x86: Add tests for PR tree-optimization/82142

Verify that PR tree-optimization/82142 testcase is properly optimized.

	PR tree-optimization/82142
	* gcc.target/i386/pr82142a.c: New file.
	* gcc.target/i386/pr82142b.c: Likewise.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>

gcc/testsuite/gcc.target/i386/pr82142a.c

+/* { dg-do compile { target { ! ia32 } } } */
+/* { dg-options "-O2 -mno-avx -msse2" } */
+/* Keep labels and directives ('.cfi_startproc', '.cfi_endproc').  */
+/* { dg-final { check-function-bodies "**" "" "" { target "*-*-*" } {^\t?\.}  } } */
+
+/*
+**assignzero:
+**.LFB0:
+**	.cfi_startproc
+**	pxor	%xmm0, %xmm0
+**	movups	%xmm0, 32\(%(?:r|e)di\)
+**	movups	%xmm0, \(%(?:r|e)di\)
+**	movups	%xmm0, 16\(%(?:r|e)di\)
+**	movups	%xmm0, 44\(%(?:r|e)di\)
+**	ret
+**...
+*/
+
+typedef struct
+{
+  int a, b, c;
+  char j, k, k1;
+  int l, m, n[8];
+  char c1, c2;
+} foo;
+
+void
+assignzero (foo *p)
+{
+  foo tmp = {};
+  *p = tmp;
+}

gcc/testsuite/gcc.target/i386/pr82142b.c

+/* { dg-do compile { target ia32 } } */
+/* { dg-options "-O2 -mno-avx -msse2" } */
+/* Keep labels and directives ('.cfi_startproc', '.cfi_endproc').  */
+/* { dg-final { check-function-bodies "**" "" "" { target "*-*-*" } {^\t?\.}  } } */
+
+/*
+**assignzero:
+**.LFB0:
+**	.cfi_startproc
+**	movl	4\(%esp\), %eax
+**	pxor	%xmm0, %xmm0
+**	movups	%xmm0, 32\(%eax\)
+**	movups	%xmm0, \(%eax\)
+**	movups	%xmm0, 16\(%eax\)
+**	movups	%xmm0, 44\(%eax\)
+**	ret
+**...
+*/
+
+#include "pr82142a.c"