I noticed that for binary expressions VRP contains the same bugs
that CCP once did (it treats UNDEFINED * 0 as UNDEFINED). Then
I noticed we never hit this bug because we never end up with
any range being UNDEFINED - which is bad, because this way we miss
value-ranges for all conditionally initialized variables.
Thus, the following patch fixes this and conservatively handles
the binary expression case (which is only of academic interest
anyway - the important part is to handle UNDEFINED in PHIs).
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
Richard.
2011-07-29 Richard Guenther rguent...@suse.de
* tree-vrp.c (get_value_range): Only set parameter default
definitions to varying, leave others at undefined.
(extract_range_from_binary_expr): Fix undefined handling.
(vrp_visit_phi_node): Handle merged undefined state.
* gcc.dg/uninit-suppress.c: Also disable VRP.
* gcc.dg/uninit-suppress_2.c: Likewise.
Index: gcc/tree-vrp.c
===
--- gcc/tree-vrp.c (revision 176869)
+++ gcc/tree-vrp.c (working copy)
@@ -692,16 +692,16 @@ get_value_range (const_tree var)
/* Defer allocating the equivalence set. */
vr-equiv = NULL;
- /* If VAR is a default definition, the variable can take any value
- in VAR's type. */
+ /* If VAR is a default definition of a parameter, the variable can
+ take any value in VAR's type. */
sym = SSA_NAME_VAR (var);
- if (SSA_NAME_IS_DEFAULT_DEF (var))
+ if (SSA_NAME_IS_DEFAULT_DEF (var)
+ TREE_CODE (sym) == PARM_DECL)
{
/* Try to use the nonnull attribute to create ~[0, 0]
anti-ranges for pointers. Note that this is only valid with
default definitions of PARM_DECLs. */
- if (TREE_CODE (sym) == PARM_DECL
- POINTER_TYPE_P (TREE_TYPE (sym))
+ if (POINTER_TYPE_P (TREE_TYPE (sym))
nonnull_arg_p (sym))
set_value_range_to_nonnull (vr, TREE_TYPE (sym));
else
@@ -2225,12 +2225,20 @@ extract_range_from_binary_expr (value_ra
else
set_value_range_to_varying (vr1);
- /* If either range is UNDEFINED, so is the result. */
- if (vr0.type == VR_UNDEFINED || vr1.type == VR_UNDEFINED)
+ /* If both ranges are UNDEFINED, so is the result. */
+ if (vr0.type == VR_UNDEFINED vr1.type == VR_UNDEFINED)
{
set_value_range_to_undefined (vr);
return;
}
+ /* If one of the ranges is UNDEFINED drop it to VARYING for the following
+ code. At some point we may want to special-case operations that
+ have UNDEFINED result for all or some value-ranges of the not UNDEFINED
+ operand. */
+ else if (vr0.type == VR_UNDEFINED)
+set_value_range_to_varying (vr0);
+ else if (vr1.type == VR_UNDEFINED)
+set_value_range_to_varying (vr1);
/* The type of the resulting value range defaults to VR0.TYPE. */
type = vr0.type;
@@ -6642,6 +6650,8 @@ vrp_visit_phi_node (gimple phi)
if (vr_result.type == VR_VARYING)
goto varying;
+ else if (vr_result.type == VR_UNDEFINED)
+goto update_range;
old_edges = vr_phi_edge_counts[SSA_NAME_VERSION (lhs)];
vr_phi_edge_counts[SSA_NAME_VERSION (lhs)] = edges;
@@ -6713,6 +6723,7 @@ vrp_visit_phi_node (gimple phi)
/* If the new range is different than the previous value, keep
iterating. */
+update_range:
if (update_value_range (lhs, vr_result))
{
if (dump_file (dump_flags TDF_DETAILS))
Index: gcc/testsuite/gcc.dg/uninit-suppress.c
===
*** gcc/testsuite/gcc.dg/uninit-suppress.c (revision 176869)
--- gcc/testsuite/gcc.dg/uninit-suppress.c (working copy)
***
*** 1,5
/* { dg-do compile } */
! /* { dg-options -fno-tree-ccp -O2 -Wuninitialized -Wno-maybe-uninitialized
} */
void blah();
int gflag;
--- 1,5
/* { dg-do compile } */
! /* { dg-options -fno-tree-ccp -fno-tree-vrp -O2 -Wuninitialized
-Wno-maybe-uninitialized } */
void blah();
int gflag;
Index: gcc/testsuite/gcc.dg/uninit-suppress_2.c
===
*** gcc/testsuite/gcc.dg/uninit-suppress_2.c(revision 176869)
--- gcc/testsuite/gcc.dg/uninit-suppress_2.c(working copy)
***
*** 1,5
/* { dg-do compile } */
! /* { dg-options -fno-tree-ccp -O2 -Wuninitialized -Werror=uninitialized
-Wno-error=maybe-uninitialized } */
void blah();
int gflag;
--- 1,5
/* { dg-do compile } */
! /* { dg-options -fno-tree-ccp -fno-tree-vrp -O2 -Wuninitialized
-Werror=uninitialized -Wno-error=maybe-uninitialized } */
void blah();
int gflag;
