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>

	Backport from mainline
	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: r261765

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index fa51ab82c4202564cf3a32cc41eb5178303905e9..2ad992e42daeeafdd35e14ada0f812cb2ad5ca40 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,12 @@
+2018-06-19  Max Filippov  <jcmvbkbc@gmail.com>
+
+       Backport from mainline
+       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.
+
 2018-06-07  Peter Bergner  <bergner@vnet.ibm.com>
 
        Backport from mainline

diff --git a/gcc/config/xtensa/xtensa.md b/gcc/config/xtensa/xtensa.md
index fcdb6c8ecadf9065727cfe1102885f7decdf204c..6b27e2ba76f942ccec493aed8b9e0d41c9cdc4a0 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))]
   ""