commit 61beb521f63db2f7178e2c41e3747982ddcc8869
Author: Kyrylo Tkachov <kyrylo.tkachov@arm.com>
Date:   Wed Mar 18 13:42:37 2015 +0000

    [expr.c] PR 65358 Avoid clobbering partial argument during sibcall

diff --git a/gcc/calls.c b/gcc/calls.c
index 3be7ca5..8159232 100644
--- a/gcc/calls.c
+++ b/gcc/calls.c
@@ -3229,6 +3229,13 @@ expand_call (tree exp, rtx target, int ignore)
 	    {
 	      rtx_insn *before_arg = get_last_insn ();
 
+	     /* On targets with weird calling conventions (e.g. PA) it's
+		hard to ensure that all cases of argument overlap between
+		stack and registers work.  Play it safe and bail out.  */
+#if defined (ARGS_GROW_DOWNWARD) && !defined (STACK_GROWS_DOWNWARD)
+	      sibcall_failure = 1;
+	      break;
+#endif
 	      if (store_one_arg (&args[i], argblock, flags,
 				 adjusted_args_size.var != 0,
 				 reg_parm_stack_space)
diff --git a/gcc/expr.c b/gcc/expr.c
index 530a944..071a335 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -4121,6 +4121,24 @@ emit_single_push_insn (machine_mode mode, rtx x, tree type)
 }
 #endif
 
+/* If reading SIZE bytes from X will end up reading from
+   Y return the number of bytes that overlap.  Return -1
+   in all other cases.  */
+
+static int
+memory_load_overlap (rtx x, rtx y, HOST_WIDE_INT size)
+{
+  rtx tmp = plus_constant (Pmode, x, size);
+  rtx sub = simplify_gen_binary (MINUS, Pmode, tmp, y);
+
+  if (!CONST_INT_P (sub))
+    return -1;
+
+  HOST_WIDE_INT val = INTVAL (sub);
+
+  return IN_RANGE (val, 1, size) ? val : -1;
+}
+
 /* Generate code to push X onto the stack, assuming it has mode MODE and
    type TYPE.
    MODE is redundant except when X is a CONST_INT (since they don't
@@ -4179,6 +4197,10 @@ emit_push_insn (rtx x, machine_mode mode, tree type, rtx size,
 
   xinner = x;
 
+  int nregs = partial / UNITS_PER_WORD;
+  rtx *tmp_regs = NULL;
+  int overlapping = 0;
+
   if (mode == BLKmode
       || (STRICT_ALIGNMENT && align < GET_MODE_ALIGNMENT (mode)))
     {
@@ -4309,6 +4331,35 @@ emit_push_insn (rtx x, machine_mode mode, tree type, rtx size,
 	     PARM_BOUNDARY.  Assume the caller isn't lying.  */
 	  set_mem_align (target, align);
 
+	  /* If part should go in registers and pushing to that part would
+	     overwrite some of the values that need to go into regs, load the
+	     overlapping values into temporary pseudos to be moved into the hard
+	     regs at the end after the stack pushing has completed.
+	     We cannot load them directly into the hard regs here because
+	     they can be clobbered by the block move expansions.
+	     See PR 65358.  */
+
+	  if (partial > 0 && reg != 0 && mode == BLKmode
+	      && GET_CODE (reg) != PARALLEL)
+	    {
+	      overlapping = memory_load_overlap (XEXP (x, 0), temp, partial);
+	      if (overlapping > 0)
+	        {
+		  gcc_assert (overlapping % UNITS_PER_WORD == 0);
+		  overlapping /= UNITS_PER_WORD;
+
+		  tmp_regs = XALLOCAVEC (rtx, overlapping);
+
+		  for (int i = 0; i < overlapping; i++)
+		    tmp_regs[i] = gen_reg_rtx (word_mode);
+
+		  for (int i = 0; i < overlapping; i++)
+		    emit_move_insn (tmp_regs[i],
+				    operand_subword_force (target, i, mode));
+	        }
+	      else
+		overlapping = 0;
+	    }
 	  emit_block_move (target, xinner, size, BLOCK_OP_CALL_PARM);
 	}
     }
@@ -4411,9 +4462,8 @@ emit_push_insn (rtx x, machine_mode mode, tree type, rtx size,
 	}
     }
 
-  /* If part should go in registers, copy that part
-     into the appropriate registers.  Do this now, at the end,
-     since mem-to-mem copies above may do function calls.  */
+  /* Move the partial arguments into the registers and any overlapping
+     values that we moved into the pseudos in tmp_regs.  */
   if (partial > 0 && reg != 0)
     {
       /* Handle calls that pass values in multiple non-contiguous locations.
@@ -4421,9 +4471,15 @@ emit_push_insn (rtx x, machine_mode mode, tree type, rtx size,
       if (GET_CODE (reg) == PARALLEL)
 	emit_group_load (reg, x, type, -1);
       else
-	{
+        {
 	  gcc_assert (partial % UNITS_PER_WORD == 0);
-	  move_block_to_reg (REGNO (reg), x, partial / UNITS_PER_WORD, mode);
+	  move_block_to_reg (REGNO (reg), x, nregs - overlapping, mode);
+
+	  for (int i = 0; i < overlapping; i++)
+	    emit_move_insn (gen_rtx_REG (word_mode, REGNO (reg)
+						    + nregs - overlapping + i),
+			    tmp_regs[i]);
+
 	}
     }
 
diff --git a/gcc/testsuite/gcc.dg/pr65358.c b/gcc/testsuite/gcc.dg/pr65358.c
new file mode 100644
index 0000000..ba89fd4
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr65358.c
@@ -0,0 +1,33 @@
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+struct pack
+{
+  int fine;
+  int victim;
+  int killer;
+};
+
+int __attribute__ ((__noinline__, __noclone__))
+bar (int a, int b, struct pack p)
+{
+  if (a != 20 || b != 30)
+    __builtin_abort ();
+  if (p.fine != 40 || p.victim != 50 || p.killer != 60)
+    __builtin_abort ();
+  return 0;
+}
+
+int __attribute__ ((__noinline__, __noclone__))
+foo (int arg1, int arg2, int arg3, struct pack p)
+{
+  return bar (arg2, arg3, p);
+}
+
+int main (void)
+{
+  struct pack p = { 40, 50, 60 };
+
+  (void) foo (10, 20, 30, p);
+  return 0;
+}
