This removes one weakness in BIT_IOR_EXPR handling which gives
up even if we can compute a fully negative range. The following
thus extends zero_nonzero_bits_from_vr to extract sign-bit
information (I believe that's the only bit we know sth about
when both vr.min and vr.max are negative). It also adjusts
BIT_IOR_EXPR handling to not give up for the min < max < 0 case.
Boostrapped on x86_64-unknown-linux-gnu, testing in progress.
I guess BIT_AND_EXPR handling will show a similar weakness but
a similar testcase (as added below) already passes. So I suppose
we have to obfuscate it a bit more ;)
Richard.
2011-08-05 Richard Guenther <rguent...@suse.de>
* tree-vrp.c (zero_nonzero_bits_from_vr): Pass in a type.
For ranges with negative values return information about the
sign-bit.
(extract_range_from_binary_expr_1): Adjust BIT_IOR_EXPR handling
to handle sign-bit information for ranges with negative values.
(simplify_bit_ops_using_ranges): Adjust.
* gcc.dg/tree-ssa/vrp60.c: New testcase.
Index: gcc/tree-vrp.c
===================================================================
*** gcc/tree-vrp.c (revision 177425)
--- gcc/tree-vrp.c (working copy)
*************** vrp_int_const_binop (enum tree_code code
*** 2138,2144 ****
the bit is 1, otherwise it might be 0 or 1. */
static bool
! zero_nonzero_bits_from_vr (value_range_t *vr, double_int *may_be_nonzero,
double_int *must_be_nonzero)
{
may_be_nonzero->low = ALL_ONES;
--- 2138,2145 ----
the bit is 1, otherwise it might be 0 or 1. */
static bool
! zero_nonzero_bits_from_vr (value_range_t *vr, tree type,
! double_int *may_be_nonzero,
double_int *must_be_nonzero)
{
may_be_nonzero->low = ALL_ONES;
*************** zero_nonzero_bits_from_vr (value_range_t
*** 2178,2183 ****
--- 2179,2192 ----
must_be_nonzero->low &= ~mask;
}
}
+ else if (tree_int_cst_sgn (vr->max) < 0)
+ {
+ /* The only thing we know when the range covers only negative
+ values is that the sign bit must be set. */
+ *may_be_nonzero = double_int_minus_one;
+ *must_be_nonzero
+ = double_int_setbit (double_int_zero, TYPE_PRECISION (type) - 1);
+ }
return true;
}
return false;
*************** extract_range_from_binary_expr_1 (value_
*** 2642,2650 ****
double_int may_be_nonzero0, may_be_nonzero1;
double_int must_be_nonzero0, must_be_nonzero1;
! int_cst_range0 = zero_nonzero_bits_from_vr (&vr0, &may_be_nonzero0,
&must_be_nonzero0);
! int_cst_range1 = zero_nonzero_bits_from_vr (&vr1, &may_be_nonzero1,
&must_be_nonzero1);
type = VR_RANGE;
--- 2651,2661 ----
double_int may_be_nonzero0, may_be_nonzero1;
double_int must_be_nonzero0, must_be_nonzero1;
! int_cst_range0 = zero_nonzero_bits_from_vr (&vr0, expr_type,
! &may_be_nonzero0,
&must_be_nonzero0);
! int_cst_range1 = zero_nonzero_bits_from_vr (&vr1, expr_type,
! &may_be_nonzero1,
&must_be_nonzero1);
type = VR_RANGE;
*************** extract_range_from_binary_expr_1 (value_
*** 2683,2699 ****
max = double_int_to_tree (expr_type,
double_int_ior (may_be_nonzero0,
may_be_nonzero1));
- if (tree_int_cst_sgn (max) < 0)
- max = NULL_TREE;
if (int_cst_range0)
! {
! if (tree_int_cst_sgn (min) < 0)
! min = vr0.min;
! else
! min = vrp_int_const_binop (MAX_EXPR, min, vr0.min);
! }
if (int_cst_range1)
min = vrp_int_const_binop (MAX_EXPR, min, vr1.min);
}
else if (code == BIT_XOR_EXPR)
{
--- 2694,2709 ----
max = double_int_to_tree (expr_type,
double_int_ior (may_be_nonzero0,
may_be_nonzero1));
if (int_cst_range0)
! min = vrp_int_const_binop (MAX_EXPR, min, vr0.min);
if (int_cst_range1)
min = vrp_int_const_binop (MAX_EXPR, min, vr1.min);
+ if (tree_int_cst_sgn (min) < 0)
+ ;
+ else if (tree_int_cst_sgn (max) >= 0)
+ ;
+ else
+ min = max = NULL_TREE;
}
else if (code == BIT_XOR_EXPR)
{
*************** simplify_bit_ops_using_ranges (gimple_st
*** 6984,6992 ****
else
return false;
! if (!zero_nonzero_bits_from_vr (&vr0, &may_be_nonzero0, &must_be_nonzero0))
return false;
! if (!zero_nonzero_bits_from_vr (&vr1, &may_be_nonzero1, &must_be_nonzero1))
return false;
switch (gimple_assign_rhs_code (stmt))
--- 6994,7004 ----
else
return false;
! if (!zero_nonzero_bits_from_vr (&vr0, TREE_TYPE (op0),
! &may_be_nonzero0, &must_be_nonzero0))
return false;
! if (!zero_nonzero_bits_from_vr (&vr1, TREE_TYPE (op1),
! &may_be_nonzero1, &must_be_nonzero1))
return false;
switch (gimple_assign_rhs_code (stmt))
Index: gcc/testsuite/gcc.dg/tree-ssa/vrp60.c
===================================================================
*** gcc/testsuite/gcc.dg/tree-ssa/vrp60.c (revision 0)
--- gcc/testsuite/gcc.dg/tree-ssa/vrp60.c (revision 0)
***************
*** 0 ****
--- 1,31 ----
+ /* { dg-do compile } */
+ /* { dg-options "-O2 -fno-tree-ccp -fno-tree-dominator-opts -fdump-tree-vrp1"
} */
+
+ int foo (int x, int b)
+ {
+ int cst;
+ if (b)
+ cst = -__INT_MAX__ - 1;
+ else
+ cst = -__INT_MAX__;
+ x = x | cst;
+ if (x >= 0)
+ return 12345;
+ return x;
+ }
+
+ int bar (int x, int b)
+ {
+ int cst;
+ if (b)
+ cst = __INT_MAX__;
+ else
+ cst = __INT_MAX__ - 1;
+ x = x & cst;
+ if (x < 0)
+ return 12345;
+ return x;
+ }
+
+ /* { dg-final { scan-tree-dump-not "12345" "vrp1" } } */
+ /* { dg-final { cleanup-tree-dump "vrp1" } } */
