i386: Fix rtl checking ICE in ix86_elim_entry_set_got [PR112837]

The following testcase ICEs with RTL checking, because it sets if
XINT (SET_SRC (set), 1) is UNSPEC_SET_GOT without checking if SET_SRC (set)
is actually an UNSPEC, so any time we see any other insn with PARALLEL
and a SET in it which is not an UNSPEC we ICE during RTL checking or
access there some other union member as if it was an rt_int.
The rest is just small cleanup.

2023-12-04  Jakub Jelinek  <jakub@redhat.com>

	PR target/112837
	* config/i386/i386.cc (ix86_elim_entry_set_got): Before checking
	for UNSPEC_SET_GOT check that SET_SRC is UNSPEC.  Use SET_SRC and
	SET_DEST macros instead of XEXP, rename vec variable to set.

	* gcc.dg/pr112837.c: New test.

gcc/config/i386/i386.cc

@@ -8607,10 +8607,11 @@ ix86_elim_entry_set_got (rtx reg)
       rtx pat = PATTERN (c_insn);
       if (GET_CODE (pat) == PARALLEL)
 	{
-	  rtx vec = XVECEXP (pat, 0, 0);
-	  if (GET_CODE (vec) == SET
-	      && XINT (XEXP (vec, 1), 1) == UNSPEC_SET_GOT
-	      && REGNO (XEXP (vec, 0)) == REGNO (reg))
+	  rtx set = XVECEXP (pat, 0, 0);
+	  if (GET_CODE (set) == SET
+	      && GET_CODE (SET_SRC (set)) == UNSPEC
+	      && XINT (SET_SRC (set), 1) == UNSPEC_SET_GOT
+	      && REGNO (SET_DEST (set)) == REGNO (reg))
 	    delete_insn (c_insn);
 	}
     }

gcc/testsuite/gcc.dg/pr112837.c

@@ -0,0 +1,11 @@
+/* PR target/112837 */
+/* { dg-do compile } */
+/* { dg-options "-fcompare-elim -fprofile" } */
+/* { dg-additional-options "-fpie" { target pie } } */
+/* { dg-require-profiling "-fprofile" } */
+
+void
+foo (int i)
+{
+  foo (i);
+}