arm.c (arm_expand_prologue): Ensure that the stack-adjustment barrier can't be…

arm.c (arm_expand_prologue): Ensure that the stack-adjustment barrier can't be ignored by the alias analysis...

* arm.c (arm_expand_prologue): Ensure that the stack-adjustment
barrier can't be ignored by the alias analysis code.

From-SVN: r35911

gcc/ChangeLog

+2000-08-23  Richard Earnshaw  (rearnsha@arm.com)
+
+	* arm.c (arm_expand_prologue): Ensure that the stack-adjustment
+	barrier can't be ignored by the alias analysis code.
+
 2000-08-12  Eli Zaretskii  <eliz@is.elta.co.il>
 
 	* fixinc/inclhack.def (sysv68_string): Fix the Sed script so it

gcc/config/arm/arm.c

@@ -7430,8 +7430,19 @@ arm_expand_prologue ()
       insn = emit_insn (gen_addsi3 (stack_pointer_rtx, stack_pointer_rtx,
 				    amount));
       RTX_FRAME_RELATED_P (insn) = 1;
-      emit_insn (gen_rtx_CLOBBER (VOIDmode, 
-				  gen_rtx_MEM (BLKmode, stack_pointer_rtx)));
+
+      /* If the frame pointer is needed, emit a special barrier that
+	 will prevent the scheduler from moving stores to the frame
+	 before the stack adjustment.  */
+      if (frame_pointer_needed)
+	{
+	  rtx unspec = gen_rtx_UNSPEC (SImode,
+				       gen_rtvec (2, stack_pointer_rtx,
+						  hard_frame_pointer_rtx), 4);
+
+	  emit_insn (gen_rtx_CLOBBER (VOIDmode,
+				      gen_rtx_MEM (BLKmode, unspec)));
+	}
     }
 
   /* If we are profiling, make sure no instructions are scheduled before