On Sun, Jul 17, 2011 at 4:34 PM, Richard Sandiford
<rdsandif...@googlemail.com> wrote:
> This patch replaces the rtxes in mem_attrs with (bool, HOST_WIDE_INT) pairs.
> There's already room for the bools in the padding after "addrspace".
> (There's room for one more bool after this patch; we could move to
> bitfields if more are needed.)
>
> The new structure is 8 bytes bigger when using a combination of a 32-bit
> host and a need_64bit_hwint target. In other cases it should be the same
> as before, and will avoid some pointer chasing. The question is whether
> that's an acceptable trade-off or not.
It sure is.
Ok.
Thanks,
Richard.
> Richard
>
>
> gcc/
> * rtl.h (mem_attrs): Turn offset and size fields into HOST_WIDE_INTs.
> Add offset_known_p and size_known_p fields.
> (MEM_OFFSET_KNOWN_P): Update accordingly.
> (MEM_OFFSET, MEM_SIZE_KNOWN_P, MEM_SIZE): Likewise.
> * emit-rtl.c (mem_attrs_htab_hash): Update after mem_attrs changes.
> (mem_attrs_eq_p, set_mem_attributes_minus_bitpos, set_mem_offset)
> (clear_mem_offset, set_mem_size, clear_mem_size, change_address)
> (adjust_address_1, widen_memory_access, set_mem_attrs_for_spill)
> (init_emit_regs): Likewise.
>
> Index: gcc/rtl.h
> ===================================================================
> --- gcc/rtl.h 2011-07-17 11:40:14.000000000 +0100
> +++ gcc/rtl.h 2011-07-17 11:40:18.000000000 +0100
> @@ -136,19 +136,38 @@ typedef struct
>
> /* Structure used to describe the attributes of a MEM. These are hashed
> so MEMs that the same attributes share a data structure. This means
> - they cannot be modified in place. If any element is nonzero, it means
> - the value of the corresponding attribute is unknown. */
> -/* ALIGN and SIZE are the alignment and size of the MEM itself,
> - while EXPR can describe a larger underlying object, which might have a
> - stricter alignment; OFFSET is the offset of the MEM within that object.
> */
> + they cannot be modified in place. */
> typedef struct GTY(()) mem_attrs
> {
> - tree expr; /* expr corresponding to MEM. */
> - rtx offset; /* Offset from start of DECL, as CONST_INT.
> */
> - rtx size; /* Size in bytes, as a CONST_INT. */
> - alias_set_type alias; /* Memory alias set. */
> - unsigned int align; /* Alignment of MEM in bits. */
> - unsigned char addrspace; /* Address space (0 for generic). */
> + /* The expression that the MEM accesses, or null if not known.
> + This expression might be larger than the memory reference itself.
> + (In other words, the MEM might access only part of the object.) */
> + tree expr;
> +
> + /* The offset of the memory reference from the start of EXPR.
> + Only valid if OFFSET_KNOWN_P. */
> + HOST_WIDE_INT offset;
> +
> + /* The size of the memory reference in bytes. Only valid if
> + SIZE_KNOWN_P. */
> + HOST_WIDE_INT size;
> +
> + /* The alias set of the memory reference. */
> + alias_set_type alias;
> +
> + /* The alignment of the reference in bits. Always a multiple of
> + BITS_PER_UNIT. Note that EXPR may have a stricter alignment
> + than the memory reference itself. */
> + unsigned int align;
> +
> + /* The address space that the memory reference uses. */
> + unsigned char addrspace;
> +
> + /* True if OFFSET is known. */
> + bool offset_known_p;
> +
> + /* True if SIZE is known. */
> + bool size_known_p;
> } mem_attrs;
>
> /* Structure used to describe the attributes of a REG in similar way as
> @@ -1303,19 +1322,19 @@ #define MEM_ALIAS_SET(RTX) (get_mem_attr
> #define MEM_EXPR(RTX) (get_mem_attrs (RTX)->expr)
>
> /* For a MEM rtx, true if its MEM_OFFSET is known. */
> -#define MEM_OFFSET_KNOWN_P(RTX) (get_mem_attrs (RTX)->offset != NULL_RTX)
> +#define MEM_OFFSET_KNOWN_P(RTX) (get_mem_attrs (RTX)->offset_known_p)
>
> /* For a MEM rtx, the offset from the start of MEM_EXPR. */
> -#define MEM_OFFSET(RTX) INTVAL (get_mem_attrs (RTX)->offset)
> +#define MEM_OFFSET(RTX) (get_mem_attrs (RTX)->offset)
>
> /* For a MEM rtx, the address space. */
> #define MEM_ADDR_SPACE(RTX) (get_mem_attrs (RTX)->addrspace)
>
> /* For a MEM rtx, true if its MEM_SIZE is known. */
> -#define MEM_SIZE_KNOWN_P(RTX) (get_mem_attrs (RTX)->size != NULL_RTX)
> +#define MEM_SIZE_KNOWN_P(RTX) (get_mem_attrs (RTX)->size_known_p)
>
> /* For a MEM rtx, the size in bytes of the MEM. */
> -#define MEM_SIZE(RTX) INTVAL (get_mem_attrs (RTX)->size)
> +#define MEM_SIZE(RTX) (get_mem_attrs (RTX)->size)
>
> /* For a MEM rtx, the alignment in bits. We can use the alignment of the
> mode as a default when STRICT_ALIGNMENT, but not if not. */
> Index: gcc/emit-rtl.c
> ===================================================================
> --- gcc/emit-rtl.c 2011-07-17 11:40:14.000000000 +0100
> +++ gcc/emit-rtl.c 2011-07-17 11:40:18.000000000 +0100
> @@ -256,8 +256,8 @@ mem_attrs_htab_hash (const void *x)
>
> return (p->alias ^ (p->align * 1000)
> ^ (p->addrspace * 4000)
> - ^ ((p->offset ? INTVAL (p->offset) : 0) * 50000)
> - ^ ((p->size ? INTVAL (p->size) : 0) * 2500000)
> + ^ ((p->offset_known_p ? p->offset : 0) * 50000)
> + ^ ((p->size_known_p ? p->size : 0) * 2500000)
> ^ (size_t) iterative_hash_expr (p->expr, 0));
> }
>
> @@ -266,8 +266,12 @@ mem_attrs_htab_hash (const void *x)
> static bool
> mem_attrs_eq_p (const struct mem_attrs *p, const struct mem_attrs *q)
> {
> - return (p->alias == q->alias && p->offset == q->offset
> - && p->size == q->size && p->align == q->align
> + return (p->alias == q->alias
> + && p->offset_known_p == q->offset_known_p
> + && (!p->offset_known_p || p->offset == q->offset)
> + && p->size_known_p == q->size_known_p
> + && (!p->size_known_p || p->size == q->size)
> + && p->align == q->align
> && p->addrspace == q->addrspace
> && (p->expr == q->expr
> || (p->expr != NULL_TREE && q->expr != NULL_TREE
> @@ -1585,7 +1589,9 @@ set_mem_attributes_minus_bitpos (rtx ref
> /* ??? Can this ever happen? Calling this routine on a MEM that
> already carries memory attributes should probably be invalid. */
> attrs.expr = refattrs->expr;
> + attrs.offset_known_p = refattrs->offset_known_p;
> attrs.offset = refattrs->offset;
> + attrs.size_known_p = refattrs->size_known_p;
> attrs.size = refattrs->size;
> attrs.align = refattrs->align;
> }
> @@ -1595,9 +1601,10 @@ set_mem_attributes_minus_bitpos (rtx ref
> {
> defattrs = mode_mem_attrs[(int) GET_MODE (ref)];
> gcc_assert (!defattrs->expr);
> - gcc_assert (!defattrs->offset);
> + gcc_assert (!defattrs->offset_known_p);
>
> /* Respect mode size. */
> + attrs.size_known_p = defattrs->size_known_p;
> attrs.size = defattrs->size;
> /* ??? Is this really necessary? We probably should always get
> the size from the type below. */
> @@ -1656,7 +1663,10 @@ set_mem_attributes_minus_bitpos (rtx ref
>
> /* If the size is known, we can set that. */
> if (TYPE_SIZE_UNIT (type) && host_integerp (TYPE_SIZE_UNIT (type), 1))
> - attrs.size = GEN_INT (tree_low_cst (TYPE_SIZE_UNIT (type), 1));
> + {
> + attrs.size_known_p = true;
> + attrs.size = tree_low_cst (TYPE_SIZE_UNIT (type), 1);
> + }
>
> /* If T is not a type, we may be able to deduce some more information about
> the expression. */
> @@ -1694,11 +1704,16 @@ set_mem_attributes_minus_bitpos (rtx ref
> if (DECL_P (t))
> {
> attrs.expr = t;
> - attrs.offset = const0_rtx;
> + attrs.offset_known_p = true;
> + attrs.offset = 0;
> apply_bitpos = bitpos;
> - attrs.size = (DECL_SIZE_UNIT (t)
> - && host_integerp (DECL_SIZE_UNIT (t), 1)
> - ? GEN_INT (tree_low_cst (DECL_SIZE_UNIT (t), 1)) : 0);
> + if (DECL_SIZE_UNIT (t) && host_integerp (DECL_SIZE_UNIT (t), 1))
> + {
> + attrs.size_known_p = true;
> + attrs.size = tree_low_cst (DECL_SIZE_UNIT (t), 1);
> + }
> + else
> + attrs.size_known_p = false;
> attrs.align = DECL_ALIGN (t);
> align_computed = true;
> }
> @@ -1721,7 +1736,8 @@ set_mem_attributes_minus_bitpos (rtx ref
> && ! DECL_BIT_FIELD (TREE_OPERAND (t, 1)))
> {
> attrs.expr = t;
> - attrs.offset = const0_rtx;
> + attrs.offset_known_p = true;
> + attrs.offset = 0;
> apply_bitpos = bitpos;
> /* ??? Any reason the field size would be different than
> the size we got from the type? */
> @@ -1762,7 +1778,7 @@ set_mem_attributes_minus_bitpos (rtx ref
> if (DECL_P (t2))
> {
> attrs.expr = t2;
> - attrs.offset = NULL;
> + attrs.offset_known_p = false;
> if (host_integerp (off_tree, 1))
> {
> HOST_WIDE_INT ioff = tree_low_cst (off_tree, 1);
> @@ -1771,17 +1787,19 @@ set_mem_attributes_minus_bitpos (rtx ref
> if (aoff && (unsigned HOST_WIDE_INT) aoff < attrs.align)
> attrs.align = aoff;
> align_computed = true;
> - attrs.offset = GEN_INT (ioff);
> + attrs.offset_known_p = true;
> + attrs.offset = ioff;
> apply_bitpos = bitpos;
> }
> }
> else if (TREE_CODE (t2) == COMPONENT_REF)
> {
> attrs.expr = t2;
> - attrs.offset = NULL;
> + attrs.offset_known_p = false;
> if (host_integerp (off_tree, 1))
> {
> - attrs.offset = GEN_INT (tree_low_cst (off_tree, 1));
> + attrs.offset_known_p = true;
> + attrs.offset = tree_low_cst (off_tree, 1);
> apply_bitpos = bitpos;
> }
> /* ??? Any reason the field size would be different than
> @@ -1792,7 +1810,8 @@ set_mem_attributes_minus_bitpos (rtx ref
> else if (TREE_CODE (t) == MEM_REF)
> {
> attrs.expr = t;
> - attrs.offset = const0_rtx;
> + attrs.offset_known_p = true;
> + attrs.offset = 0;
> apply_bitpos = bitpos;
> }
> }
> @@ -1802,7 +1821,8 @@ set_mem_attributes_minus_bitpos (rtx ref
> || TREE_CODE (t) == TARGET_MEM_REF)
> {
> attrs.expr = t;
> - attrs.offset = const0_rtx;
> + attrs.offset_known_p = true;
> + attrs.offset = 0;
> apply_bitpos = bitpos;
> }
>
> @@ -1818,10 +1838,10 @@ set_mem_attributes_minus_bitpos (rtx ref
> object to contain the negative offset. */
> if (apply_bitpos)
> {
> - attrs.offset = plus_constant (attrs.offset,
> - -(apply_bitpos / BITS_PER_UNIT));
> - if (attrs.size)
> - attrs.size = plus_constant (attrs.size, apply_bitpos / BITS_PER_UNIT);
> + gcc_assert (attrs.offset_known_p);
> + attrs.offset -= apply_bitpos / BITS_PER_UNIT;
> + if (attrs.size_known_p)
> + attrs.size += apply_bitpos / BITS_PER_UNIT;
> }
>
> /* Now set the attributes we computed above. */
> @@ -1903,7 +1923,8 @@ set_mem_offset (rtx mem, HOST_WIDE_INT o
> struct mem_attrs attrs;
>
> attrs = *get_mem_attrs (mem);
> - attrs.offset = GEN_INT (offset);
> + attrs.offset_known_p = true;
> + attrs.offset = offset;
> set_mem_attrs (mem, &attrs);
> }
>
> @@ -1915,7 +1936,7 @@ clear_mem_offset (rtx mem)
> struct mem_attrs attrs;
>
> attrs = *get_mem_attrs (mem);
> - attrs.offset = NULL_RTX;
> + attrs.offset_known_p = false;
> set_mem_attrs (mem, &attrs);
> }
>
> @@ -1927,7 +1948,8 @@ set_mem_size (rtx mem, HOST_WIDE_INT siz
> struct mem_attrs attrs;
>
> attrs = *get_mem_attrs (mem);
> - attrs.size = GEN_INT (size);
> + attrs.size_known_p = true;
> + attrs.size = size;
> set_mem_attrs (mem, &attrs);
> }
>
> @@ -1939,7 +1961,7 @@ clear_mem_size (rtx mem)
> struct mem_attrs attrs;
>
> attrs = *get_mem_attrs (mem);
> - attrs.size = NULL_RTX;
> + attrs.size_known_p = false;
> set_mem_attrs (mem, &attrs);
> }
>
> @@ -1993,8 +2015,9 @@ change_address (rtx memref, enum machine
>
> attrs = *get_mem_attrs (memref);
> defattrs = mode_mem_attrs[(int) mmode];
> - attrs.expr = defattrs->expr;
> - attrs.offset = defattrs->offset;
> + attrs.expr = NULL_TREE;
> + attrs.offset_known_p = false;
> + attrs.size_known_p = defattrs->size_known_p;
> attrs.size = defattrs->size;
> attrs.align = defattrs->align;
>
> @@ -2076,8 +2099,8 @@ adjust_address_1 (rtx memref, enum machi
>
> /* Compute the new values of the memory attributes due to this adjustment.
> We add the offsets and update the alignment. */
> - if (attrs.offset)
> - attrs.offset = GEN_INT (offset + INTVAL (attrs.offset));
> + if (attrs.offset_known_p)
> + attrs.offset += offset;
>
> /* Compute the new alignment by taking the MIN of the alignment and the
> lowest-order set bit in OFFSET, but don't change the alignment if OFFSET
> @@ -2090,10 +2113,13 @@ adjust_address_1 (rtx memref, enum machi
>
> /* We can compute the size in a number of ways. */
> defattrs = mode_mem_attrs[(int) GET_MODE (new_rtx)];
> - if (defattrs->size)
> - attrs.size = defattrs->size;
> - else if (attrs.size)
> - attrs.size = plus_constant (attrs.size, -offset);
> + if (defattrs->size_known_p)
> + {
> + attrs.size_known_p = true;
> + attrs.size = defattrs->size;
> + }
> + else if (attrs.size_known_p)
> + attrs.size -= offset;
>
> set_mem_attrs (new_rtx, &attrs);
>
> @@ -2124,7 +2150,7 @@ offset_address (rtx memref, rtx offset,
> {
> rtx new_rtx, addr = XEXP (memref, 0);
> enum machine_mode address_mode;
> - struct mem_attrs attrs;
> + struct mem_attrs attrs, *defattrs;
>
> attrs = *get_mem_attrs (memref);
> address_mode = targetm.addr_space.address_mode (attrs.addrspace);
> @@ -2155,8 +2181,10 @@ offset_address (rtx memref, rtx offset,
>
> /* Update the alignment to reflect the offset. Reset the offset, which
> we don't know. */
> - attrs.offset = 0;
> - attrs.size = mode_mem_attrs[(int) GET_MODE (new_rtx)]->size;
> + defattrs = mode_mem_attrs[(int) GET_MODE (new_rtx)];
> + attrs.offset_known_p = false;
> + attrs.size_known_p = defattrs->size_known_p;
> + attrs.size = defattrs->size;
> attrs.align = MIN (attrs.align, pow2 * BITS_PER_UNIT);
> set_mem_attrs (new_rtx, &attrs);
> return new_rtx;
> @@ -2204,7 +2232,7 @@ widen_memory_access (rtx memref, enum ma
>
> /* If we don't know what offset we were at within the expression, then
> we can't know if we've overstepped the bounds. */
> - if (! attrs.offset)
> + if (! attrs.offset_known_p)
> attrs.expr = NULL_TREE;
>
> while (attrs.expr)
> @@ -2224,7 +2252,7 @@ widen_memory_access (rtx memref, enum ma
> otherwise strip back to the containing structure. */
> if (TREE_CODE (DECL_SIZE_UNIT (field)) == INTEGER_CST
> && compare_tree_int (DECL_SIZE_UNIT (field), size) >= 0
> - && INTVAL (attrs.offset) >= 0)
> + && attrs.offset >= 0)
> break;
>
> if (! host_integerp (offset, 1))
> @@ -2234,18 +2262,16 @@ widen_memory_access (rtx memref, enum ma
> }
>
> attrs.expr = TREE_OPERAND (attrs.expr, 0);
> - attrs.offset
> - = (GEN_INT (INTVAL (attrs.offset)
> - + tree_low_cst (offset, 1)
> - + (tree_low_cst (DECL_FIELD_BIT_OFFSET (field), 1)
> - / BITS_PER_UNIT)));
> + attrs.offset += tree_low_cst (offset, 1);
> + attrs.offset += (tree_low_cst (DECL_FIELD_BIT_OFFSET (field), 1)
> + / BITS_PER_UNIT);
> }
> /* Similarly for the decl. */
> else if (DECL_P (attrs.expr)
> && DECL_SIZE_UNIT (attrs.expr)
> && TREE_CODE (DECL_SIZE_UNIT (attrs.expr)) == INTEGER_CST
> && compare_tree_int (DECL_SIZE_UNIT (attrs.expr), size) >= 0
> - && (! attrs.offset || INTVAL (attrs.offset) >= 0))
> + && (! attrs.offset_known_p || attrs.offset >= 0))
> break;
> else
> {
> @@ -2257,12 +2283,13 @@ widen_memory_access (rtx memref, enum ma
> }
>
> if (! attrs.expr)
> - attrs.offset = NULL_RTX;
> + attrs.offset_known_p = false;
>
> /* The widened memory may alias other stuff, so zap the alias set. */
> /* ??? Maybe use get_alias_set on any remaining expression. */
> attrs.alias = 0;
> - attrs.size = GEN_INT (size);
> + attrs.size_known_p = true;
> + attrs.size = size;
> set_mem_attrs (new_rtx, &attrs);
> return new_rtx;
> }
> @@ -2319,10 +2346,11 @@ set_mem_attrs_for_spill (rtx mem)
> (mem:MODE (plus (reg sfp) (const_int offset)))
> with perhaps the plus missing for offset = 0. */
> addr = XEXP (mem, 0);
> - attrs.offset = const0_rtx;
> + attrs.offset_known_p = true;
> + attrs.offset = 0;
> if (GET_CODE (addr) == PLUS
> && CONST_INT_P (XEXP (addr, 1)))
> - attrs.offset = XEXP (addr, 1);
> + attrs.offset = INTVAL (XEXP (addr, 1));
>
> set_mem_attrs (mem, &attrs);
> MEM_NOTRAP_P (mem) = 1;
> @@ -5522,7 +5550,8 @@ init_emit_regs (void)
> attrs->addrspace = ADDR_SPACE_GENERIC;
> if (mode != BLKmode)
> {
> - attrs->size = GEN_INT (GET_MODE_SIZE (mode));
> + attrs->size_known_p = true;
> + attrs->size = GET_MODE_SIZE (mode);
> if (STRICT_ALIGNMENT)
> attrs->align = GET_MODE_ALIGNMENT (mode);
> }
>
