return simplify_replace_fn_rtx (x, old_rtx, 0, new_rtx);
}
\f
+/* Try to simplify a MODE truncation of OP, which has OP_MODE.
+ Only handle cases where the truncated value is inherently an rvalue.
+
+ RTL provides two ways of truncating a value:
+
+ 1. a lowpart subreg. This form is only a truncation when both
+ the outer and inner modes (here MODE and OP_MODE respectively)
+ are scalar integers, and only then when the subreg is used as
+ an rvalue.
+
+ It is only valid to form such truncating subregs if the
+ truncation requires no action by the target. The onus for
+ proving this is on the creator of the subreg -- e.g. the
+ caller to simplify_subreg or simplify_gen_subreg -- and typically
+ involves either TRULY_NOOP_TRUNCATION_MODES_P or truncated_to_mode.
+
+ 2. a TRUNCATE. This form handles both scalar and compound integers.
+
+ The first form is preferred where valid. However, the TRUNCATE
+ handling in simplify_unary_operation turns the second form into the
+ first form when TRULY_NOOP_TRUNCATION_MODES_P or truncated_to_mode allow,
+ so it is generally safe to form rvalue truncations using:
+
+ simplify_gen_unary (TRUNCATE, ...)
+
+ and leave simplify_unary_operation to work out which representation
+ should be used.
+
+ Because of the proof requirements on (1), simplify_truncation must
+ also use simplify_gen_unary (TRUNCATE, ...) to truncate parts of OP,
+ regardless of whether the outer truncation came from a SUBREG or a
+ TRUNCATE. For example, if the caller has proven that an SImode
+ truncation of:
+
+ (and:DI X Y)
+
+ is a no-op and can be represented as a subreg, it does not follow
+ that SImode truncations of X and Y are also no-ops. On a target
+ like 64-bit MIPS that requires SImode values to be stored in
+ sign-extended form, an SImode truncation of:
+
+ (and:DI (reg:DI X) (const_int 63))
+
+ is trivially a no-op because only the lower 6 bits can be set.
+ However, X is still an arbitrary 64-bit number and so we cannot
+ assume that truncating it too is a no-op. */
+
+static rtx
+simplify_truncation (enum machine_mode mode, rtx op,
+ enum machine_mode op_mode)
+{
+ unsigned int precision = GET_MODE_UNIT_PRECISION (mode);
+ unsigned int op_precision = GET_MODE_UNIT_PRECISION (op_mode);
+ gcc_assert (precision <= op_precision);
+
+ /* Optimize truncations of zero and sign extended values. */
+ if (GET_CODE (op) == ZERO_EXTEND
+ || GET_CODE (op) == SIGN_EXTEND)
+ {
+ /* There are three possibilities. If MODE is the same as the
+ origmode, we can omit both the extension and the subreg.
+ If MODE is not larger than the origmode, we can apply the
+ truncation without the extension. Finally, if the outermode
+ is larger than the origmode, we can just extend to the appropriate
+ mode. */
+ enum machine_mode origmode = GET_MODE (XEXP (op, 0));
+ if (mode == origmode)
+ return XEXP (op, 0);
+ else if (precision <= GET_MODE_UNIT_PRECISION (origmode))
+ return simplify_gen_unary (TRUNCATE, mode,
+ XEXP (op, 0), origmode);
+ else
+ return simplify_gen_unary (GET_CODE (op), mode,
+ XEXP (op, 0), origmode);
+ }
+
+ /* Simplify (truncate:SI (op:DI (x:DI) (y:DI)))
+ to (op:SI (truncate:SI (x:DI)) (truncate:SI (x:DI))). */
+ if (GET_CODE (op) == PLUS
+ || GET_CODE (op) == MINUS
+ || GET_CODE (op) == MULT)
+ {
+ rtx op0 = simplify_gen_unary (TRUNCATE, mode, XEXP (op, 0), op_mode);
+ if (op0)
+ {
+ rtx op1 = simplify_gen_unary (TRUNCATE, mode, XEXP (op, 1), op_mode);
+ if (op1)
+ return simplify_gen_binary (GET_CODE (op), mode, op0, op1);
+ }
+ }
+
+ /* Simplify (truncate:QI (lshiftrt:SI (sign_extend:SI (x:QI)) C)) into
+ to (ashiftrt:QI (x:QI) C), where C is a suitable small constant and
+ the outer subreg is effectively a truncation to the original mode. */
+ if ((GET_CODE (op) == LSHIFTRT
+ || GET_CODE (op) == ASHIFTRT)
+ /* Ensure that OP_MODE is at least twice as wide as MODE
+ to avoid the possibility that an outer LSHIFTRT shifts by more
+ than the sign extension's sign_bit_copies and introduces zeros
+ into the high bits of the result. */
+ && 2 * precision <= op_precision
+ && CONST_INT_P (XEXP (op, 1))
+ && GET_CODE (XEXP (op, 0)) == SIGN_EXTEND
+ && GET_MODE (XEXP (XEXP (op, 0), 0)) == mode
+ && INTVAL (XEXP (op, 1)) < precision)
+ return simplify_gen_binary (ASHIFTRT, mode,
+ XEXP (XEXP (op, 0), 0), XEXP (op, 1));
+
+ /* Likewise (truncate:QI (lshiftrt:SI (zero_extend:SI (x:QI)) C)) into
+ to (lshiftrt:QI (x:QI) C), where C is a suitable small constant and
+ the outer subreg is effectively a truncation to the original mode. */
+ if ((GET_CODE (op) == LSHIFTRT
+ || GET_CODE (op) == ASHIFTRT)
+ && CONST_INT_P (XEXP (op, 1))
+ && GET_CODE (XEXP (op, 0)) == ZERO_EXTEND
+ && GET_MODE (XEXP (XEXP (op, 0), 0)) == mode
+ && INTVAL (XEXP (op, 1)) < precision)
+ return simplify_gen_binary (LSHIFTRT, mode,
+ XEXP (XEXP (op, 0), 0), XEXP (op, 1));
+
+ /* Likewise (truncate:QI (ashift:SI (zero_extend:SI (x:QI)) C)) into
+ to (ashift:QI (x:QI) C), where C is a suitable small constant and
+ the outer subreg is effectively a truncation to the original mode. */
+ if (GET_CODE (op) == ASHIFT
+ && CONST_INT_P (XEXP (op, 1))
+ && (GET_CODE (XEXP (op, 0)) == ZERO_EXTEND
+ || GET_CODE (XEXP (op, 0)) == SIGN_EXTEND)
+ && GET_MODE (XEXP (XEXP (op, 0), 0)) == mode
+ && INTVAL (XEXP (op, 1)) < precision)
+ return simplify_gen_binary (ASHIFT, mode,
+ XEXP (XEXP (op, 0), 0), XEXP (op, 1));
+
+ /* Recognize a word extraction from a multi-word subreg. */
+ if ((GET_CODE (op) == LSHIFTRT
+ || GET_CODE (op) == ASHIFTRT)
+ && SCALAR_INT_MODE_P (mode)
+ && SCALAR_INT_MODE_P (op_mode)
+ && precision >= BITS_PER_WORD
+ && 2 * precision <= op_precision
+ && CONST_INT_P (XEXP (op, 1))
+ && (INTVAL (XEXP (op, 1)) & (precision - 1)) == 0
+ && INTVAL (XEXP (op, 1)) >= 0
+ && INTVAL (XEXP (op, 1)) < op_precision)
+ {
+ int byte = subreg_lowpart_offset (mode, op_mode);
+ int shifted_bytes = INTVAL (XEXP (op, 1)) / BITS_PER_UNIT;
+ return simplify_gen_subreg (mode, XEXP (op, 0), op_mode,
+ (WORDS_BIG_ENDIAN
+ ? byte - shifted_bytes
+ : byte + shifted_bytes));
+ }
+
+ /* If we have a TRUNCATE of a right shift of MEM, make a new MEM
+ and try replacing the TRUNCATE and shift with it. Don't do this
+ if the MEM has a mode-dependent address. */
+ if ((GET_CODE (op) == LSHIFTRT
+ || GET_CODE (op) == ASHIFTRT)
+ && SCALAR_INT_MODE_P (op_mode)
+ && MEM_P (XEXP (op, 0))
+ && CONST_INT_P (XEXP (op, 1))
+ && (INTVAL (XEXP (op, 1)) % GET_MODE_BITSIZE (mode)) == 0
+ && INTVAL (XEXP (op, 1)) > 0
+ && INTVAL (XEXP (op, 1)) < GET_MODE_BITSIZE (op_mode)
+ && ! mode_dependent_address_p (XEXP (XEXP (op, 0), 0),
+ MEM_ADDR_SPACE (XEXP (op, 0)))
+ && ! MEM_VOLATILE_P (XEXP (op, 0))
+ && (GET_MODE_SIZE (mode) >= UNITS_PER_WORD
+ || WORDS_BIG_ENDIAN == BYTES_BIG_ENDIAN))
+ {
+ int byte = subreg_lowpart_offset (mode, op_mode);
+ int shifted_bytes = INTVAL (XEXP (op, 1)) / BITS_PER_UNIT;
+ return adjust_address_nv (XEXP (op, 0), mode,
+ (WORDS_BIG_ENDIAN
+ ? byte - shifted_bytes
+ : byte + shifted_bytes));
+ }
+
+ /* (truncate:SI (OP:DI ({sign,zero}_extend:DI foo:SI))) is
+ (OP:SI foo:SI) if OP is NEG or ABS. */
+ if ((GET_CODE (op) == ABS
+ || GET_CODE (op) == NEG)
+ && (GET_CODE (XEXP (op, 0)) == SIGN_EXTEND
+ || GET_CODE (XEXP (op, 0)) == ZERO_EXTEND)
+ && GET_MODE (XEXP (XEXP (op, 0), 0)) == mode)
+ return simplify_gen_unary (GET_CODE (op), mode,
+ XEXP (XEXP (op, 0), 0), mode);
+
+ /* (truncate:A (subreg:B (truncate:C X) 0)) is
+ (truncate:A X). */
+ if (GET_CODE (op) == SUBREG
+ && SCALAR_INT_MODE_P (mode)
+ && SCALAR_INT_MODE_P (op_mode)
+ && SCALAR_INT_MODE_P (GET_MODE (SUBREG_REG (op)))
+ && GET_CODE (SUBREG_REG (op)) == TRUNCATE
+ && subreg_lowpart_p (op))
+ return simplify_gen_unary (TRUNCATE, mode, XEXP (SUBREG_REG (op), 0),
+ GET_MODE (XEXP (SUBREG_REG (op), 0)));
+
+ /* (truncate:A (truncate:B X)) is (truncate:A X). */
+ if (GET_CODE (op) == TRUNCATE)
+ return simplify_gen_unary (TRUNCATE, mode, XEXP (op, 0),
+ GET_MODE (XEXP (op, 0)));
+
+ return NULL_RTX;
+}
+\f
/* Try to simplify a unary operation CODE whose output mode is to be
MODE with input operand OP whose mode was originally OP_MODE.
Return zero if no simplification can be made. */
break;
case TRUNCATE:
- /* We can't handle truncation to a partial integer mode here
- because we don't know the real bitsize of the partial
- integer mode. */
- if (GET_MODE_CLASS (mode) == MODE_PARTIAL_INT)
- break;
-
- /* (truncate:SI ({sign,zero}_extend:DI foo:SI)) == foo:SI. */
- if ((GET_CODE (op) == SIGN_EXTEND
- || GET_CODE (op) == ZERO_EXTEND)
- && GET_MODE (XEXP (op, 0)) == mode)
- return XEXP (op, 0);
+ /* Don't optimize (lshiftrt (mult ...)) as it would interfere
+ with the umulXi3_highpart patterns. */
+ if (GET_CODE (op) == LSHIFTRT
+ && GET_CODE (XEXP (op, 0)) == MULT)
+ break;
- /* (truncate:SI (OP:DI ({sign,zero}_extend:DI foo:SI))) is
- (OP:SI foo:SI) if OP is NEG or ABS. */
- if ((GET_CODE (op) == ABS
- || GET_CODE (op) == NEG)
- && (GET_CODE (XEXP (op, 0)) == SIGN_EXTEND
- || GET_CODE (XEXP (op, 0)) == ZERO_EXTEND)
- && GET_MODE (XEXP (XEXP (op, 0), 0)) == mode)
- return simplify_gen_unary (GET_CODE (op), mode,
- XEXP (XEXP (op, 0), 0), mode);
+ if (GET_MODE_CLASS (mode) == MODE_PARTIAL_INT)
+ {
+ if (TRULY_NOOP_TRUNCATION_MODES_P (mode, GET_MODE (op)))
+ return rtl_hooks.gen_lowpart_no_emit (mode, op);
+ /* We can't handle truncation to a partial integer mode here
+ because we don't know the real bitsize of the partial
+ integer mode. */
+ break;
+ }
- /* (truncate:A (subreg:B (truncate:C X) 0)) is
- (truncate:A X). */
- if (GET_CODE (op) == SUBREG
- && GET_CODE (SUBREG_REG (op)) == TRUNCATE
- && subreg_lowpart_p (op))
- return simplify_gen_unary (TRUNCATE, mode, XEXP (SUBREG_REG (op), 0),
- GET_MODE (XEXP (SUBREG_REG (op), 0)));
+ if (GET_MODE (op) != VOIDmode)
+ {
+ temp = simplify_truncation (mode, op, GET_MODE (op));
+ if (temp)
+ return temp;
+ }
/* If we know that the value is already truncated, we can
- replace the TRUNCATE with a SUBREG. Note that this is also
- valid if TRULY_NOOP_TRUNCATION is false for the corresponding
- modes we just have to apply a different definition for
- truncation. But don't do this for an (LSHIFTRT (MULT ...))
- since this will cause problems with the umulXi3_highpart
- patterns. */
- if ((TRULY_NOOP_TRUNCATION_MODES_P (mode, GET_MODE (op))
- ? (num_sign_bit_copies (op, GET_MODE (op))
- > (unsigned int) (GET_MODE_PRECISION (GET_MODE (op))
- - GET_MODE_PRECISION (mode)))
- : truncated_to_mode (mode, op))
- && ! (GET_CODE (op) == LSHIFTRT
- && GET_CODE (XEXP (op, 0)) == MULT))
+ replace the TRUNCATE with a SUBREG. */
+ if (GET_MODE_NUNITS (mode) == 1
+ && (TRULY_NOOP_TRUNCATION_MODES_P (mode, GET_MODE (op))
+ || truncated_to_mode (mode, op)))
return rtl_hooks.gen_lowpart_no_emit (mode, op);
/* A truncate of a comparison can be replaced with a subreg if
return NULL_RTX;
}
- /* Merge implicit and explicit truncations. */
-
- if (GET_CODE (op) == TRUNCATE
- && GET_MODE_SIZE (outermode) < GET_MODE_SIZE (innermode)
- && subreg_lowpart_offset (outermode, innermode) == byte)
- return simplify_gen_unary (TRUNCATE, outermode, XEXP (op, 0),
- GET_MODE (XEXP (op, 0)));
-
/* SUBREG of a hard register => just change the register number
and/or mode. If the hard register is not valid in that mode,
suppress this simplification. If the hard register is the stack,
return NULL_RTX;
}
- /* Optimize SUBREG truncations of zero and sign extended values. */
- if ((GET_CODE (op) == ZERO_EXTEND
- || GET_CODE (op) == SIGN_EXTEND)
- && SCALAR_INT_MODE_P (innermode)
- && GET_MODE_PRECISION (outermode) < GET_MODE_PRECISION (innermode))
+ /* A SUBREG resulting from a zero extension may fold to zero if
+ it extracts higher bits that the ZERO_EXTEND's source bits. */
+ if (GET_CODE (op) == ZERO_EXTEND)
{
unsigned int bitpos = subreg_lsb_1 (outermode, innermode, byte);
-
- /* If we're requesting the lowpart of a zero or sign extension,
- there are three possibilities. If the outermode is the same
- as the origmode, we can omit both the extension and the subreg.
- If the outermode is not larger than the origmode, we can apply
- the truncation without the extension. Finally, if the outermode
- is larger than the origmode, but both are integer modes, we
- can just extend to the appropriate mode. */
- if (bitpos == 0)
- {
- enum machine_mode origmode = GET_MODE (XEXP (op, 0));
- if (outermode == origmode)
- return XEXP (op, 0);
- if (GET_MODE_PRECISION (outermode) <= GET_MODE_PRECISION (origmode))
- return simplify_gen_subreg (outermode, XEXP (op, 0), origmode,
- subreg_lowpart_offset (outermode,
- origmode));
- if (SCALAR_INT_MODE_P (outermode))
- return simplify_gen_unary (GET_CODE (op), outermode,
- XEXP (op, 0), origmode);
- }
-
- /* A SUBREG resulting from a zero extension may fold to zero if
- it extracts higher bits that the ZERO_EXTEND's source bits. */
- if (GET_CODE (op) == ZERO_EXTEND
- && bitpos >= GET_MODE_PRECISION (GET_MODE (XEXP (op, 0))))
+ if (bitpos >= GET_MODE_PRECISION (GET_MODE (XEXP (op, 0))))
return CONST0_RTX (outermode);
}
- /* Simplify (subreg:SI (op:DI ((x:DI) (y:DI)), 0)
- to (op:SI (subreg:SI (x:DI) 0) (subreg:SI (x:DI) 0)), where
- the outer subreg is effectively a truncation to the original mode. */
- if ((GET_CODE (op) == PLUS
- || GET_CODE (op) == MINUS
- || GET_CODE (op) == MULT)
- && SCALAR_INT_MODE_P (outermode)
+ if (SCALAR_INT_MODE_P (outermode)
&& SCALAR_INT_MODE_P (innermode)
&& GET_MODE_PRECISION (outermode) < GET_MODE_PRECISION (innermode)
&& byte == subreg_lowpart_offset (outermode, innermode))
{
- rtx op0 = simplify_gen_subreg (outermode, XEXP (op, 0),
- innermode, byte);
- if (op0)
- {
- rtx op1 = simplify_gen_subreg (outermode, XEXP (op, 1),
- innermode, byte);
- if (op1)
- return simplify_gen_binary (GET_CODE (op), outermode, op0, op1);
- }
- }
-
- /* Simplify (subreg:QI (lshiftrt:SI (sign_extend:SI (x:QI)) C), 0) into
- to (ashiftrt:QI (x:QI) C), where C is a suitable small constant and
- the outer subreg is effectively a truncation to the original mode. */
- if ((GET_CODE (op) == LSHIFTRT
- || GET_CODE (op) == ASHIFTRT)
- && SCALAR_INT_MODE_P (outermode)
- && SCALAR_INT_MODE_P (innermode)
- /* Ensure that OUTERMODE is at least twice as wide as the INNERMODE
- to avoid the possibility that an outer LSHIFTRT shifts by more
- than the sign extension's sign_bit_copies and introduces zeros
- into the high bits of the result. */
- && (2 * GET_MODE_PRECISION (outermode)) <= GET_MODE_PRECISION (innermode)
- && CONST_INT_P (XEXP (op, 1))
- && GET_CODE (XEXP (op, 0)) == SIGN_EXTEND
- && GET_MODE (XEXP (XEXP (op, 0), 0)) == outermode
- && INTVAL (XEXP (op, 1)) < GET_MODE_PRECISION (outermode)
- && subreg_lsb_1 (outermode, innermode, byte) == 0)
- return simplify_gen_binary (ASHIFTRT, outermode,
- XEXP (XEXP (op, 0), 0), XEXP (op, 1));
-
- /* Likewise (subreg:QI (lshiftrt:SI (zero_extend:SI (x:QI)) C), 0) into
- to (lshiftrt:QI (x:QI) C), where C is a suitable small constant and
- the outer subreg is effectively a truncation to the original mode. */
- if ((GET_CODE (op) == LSHIFTRT
- || GET_CODE (op) == ASHIFTRT)
- && SCALAR_INT_MODE_P (outermode)
- && SCALAR_INT_MODE_P (innermode)
- && GET_MODE_PRECISION (outermode) < GET_MODE_PRECISION (innermode)
- && CONST_INT_P (XEXP (op, 1))
- && GET_CODE (XEXP (op, 0)) == ZERO_EXTEND
- && GET_MODE (XEXP (XEXP (op, 0), 0)) == outermode
- && INTVAL (XEXP (op, 1)) < GET_MODE_PRECISION (outermode)
- && subreg_lsb_1 (outermode, innermode, byte) == 0)
- return simplify_gen_binary (LSHIFTRT, outermode,
- XEXP (XEXP (op, 0), 0), XEXP (op, 1));
-
- /* Likewise (subreg:QI (ashift:SI (zero_extend:SI (x:QI)) C), 0) into
- to (ashift:QI (x:QI) C), where C is a suitable small constant and
- the outer subreg is effectively a truncation to the original mode. */
- if (GET_CODE (op) == ASHIFT
- && SCALAR_INT_MODE_P (outermode)
- && SCALAR_INT_MODE_P (innermode)
- && GET_MODE_PRECISION (outermode) < GET_MODE_PRECISION (innermode)
- && CONST_INT_P (XEXP (op, 1))
- && (GET_CODE (XEXP (op, 0)) == ZERO_EXTEND
- || GET_CODE (XEXP (op, 0)) == SIGN_EXTEND)
- && GET_MODE (XEXP (XEXP (op, 0), 0)) == outermode
- && INTVAL (XEXP (op, 1)) < GET_MODE_PRECISION (outermode)
- && subreg_lsb_1 (outermode, innermode, byte) == 0)
- return simplify_gen_binary (ASHIFT, outermode,
- XEXP (XEXP (op, 0), 0), XEXP (op, 1));
-
- /* Recognize a word extraction from a multi-word subreg. */
- if ((GET_CODE (op) == LSHIFTRT
- || GET_CODE (op) == ASHIFTRT)
- && SCALAR_INT_MODE_P (innermode)
- && GET_MODE_PRECISION (outermode) >= BITS_PER_WORD
- && GET_MODE_PRECISION (innermode) >= (2 * GET_MODE_PRECISION (outermode))
- && CONST_INT_P (XEXP (op, 1))
- && (INTVAL (XEXP (op, 1)) & (GET_MODE_PRECISION (outermode) - 1)) == 0
- && INTVAL (XEXP (op, 1)) >= 0
- && INTVAL (XEXP (op, 1)) < GET_MODE_PRECISION (innermode)
- && byte == subreg_lowpart_offset (outermode, innermode))
- {
- int shifted_bytes = INTVAL (XEXP (op, 1)) / BITS_PER_UNIT;
- return simplify_gen_subreg (outermode, XEXP (op, 0), innermode,
- (WORDS_BIG_ENDIAN
- ? byte - shifted_bytes
- : byte + shifted_bytes));
- }
-
- /* If we have a lowpart SUBREG of a right shift of MEM, make a new MEM
- and try replacing the SUBREG and shift with it. Don't do this if
- the MEM has a mode-dependent address or if we would be widening it. */
-
- if ((GET_CODE (op) == LSHIFTRT
- || GET_CODE (op) == ASHIFTRT)
- && SCALAR_INT_MODE_P (innermode)
- && MEM_P (XEXP (op, 0))
- && CONST_INT_P (XEXP (op, 1))
- && GET_MODE_SIZE (outermode) < GET_MODE_SIZE (GET_MODE (op))
- && (INTVAL (XEXP (op, 1)) % GET_MODE_BITSIZE (outermode)) == 0
- && INTVAL (XEXP (op, 1)) > 0
- && INTVAL (XEXP (op, 1)) < GET_MODE_BITSIZE (innermode)
- && ! mode_dependent_address_p (XEXP (XEXP (op, 0), 0),
- MEM_ADDR_SPACE (XEXP (op, 0)))
- && ! MEM_VOLATILE_P (XEXP (op, 0))
- && byte == subreg_lowpart_offset (outermode, innermode)
- && (GET_MODE_SIZE (outermode) >= UNITS_PER_WORD
- || WORDS_BIG_ENDIAN == BYTES_BIG_ENDIAN))
- {
- int shifted_bytes = INTVAL (XEXP (op, 1)) / BITS_PER_UNIT;
- return adjust_address_nv (XEXP (op, 0), outermode,
- (WORDS_BIG_ENDIAN
- ? byte - shifted_bytes
- : byte + shifted_bytes));
+ rtx tem = simplify_truncation (outermode, op, innermode);
+ if (tem)
+ return tem;
}
return NULL_RTX;
projects / gcc.git / commitdiff