[3/4] VN: Handle `(A CMP B) !=/== 0` for predicates [PR117414]

Message ID 20241102150921.3319089-3-quic_apinski@quicinc.com
State New
Headers
Series [1/4] VN: Factor out inserting predicates for conditional |

Commit Message

Andrew Pinski Nov. 2, 2024, 3:09 p.m. UTC
  After the last patch, we also want to record `(A CMP B) != 0`
as `(A CMP B)` and `(A CMP B) == 0` as `(A CMP B)` with the
true/false edges swapped.

This is enough to fix the original issue in `gcc.dg/tree-ssa/pr111456-1.c`
and make sure we don't regress it when enhancing ifcombine.

This adds that predicate and allows us to optimize f
in fre-predicated-3.c.

Bootstrapped and tested on x86_64-linux-gnu.

	PR tree-optimization/117414

gcc/ChangeLog:

	* tree-ssa-sccvn.cc (insert_predicates_for_cond):

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/fre-predicated-3.c: New test.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>
---
 .../gcc.dg/tree-ssa/fre-predicated-3.c        | 46 +++++++++++++++++++
 gcc/tree-ssa-sccvn.cc                         | 14 ++++++
 2 files changed, 60 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-3.c
  

Comments

Richard Biener Nov. 6, 2024, 12:55 p.m. UTC | #1
On Sat, Nov 2, 2024 at 4:10 PM Andrew Pinski <quic_apinski@quicinc.com> wrote:
>
> After the last patch, we also want to record `(A CMP B) != 0`
> as `(A CMP B)` and `(A CMP B) == 0` as `(A CMP B)` with the
> true/false edges swapped.
>
> This is enough to fix the original issue in `gcc.dg/tree-ssa/pr111456-1.c`
> and make sure we don't regress it when enhancing ifcombine.
>
> This adds that predicate and allows us to optimize f
> in fre-predicated-3.c.
>
> Bootstrapped and tested on x86_64-linux-gnu.
>
>         PR tree-optimization/117414
>
> gcc/ChangeLog:
>
>         * tree-ssa-sccvn.cc (insert_predicates_for_cond):
>
> gcc/testsuite/ChangeLog:
>
>         * gcc.dg/tree-ssa/fre-predicated-3.c: New test.
>
> Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>
> ---
>  .../gcc.dg/tree-ssa/fre-predicated-3.c        | 46 +++++++++++++++++++
>  gcc/tree-ssa-sccvn.cc                         | 14 ++++++
>  2 files changed, 60 insertions(+)
>  create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-3.c
>
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-3.c b/gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-3.c
> new file mode 100644
> index 00000000000..4a89372fd70
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-3.c
> @@ -0,0 +1,46 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized" } */
> +
> +/* PR tree-optimization/117414 */
> +
> +/* Fre1 should figure out that `*aaa != 0`
> +   For f0, f1, and f2. */
> +
> +void foo();
> +int f(int *aaa, int j, int t)
> +{
> +  int b = *aaa;
> +  int c = b == 0;
> +  int d = t != 1;
> +  if (c | d)
> +    return 0;
> +
> +  for(int i = 0; i < j; i++)
> +  {
> +    if (*aaa)
> +      ;
> +    else
> +      foo();
> +  }
> +  return 0;
> +}
> +
> +int f1(int *aaa, int j, int t)
> +{
> +  int b = *aaa;
> +  if (b == 0)
> +    return 0;
> +  if (t != 1)
> +    return 0;
> +  for(int i = 0; i < j; i++)
> +  {
> +    if (*aaa)
> +      ;
> +    else
> +      foo();
> +  }
> +  return 0;
> +}
> +
> +/* { dg-final { scan-tree-dump-not "foo " "optimized" } } */
> +/* { dg-final { scan-tree-dump "return 0;" "optimized" } } */
> diff --git a/gcc/tree-ssa-sccvn.cc b/gcc/tree-ssa-sccvn.cc
> index b3e6cd09007..190b7d24f1a 100644
> --- a/gcc/tree-ssa-sccvn.cc
> +++ b/gcc/tree-ssa-sccvn.cc
> @@ -7937,6 +7937,20 @@ insert_predicates_for_cond (tree_code code, tree lhs, tree rhs,
>        && TREE_CODE (lhs) == SSA_NAME)
>      {
>        gimple *def_stmt = SSA_NAME_DEF_STMT (lhs);
> +      /* (A CMP B) != 0 is the same as (A CMP B).
> +        (A CMP B) == 0 is just (A CMP B) with the edges swapped.  */
> +      if (is_gimple_assign (def_stmt)
> +         && TREE_CODE_CLASS (gimple_assign_rhs_code (def_stmt)) == tcc_comparison)
> +         {
> +           tree_code nc = gimple_assign_rhs_code (def_stmt);
> +           tree nlhs = gimple_assign_rhs1 (def_stmt);
> +           tree nrhs = gimple_assign_rhs2 (def_stmt);

Same as with the other patch.

We do forward/fold compares quite aggressively, so I wonder why (A CMP
B) != 0 wasn't
simplified earlier?

Otherwise OK.

Thanks,
Richard.

> +           edge nt = true_e;
> +           edge nf = false_e;
> +           if (code == EQ_EXPR)
> +             std::swap (nt, nf);
> +           insert_predicates_for_cond (nc, nlhs, nrhs, nt, nf);
> +         }
>        /* (a | b) == 0 ->
>             on true edge assert: a == 0 & b == 0. */
>        /* (a | b) != 0 ->
> --
> 2.43.0
>
  
Andrew Pinski Nov. 6, 2024, 4:53 p.m. UTC | #2
On Wed, Nov 6, 2024 at 4:56 AM Richard Biener
<richard.guenther@gmail.com> wrote:
>
> On Sat, Nov 2, 2024 at 4:10 PM Andrew Pinski <quic_apinski@quicinc.com> wrote:
> >
> > After the last patch, we also want to record `(A CMP B) != 0`
> > as `(A CMP B)` and `(A CMP B) == 0` as `(A CMP B)` with the
> > true/false edges swapped.
> >
> > This is enough to fix the original issue in `gcc.dg/tree-ssa/pr111456-1.c`
> > and make sure we don't regress it when enhancing ifcombine.
> >
> > This adds that predicate and allows us to optimize f
> > in fre-predicated-3.c.
> >
> > Bootstrapped and tested on x86_64-linux-gnu.
> >
> >         PR tree-optimization/117414
> >
> > gcc/ChangeLog:
> >
> >         * tree-ssa-sccvn.cc (insert_predicates_for_cond):
> >
> > gcc/testsuite/ChangeLog:
> >
> >         * gcc.dg/tree-ssa/fre-predicated-3.c: New test.
> >
> > Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>
> > ---
> >  .../gcc.dg/tree-ssa/fre-predicated-3.c        | 46 +++++++++++++++++++
> >  gcc/tree-ssa-sccvn.cc                         | 14 ++++++
> >  2 files changed, 60 insertions(+)
> >  create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-3.c
> >
> > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-3.c b/gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-3.c
> > new file mode 100644
> > index 00000000000..4a89372fd70
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-3.c
> > @@ -0,0 +1,46 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2 -fdump-tree-optimized" } */
> > +
> > +/* PR tree-optimization/117414 */
> > +
> > +/* Fre1 should figure out that `*aaa != 0`
> > +   For f0, f1, and f2. */
> > +
> > +void foo();
> > +int f(int *aaa, int j, int t)
> > +{
> > +  int b = *aaa;
> > +  int c = b == 0;
> > +  int d = t != 1;
> > +  if (c | d)
> > +    return 0;
> > +
> > +  for(int i = 0; i < j; i++)
> > +  {
> > +    if (*aaa)
> > +      ;
> > +    else
> > +      foo();
> > +  }
> > +  return 0;
> > +}
> > +
> > +int f1(int *aaa, int j, int t)
> > +{
> > +  int b = *aaa;
> > +  if (b == 0)
> > +    return 0;
> > +  if (t != 1)
> > +    return 0;
> > +  for(int i = 0; i < j; i++)
> > +  {
> > +    if (*aaa)
> > +      ;
> > +    else
> > +      foo();
> > +  }
> > +  return 0;
> > +}
> > +
> > +/* { dg-final { scan-tree-dump-not "foo " "optimized" } } */
> > +/* { dg-final { scan-tree-dump "return 0;" "optimized" } } */
> > diff --git a/gcc/tree-ssa-sccvn.cc b/gcc/tree-ssa-sccvn.cc
> > index b3e6cd09007..190b7d24f1a 100644
> > --- a/gcc/tree-ssa-sccvn.cc
> > +++ b/gcc/tree-ssa-sccvn.cc
> > @@ -7937,6 +7937,20 @@ insert_predicates_for_cond (tree_code code, tree lhs, tree rhs,
> >        && TREE_CODE (lhs) == SSA_NAME)
> >      {
> >        gimple *def_stmt = SSA_NAME_DEF_STMT (lhs);
> > +      /* (A CMP B) != 0 is the same as (A CMP B).
> > +        (A CMP B) == 0 is just (A CMP B) with the edges swapped.  */
> > +      if (is_gimple_assign (def_stmt)
> > +         && TREE_CODE_CLASS (gimple_assign_rhs_code (def_stmt)) == tcc_comparison)
> > +         {
> > +           tree_code nc = gimple_assign_rhs_code (def_stmt);
> > +           tree nlhs = gimple_assign_rhs1 (def_stmt);
> > +           tree nrhs = gimple_assign_rhs2 (def_stmt);
>
> Same as with the other patch.

I will make the change to use vn_valueize and test it.

>
> We do forward/fold compares quite aggressively, so I wonder why (A CMP
> B) != 0 wasn't
> simplified earlier?

Because in this case, we are handling this recursively. We originally
had `((A CMP B) | (C CMP D)) != 0` which
then insert_predicates_for_cond gets called (again) with `bool0 != 0`
, we want to see that bool0 was defined as `A CMP B`.
The testcase is testing the above recursively call sequence rather
than the unfolled sequence you are thinking of.

Thanks,
Andrew Pinski


>
> Otherwise OK.
>
> Thanks,
> Richard.
>
> > +           edge nt = true_e;
> > +           edge nf = false_e;
> > +           if (code == EQ_EXPR)
> > +             std::swap (nt, nf);
> > +           insert_predicates_for_cond (nc, nlhs, nrhs, nt, nf);
> > +         }
> >        /* (a | b) == 0 ->
> >             on true edge assert: a == 0 & b == 0. */
> >        /* (a | b) != 0 ->
> > --
> > 2.43.0
> >
  

Patch

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-3.c b/gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-3.c
new file mode 100644
index 00000000000..4a89372fd70
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-3.c
@@ -0,0 +1,46 @@ 
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+/* PR tree-optimization/117414 */
+
+/* Fre1 should figure out that `*aaa != 0`
+   For f0, f1, and f2. */
+
+void foo();
+int f(int *aaa, int j, int t)
+{
+  int b = *aaa;
+  int c = b == 0;
+  int d = t != 1;
+  if (c | d)
+    return 0;
+
+  for(int i = 0; i < j; i++)
+  {
+    if (*aaa)
+      ;
+    else
+      foo();
+  }
+  return 0;
+}
+
+int f1(int *aaa, int j, int t)
+{
+  int b = *aaa;
+  if (b == 0)
+    return 0;
+  if (t != 1)
+    return 0;
+  for(int i = 0; i < j; i++)
+  {
+    if (*aaa)
+      ;
+    else
+      foo();
+  }
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-not "foo " "optimized" } } */
+/* { dg-final { scan-tree-dump "return 0;" "optimized" } } */
diff --git a/gcc/tree-ssa-sccvn.cc b/gcc/tree-ssa-sccvn.cc
index b3e6cd09007..190b7d24f1a 100644
--- a/gcc/tree-ssa-sccvn.cc
+++ b/gcc/tree-ssa-sccvn.cc
@@ -7937,6 +7937,20 @@  insert_predicates_for_cond (tree_code code, tree lhs, tree rhs,
       && TREE_CODE (lhs) == SSA_NAME)
     {
       gimple *def_stmt = SSA_NAME_DEF_STMT (lhs);
+      /* (A CMP B) != 0 is the same as (A CMP B).
+	 (A CMP B) == 0 is just (A CMP B) with the edges swapped.  */
+      if (is_gimple_assign (def_stmt)
+	  && TREE_CODE_CLASS (gimple_assign_rhs_code (def_stmt)) == tcc_comparison)
+	  {
+	    tree_code nc = gimple_assign_rhs_code (def_stmt);
+	    tree nlhs = gimple_assign_rhs1 (def_stmt);
+	    tree nrhs = gimple_assign_rhs2 (def_stmt);
+	    edge nt = true_e;
+	    edge nf = false_e;
+	    if (code == EQ_EXPR)
+	      std::swap (nt, nf);
+	    insert_predicates_for_cond (nc, nlhs, nrhs, nt, nf);
+	  }
       /* (a | b) == 0 ->
 	    on true edge assert: a == 0 & b == 0. */
       /* (a | b) != 0 ->