diff mbox

[0/7] Type promotion pass and elimination of zext/sext

Message ID 56468B17.6020903@linaro.org
State New
Headers show

Commit Message

Kugan Vivekanandarajah Nov. 14, 2015, 1:15 a.m. UTC 
Attached is the latest version of the patch. With the patches
0001-Add-new-SEXT_EXPR-tree-code.patch,
0002-Add-type-promotion-pass.patch and
0003-Optimize-ZEXT_EXPR-with-tree-vrp.patch.

I did bootstrap on ppc64-linux-gnu, aarch64-linux-gnu and
x64-64-linux-gnu and regression testing on ppc64-linux-gnu,
aarch64-linux-gnu arm64-linux-gnu and x64-64-linux-gnu. I ran into three
issues in ppc64-linux-gnu regression testing. There are some other test
cases which needs adjustment for scanning for some patterns that are not
valid now.

1. rtl fwprop was going into infinite loop. Works with the following patch:
   /* forward_propagate_subreg may be operating on an instruction with

2. gcc.dg/torture/ftrapv-1.c fails
This is because we are checking for the  SImode trapping. With the
promotion of the operation to wider mode, this is i think expected. I
think the testcase needs updating.
3. gcc.dg/sms-3.c fails
It fails with  -fmodulo-sched-allow-regmoves  and OK when I remove it. I
am looking into it.


I also have the following issues based on the previous review (as posted
in the previous patch). Copying again for the review purpose.

1.
> you still call promote_ssa on both DEFs and USEs and promote_ssa looks

> at SSA_NAME_DEF_STMT of the passed arg.  Please call promote_ssa just

> on DEFs and fixup_uses on USEs.


I am doing this to promote SSA that are defined with GIMPLE_NOP. Is
there anyway to iterate over this. I have added gcc_assert to make sure
that promote_ssa is called only once.

2.
> Instead of this you should, in promote_all_stmts, walk over all uses

doing what
> fixup_uses does and then walk over all defs, doing what promote_ssa does.

>

> +    case GIMPLE_NOP:

> +       {

> +         if (SSA_NAME_VAR (def) == NULL)

> +           {

> +             /* Promote def by fixing its type for anonymous def.  */

> +             TREE_TYPE (def) = promoted_type;

> +           }

> +         else

> +           {

> +             /* Create a promoted copy of parameters.  */

> +             bb = single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun));

>

> I think the uninitialized vars are somewhat tricky and it would be best

> to create a new uninit anonymous SSA name for them.  You can

> have SSA_NAME_VAR != NULL and def _not_ being a parameter

> btw.


I experimented with get_or_create_default_def. Here  we have to have a
SSA_NAME_VAR (def) of promoted type.

In the attached patch I am doing the following and seems to work. Does
this looks OK?

+	  }
+	else if (TREE_CODE (SSA_NAME_VAR (def)) != PARM_DECL)
+	  {
+	    tree var = copy_node (SSA_NAME_VAR (def));
+	    TREE_TYPE (var) = promoted_type;
+	    TREE_TYPE (def) = promoted_type;
+	    SET_SSA_NAME_VAR_OR_IDENTIFIER (def, var);
+	  }

I prefer to promote def as otherwise iterating over the uses and
promoting can look complicated (have to look at all the different types
of stmts again and do the right thing as It was in the earlier version
of this before we move to this approach)

3)
> you can also transparently handle constants for the cases where promoting

> is required.  At the moment their handling is interwinded with the def

promotion
> code.  That makes the whole thing hard to follow.



I have updated the comments with:

+/* Promote constants in STMT to TYPE.  If PROMOTE_COND_EXPR is true,
+   promote only the constants in conditions part of the COND_EXPR.
+
+   We promote the constants when the associated operands are promoted.
+   This usually means that we promote the constants when we promote the
+   defining stmnts (as part of promote_ssa). However for COND_EXPR, we
+   can promote only when we promote the other operand. Therefore, this
+   is done during fixup_use.  */


4)
I am handling gimple_debug separately to avoid any code difference with
and without -g option. I have updated the comments for this.

5)
I also noticed that tree-ssa-uninit sometimes gives false positives due
to the assumptions
it makes. Is it OK to move this pass before type promotion? I can do the
testings and post a separate patch with this if this OK.

6)
I also removed the optimization that prevents some of the redundant
truncation/extensions from type promotion pass, as it dosent do much as
of now. I can send a proper follow up patch. Is that OK?

I also did a simple test with coremark for the latest patch. I compared
the code size for coremark for linux-gcc with -Os. Results are as
reported by the "size" utility. I know this doesn't mean much but can
give some indication.
	Base   		with pass	Percentage improvement
==============================================================
arm	10476		10372		0.9927453226
aarch64	9545		9521		0.2514405448
ppc64	12236		12052		1.5037593985


After resolving the above issues, I would like propose that we  commit
the pass as not enabled by default (even though the patch as it stands
enabled by default - I am doing it for testing purposes).

Thanks,
Kugan
diff mbox

Patch

From c0ce364e3a422912a08189645efde46c36583753 Mon Sep 17 00:00:00 2001
From: Kugan Vivekanandarajah <kugan.vivekanandarajah@linaro.org>
Date: Thu, 22 Oct 2015 10:51:42 +1100
Subject: [PATCH 1/5] Add new SEXT_EXPR tree code

---
 gcc/cfgexpand.c         | 12 ++++++++++++
 gcc/expr.c              | 20 ++++++++++++++++++++
 gcc/fold-const.c        |  4 ++++
 gcc/tree-cfg.c          | 12 ++++++++++++
 gcc/tree-inline.c       |  1 +
 gcc/tree-pretty-print.c | 11 +++++++++++
 gcc/tree.def            |  5 +++++
 7 files changed, 65 insertions(+)

diff --git a/gcc/cfgexpand.c b/gcc/cfgexpand.c
index eaad859..aeb64bb 100644
--- a/gcc/cfgexpand.c
+++ b/gcc/cfgexpand.c
@@ -5054,6 +5054,18 @@  expand_debug_expr (tree exp)
     case FMA_EXPR:
       return simplify_gen_ternary (FMA, mode, inner_mode, op0, op1, op2);
 
+    case SEXT_EXPR:
+      gcc_assert (CONST_INT_P (op1));
+      inner_mode = mode_for_size (INTVAL (op1), MODE_INT, 0);
+      gcc_assert (GET_MODE_BITSIZE (inner_mode) == INTVAL (op1));
+
+      if (mode != inner_mode)
+	op0 = simplify_gen_unary (SIGN_EXTEND,
+				  mode,
+				  gen_lowpart_SUBREG (inner_mode, op0),
+				  inner_mode);
+      return op0;
+
     default:
     flag_unsupported:
 #ifdef ENABLE_CHECKING
diff --git a/gcc/expr.c b/gcc/expr.c
index da68870..c2f535f 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -9318,6 +9318,26 @@  expand_expr_real_2 (sepops ops, rtx target, machine_mode tmode,
       target = expand_vec_cond_expr (type, treeop0, treeop1, treeop2, target);
       return target;
 
+    case SEXT_EXPR:
+	{
+	  machine_mode inner_mode = mode_for_size (tree_to_uhwi (treeop1),
+						   MODE_INT, 0);
+	  rtx temp, result;
+	  rtx op0 = expand_normal (treeop0);
+	  op0 = force_reg (mode, op0);
+	  if (mode != inner_mode)
+	    {
+	      result = gen_reg_rtx (mode);
+	      temp = simplify_gen_unary (SIGN_EXTEND, mode,
+					 gen_lowpart_SUBREG (inner_mode, op0),
+					 inner_mode);
+	      convert_move (result, temp, 0);
+	    }
+	  else
+	    result = op0;
+	  return result;
+	}
+
     default:
       gcc_unreachable ();
     }
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 602ea24..a149bad 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -987,6 +987,10 @@  int_const_binop_1 (enum tree_code code, const_tree arg1, const_tree parg2,
       res = wi::bit_and (arg1, arg2);
       break;
 
+    case SEXT_EXPR:
+      res = wi::sext (arg1, arg2.to_uhwi ());
+      break;
+
     case RSHIFT_EXPR:
     case LSHIFT_EXPR:
       if (wi::neg_p (arg2))
diff --git a/gcc/tree-cfg.c b/gcc/tree-cfg.c
index 8e3e810..d18b3f7 100644
--- a/gcc/tree-cfg.c
+++ b/gcc/tree-cfg.c
@@ -3752,6 +3752,18 @@  verify_gimple_assign_binary (gassign *stmt)
         return false;
       }
 
+    case SEXT_EXPR:
+      {
+	if (!INTEGRAL_TYPE_P (lhs_type)
+	    || !useless_type_conversion_p (lhs_type, rhs1_type)
+	    || !tree_fits_uhwi_p (rhs2))
+	  {
+	    error ("invalid operands in sext expr");
+	    return true;
+	  }
+	return false;
+      }
+
     case VEC_WIDEN_LSHIFT_HI_EXPR:
     case VEC_WIDEN_LSHIFT_LO_EXPR:
       {
diff --git a/gcc/tree-inline.c b/gcc/tree-inline.c
index b8269ef..e61c200 100644
--- a/gcc/tree-inline.c
+++ b/gcc/tree-inline.c
@@ -3893,6 +3893,7 @@  estimate_operator_cost (enum tree_code code, eni_weights *weights,
     case BIT_XOR_EXPR:
     case BIT_AND_EXPR:
     case BIT_NOT_EXPR:
+    case SEXT_EXPR:
 
     case TRUTH_ANDIF_EXPR:
     case TRUTH_ORIF_EXPR:
diff --git a/gcc/tree-pretty-print.c b/gcc/tree-pretty-print.c
index 11f90051..bec9082 100644
--- a/gcc/tree-pretty-print.c
+++ b/gcc/tree-pretty-print.c
@@ -1923,6 +1923,14 @@  dump_generic_node (pretty_printer *pp, tree node, int spc, int flags,
       }
       break;
 
+    case SEXT_EXPR:
+      pp_string (pp, "SEXT_EXPR <");
+      dump_generic_node (pp, TREE_OPERAND (node, 0), spc, flags, false);
+      pp_string (pp, ", ");
+      dump_generic_node (pp, TREE_OPERAND (node, 1), spc, flags, false);
+      pp_greater (pp);
+      break;
+
     case MODIFY_EXPR:
     case INIT_EXPR:
       dump_generic_node (pp, TREE_OPERAND (node, 0), spc, flags,
@@ -3561,6 +3569,9 @@  op_symbol_code (enum tree_code code)
     case MIN_EXPR:
       return "min";
 
+    case SEXT_EXPR:
+      return "sext";
+
     default:
       return "<<< ??? >>>";
     }
diff --git a/gcc/tree.def b/gcc/tree.def
index d0a3bd6..789cfdd 100644
--- a/gcc/tree.def
+++ b/gcc/tree.def
@@ -760,6 +760,11 @@  DEFTREECODE (BIT_XOR_EXPR, "bit_xor_expr", tcc_binary, 2)
 DEFTREECODE (BIT_AND_EXPR, "bit_and_expr", tcc_binary, 2)
 DEFTREECODE (BIT_NOT_EXPR, "bit_not_expr", tcc_unary, 1)
 
+/*  Sign-extend operation.  It will sign extend first operand from
+ the sign bit specified by the second operand.  The type of the
+ result is that of the first operand.  */
+DEFTREECODE (SEXT_EXPR, "sext_expr", tcc_binary, 2)
+
 /* ANDIF and ORIF allow the second operand not to be computed if the
    value of the expression is determined from the first operand.  AND,
    OR, and XOR always compute the second operand whether its value is
-- 
1.9.1