rtlanal: dead_or_set_regno_p should handle CLOBBER (PR83424)

In PR83424 combine's move_deaths puts a REG_DEAD note in the wrong place
because dead_or_set_regno_p does not account for CLOBBER insns.  This
fixes it.


	PR rtl-optimization/83424
	* rtlanal.c (dead_or_set_regno_p): Handle CLOBBER just like SET.

gcc/testsuite/
	PR rtl-optimization/83424
	* gcc.dg/pr83424.c: New testsuite.

From-SVN: r255787

gcc/ChangeLog

+2017-12-18  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	PR rtl-optimization/83424
+	* rtlanal.c (dead_or_set_regno_p): Handle CLOBBER just like SET.
+
 2017-12-18  Marek Polacek  <polacek@redhat.com>
 
 	PR middle-end/83463

gcc/rtlanal.c

@@ -2082,7 +2082,7 @@ dead_or_set_regno_p (const rtx_insn *insn, unsigned int test_regno)
   if (GET_CODE (pattern) == COND_EXEC)
     return 0;
 
-  if (GET_CODE (pattern) == SET)
+  if (GET_CODE (pattern) == SET || GET_CODE (pattern) == CLOBBER)
     return covers_regno_p (SET_DEST (pattern), test_regno);
   else if (GET_CODE (pattern) == PARALLEL)
     {

gcc/testsuite/ChangeLog

+2017-12-18  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	PR rtl-optimization/83424
+	* gcc.dg/pr83424.c: New testcase.
+
 2017-12-18  David Malcolm  <dmalcolm@redhat.com>
 
 	PR tree-optimization/83336

gcc/testsuite/gcc.dg/pr83424.c

+/* PR rtl-optimization/83424 */
+/* { dg-do run { target int128 } } */
+/* { dg-options "-O -fno-tree-ccp -fno-tree-coalesce-vars" } */
+
+typedef unsigned char u8;
+typedef unsigned int u32;
+typedef unsigned __int128 u128;
+
+u32 a, c;
+u8 b;
+
+static u128 __attribute__ ((noinline, noclone))
+foo (u128 p)
+{
+  u8 x = ~b;
+  p &= c;
+  x *= -p;
+  x &= a == 0;
+  x >>= 1;
+  return p + x;
+}
+
+int
+main (void)
+{
+  u128 x = foo (0);
+  if (x != 0)
+    __builtin_abort ();
+  return 0;
+}