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[ARC] Prevent moving stores to the frame before the stack adjustment. 

If the stack pointer is needed, emit a special barrier that will prevent
the scheduler from moving stores to the frame before the stack adjustment.

For example:

[snip]
	mov_s	fp,sp 	; frame pointer is set here
[snip]
	st	r1,[fp,-24]	; frame pointer is used here
[snip]
	sub_s	sp,sp,0x20	; stack pointer adjusted

So we can easily see that any interrupt between the `st` and `sub`
instruction will lead to faulty code as the interrupt routine will use
a faulty sp register, and, potentially, overwriting the value stored
by 'st' instruction. Thus, adding a scheduler barrier will force the
compiler to emit the `sub` instruction before the store one.

2017-06-01  Claudiu Zissulescu  <claziss@synopsys.com>

	* config/arc/arc.c (arc_expand_prologue): Emit a special barrier
	to prevent store reordering.
	* config/arc/arc.md (UNSPEC_ARC_STKTIE): Define.
	(type): Add block type.
	(stack_tie): Define special instruction to be used in
	expand_prologue.

From-SVN: r248781
This commit is contained in:
Claudiu Zissulescu 2017-06-01 11:42:49 +02:00 committed by Claudiu Zissulescu
parent 6f70ebc3d1
commit 2daad50b02
3 changed files with 32 additions and 2 deletions
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9
gcc/ChangeLog
View File

@ -1,3 +1,12 @@
2017-06-01 Claudiu Zissulescu <claziss@synopsys.com>
* config/arc/arc.c (arc_expand_prologue): Emit a special barrier
to prevent store reordering.
* config/arc/arc.md (UNSPEC_ARC_STKTIE): Define.
(type): Add block type.
(stack_tie): Define special instruction to be used in
expand_prologue.
2017-06-01 Claudiu Zissulescu <claziss@synopsys.com>
* config/arc/arc.md (commutative_binary_comparison): Remove 'I'

8
gcc/config/arc/arc.c
View File

@ -2968,7 +2968,15 @@ arc_expand_prologue (void)
frame_size_to_allocate -= first_offset;
/* Allocate the stack frame. */
if (frame_size_to_allocate > 0)
{
frame_stack_add ((HOST_WIDE_INT) 0 - frame_size_to_allocate);
/* If the frame pointer is needed, emit a special barrier that
will prevent the scheduler from moving stores to the frame
before the stack adjustment. */
if (arc_frame_pointer_needed ())
emit_insn (gen_stack_tie (stack_pointer_rtx,
hard_frame_pointer_rtx));
}
/* Setup the gp register, if needed. */
if (crtl->uses_pic_offset_table)

15
gcc/config/arc/arc.md
View File

@ -135,6 +135,7 @@
UNSPEC_ARC_VMAC2HU
UNSPEC_ARC_VMPY2H
UNSPEC_ARC_VMPY2HU
UNSPEC_ARC_STKTIE
])
(define_c_enum "vunspec" [
@ -205,7 +206,7 @@
simd_vcompare, simd_vpermute, simd_vpack, simd_vpack_with_acc,
simd_valign, simd_valign_with_acc, simd_vcontrol,
simd_vspecial_3cycle, simd_vspecial_4cycle, simd_dma, mul16_em, div_rem,
fpu"
fpu, block"
(cond [(eq_attr "is_sfunc" "yes")
(cond [(match_test "!TARGET_LONG_CALLS_SET && (!TARGET_MEDIUM_CALLS || GET_CODE (PATTERN (insn)) != COND_EXEC)") (const_string "call")
(match_test "flag_pic") (const_string "sfunc")]
@ -6606,6 +6607,18 @@
(set_attr "predicable" "yes,no,no,yes,no")
(set_attr "cond" "canuse,nocond,nocond,canuse_limm,nocond")])
(define_insn "stack_tie"
[(set (mem:BLK (scratch))
(unspec:BLK [(match_operand:SI 0 "register_operand" "rb")
(match_operand:SI 1 "register_operand" "rb")]
UNSPEC_ARC_STKTIE))]
""
""
[(set_attr "length" "0")
(set_attr "iscompact" "false")
(set_attr "type" "block")]
)
;; include the arc-FPX instructions
(include "fpx.md")