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+From 87fda0741d210727672cba5e54a37a189e8ac04e Mon Sep 17 00:00:00 2001
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+From: Max Filippov <jcmvbkbc@gmail.com>
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+Date: Sun, 17 Jun 2018 21:18:39 -0700
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+Subject: [PATCH] xtensa: fix PR target/65416
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+
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+The issue is caused by reordering of stack pointer update after stack
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+space allocation with instructions that write to the allocated stack
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+space. In windowed ABI register spill area for the previous call frame
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+is located just below the stack pointer and may be reloaded back into
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+the register file on movsp.
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+Implement allocate_stack pattern for windowed ABI configuration and
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+insert an instruction that prevents reordering of frame memory access
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+and stack pointer update.
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+
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+gcc/
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+2018-06-19 Max Filippov <jcmvbkbc@gmail.com>
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+
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+ * config/xtensa/xtensa.md (UNSPEC_FRAME_BLOCKAGE): New unspec
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+ constant.
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+ (allocate_stack, frame_blockage, *frame_blockage): New patterns.
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+
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+Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
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+Backported from: r261755
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+---
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+ gcc/config/xtensa/xtensa.md | 46 +++++++++++++++++++++++++++++++++++++++++++++
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+ 1 file changed, 46 insertions(+)
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+
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+diff --git a/gcc/config/xtensa/xtensa.md b/gcc/config/xtensa/xtensa.md
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+index 84967dbedc08..209f839cfb0f 100644
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+--- a/gcc/config/xtensa/xtensa.md
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++++ b/gcc/config/xtensa/xtensa.md
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+@@ -38,6 +38,7 @@
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+ (UNSPEC_MEMW 11)
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+ (UNSPEC_LSETUP_START 12)
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+ (UNSPEC_LSETUP_END 13)
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++ (UNSPEC_FRAME_BLOCKAGE 14)
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+
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+ (UNSPECV_SET_FP 1)
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+ (UNSPECV_ENTRY 2)
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+@@ -1676,6 +1677,32 @@
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+
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+ ;; Miscellaneous instructions.
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+
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++;; In windowed ABI stack pointer adjustment must happen before any access
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++;; to the space allocated on stack is allowed, otherwise register spill
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++;; area may be clobbered. That's what frame blockage is supposed to enforce.
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++
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++(define_expand "allocate_stack"
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++ [(set (match_operand 0 "nonimmed_operand")
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++ (minus (reg A1_REG) (match_operand 1 "add_operand")))
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++ (set (reg A1_REG)
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++ (minus (reg A1_REG) (match_dup 1)))]
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++ "TARGET_WINDOWED_ABI"
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++{
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++ if (CONST_INT_P (operands[1]))
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++ {
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++ rtx neg_op0 = GEN_INT (-INTVAL (operands[1]));
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++ emit_insn (gen_addsi3 (stack_pointer_rtx, stack_pointer_rtx, neg_op0));
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++ }
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++ else
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++ {
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++ emit_insn (gen_subsi3 (stack_pointer_rtx, stack_pointer_rtx,
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++ operands[1]));
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++ }
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++ emit_move_insn (operands[0], virtual_stack_dynamic_rtx);
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++ emit_insn (gen_frame_blockage ());
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++ DONE;
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++})
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++
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+ (define_expand "prologue"
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+ [(const_int 0)]
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+ ""
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+@@ -1767,6 +1794,25 @@
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+ [(set_attr "length" "0")
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+ (set_attr "type" "nop")])
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+
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++;; Do not schedule instructions accessing memory before this point.
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++
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++(define_expand "frame_blockage"
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++ [(set (match_dup 0)
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++ (unspec:BLK [(match_dup 1)] UNSPEC_FRAME_BLOCKAGE))]
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++ ""
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++{
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++ operands[0] = gen_rtx_MEM (BLKmode, gen_rtx_SCRATCH (Pmode));
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++ MEM_VOLATILE_P (operands[0]) = 1;
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++ operands[1] = stack_pointer_rtx;
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++})
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++
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++(define_insn "*frame_blockage"
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++ [(set (match_operand:BLK 0 "" "")
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++ (unspec:BLK [(match_operand:SI 1 "" "")] UNSPEC_FRAME_BLOCKAGE))]
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++ ""
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++ ""
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++ [(set_attr "length" "0")])
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++
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+ (define_insn "trap"
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+ [(trap_if (const_int 1) (const_int 0))]
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+ ""
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+--
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+2.11.0
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+
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Max Filippov