x86: Improve vector_loop/unrolled_loop for memset/memcpy

x86: Improve vector_loop/unrolled_loop for memset/memcpy

1. Don't generate the loop if the loop count is 1.
2. For memset with vector on small size, use vector if small size supports
vector, otherwise use the scalar value.
3. Always expand vector-version of memset for vector_loop.
4. Always duplicate the promoted scalar value for vector_loop if not 0 nor
-1.
5. Use misaligned prologue if alignment isn't needed.  When misaligned
prologue is used, check if destination is actually aligned and update
destination alignment if aligned.
6. Use move_by_pieces and store_by_pieces for memcpy and memset epilogues
with the fixed epilogue size to enable overlapping moves and stores.

The included tests show that codegen of vector_loop/unrolled_loop for
memset/memcpy are significantly improved.  For

void
foo (void *p1, size_t len)
{
  __builtin_memset (p1, 0, len);
}

with

-O2 -minline-all-stringops -mmemset-strategy=vector_loop:256:noalign,libcall:-1:noalign -march=x86-64

we used to generate

foo:
.LFB0:
	.cfi_startproc
	movq	%rdi, %rax
	pxor	%xmm0, %xmm0
	cmpq	$64, %rsi
	jnb	.L18
.L2:
	andl	$63, %esi
	je	.L1
	xorl	%edx, %edx
	testb	$1, %sil
	je	.L5
	movl	$1, %edx
	movb	$0, (%rax)
	cmpq	%rsi, %rdx
	jnb	.L19
.L5:
	movb	$0, (%rax,%rdx)
	movb	$0, 1(%rax,%rdx)
	addq	$2, %rdx
	cmpq	%rsi, %rdx
	jb	.L5
.L1:
	ret
	.p2align 4,,10
	.p2align 3
.L18:
	movq	%rsi, %rdx
	xorl	%eax, %eax
	andq	$-64, %rdx
.L3:
	movups	%xmm0, (%rdi,%rax)
	movups	%xmm0, 16(%rdi,%rax)
	movups	%xmm0, 32(%rdi,%rax)
	movups	%xmm0, 48(%rdi,%rax)
	addq	$64, %rax
	cmpq	%rdx, %rax
	jb	.L3
	addq	%rdi, %rax
	jmp	.L2
.L19:
	ret
	.cfi_endproc

with very poor prologue/epilogue.  With this patch, we now generate:

foo:
.LFB0:
	.cfi_startproc
	pxor	%xmm0, %xmm0
	cmpq	$64, %rsi
	jnb	.L2
	testb	$32, %sil
	jne	.L19
	testb	$16, %sil
	jne	.L20
	testb	$8, %sil
	jne	.L21
	testb	$4, %sil
	jne	.L22
	testq	%rsi, %rsi
	jne	.L23
.L1:
	ret
	.p2align 4,,10
	.p2align 3
.L2:
	movups	%xmm0, -64(%rdi,%rsi)
	movups	%xmm0, -48(%rdi,%rsi)
	movups	%xmm0, -32(%rdi,%rsi)
	movups	%xmm0, -16(%rdi,%rsi)
	subq	$1, %rsi
	cmpq	$64, %rsi
	jb	.L1
	andq	$-64, %rsi
	xorl	%eax, %eax
.L9:
	movups	%xmm0, (%rdi,%rax)
	movups	%xmm0, 16(%rdi,%rax)
	movups	%xmm0, 32(%rdi,%rax)
	movups	%xmm0, 48(%rdi,%rax)
	addq	$64, %rax
	cmpq	%rsi, %rax
	jb	.L9
	ret
	.p2align 4,,10
	.p2align 3
.L23:
	movb	$0, (%rdi)
	testb	$2, %sil
	je	.L1
	xorl	%eax, %eax
	movw	%ax, -2(%rdi,%rsi)
	ret
	.p2align 4,,10
	.p2align 3
.L19:
	movups	%xmm0, (%rdi)
	movups	%xmm0, 16(%rdi)
	movups	%xmm0, -32(%rdi,%rsi)
	movups	%xmm0, -16(%rdi,%rsi)
	ret
	.p2align 4,,10
	.p2align 3
.L20:
	movups	%xmm0, (%rdi)
	movups	%xmm0, -16(%rdi,%rsi)
	ret
	.p2align 4,,10
	.p2align 3
.L21:
	movq	$0, (%rdi)
	movq	$0, -8(%rdi,%rsi)
	ret
	.p2align 4,,10
	.p2align 3
.L22:
	movl	$0, (%rdi)
	movl	$0, -4(%rdi,%rsi)
	ret
	.cfi_endproc

gcc/

	PR target/120670
	PR target/120683
	* config/i386/i386-expand.cc (expand_set_or_cpymem_via_loop):
	Don't generate the loop if the loop count is 1.
	(expand_cpymem_epilogue): Use move_by_pieces.
	(setmem_epilogue_gen_val): New.
	(expand_setmem_epilogue): Use store_by_pieces.
	(expand_small_cpymem_or_setmem): Choose cpymem mode from MOVE_MAX.
	For memset with vector and the size is smaller than the vector
	size, first try the narrower vector, otherwise, use the scalar
	value.
	(promote_duplicated_reg): Duplicate the scalar value for vector.
	(ix86_expand_set_or_cpymem): Always expand vector-version of
	memset for vector_loop.  Use misaligned prologue if alignment
	isn't needed and destination isn't aligned.  Always initialize
	vec_promoted_val from the promoted scalar value for vector_loop.

gcc/testsuite/

	PR target/120670
	PR target/120683
	* gcc.target/i386/auto-init-padding-9.c: Updated.
	* gcc.target/i386/memcpy-strategy-12.c: Likewise.
	* gcc.target/i386/memset-strategy-25.c: Likewise.
	* gcc.target/i386/memset-strategy-29.c: Likewise.
	* gcc.target/i386/memset-strategy-30.c: Likewise.
	* gcc.target/i386/memset-strategy-31.c: Likewise.
	* gcc.target/i386/memcpy-pr120683-1.c: New test.
	* gcc.target/i386/memcpy-pr120683-2.c: Likewise.
	* gcc.target/i386/memcpy-pr120683-3.c: Likewise.
	* gcc.target/i386/memcpy-pr120683-4.c: Likewise.
	* gcc.target/i386/memcpy-pr120683-5.c: Likewise.
	* gcc.target/i386/memcpy-pr120683-6.c: Likewise.
	* gcc.target/i386/memcpy-pr120683-7.c: Likewise.
	* gcc.target/i386/memset-pr120683-1.c: Likewise.
	* gcc.target/i386/memset-pr120683-2.c: Likewise.
	* gcc.target/i386/memset-pr120683-3.c: Likewise.
	* gcc.target/i386/memset-pr120683-4.c: Likewise.
	* gcc.target/i386/memset-pr120683-5.c: Likewise.
	* gcc.target/i386/memset-pr120683-6.c: Likewise.
	* gcc.target/i386/memset-pr120683-7.c: Likewise.
	* gcc.target/i386/memset-pr120683-8.c: Likewise.
	* gcc.target/i386/memset-pr120683-9.c: Likewise.
	* gcc.target/i386/memset-pr120683-10.c: Likewise.
	* gcc.target/i386/memset-pr120683-11.c: Likewise.
	* gcc.target/i386/memset-pr120683-12.c: Likewise.
	* gcc.target/i386/memset-pr120683-13.c: Likewise.
	* gcc.target/i386/memset-pr120683-14.c: Likewise.
	* gcc.target/i386/memset-pr120683-15.c: Likewise.
	* gcc.target/i386/memset-pr120683-16.c: Likewise.
	* gcc.target/i386/memset-pr120683-17.c: Likewise.
	* gcc.target/i386/memset-pr120683-18.c: Likewise.
	* gcc.target/i386/memset-pr120683-19.c: Likewise.
	* gcc.target/i386/memset-pr120683-20.c: Likewise.
	* gcc.target/i386/memset-pr120683-21.c: Likewise.
	* gcc.target/i386/memset-pr120683-22.c: Likewise.
	* gcc.target/i386/memset-pr120683-23.c: Likewise.