[PATCH 1/2] arc: Use @pcl assembler syntax instead of invalid expressions

[PATCH 1/2] arc: Use @pcl assembler syntax instead of invalid expressions

[Andrew Burgess]

The old ARC assembler would accept expressions like 'LABEL-(.&-4)'
which would calculate the offset from the PCL to LABEL.  The new ARC
assembler does not accept these expressions, instead there's an @pcl
synax, used like LABEL@pcl which gives the offset from PCL to LABEL.

Most of the use of the old expression syntax have been removed,
however, this one got missed.

gcc/ChangeLog:

	* config/arc/arc.md (doloop_begin_i): Use @pcl assembler syntax.
---
 gcc/ChangeLog         | 4 ++++
 gcc/config/arc/arc.md | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/gcc/config/arc/arc.md b/gcc/config/arc/arc.md
index 88b7fca..f707bd0 100644
--- a/gcc/config/arc/arc.md
+++ b/gcc/config/arc/arc.md
@@ -5070,7 +5070,7 @@
     {
       /* ??? Can do better for when a scratch register
 	 is known.  But that would require extra testing.  */
-      return "push_s r0\;add r0,pcl,%4-(.&-4)\;sr r0,[2]; LP_START\;add r0,pcl,.L__GCC__LP%1-(.&-4)\;sr r0,[3]; LP_END\;pop_s r0";
+      return "push_s r0\;add r0,pcl,%4@pcl\;sr r0,[2]; LP_START\;add r0,pcl,.L__GCC__LP%1@pcl\;sr r0,[3]; LP_END\;pop_s r0";
     }
   /* Check if the loop end is in range to be set by the lp instruction.  */
   size = INTVAL (operands[3]) < 2 ? 0 : 2048;
-- 
2.4.11

[PATCH 2/2] arc: Fix for loop end detection

[Andrew Burgess]

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.
---
 gcc/ChangeLog                         |  6 +++++
 gcc/config/arc/arc.c                  |  5 ++--
 gcc/testsuite/ChangeLog               |  4 ++++
 gcc/testsuite/gcc.target/arc/loop-1.c | 45 +++++++++++++++++++++++++++++++++++
 4 files changed, 58 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/arc/loop-1.c

diff --git a/gcc/config/arc/arc.c b/gcc/config/arc/arc.c
index 0563a74..39b198d 100644
--- a/gcc/config/arc/arc.c
+++ b/gcc/config/arc/arc.c
@@ -6573,8 +6573,6 @@ 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;
@@ -6585,6 +6583,9 @@ 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)
diff --git a/gcc/testsuite/gcc.target/arc/loop-1.c b/gcc/testsuite/gcc.target/arc/loop-1.c
new file mode 100644
index 0000000..1afe8eb
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arc/loop-1.c
@@ -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__" } } */
-- 
2.4.11

[PATCH 0/2] ARC Zero Overhead Loop Fixes

[Andrew Burgess]

Found two issues with the ARC loop detection.  The first generates
code that the current assembler can't handle, while the second causes
some loops to be missed.

--

Andrew Burgess (2):
  arc: Use @pcl assembler syntax instead of invalid expressions
  arc: Fix for loop end detection

 gcc/ChangeLog                         | 10 ++++++++
 gcc/config/arc/arc.c                  |  5 ++--
 gcc/config/arc/arc.md                 |  2 +-
 gcc/testsuite/ChangeLog               |  4 ++++
 gcc/testsuite/gcc.target/arc/loop-1.c | 45 +++++++++++++++++++++++++++++++++++
 5 files changed, 63 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/arc/loop-1.c

-- 
2.4.11

RE: [PATCH 0/2] ARC Zero Overhead Loop Fixes

[Claudiu Zissulescu]

Hi,
 
> Andrew Burgess (2):
>   arc: Use @pcl assembler syntax instead of invalid expressions
>   arc: Fix for loop end detection
> 

Both patches looks good to me. 
Claudiu

Re: [PATCH 0/2] ARC Zero Overhead Loop Fixes

[Andrew Burgess]

* Claudiu Zissulescu <Claudiu.Zissulescu@synopsys.com> [2017-04-14 11:20:43 +0000]:

> Hi,
>  
> > Andrew Burgess (2):
> >   arc: Use @pcl assembler syntax instead of invalid expressions
> >   arc: Fix for loop end detection
> > 
> 
> Both patches looks good to me. 

Thanks committed as r246932 and r246933.

Andrew