Hi Richard,
On 6 March 2018 at 02:24, Richard Biener <richard.guent...@gmail.com> wrote:
> On Thu, Feb 8, 2018 at 1:41 AM, Kugan Vivekanandarajah
> <kugan.vivekanandara...@linaro.org> wrote:
>> Hi Richard,
>>
>> On 1 February 2018 at 23:21, Richard Biener <richard.guent...@gmail.com>
>> wrote:
>>> On Thu, Feb 1, 2018 at 5:07 AM, Kugan Vivekanandarajah
>>> <kugan.vivekanandara...@linaro.org> wrote:
>>>> Hi Richard,
>>>>
>>>> On 31 January 2018 at 21:39, Richard Biener <richard.guent...@gmail.com>
>>>> wrote:
>>>>> On Wed, Jan 31, 2018 at 11:28 AM, Kugan Vivekanandarajah
>>>>> <kugan.vivekanandara...@linaro.org> wrote:
>>>>>> Hi Richard,
>>>>>>
>>>>>> Thanks for the review.
>>>>>> On 25 January 2018 at 20:04, Richard Biener <richard.guent...@gmail.com>
>>>>>> wrote:
>>>>>>> On Wed, Jan 24, 2018 at 10:56 PM, Kugan Vivekanandarajah
>>>>>>> <kugan.vivekanandara...@linaro.org> wrote:
>>>>>>>> Hi All,
>>>>>>>>
>>>>>>>> Here is a patch for popcount builtin detection similar to LLVM. I
>>>>>>>> would like to queue this for review for next stage 1.
>>>>>>>>
>>>>>>>> 1. This is done part of loop-distribution and effective for -O3 and
>>>>>>>> above.
>>>>>>>> 2. This does not distribute loop to detect popcount (like
>>>>>>>> memcpy/memmove). I dont think that happens in practice. Please correct
>>>>>>>> me if I am wrong.
>>>>>>>
>>>>>>> But then it has no business inside loop distribution but instead is
>>>>>>> doing final value
>>>>>>> replacement, right? You are pattern-matching the whole loop after all.
>>>>>>> I think
>>>>>>> final value replacement would already do the correct thing if you
>>>>>>> teached number of
>>>>>>> iteration analysis that niter for
>>>>>>>
>>>>>>> <bb 3> [local count: 955630224]:
>>>>>>> # b_11 = PHI <b_5(5), b_8(6)>
>>>>>>> _1 = b_11 + -1;
>>>>>>> b_8 = _1 & b_11;
>>>>>>> if (b_8 != 0)
>>>>>>> goto <bb 6>; [89.00%]
>>>>>>> else
>>>>>>> goto <bb 8>; [11.00%]
>>>>>>>
>>>>>>> <bb 6> [local count: 850510900]:
>>>>>>> goto <bb 3>; [100.00%]
>>>>>>
>>>>>> I am looking into this approach. What should be the scalar evolution
>>>>>> for b_8 (i.e. b & (b -1) in a loop) should be? This is not clear to me
>>>>>> and can this be represented with the scev?
>>>>>
>>>>> No, it's not affine and thus cannot be represented. You only need the
>>>>> scalar evolution of the counting IV which is already handled and
>>>>> the number of iteration analysis needs to handle the above IV - this
>>>>> is the missing part.
>>>> Thanks for the clarification. I am now matching this loop pattern in
>>>> number_of_iterations_exit when number_of_iterations_exit_assumptions
>>>> fails. If the pattern matches, I am inserting the _builtin_popcount in
>>>> the loop preheater and setting the loop niter with this. This will be
>>>> used by the final value replacement. Is this what you wanted?
>>>
>>> No, you shouldn't insert a popcount stmt but instead the niter
>>> GENERIC tree should be a CALL_EXPR to popcount with the
>>> appropriate argument.
>>
>> Thats what I tried earlier but ran into some ICEs. I wasn't sure if
>> niter in tree_niter_desc can take such.
>>
>> Attached patch now does this. Also had to add support for CALL_EXPR in
>> few places to handle niter with CALL_EXPR. Does this look OK?
>
> Overall this looks ok - the patch includes changes in places that I don't
> think
> need changes such as chrec_convert_1 or extract_ops_from_tree.
> The expression_expensive_p change should be more specific than making
> all calls inexpensive as well.
Changed it.
>
> The verify_ssa change looks bogus, you do
>
> + dest = gimple_phi_result (count_phi);
> + tree var = make_ssa_name (TREE_TYPE (dest), NULL);
> + tree fn = builtin_decl_implicit (BUILT_IN_POPCOUNT);
> +
> + var = build_call_expr (fn, 1, src);
> + *niter = fold_build2 (MINUS_EXPR, TREE_TYPE (dest), var,
> + build_int_cst (TREE_TYPE (dest), 1));
>
> why do you allocate a new SSA name here? It seems unused
> as you overwrive 'var' with the CALL_EXPR immediately.
Changed now.
>
> I didn't review the pattern matching thoroughly nor the exact place you
> call it. But
>
> + if (check_popcount_pattern (loop, &count))
> + {
> + niter->assumptions = boolean_false_node;
> + niter->control.base = NULL_TREE;
> + niter->control.step = NULL_TREE;
> + niter->control.no_overflow = false;
> + niter->niter = count;
> + niter->assumptions = boolean_true_node;
> + niter->may_be_zero = boolean_false_node;
> + niter->max = -1;
> + niter->bound = NULL_TREE;
> + niter->cmp = ERROR_MARK;
> + return true;
> + }
>
> simply setting may_be_zero to false looks fishy.
Should I set this to (argument to popcount == zero)?
> Try with -fno-tree-loop-ch.
I changed the pattern matching to handle loop without header copying
too. Looks a bit complicated checking all the conditions. Wondering if
this can be done in a simpler and easier to read way.
> Also max should not be negative,
> it should be the number of bits in the IV type?
Changed this too.
>
> A related testcase could be that we can completely peel
> a loop like the following which iterates at most 8 times:
>
> int a[8];
> void foo (unsigned char ctrl)
> {
> int c = 0;
> while (ctrl)
> {
> ctrl = ctrl & (ctrl - 1);
> a[c++] = ctrl;
> }
> }
Hmm, this is an interesting test case but as I am now trying to match
a loop which does popcount, this is not handled.
Attaching the current version for review.
Thanks,
Kugan
>
> This is now stage1 material so please update and re-post. Maybe Bin has
> further suggestions as well.
>
> Thanks,
> Richard.
>
>> Thanks,
>> Kugan
>>
>>
>> gcc/ChangeLog:
>>
>> 2018-02-08 Kugan Vivekanandarajah <kug...@linaro.org>
>>
>> * gimple-expr.c (extract_ops_from_tree): Handle CALL_EXPR.
>> * tree-chrec.c (chrec_convert_1): Likewise.
>> * tree-scalar-evolution.c (expression_expensive_p): Likewise.
>> * tree-ssa-loop-ivopts.c (contains_abnormal_ssa_name_p): Likewise.
>> * tree-ssa-loop-niter.c (check_popcount_pattern): New.
>> (number_of_iterations_exit): Record niter for popcount patern.
>> * tree-ssa.c (verify_ssa): Check stmt to be non NULL.
>>
>> gcc/testsuite/ChangeLog:
>>
>> 2018-02-08 Kugan Vivekanandarajah <kug...@linaro.org>
>>
>> * gcc.dg/tree-ssa/popcount.c: New test.
>>
>>
>>>
>>>> In general, there is also a condition gating the loop like
>>>>
>>>> if (b_4 != 0)
>>>> goto loop;
>>>> else
>>>> end:
>>>>
>>>> This of course will not be removed by final value replacement. Since
>>>> popcount (0) is defined, this is redundant and could be removed but
>>>> not removed.
>>>
>>> Yeah, that's probably sth for another pass though. I suppose the
>>> end: case just uses zero in which case you'll have a PHI and you
>>> can optimize
>>>
>>> if (b != 0)
>>> return popcount (b);
>>> return 0;
>>>
>>> in phiopt.
>>>
>>> Richard.
>>>
>>>> Thanks,
>>>> Kugan
>>>>
>>>>>
>>>>> Richard.
>>>>>
>>>>>> Thanks,
>>>>>> Kugan
>>>>>>>
>>>>>>> is related to popcount (b_5).
>>>>>>>
>>>>>>> Richard.
>>>>>>>
>>>>>>>> Bootstrapped and regression tested on aarch64-linux-gnu with no new
>>>>>>>> regressions.
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>> Kugan
>>>>>>>>
>>>>>>>> gcc/ChangeLog:
>>>>>>>>
>>>>>>>> 2018-01-25 Kugan Vivekanandarajah <kug...@linaro.org>
>>>>>>>>
>>>>>>>> PR middle-end/82479
>>>>>>>> * tree-loop-distribution.c (handle_popcount): New.
>>>>>>>> (pass_loop_distribution::execute): Use handle_popcount.
>>>>>>>>
>>>>>>>> gcc/testsuite/ChangeLog:
>>>>>>>>
>>>>>>>> 2018-01-25 Kugan Vivekanandarajah <kug...@linaro.org>
>>>>>>>>
>>>>>>>> PR middle-end/82479
>>>>>>>> * gcc.dg/tree-ssa/popcount.c: New test.
From 69093cbf4c2a2c86628f78acd563a56081e234f6 Mon Sep 17 00:00:00 2001
From: Kugan Vivekanandarajah <kugan.vivekanandara...@linaro.org>
Date: Thu, 10 May 2018 21:41:53 +1000
Subject: [PATCH] popcount
Change-Id: I49b8557601cabffb5257e1daabeb5c59979fca96
---
gcc/ipa-fnsummary.c | 4 +
gcc/testsuite/gcc.dg/tree-ssa/popcount.c | 41 +++++++++
gcc/testsuite/gcc.dg/tree-ssa/popcount2.c | 29 ++++++
gcc/testsuite/gcc.dg/tree-ssa/popcount3.c | 28 ++++++
gcc/tree-scalar-evolution.c | 7 ++
gcc/tree-ssa-loop-ivopts.c | 10 ++
gcc/tree-ssa-loop-niter.c | 148 +++++++++++++++++++++++++++++-
7 files changed, 266 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/popcount.c
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/popcount2.c
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/popcount3.c
diff --git a/gcc/ipa-fnsummary.c b/gcc/ipa-fnsummary.c
index bdf9ba1..4dc156a 100644
--- a/gcc/ipa-fnsummary.c
+++ b/gcc/ipa-fnsummary.c
@@ -1485,6 +1485,10 @@ will_be_nonconstant_expr_predicate (struct ipa_node_params *info,
nonconstant_names);
return p2.or_with (summary->conds, p1);
}
+ else if (TREE_CODE (expr) == CALL_EXPR)
+ {
+ return false;
+ }
else
{
debug_tree (expr);
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/popcount.c b/gcc/testsuite/gcc.dg/tree-ssa/popcount.c
new file mode 100644
index 0000000..86a66cb
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/popcount.c
@@ -0,0 +1,41 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -fdump-tree-optimized" } */
+
+extern int foo (int);
+
+int PopCount (long b) {
+ int c = 0;
+ b++;
+
+ while (b) {
+ b &= b - 1;
+ c++;
+ }
+ return c;
+}
+int PopCount2 (long b) {
+ int c = 0;
+
+ while (b) {
+ b &= b - 1;
+ c++;
+ }
+ foo (c);
+ return foo (c);
+}
+
+void PopCount3 (long b1) {
+
+ for (long i = 0; i < b1; ++i)
+ {
+ long b = i;
+ int c = 0;
+ while (b) {
+ b &= b - 1;
+ c++;
+ }
+ foo (c);
+ }
+}
+
+/* { dg-final { scan-tree-dump-times "__builtin_popcount" 3 "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/popcount2.c b/gcc/testsuite/gcc.dg/tree-ssa/popcount2.c
new file mode 100644
index 0000000..52afc2d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/popcount2.c
@@ -0,0 +1,29 @@
+/* { dg-do execute } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int
+__attribute__ ((noinline, noclone))
+foo (int i, long b)
+{
+ int c = i;
+
+ while (b) {
+ b &= b - 1;
+ c++;
+ }
+ return c;
+}
+
+int main()
+{
+
+ if (foo (1, 7) != 4)
+ __builtin_abort ();
+ if (foo (0, 0) != 0)
+ __builtin_abort ();
+ if (foo (8, 0xff) != 16)
+ __builtin_abort ();
+ return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "__builtin_popcount" 1 "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/popcount3.c b/gcc/testsuite/gcc.dg/tree-ssa/popcount3.c
new file mode 100644
index 0000000..0c69d97
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/popcount3.c
@@ -0,0 +1,28 @@
+/* { dg-do execute } */
+/* { dg-options "-O2 -fno-tree-ch -fdump-tree-optimized" } */
+
+int
+__attribute__ ((noinline, noclone))
+foo (long b)
+{
+ int c = i;
+
+ while (b) {
+ b &= b - 1;
+ c++;
+ }
+ return c;
+}
+
+int main()
+{
+ if (foo (7) != 3)
+ __builtin_abort ();
+ if (foo (0) != 0)
+ __builtin_abort ();
+ if (foo (0xff) != 8)
+ __builtin_abort ();
+ return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "__builtin_popcount" 1 "optimized" } } */
diff --git a/gcc/tree-scalar-evolution.c b/gcc/tree-scalar-evolution.c
index fefc9de..967b154 100644
--- a/gcc/tree-scalar-evolution.c
+++ b/gcc/tree-scalar-evolution.c
@@ -1984,6 +1984,7 @@ interpret_expr (struct loop *loop, gimple *at_stmt, tree expr)
return expr;
if (TREE_CODE (expr) == POLYNOMIAL_CHREC
+ || TREE_CODE (expr) == CALL_EXPR
|| get_gimple_rhs_class (TREE_CODE (expr)) == GIMPLE_TERNARY_RHS)
return chrec_dont_know;
@@ -3472,6 +3473,7 @@ bool
expression_expensive_p (tree expr)
{
enum tree_code code;
+ tree fndecl;
if (is_gimple_val (expr))
return false;
@@ -3492,6 +3494,11 @@ expression_expensive_p (tree expr)
if (!integer_pow2p (TREE_OPERAND (expr, 1)))
return true;
}
+ if (code == CALL_EXPR
+ && (fndecl = get_callee_fndecl (expr))
+ && DECL_BUILT_IN_CLASS (fndecl) == BUILT_IN_NORMAL
+ && (BUILT_IN_POPCOUNT == DECL_FUNCTION_CODE (fndecl)))
+ return false;
switch (TREE_CODE_CLASS (code))
{
diff --git a/gcc/tree-ssa-loop-ivopts.c b/gcc/tree-ssa-loop-ivopts.c
index b313571..519649a 100644
--- a/gcc/tree-ssa-loop-ivopts.c
+++ b/gcc/tree-ssa-loop-ivopts.c
@@ -985,6 +985,16 @@ contains_abnormal_ssa_name_p (tree expr)
code = TREE_CODE (expr);
codeclass = TREE_CODE_CLASS (code);
+ if (code == CALL_EXPR)
+ {
+ tree arg;
+ call_expr_arg_iterator iter;
+ FOR_EACH_CALL_EXPR_ARG (arg, iter, expr)
+ if (contains_abnormal_ssa_name_p (arg))
+ return true;
+ return false;
+ }
+
if (code == SSA_NAME)
return SSA_NAME_OCCURS_IN_ABNORMAL_PHI (expr) != 0;
diff --git a/gcc/tree-ssa-loop-niter.c b/gcc/tree-ssa-loop-niter.c
index 7a54c5f..f390321 100644
--- a/gcc/tree-ssa-loop-niter.c
+++ b/gcc/tree-ssa-loop-niter.c
@@ -2430,6 +2430,134 @@ number_of_iterations_exit_assumptions (struct loop *loop, edge exit,
return (!integer_zerop (niter->assumptions));
}
+/* See if LOOP is a popcout implementation of the form
+
+ int c = 0;
+ while (b) {
+ b = b & (b - 1);
+ c++;
+ }
+
+ If so, Set NITER to __builtin_popcount (b) - 1
+ return true if we did, false otherwise. */
+
+static bool
+check_popcount_pattern (loop_p loop, tree *niter, HOST_WIDE_INT *max)
+{
+ tree lhs, rhs;
+ tree dest;
+ gimple *and_minus_one;
+ gimple *phi;
+ int count = 0;
+ gimple *count_stmt = NULL;
+ bool adjust = true;
+
+ if (!single_exit (loop))
+ return false;
+
+ /* Check loop terminating branch is like
+ if (b != 0). */
+ gimple *stmt = last_stmt (loop->header);
+ if (!stmt
+ || gimple_code (stmt) != GIMPLE_COND
+ || !zerop (gimple_cond_rhs (stmt)))
+ return false;
+
+ /* Check the loop closed SSA definition for just the variable c defined in
+ loop. */
+ basic_block bb = single_exit (loop)->dest;
+ for (gphi_iterator gpi = gsi_start_phis (bb);
+ !gsi_end_p (gpi); gsi_next (&gpi))
+ {
+ phi = gpi.phi ();
+ count++;
+ }
+
+ if (count != 1)
+ return false;
+
+ rhs = gimple_phi_arg_def (phi, single_exit (loop)->dest_idx);
+ if (TREE_CODE (rhs) != SSA_NAME)
+ return false;
+ count_stmt = SSA_NAME_DEF_STMT (rhs);
+ lhs = gimple_cond_lhs (stmt);
+ if (TREE_CODE (lhs) != SSA_NAME)
+ return false;
+ gimple *and_stmt = SSA_NAME_DEF_STMT (lhs);
+
+ /* Depending on copy-header is performed, feeding PHI stmts might be in
+ the loop header or loop exit, handle this. */
+ if (gimple_code (count_stmt) == GIMPLE_PHI)
+ {
+ tree t;
+ if (gimple_code (and_stmt) != GIMPLE_PHI
+ || gimple_bb (and_stmt) != single_exit (loop)->src
+ || gimple_bb (count_stmt) != single_exit (loop)->src)
+ return false;
+ t = gimple_phi_arg_def (count_stmt, loop_latch_edge (loop)->dest_idx);
+ if (TREE_CODE (t) != SSA_NAME)
+ return false;
+ count_stmt = SSA_NAME_DEF_STMT (t);
+ t = gimple_phi_arg_def (and_stmt, loop_latch_edge (loop)->dest_idx);
+ if (TREE_CODE (t) != SSA_NAME)
+ return false;
+ and_stmt = SSA_NAME_DEF_STMT (t);
+ adjust = false;
+ }
+
+ /* Make sure we have a count by one. */
+ if (!is_gimple_assign (count_stmt)
+ || (gimple_assign_rhs_code (count_stmt) != PLUS_EXPR)
+ || !integer_onep (gimple_assign_rhs2 (count_stmt)))
+ return false;
+
+ /* Cheeck "b = b & (b - 1)" is calculated. */
+ if (!is_gimple_assign (and_stmt)
+ || gimple_assign_rhs_code (and_stmt) != BIT_AND_EXPR)
+ return false;
+
+ lhs = gimple_assign_rhs1 (and_stmt);
+ rhs = gimple_assign_rhs2 (and_stmt);
+ if (TREE_CODE (lhs) == SSA_NAME
+ && (and_minus_one = SSA_NAME_DEF_STMT (lhs))
+ && is_gimple_assign (and_minus_one)
+ && (gimple_assign_rhs_code (and_minus_one) == PLUS_EXPR)
+ && integer_minus_onep (gimple_assign_rhs2 (and_minus_one)))
+ lhs = rhs;
+ else if (TREE_CODE (rhs) == SSA_NAME
+ && (and_minus_one = SSA_NAME_DEF_STMT (rhs))
+ && is_gimple_assign (and_minus_one)
+ && (gimple_assign_rhs_code (and_minus_one) == PLUS_EXPR)
+ && integer_minus_onep (gimple_assign_rhs2 (and_minus_one)))
+ ;
+ else
+ return false;
+
+ if ((gimple_assign_rhs1 (and_stmt) != gimple_assign_rhs1 (and_minus_one))
+ && (gimple_assign_rhs2 (and_stmt) != gimple_assign_rhs1 (and_minus_one)))
+ return false;
+
+ /* Check the recurrence. */
+ phi = SSA_NAME_DEF_STMT (gimple_assign_rhs1 (and_minus_one));
+ gimple *src_phi = SSA_NAME_DEF_STMT (lhs);
+ if (gimple_code (phi) != GIMPLE_PHI
+ || gimple_code (src_phi) != GIMPLE_PHI)
+ return false;
+
+ dest = gimple_assign_lhs (count_stmt);
+ tree fn = builtin_decl_implicit (BUILT_IN_POPCOUNT);
+ tree src = gimple_phi_arg_def (src_phi, loop_preheader_edge (loop)->dest_idx);
+ if (adjust)
+ *niter = fold_build2 (MINUS_EXPR, TREE_TYPE (dest),
+ build_call_expr (fn, 1, src),
+ build_int_cst (TREE_TYPE (dest), 1));
+ else
+ *niter = build_call_expr (fn, 1, src);
+ *max = int_cst_value (TYPE_MAX_VALUE (TREE_TYPE (dest)));
+ return true;
+}
+
+
/* Like number_of_iterations_exit_assumptions, but return TRUE only if
the niter information holds unconditionally. */
@@ -2441,7 +2569,25 @@ number_of_iterations_exit (struct loop *loop, edge exit,
gcond *stmt;
if (!number_of_iterations_exit_assumptions (loop, exit, niter,
&stmt, every_iteration))
- return false;
+ {
+ tree count;
+ HOST_WIDE_INT max;
+ if (check_popcount_pattern (loop, &count, &max))
+ {
+ niter->assumptions = boolean_false_node;
+ niter->control.base = NULL_TREE;
+ niter->control.step = NULL_TREE;
+ niter->control.no_overflow = false;
+ niter->niter = count;
+ niter->assumptions = boolean_true_node;
+ niter->may_be_zero = boolean_false_node;
+ niter->max = max;
+ niter->bound = NULL_TREE;
+ niter->cmp = ERROR_MARK;
+ return true;
+ }
+ return false;
+ }
if (integer_nonzerop (niter->assumptions))
return true;
--
2.7.4
