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arc: Fix for loop end detection 

We use a negative ID number to link together the doloop_begin and
doloop_end instructions.  This negative ID number is setup within
doloop_begin, at this point the ID is stored into the loop end
instruction (doloop_end_i) and placed into the doloop_begin_i
instruction.

In arc.c (arc_reorg) we extract the ID from the doloop_end_i
instruction in order to find the matching doloop_begin_i instruction,
though the ID is only used in some cases.

Currently in arc_reorg when we extract the ID we negate it.  This
negation is invalid.  The ID stored in both doloop_end_i and
doloop_begin_i is already negative, the negation in arc_reorg means
that if we need to use the ID to find the doloop_begin_i then we will
never find it (as the IDs will never match).

This commit removes the unneeded negation, moves the extraction of the
ID into a more appropriately scoped block and adds a new test for this
issue.

gcc/ChangeLog:

	* config/arc/arc.c (arc_reorg): Move loop_end_id into a more local
	block, and do not negate it, the stored id is already negative.

gcc/testsuite/ChangeLog:

	* gcc.target/arc/loop-1.c: New file.


Co-Authored-By: Guy Benyei <guybe@mellanox.com>

From-SVN: r246933
This commit is contained in:
Andrew Burgess 2017-04-14 22:14:34 +01:00 committed by Andrew Burgess
parent 8c1d6b64e3
commit dd3d6a42fc
4 changed files with 58 additions and 2 deletions
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6
gcc/ChangeLog
View File

@ -1,3 +1,9 @@
2017-04-14 Andrew Burgess <andrew.burgess@embecosm.com>
Guy Benyei <guybe@mellanox.com>
* config/arc/arc.c (arc_reorg): Move loop_end_id into a more local
block, and do not negate it, the stored id is already negative.
2017-04-14 Andrew Burgess <andrew.burgess@embecosm.com>
* config/arc/arc.md (doloop_begin_i): Use @pcl assembler syntax.

5
gcc/config/arc/arc.c
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@ -6569,8 +6569,6 @@ arc_reorg (void)
rtx_insn *lp_simple = NULL;
rtx_insn *next = NULL;
rtx op0 = XEXP (XVECEXP (PATTERN (insn), 0, 1), 0);
HOST_WIDE_INT loop_end_id
= -INTVAL (XEXP (XVECEXP (PATTERN (insn), 0, 4), 0));
int seen_label = 0;
for (lp = prev;
@ -6581,6 +6579,9 @@ arc_reorg (void)
if (!lp || !NONJUMP_INSN_P (lp)
|| dead_or_set_regno_p (lp, LP_COUNT))
{
HOST_WIDE_INT loop_end_id
= INTVAL (XEXP (XVECEXP (PATTERN (insn), 0, 4), 0));
for (prev = next = insn, lp = NULL ; prev || next;)
{
if (prev)

4
gcc/testsuite/ChangeLog
View File

@ -1,3 +1,7 @@
2017-04-14 Andrew Burgess <andrew.burgess@embecosm.com>
* gcc.target/arc/loop-1.c: New file.
2017-04-14 Michael Meissner <meissner@linux.vnet.ibm.com>
PR target/80098

45
gcc/testsuite/gcc.target/arc/loop-1.c Normal file
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@ -0,0 +1,45 @@
/* { dg-do compile } */
/* { dg-options "-O2" } */
/* This case would fail to make use of the zero-overhead loop
instruction at one time due to a bug. */
extern char a[];
struct some_t
{
struct
{
int aaa;
short bbb;
char ccc;
char ddd;
} ppp[8];
int www[1];
};
int b;
void
some_function ()
{
struct some_t *tmp = (struct some_t *) a;
while ((*tmp).ppp[b].ccc)
while(0);
for (; b; b++)
{
if (tmp->ppp[b].ccc)
{
int c = tmp->ppp[b].bbb;
int d = tmp->ppp[b].aaa;
int e = d - tmp->www[c];
if (e)
tmp->ppp[b].ddd = 1;
}
}
}
/* { dg-final { scan-assembler "\[^\n\]+lp \\.L__GCC__" } } */