The following patch teaches VRP to disregard the intermediate
conversion in a sequence (T1)(T2)val if that sequence is
value-preserving for val. There are possibly some more
cases that could be handled when a sign-change is involved
but the following is a first safe step.
Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
Richard.
2011-07-07 Richard Guenther <rguent...@suse.de>
* tree-vrp.c (simplify_conversion_using_ranges): New function.
(simplify_stmt_using_ranges): Call it.
* gcc.dg/tree-ssa/vrp58.c: New testcase.
Index: gcc/tree-vrp.c
===================================================================
*** gcc/tree-vrp.c (revision 175962)
--- gcc/tree-vrp.c (working copy)
*************** simplify_switch_using_ranges (gimple stm
*** 7342,7347 ****
--- 7342,7378 ----
return false;
}
+ /* Simplify an integral conversion from an SSA name in STMT. */
+
+ static bool
+ simplify_conversion_using_ranges (gimple stmt)
+ {
+ tree rhs1 = gimple_assign_rhs1 (stmt);
+ gimple def_stmt = SSA_NAME_DEF_STMT (rhs1);
+ value_range_t *final, *inner;
+
+ /* Obtain final and inner value-ranges for a conversion
+ sequence (final-type)(intermediate-type)inner-type. */
+ final = get_value_range (gimple_assign_lhs (stmt));
+ if (final->type != VR_RANGE)
+ return false;
+ if (!is_gimple_assign (def_stmt)
+ || !CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (def_stmt)))
+ return false;
+ rhs1 = gimple_assign_rhs1 (def_stmt);
+ if (TREE_CODE (rhs1) != SSA_NAME)
+ return false;
+ inner = get_value_range (rhs1);
+ if (inner->type != VR_RANGE)
+ return false;
+ if (!tree_int_cst_equal (final->min, inner->min)
+ || !tree_int_cst_equal (final->max, inner->max))
+ return false;
+ gimple_assign_set_rhs1 (stmt, rhs1);
+ update_stmt (stmt);
+ return true;
+ }
+
/* Simplify STMT using ranges if possible. */
static bool
*************** simplify_stmt_using_ranges (gimple_stmt_
*** 7351,7356 ****
--- 7382,7388 ----
if (is_gimple_assign (stmt))
{
enum tree_code rhs_code = gimple_assign_rhs_code (stmt);
+ tree rhs1 = gimple_assign_rhs1 (stmt);
switch (rhs_code)
{
*************** simplify_stmt_using_ranges (gimple_stmt_
*** 7364,7370 ****
or identity if the RHS is zero or one, and the LHS are known
to be boolean values. Transform all TRUTH_*_EXPR into
BIT_*_EXPR if both arguments are known to be boolean values. */
! if (INTEGRAL_TYPE_P (TREE_TYPE (gimple_assign_rhs1 (stmt))))
return simplify_truth_ops_using_ranges (gsi, stmt);
break;
--- 7396,7402 ----
or identity if the RHS is zero or one, and the LHS are known
to be boolean values. Transform all TRUTH_*_EXPR into
BIT_*_EXPR if both arguments are known to be boolean values. */
! if (INTEGRAL_TYPE_P (TREE_TYPE (rhs1)))
return simplify_truth_ops_using_ranges (gsi, stmt);
break;
*************** simplify_stmt_using_ranges (gimple_stmt_
*** 7373,7387 ****
than zero and the second operand is an exact power of two. */
case TRUNC_DIV_EXPR:
case TRUNC_MOD_EXPR:
! if (INTEGRAL_TYPE_P (TREE_TYPE (gimple_assign_rhs1 (stmt)))
&& integer_pow2p (gimple_assign_rhs2 (stmt)))
return simplify_div_or_mod_using_ranges (stmt);
break;
/* Transform ABS (X) into X or -X as appropriate. */
case ABS_EXPR:
! if (TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME
! && INTEGRAL_TYPE_P (TREE_TYPE (gimple_assign_rhs1 (stmt))))
return simplify_abs_using_ranges (stmt);
break;
--- 7405,7419 ----
than zero and the second operand is an exact power of two. */
case TRUNC_DIV_EXPR:
case TRUNC_MOD_EXPR:
! if (INTEGRAL_TYPE_P (TREE_TYPE (rhs1))
&& integer_pow2p (gimple_assign_rhs2 (stmt)))
return simplify_div_or_mod_using_ranges (stmt);
break;
/* Transform ABS (X) into X or -X as appropriate. */
case ABS_EXPR:
! if (TREE_CODE (rhs1) == SSA_NAME
! && INTEGRAL_TYPE_P (TREE_TYPE (rhs1)))
return simplify_abs_using_ranges (stmt);
break;
*************** simplify_stmt_using_ranges (gimple_stmt_
*** 7390,7399 ****
/* Optimize away BIT_AND_EXPR and BIT_IOR_EXPR
if all the bits being cleared are already cleared or
all the bits being set are already set. */
! if (INTEGRAL_TYPE_P (TREE_TYPE (gimple_assign_rhs1 (stmt))))
return simplify_bit_ops_using_ranges (gsi, stmt);
break;
default:
break;
}
--- 7422,7437 ----
/* Optimize away BIT_AND_EXPR and BIT_IOR_EXPR
if all the bits being cleared are already cleared or
all the bits being set are already set. */
! if (INTEGRAL_TYPE_P (TREE_TYPE (rhs1)))
return simplify_bit_ops_using_ranges (gsi, stmt);
break;
+ CASE_CONVERT:
+ if (TREE_CODE (rhs1) == SSA_NAME
+ && INTEGRAL_TYPE_P (TREE_TYPE (rhs1)))
+ return simplify_conversion_using_ranges (stmt);
+ break;
+
default:
break;
}
Index: gcc/testsuite/gcc.dg/tree-ssa/vrp58.c
===================================================================
*** gcc/testsuite/gcc.dg/tree-ssa/vrp58.c (revision 0)
--- gcc/testsuite/gcc.dg/tree-ssa/vrp58.c (revision 0)
***************
*** 0 ****
--- 1,12 ----
+ /* { dg-do compile } */
+ /* { dg-options "-O2 -fdump-tree-vrp1-details" } */
+
+ long long
+ foo (long long a, signed char b, signed char c)
+ {
+ int bc = b * c;
+ return a + (short)bc;
+ }
+
+ /* { dg-final { scan-tree-dump "Folded into" "vrp1" } } */
+ /* { dg-final { cleanup-tree-dump "vrp1" } } */
