xtensa: fix PR target/65416

The issue is caused by reordering of stack pointer update after stack
space allocation with instructions that write to the allocated stack
space. In windowed ABI register spill area for the previous call frame
is located just below the stack pointer and may be reloaded back into
the register file on movsp.
Implement allocate_stack pattern for windowed ABI configuration and
insert an instruction that prevents reordering of frame memory access
and stack pointer update.

gcc/
2018-06-19  Max Filippov  <jcmvbkbc@gmail.com>

	* config/xtensa/xtensa.md (UNSPEC_FRAME_BLOCKAGE): New unspec
	constant.
	(allocate_stack, frame_blockage, *frame_blockage): New patterns.

From-SVN: r261755

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 4d59d2d1ee08b1f410c8f6fc8170379b3df5d22b..7e93801049cd6c2e49d45bc084f2267e57996fe7 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2018-06-19  Max Filippov  <jcmvbkbc@gmail.com>
+
+       * config/xtensa/xtensa.md (UNSPEC_FRAME_BLOCKAGE): New unspec
+       constant.
+       (allocate_stack, frame_blockage, *frame_blockage): New patterns.
+
 2018-06-19  Jan Hubicka  <hubicka@ucw.cz>
 
        * tree.c (find_decls_types_r): Remove all non-VAR_DECLs from

diff --git a/gcc/config/xtensa/xtensa.md b/gcc/config/xtensa/xtensa.md
index 84967dbedc084aafd880525ff0368d93381c90da..209f839cfb0f929d68469bb35dc5f5e5a9a8728c 100644 (file)
--- a/gcc/config/xtensa/xtensa.md
+++ b/gcc/config/xtensa/xtensa.md
@@ -38,6 +38,7 @@
   (UNSPEC_MEMW         11)
   (UNSPEC_LSETUP_START  12)
   (UNSPEC_LSETUP_END    13)
+  (UNSPEC_FRAME_BLOCKAGE 14)
 
   (UNSPECV_SET_FP      1)
   (UNSPECV_ENTRY       2)
@@ -1676,6 +1677,32 @@
 \f
 ;; Miscellaneous instructions.
 
+;; In windowed ABI stack pointer adjustment must happen before any access
+;; to the space allocated on stack is allowed, otherwise register spill
+;; area may be clobbered.  That's what frame blockage is supposed to enforce.
+
+(define_expand "allocate_stack"
+  [(set (match_operand 0 "nonimmed_operand")
+        (minus (reg A1_REG) (match_operand 1 "add_operand")))
+   (set (reg A1_REG)
+        (minus (reg A1_REG) (match_dup 1)))]
+  "TARGET_WINDOWED_ABI"
+{
+  if (CONST_INT_P (operands[1]))
+    {
+      rtx neg_op0 = GEN_INT (-INTVAL (operands[1]));
+      emit_insn (gen_addsi3 (stack_pointer_rtx, stack_pointer_rtx, neg_op0));
+    }
+  else
+    {
+      emit_insn (gen_subsi3 (stack_pointer_rtx, stack_pointer_rtx,
+                            operands[1]));
+    }
+  emit_move_insn (operands[0], virtual_stack_dynamic_rtx);
+  emit_insn (gen_frame_blockage ());
+  DONE;
+})
+
 (define_expand "prologue"
   [(const_int 0)]
   ""
@@ -1767,6 +1794,25 @@
   [(set_attr "length" "0")
    (set_attr "type" "nop")])
 
+;; Do not schedule instructions accessing memory before this point.
+
+(define_expand "frame_blockage"
+  [(set (match_dup 0)
+        (unspec:BLK [(match_dup 1)] UNSPEC_FRAME_BLOCKAGE))]
+  ""
+{
+  operands[0] = gen_rtx_MEM (BLKmode, gen_rtx_SCRATCH (Pmode));
+  MEM_VOLATILE_P (operands[0]) = 1;
+  operands[1] = stack_pointer_rtx;
+})
+
+(define_insn "*frame_blockage"
+  [(set (match_operand:BLK 0 "" "")
+        (unspec:BLK [(match_operand:SI 1 "" "")] UNSPEC_FRAME_BLOCKAGE))]
+  ""
+  ""
+  [(set_attr "length" "0")])
+
 (define_insn "trap"
   [(trap_if (const_int 1) (const_int 0))]
   ""