(mark_used_regs): When adding REG_DEAD notes...

(mark_used_regs): When adding REG_DEAD notes, check for
the case where a multiple register hard reg overlaps a register
set by the insn.

From-SVN: r7921

gcc/flow.c

@@ -2403,6 +2403,16 @@ mark_used_regs (needed, live, x, final, insn)
 #endif
 		)
 	      {
+		/* Check for the case where the register dying partially
+		   overlaps the register set by this insn.  */
+		if (regno < FIRST_PSEUDO_REGISTER
+		    && HARD_REGNO_NREGS (regno, GET_MODE (x)) > 1)
+		  {
+		    int n = HARD_REGNO_NREGS (regno, GET_CODE (x));
+		    while (--n >= 0)
+		      some_needed |= dead_or_set_regno_p (insn, regno + n);
+		  }
+
 		/* If none of the words in X is needed, make a REG_DEAD
 		   note.  Otherwise, we must make partial REG_DEAD notes.  */
 		if (! some_needed)