 @@ optimized for speed rather than size.
 If you don't define this, it defaults to the value of @code{MOVE_RATIO}.
 @end defmac
 
+@defmac TARGET_HAS_FAST_MEMPCPY_ROUTINE
+By default do not generate libcall to mempcpy and rather use
+libcall to memcpy and adjustment of return value.
+@end defmac
+
 @defmac USE_LOAD_POST_INCREMENT (@var{mode})
 A C expression used to determine whether a load postincrement is a good
 thing to use for a given mode.  Defaults to the value of
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index b0207146e8c..e7ef85ab78e 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -4560,6 +4560,11 @@ optimized for speed rather than size.
 If you don't define this, it defaults to the value of @code{MOVE_RATIO}.
 @end defmac
 
+@defmac TARGET_HAS_FAST_MEMPCPY_ROUTINE
+By default do not generate libcall to mempcpy and rather use
+libcall to memcpy and adjustment of return value.
+@end defmac
+
 @defmac USE_LOAD_POST_INCREMENT (@var{mode})
 A C expression used to determine whether a load postincrement is a good
 thing to use for a given mode.  Defaults to the value of
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/testsuite/gcc.dg/string-opt-1.c b/gcc/testsuite/gcc.dg/string-opt-1.c
index 2f060732bf0..851c8b04a33 100644
--- 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-*-* } } } } } */