10.4 Access to Special Operands
- If 0, x is not in any alias set, and may alias anything. Otherwise,
x can only alias
MEMs in a conflicting alias set. This value is set in a language-dependent manner in the front-end, and should not be altered in the back-end. In some front-ends, these numbers may correspond in some way to types, or other language-level entities, but they need not, and the back-end makes no such assumptions. These set numbers are tested with
- If this register is known to hold the value of some user-level
declaration, this is that tree node. It may also be a
COMPONENT_REF, in which case this is some field reference, and
, 0)contains the declaration, or another
COMPONENT_REF, or null if there is no compile-time object associated with the reference.
- The offset from the start of
- The size in bytes of the memory reference as a
CONST_INTrtx. This is mostly relevant for
BLKmodereferences as otherwise the size is implied by the mode.
- The known alignment in bits of the memory reference.
- This field holds the number the register “originally” had; for a pseudo register turned into a hard reg this will hold the old pseudo register number.
- If this register is known to hold the value of some user-level declaration, this is that tree node.
- If this register is known to hold the value of some user-level declaration, this is the offset into that logical storage.
- If the
symbol_refx was created for a
FUNCTION_DECL, that tree is recorded here. If this value is null, then x was created by back end code generation routines, and there is no associated front end symbol table entry.
SYMBOL_REF_DECLmay also point to a tree of class
'c', that is, some sort of constant. In this case, the
symbol_refis an entry in the per-file constant pool; again, there is no associated front end symbol table entry.
- If CONSTANT_POOL_ADDRESS_P (x) is true, this is the constant pool entry for x. It is null otherwise.
- A field of opaque type used to store
- In a
symbol_ref, this is used to communicate various predicates about the symbol. Some of these are common enough to be computed by common code, some are specific to the target. The common bits are:
- Set if the symbol refers to a function.
- Set if the symbol is local to this “module”.
- Set if this symbol is not defined in this translation unit.
Note that this is not the inverse of
- Set if the symbol is located in the small data section.
- This is a multi-bit field accessor that returns the
tls_modelto be used for a thread-local storage symbol. It returns zero for non-thread-local symbols.
- Set if the symbol has
- Set if the symbol is used as a section anchor. “Section anchors”
are symbols that have a known position within an
object_blockand that can be used to access nearby members of that block. They are used to implement -fsection-anchors.
If this flag is set, then
SYMBOL_FLAG_HAS_BLOCK_INFOwill be too.
Bits beginning with
SYMBOL_FLAG_MACH_DEPare available for the target's use.
- If SYMBOL_REF_HAS_BLOCK_INFO_P (x), this is the
object_block structure to which the symbol belongs,
NULLif it has not been assigned a block.
- If SYMBOL_REF_HAS_BLOCK_INFO_P (x), this is the offset of x from the first object in SYMBOL_REF_BLOCK (x). The value is negative if x has not yet been assigned to a block, or it has not been given an offset within that block.