ipa: special pass-through op for Fortran strides

when Fortran functions pass array descriptors they receive as a
parameter to another function, they actually rebuild it.  Thanks to
work done mainly by Feng, IPA-CP can already handle the cases when
they pass directly the values loaded from the original descriptor.
Unfortunately, perhaps the most important one, stride, is first
checked against zero and is replaced with one in that case:

  _12 = *a_11(D).dim[0].stride;
  if (_12 != 0)
    goto <bb 4>; [50.00%]
  else
    goto <bb 3>; [50.00%]

  <bb 3>
    // empty BB
  <bb 4>
  # iftmp.22_9 = PHI <_12(2), 1(3)>
   ...
   parm.6.dim[0].stride = iftmp.22_9;
   ...
   __x_MOD_foo (&parm.6, b_31(D));

in the most important and hopefully common cases, the incoming value
is already 1 and we fail to propagate it.

I would therefore like to propose the following way of encoding this
situation in pass-through jump functions using using ASSERTT_EXPR
operation code meaning that if the incoming value is the same as the
"operand" in the jump function, it is passed on, otherwise the result
is unknown.  This of course captures only the single (but most
important) case but is an improvement and does not need enlarging the
jump function structure and is simple to pattern match.  Encoding that
zero needs to be changed to one would need another field and matching
it would be slightly more complicated too.

gcc/
2020-06-12  Martin Jambor  <mjambor@suse.cz>

	* ipa-prop.h (ipa_pass_through_data): Expand comment describing
	operation.
	* ipa-prop.c (analyze_agg_content_value): Detect new special case and
	encode it as ASSERT_EXPR.
	* ipa-cp.c (values_equal_for_ipcp_p): Move before
	ipa_get_jf_arith_result.
	(ipa_get_jf_arith_result): Special case ASSERT_EXPR.

gcc/testsuite/
2020-06-12  Martin Jambor  <mjambor@suse.cz>
	* gfortran.dg/ipcp-array-2.f90: New test.

diff --git a/gcc/ipa-cp.c b/gcc/ipa-cp.c
index c3ee71e16e1d5f0235b3f6d938e38de26f1c89e2..a06b4d151dd7d0bcaa7caa7be10ef3d4c252251f 100644 (file)
--- a/gcc/ipa-cp.c
+++ b/gcc/ipa-cp.c
@@ -1304,6 +1304,26 @@ initialize_node_lattices (struct cgraph_node *node)
       }
 }
 
+/* Return true iff X and Y should be considered equal values by IPA-CP.  */
+
+static bool
+values_equal_for_ipcp_p (tree x, tree y)
+{
+  gcc_checking_assert (x != NULL_TREE && y != NULL_TREE);
+
+  if (x == y)
+    return true;
+
+  if (TREE_CODE (x) == ADDR_EXPR
+      && TREE_CODE (y) == ADDR_EXPR
+      && TREE_CODE (TREE_OPERAND (x, 0)) == CONST_DECL
+      && TREE_CODE (TREE_OPERAND (y, 0)) == CONST_DECL)
+    return operand_equal_p (DECL_INITIAL (TREE_OPERAND (x, 0)),
+                           DECL_INITIAL (TREE_OPERAND (y, 0)), 0);
+  else
+    return operand_equal_p (x, y, 0);
+}
+
 /* Return the result of a (possibly arithmetic) operation on the constant
    value INPUT.  OPERAND is 2nd operand for binary operation.  RES_TYPE is
    the type of the parameter to which the result is passed.  Return
@@ -1321,6 +1341,14 @@ ipa_get_jf_arith_result (enum tree_code opcode, tree input, tree operand,
   if (!is_gimple_ip_invariant (input))
     return NULL_TREE;
 
+  if (opcode == ASSERT_EXPR)
+    {
+      if (values_equal_for_ipcp_p (input, operand))
+       return input;
+      else
+       return NULL_TREE;
+    }
+
   if (!res_type)
     {
       if (TREE_CODE_CLASS (opcode) == tcc_comparison)
@@ -1753,26 +1781,6 @@ ipcp_verify_propagated_values (void)
     }
 }
 
-/* Return true iff X and Y should be considered equal values by IPA-CP.  */
-
-static bool
-values_equal_for_ipcp_p (tree x, tree y)
-{
-  gcc_checking_assert (x != NULL_TREE && y != NULL_TREE);
-
-  if (x == y)
-    return true;
-
-  if (TREE_CODE (x) ==  ADDR_EXPR
-      && TREE_CODE (y) ==  ADDR_EXPR
-      && TREE_CODE (TREE_OPERAND (x, 0)) == CONST_DECL
-      && TREE_CODE (TREE_OPERAND (y, 0)) == CONST_DECL)
-    return operand_equal_p (DECL_INITIAL (TREE_OPERAND (x, 0)),
-                           DECL_INITIAL (TREE_OPERAND (y, 0)), 0);
-  else
-    return operand_equal_p (x, y, 0);
-}
-
 /* Return true iff X and Y should be considered equal contexts by IPA-CP.  */
 
 static bool

diff --git a/gcc/ipa-prop.c b/gcc/ipa-prop.c
index 904a8f7d18b8654ded562ecfdd3226c52cc169b2..130b2f84b78bf7a352dacef84618652430ff66d2 100644 (file)
--- a/gcc/ipa-prop.c
+++ b/gcc/ipa-prop.c
@@ -1775,75 +1775,123 @@ analyze_agg_content_value (struct ipa_func_body_info *fbi,
 
       stmt = SSA_NAME_DEF_STMT (rhs1);
       if (!is_gimple_assign (stmt))
-       return;
+       break;
 
       rhs1 = gimple_assign_rhs1 (stmt);
     }
 
-  code = gimple_assign_rhs_code (stmt);
-  switch (gimple_assign_rhs_class (stmt))
+  if (gphi *phi = dyn_cast<gphi *> (stmt))
     {
-    case GIMPLE_SINGLE_RHS:
-      if (is_gimple_ip_invariant (rhs1))
-       {
-         agg_value->pass_through.operand = rhs1;
-         return;
-       }
-      code = NOP_EXPR;
-      break;
+      /* Also special case like the following (a is a formal parameter):
+
+          _12 = *a_11(D).dim[0].stride;
+          ...
+          # iftmp.22_9 = PHI <_12(2), 1(3)>
+          ...
+          parm.6.dim[0].stride = iftmp.22_9;
+          ...
+          __x_MOD_foo (&parm.6, b_31(D));
 
-    case GIMPLE_UNARY_RHS:
-      /* NOTE: A GIMPLE_UNARY_RHS operation might not be tcc_unary
-        (truth_not_expr is example), GIMPLE_BINARY_RHS does not imply
-        tcc_binary, this subtleness is somewhat misleading.
+        The aggregate function describing parm.6.dim[0].stride is encoded as a
+        PASS-THROUGH jump function with ASSERT_EXPR operation whith operand 1
+        (the constant from the PHI node).  */
 
-        Since tcc_unary is widely used in IPA-CP code to check an operation
-        with one operand, here we only allow tc_unary operation to avoid
-        possible problem.  Then we can use (opclass == tc_unary) or not to
-        distinguish unary and binary.  */
-      if (TREE_CODE_CLASS (code) != tcc_unary || CONVERT_EXPR_CODE_P (code))
+      if (gimple_phi_num_args (phi) != 2)
+       return;
+      tree arg0 = gimple_phi_arg_def (phi, 0);
+      tree arg1 = gimple_phi_arg_def (phi, 1);
+      tree operand;
+
+      if (is_gimple_ip_invariant (arg1))
+       {
+         operand = arg1;
+         rhs1 = arg0;
+       }
+      else if (is_gimple_ip_invariant (arg0))
+       {
+         operand = arg0;
+         rhs1 = arg1;
+       }
+      else
        return;
 
       rhs1 = get_ssa_def_if_simple_copy (rhs1, &stmt);
-      break;
+      if (!is_gimple_assign (stmt))
+       return;
 
-    case GIMPLE_BINARY_RHS:
-      {
-       gimple *rhs1_stmt = stmt;
-       gimple *rhs2_stmt = stmt;
-       tree rhs2 = gimple_assign_rhs2 (stmt);
+      code = ASSERT_EXPR;
+      agg_value->pass_through.operand = operand;
+    }
+  else if (is_gimple_assign (stmt))
+    {
+      code = gimple_assign_rhs_code (stmt);
+      switch (gimple_assign_rhs_class (stmt))
+       {
+       case GIMPLE_SINGLE_RHS:
+         if (is_gimple_ip_invariant (rhs1))
+           {
+             agg_value->pass_through.operand = rhs1;
+             return;
+           }
+         code = NOP_EXPR;
+         break;
 
-       rhs1 = get_ssa_def_if_simple_copy (rhs1, &rhs1_stmt);
-       rhs2 = get_ssa_def_if_simple_copy (rhs2, &rhs2_stmt);
+       case GIMPLE_UNARY_RHS:
+         /* NOTE: A GIMPLE_UNARY_RHS operation might not be tcc_unary
+            (truth_not_expr is example), GIMPLE_BINARY_RHS does not imply
+            tcc_binary, this subtleness is somewhat misleading.
+
+            Since tcc_unary is widely used in IPA-CP code to check an operation
+            with one operand, here we only allow tc_unary operation to avoid
+            possible problem.  Then we can use (opclass == tc_unary) or not to
+            distinguish unary and binary.  */
+         if (TREE_CODE_CLASS (code) != tcc_unary || CONVERT_EXPR_CODE_P (code))
+           return;
 
-       if (is_gimple_ip_invariant (rhs2))
-         {
-           agg_value->pass_through.operand = rhs2;
-           stmt = rhs1_stmt;
-         }
-       else if (is_gimple_ip_invariant (rhs1))
+         rhs1 = get_ssa_def_if_simple_copy (rhs1, &stmt);
+         break;
+
+       case GIMPLE_BINARY_RHS:
          {
-           if (TREE_CODE_CLASS (code) == tcc_comparison)
-             code = swap_tree_comparison (code);
-           else if (!commutative_tree_code (code))
+           gimple *rhs1_stmt = stmt;
+           gimple *rhs2_stmt = stmt;
+           tree rhs2 = gimple_assign_rhs2 (stmt);
+
+           rhs1 = get_ssa_def_if_simple_copy (rhs1, &rhs1_stmt);
+           rhs2 = get_ssa_def_if_simple_copy (rhs2, &rhs2_stmt);
+
+           if (is_gimple_ip_invariant (rhs2))
+             {
+               agg_value->pass_through.operand = rhs2;
+               stmt = rhs1_stmt;
+             }
+           else if (is_gimple_ip_invariant (rhs1))
+             {
+               if (TREE_CODE_CLASS (code) == tcc_comparison)
+                 code = swap_tree_comparison (code);
+               else if (!commutative_tree_code (code))
+                 return;
+
+               agg_value->pass_through.operand = rhs1;
+               stmt = rhs2_stmt;
+               rhs1 = rhs2;
+             }
+           else
              return;
 
-           agg_value->pass_through.operand = rhs1;
-           stmt = rhs2_stmt;
-           rhs1 = rhs2;
+           if (TREE_CODE_CLASS (code) != tcc_comparison
+               && !useless_type_conversion_p (TREE_TYPE (lhs),
+                                              TREE_TYPE (rhs1)))
+             return;
          }
-       else
-         return;
+         break;
 
-       if (TREE_CODE_CLASS (code) != tcc_comparison
-           && !useless_type_conversion_p (TREE_TYPE (lhs), TREE_TYPE (rhs1)))
+       default:
          return;
-      }
-      break;
-
-    default:
-      return;
-  }
+       }
+    }
+  else
+    return;
 
   if (TREE_CODE (rhs1) != SSA_NAME)
     index = load_from_unmodified_param_or_agg (fbi, fbi->info, stmt,

diff --git a/gcc/ipa-prop.h b/gcc/ipa-prop.h
index 56e80559cf4b7bc56b217bc56fdf59d1214df7f0..112a1ba580bf59520322c45ba2ddc6a59b05dd7f 100644 (file)
--- a/gcc/ipa-prop.h
+++ b/gcc/ipa-prop.h
@@ -94,9 +94,14 @@ struct GTY(()) ipa_pass_through_data
   /* Number of the caller's formal parameter being passed.  */
   int formal_id;
   /* Operation that is performed on the argument before it is passed on.
-     NOP_EXPR means no operation.  Otherwise oper must be a simple binary
-     arithmetic operation where the caller's parameter is the first operand and
-     operand field from this structure is the second one.  */
+     Special values which have other meaning than in normal contexts:
+       - NOP_EXPR means no operation, not even type conversion.
+       - ASSERT_EXPR means that only the value in operand is allowed to pass
+         through (without any change), for all other values the result is
+         unknown.
+     Otherwise operation must be a simple binary or unary arithmetic operation
+     where the caller's parameter is the first operand and (for binary
+     operations) the operand field from this structure is the second one.  */
   enum tree_code operation;
   /* When the passed value is a pointer, it is set to true only when we are
      certain that no write to the object it points to has occurred since the

diff --git a/gcc/testsuite/gfortran.dg/ipcp-array-2.f90 b/gcc/testsuite/gfortran.dg/ipcp-array-2.f90
new file mode 100644 (file)
index 0000000..9af8fff
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/ipcp-array-2.f90
@@ -0,0 +1,45 @@
+! { dg-do compile }
+! { dg-options "-O3 -fno-inline -fwhole-program -fdump-ipa-cp-details -fdump-tree-lversion-details" }
+
+module x
+  implicit none
+contains
+  subroutine foo(a, b)
+    real :: a(:,:)
+    real :: b
+    integer :: i,j
+    b = 0.
+    do j=1,size(a,2)
+       do i=1,size(a,1)
+          b = b + a(i,j) * i * j
+       end do
+    end do
+  end subroutine foo
+
+  subroutine bar(a, b)
+    real :: a(:,:)
+    real :: b
+    call foo (a,b)
+  end subroutine bar
+
+end module x
+
+program main
+  use x
+  implicit none
+  integer :: n, m
+  real, dimension(4,3) :: a
+  real, dimension(3,4) :: c     
+  real :: b
+  call random_number(a)
+  call bar(a,b)
+  print *,b
+  
+  call random_number(c)
+  call bar(c,b)
+  print *,b
+  
+end program main
+
+! { dg-final { scan-ipa-dump "op assert_expr 1" "cp" } }
+! { dg-final { scan-tree-dump-not "versioned this loop for when certain strides are 1" "lversion" } }