>
> I think you want get_addr_base_and_unit_offset here. But I really wonder
I copied what I found in tree-ssa-alias. The differenc eis that
get_addr_base_and_unit_offset won't give a range for variable sized accesses
right?
> what cases this code catches that the code in fold_comparison you touched
> above does not? (apart from previously being bogus in different kind of
> ways)
>
> So I'd rather remove the code in fold_binary.
Well, the code in fold_binary only handles comparsions where base addresses are
known
to be different. I.e. &a==&b returning false.
All the other cases are handled here. I.. &a==&a or &a[5]==&b[7] etc.
Perhaps the code should be in fold_comparison?
Honza
>
> Thanks,
> Richard.
>
> > + offset_int offset0 = hwi_offset0;
> > + offset_int offset1 = hwi_offset1;
> > +
> > + /* Add constant offset of MEM_REF to OFFSET, if possible. */
> > + if (base0 && TREE_CODE (base0) == MEM_REF
> > + && TREE_CODE (TREE_OPERAND (base0, 1)) == INTEGER_CST)
> > + {
> > + offset0 += wi::lshift (mem_ref_offset (base0),
> > LOG2_BITS_PER_UNIT);
> > + base0 = TREE_OPERAND (base0, 0);
> > + }
> > + if (base1 && TREE_CODE (base1) == MEM_REF
> > + && TREE_CODE (TREE_OPERAND (base1, 1)) == INTEGER_CST)
> > + {
> > + offset1 += wi::lshift (mem_ref_offset (base1),
> > LOG2_BITS_PER_UNIT);
> > + base1 = TREE_OPERAND (base1, 0);
> > + }
> > + /* If both offsets of MEM_REF are the same, just ignore them. */
> > + if (base0 && base1
> > + && TREE_CODE (base0) == MEM_REF
> > + && TREE_CODE (base1) == MEM_REF
> > + && operand_equal_p (TREE_OPERAND (base0, 1), TREE_OPERAND
> > (base1, 1), 0))
> > + {
> > + base0 = TREE_OPERAND (base0, 0);
> > + base1 = TREE_OPERAND (base1, 1);
> > + }
> > + /* If we see MEM_REF with variable offset, just modify MAX_SIZE
> > to declare that
> > + sizes are unknown. We can still prove that bases points to
> > different memory
> > + locations. */
> > + if (base0 && TREE_CODE (base0) == MEM_REF)
> > + {
> > + base0 = TREE_OPERAND (base0, 0);
> > + max_size0 = -1;
> > + }
> > + if (base1 && TREE_CODE (base1) == MEM_REF)
> > + {
> > + base1 = TREE_OPERAND (base1, 0);
> > + max_size1 = -1;
> > + }
> > +
> > + /* If bases are equal or they are both declarations, we can
> > disprove equivalency by
> > + proving that offsets are different. */
> > + if (base0 && base1 && (base0 == base1 || (DECL_P (base0) &&
> > DECL_P (base1))))
> > + {
> > + if ((wi::ltu_p (offset0 + max_size0 - size0, offset1)
> > + || (wi::ltu_p (offset1 + max_size1 - size1, offset0)))
> > + && max_size0 != -1 && max_size1 != -1
> > + && size0 != -1 && size1 != -1)
> > + return constant_boolean_node (code != EQ_EXPR, type);
> > + }
> > + /* If bases are equal, then addresses are equal if offsets are.
> > + We can work hader here for non-constant offsets. */
> > + if (base0 && base0 == base1)
> > + {
> > + if (base0 == base1
> > + && size0 != -1 && size1 != -1
> > + && (max_size0 == size0) && (max_size1 == size1))
> > + return constant_boolean_node (code == EQ_EXPR, type);
> > + }
> > +
> > + if (base0 && base1 && DECL_P (base0) && DECL_P (base1))
> > + {
> > + bool in_symtab0 = decl_in_symtab_p (base0);
> > + bool in_symtab1 = decl_in_symtab_p (base1);
> > +
> > + /* Symtab and non-symtab declarations never overlap. */
> > + if (in_symtab0 != in_symtab1)
> > + return constant_boolean_node (code != EQ_EXPR, type);
> > + /* Non-symtab nodes never have aliases: different declaration
> > means
> > + different memory object. */
> > + if (!in_symtab0)
> > + {
> > + if (base0 != base1 && TREE_CODE (base0) != TREE_CODE
> > (base1))
> > + return constant_boolean_node (code != EQ_EXPR, type);
> > + }
> > + else
> > + {
> > + struct symtab_node *symbol0 = symtab_node::get_create
> > (base0);
> > + struct symtab_node *symbol1 = symtab_node::get_create
> > (base1);
> > + int cmp = symbol0->equal_address_to (symbol1);
> > +
> > + if (cmp == 0)
> > + return constant_boolean_node (code != EQ_EXPR, type);
> > + if (cmp == 1
> > + && size0 != -1 && size1 != -1
> > + && (max_size0 == size0) && (max_size1 == size1))
> > + return constant_boolean_node (code == EQ_EXPR, type);
> > + }
> > + }
> > + }
> > +
> > /* Transform comparisons of the form X +- Y CMP X to Y CMP 0. */
> > if ((TREE_CODE (arg0) == PLUS_EXPR
> > || TREE_CODE (arg0) == POINTER_PLUS_EXPR
> > Index: symtab.c
> > ===================================================================
> > --- symtab.c (revision 218286)
> > +++ symtab.c (working copy)
> > @@ -1860,3 +1860,90 @@
> > return true;
> > return false;
> > }
> > +
> > +/* Return 0 if symbol is known to have different address than S2,
> > + Return 1 if symbol is known to have same address as S2,
> > + return 2 otherwise. */
> > +int
> > +symtab_node::equal_address_to (symtab_node *s2)
> > +{
> > + enum availability avail1, avail2;
> > +
> > + /* A Shortcut: equivalent symbols are always equivalent. */
> > + if (this == s2)
> > + return 1;
> > +
> > + /* For non-interposable aliases, lookup and compare their actual
> > definitions.
> > + Also check if the symbol needs to bind to given definition. */
> > + symtab_node *rs1 = ultimate_alias_target (&avail1);
> > + symtab_node *rs2 = s2->ultimate_alias_target (&avail2);
> > + bool binds_local1 = rs1->analyzed && decl_binds_to_current_def_p
> > (this->decl);
> > + bool binds_local2 = rs2->analyzed && decl_binds_to_current_def_p
> > (s2->decl);
> > + bool really_binds_local1 = binds_local1;
> > + bool really_binds_local2 = binds_local2;
> > +
> > + /* Addresses of vtables and virtual functions can not be used by user
> > + code and are used only within speculation. In this case we may make
> > + symbol equivalent to its alias even if interposition may break this
> > + rule. Doing so will allow us to turn speculative inlining into
> > + non-speculative more agressively. */
> > + if (DECL_VIRTUAL_P (this->decl) && avail1 >= AVAIL_AVAILABLE)
> > + binds_local1 = true;
> > + if (DECL_VIRTUAL_P (s2->decl) && avail2 >= AVAIL_AVAILABLE)
> > + binds_local2 = true;
> > +
> > + /* If both definitions are available we know that even if they are bound
> > + to other unit they must be defined same way and therefore we can use
> > + equivalence test. */
> > + if (rs1 != rs2 && avail1 >= AVAIL_AVAILABLE && avail2 >= AVAIL_AVAILABLE)
> > + binds_local1 = binds_local2 = true;
> > +
> > + if ((binds_local1 ? rs1 : this)
> > + == (binds_local2 ? rs2 : s2))
> > + {
> > + /* We made use of the fact that alias is not weak. */
> > + if (binds_local1 && rs1 != this)
> > + refuse_visibility_changes = true;
> > + if (binds_local2 && rs2 != s2)
> > + s2->refuse_visibility_changes = true;
> > + return 1;
> > + }
> > +
> > + /* If both symbols may resolve to NULL, we can not really prove them
> > different. */
> > + if (!nonzero_address () && !s2->nonzero_address ())
> > + return 2;
> > +
> > + /* Except for NULL, functions and variables never overlap. */
> > + if (TREE_CODE (decl) != TREE_CODE (s2->decl))
> > + return 0;
> > +
> > + /* If one of the symbols is unresolved alias, punt. */
> > + if (rs1->alias || rs2->alias)
> > + return 2;
> > +
> > + /* If we have a non-interposale definition of at least one of the symbols
> > + and the other symbol is different, we know other unit can not
> > interpose
> > + it to the first symbol; all aliases of the definition needs to be
> > + present in the current unit. */
> > + if (((really_binds_local1 || really_binds_local2)
> > + /* If we have both definitions and they are different, we know they
> > + will be different even in units they binds to. */
> > + || (binds_local1 && binds_local2))
> > + && rs1 != rs2)
> > + {
> > + /* We make use of the fact that one symbol is not alias of the other
> > + and that the definition is non-interposable. */
> > + refuse_visibility_changes = true;
> > + s2->refuse_visibility_changes = true;
> > + rs1->refuse_visibility_changes = true;
> > + rs2->refuse_visibility_changes = true;
> > + return 0;
> > + }
> > +
> > + /* TODO: Alias oracle basically assume that addresses of global variables
> > + are different unless they are declared as alias of one to another.
> > + We probably should be consistent and use this fact here, too, and
> > update
> > + alias oracle to use this predicate. */
> > +
> > + return 2;
> > +}
> > Index: testsuite/gcc.dg/addr_equal-1.c
> > ===================================================================
> > --- testsuite/gcc.dg/addr_equal-1.c (revision 0)
> > +++ testsuite/gcc.dg/addr_equal-1.c (working copy)
> > @@ -0,0 +1,107 @@
> > +/* { dg-do run } */
> > +/* { dg-require-weak "" } */
> > +/* { dg-require-alias "" } */
> > +/* { dg-options "-O2" } */
> > +void abort (void);
> > +extern int undef_var0, undef_var1;
> > +extern __attribute__ ((weak)) int weak_undef_var0;
> > +extern __attribute__ ((weak)) int weak_undef_var1;
> > +__attribute__ ((weak)) int weak_def_var0;
> > +int def_var0=0, def_var1=0;
> > +static int alias_var0 __attribute__ ((alias("def_var0")));
> > +extern int weak_alias_var0 __attribute__ ((alias("def_var0")))
> > __attribute__ ((weak));
> > +void undef_fn0(void);
> > +void undef_fn1(void);
> > +void def_fn0(void)
> > +{
> > +}
> > +void def_fn1(void)
> > +{
> > +}
> > +__attribute__ ((weak))
> > +void weak_def_fn0(void)
> > +{
> > +}
> > +__attribute__ ((weak))
> > +void weak_def_fn1(void)
> > +{
> > +}
> > +__attribute__ ((weak)) void weak_undef_fn0(void);
> > +
> > +inline
> > +void inline_fn0(void)
> > +{
> > +}
> > +inline
> > +void inline_fn1(void)
> > +{
> > +}
> > +
> > +int
> > +main(int argc, char **argv)
> > +{
> > + /* Two definitions are always different unless they can be interposed.
> > */
> > + if (!__builtin_constant_p (def_fn0 == def_fn1))
> > + abort();
> > + if (def_fn0 == def_fn1)
> > + abort();
> > +
> > + if (!__builtin_constant_p (&def_var0 == &def_var1))
> > + abort();
> > + if (&def_var0 == &def_var1)
> > + abort();
> > +
> > + /* Same symbol is the same no matter on interposition. */
> > + if (!__builtin_constant_p (undef_fn0 != undef_fn0))
> > + abort ();
> > + if (undef_fn0 != undef_fn0)
> > + abort ();
> > +
> > + /* Do not get confused by same offset. */
> > + if (!__builtin_constant_p (&undef_var0 + argc != &undef_var0 + argc))
> > + abort ();
> > + if (&undef_var0 + argc != &undef_var0 + argc)
> > + abort ();
> > +
> > + /* Alias and its target is equivalent unless one of them can be
> > interposed. */
> > + if (!__builtin_constant_p (&def_var0 != &alias_var0))
> > + abort ();
> > + if (&def_var0 != &alias_var0 )
> > + abort ();
> > +
> > + if (__builtin_constant_p (&def_var0 != &weak_alias_var0))
> > + abort ();
> > + if (&def_var0 != &weak_alias_var0)
> > + abort ();
> > +
> > + /* Weak definitions may be both NULL. */
> > + if (__builtin_constant_p ((void *)weak_undef_fn0 == (void
> > *)&weak_undef_var0))
> > + abort ();
> > + if ((void *)weak_undef_fn0 != (void *)&weak_undef_var0)
> > + abort ();
> > +
> > + /* Different offsets makes it safe to assume addresses are different. */
> > + if (!__builtin_constant_p ((char *)weak_undef_fn0 + 4 != (char
> > *)&weak_undef_var1 + 8))
> > + abort ();
> > + if ((char *)weak_undef_fn0 + 4 == (char *)&weak_undef_var1 + 8)
> > + abort ();
> > +
> > + /* Variables and functions do not share same memory locations otherwise.
> > */
> > + if (!__builtin_constant_p ((void *)undef_fn0 == (void *)&undef_var0))
> > + abort ();
> > + if ((void *)undef_fn0 == (void *)&undef_var0)
> > + abort ();
> > +
> > + /* This works for cases where one object is just weakly defined, too. */
> > + if (!__builtin_constant_p ((void *)weak_undef_fn0 == (void
> > *)&weak_def_var0))
> > + abort ();
> > + if ((void *)weak_undef_fn0 == (void *)&weak_def_var0)
> > + abort ();
> > +
> > + /* Inline functions are known to be different. */
> > + if (!__builtin_constant_p (inline_fn0 != inline_fn1))
> > + abort ();
> > + if (inline_fn0 == inline_fn1)
> > + abort ();
> > + return 0;
> > +}
