re PR rtl-optimization/21848 (load_mems / replace_loop_mems bug causes miscompilation of jcf-io.c / SEGV while processing java/lang/AbstractMethodError)

	PR rtl-optimization/21848
	* calls.c (emit_library_call_value_1): For const functions, add
	USEs of the stack slots to CALL_INSN_FUNCTION_USAGE.

From-SVN: r102281

1 files changed, 22 insertions, 0 deletions

diff --git a/gcc/calls.c b/gcc/calls.c
index f21426f..8e87886 100644
--- a/gcc/calls.c
+++ b/gcc/calls.c
@@ -3623,6 +3623,28 @@ emit_library_call_value_1 (int retval, rtx orgfun, rtx value,
 	      stack_usage_map[i] = 1;
 
 	  NO_DEFER_POP;
+
+	  if (flags & ECF_CONST)
+	    {
+	      rtx use;
+
+	      /* Indicate argument access so that alias.c knows that these
+		 values are live.  */
+	      if (argblock)
+		use = plus_constant (argblock,
+				     argvec[argnum].locate.offset.constant);
+	      else
+		/* When arguemnts are pushed, trying to tell alias.c where
+		   exactly this argument is won't work, because the
+		   auto-increment causes confusion.  So we merely indicate
+		   that we access something with a known mode somewhere on
+		   the stack.  */
+	        use = gen_rtx_PLUS (Pmode, virtual_outgoing_args_rtx,
+				    gen_rtx_SCRATCH (Pmode));
+	      use = gen_rtx_MEM (argvec[argnum].mode, use);
+	      use = gen_rtx_USE (VOIDmode, use);
+	      call_fusage = gen_rtx_EXPR_LIST (VOIDmode, use, call_fusage);
+	    }
 	}
     }