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simplify-rtx.c (simplify_subreg): Simplify truncations of shifts of sign or zero extended values.

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* simplify-rtx.c (simplify_subreg): Simplify truncations of shifts
	of sign or zero extended values.

From-SVN: r93022
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Roger Sayle 2005-01-07 00:47:13 +00:00 committed by Roger Sayle
parent 59d7d76786
commit c79fc2963d
2 changed files with 54 additions and 0 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
2005-01-06 Roger Sayle <roger@eyesopen.com>
* simplify-rtx.c (simplify_subreg): Simplify truncations of shifts
of sign or zero extended values.
2005-01-06 Geoffrey Keating <geoffk@apple.com>
* c-cppbuiltin.c (builtin_define_float_constants): Set __*_EPSILON__

49
gcc/simplify-rtx.c
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@ -3829,6 +3829,55 @@ simplify_subreg (enum machine_mode outermode, rtx op,
return CONST0_RTX (outermode);
}
/* 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)
/* 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_BITSIZE (outermode)) <= GET_MODE_BITSIZE (innermode)
&& GET_CODE (XEXP (op, 1)) == CONST_INT
&& GET_CODE (XEXP (op, 0)) == SIGN_EXTEND
&& GET_MODE (XEXP (XEXP (op, 0), 0)) == outermode
&& INTVAL (XEXP (op, 1)) < GET_MODE_BITSIZE (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)
&& GET_MODE_BITSIZE (outermode) < GET_MODE_BITSIZE (innermode)
&& GET_CODE (XEXP (op, 1)) == CONST_INT
&& GET_CODE (XEXP (op, 0)) == ZERO_EXTEND
&& GET_MODE (XEXP (XEXP (op, 0), 0)) == outermode
&& INTVAL (XEXP (op, 1)) < GET_MODE_BITSIZE (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)
&& GET_MODE_BITSIZE (outermode) < GET_MODE_BITSIZE (innermode)
&& GET_CODE (XEXP (op, 1)) == CONST_INT
&& (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_BITSIZE (outermode)
&& subreg_lsb_1 (outermode, innermode, byte) == 0)
return simplify_gen_binary (ASHIFT, outermode,
XEXP (XEXP (op, 0), 0), XEXP (op, 1));
return NULL_RTX;
}