From 3b1da8bb77bb07285272f2ad9e516197f3fe0835 Mon Sep 17 00:00:00 2001 From: Segher Boessenkool Date: Wed, 11 Nov 2015 15:09:30 +0100 Subject: [PATCH] simplify-rtx: Simplify trunc of and of shiftrt If we have (truncate:M1 (and:M2 (lshiftrt:M2 (x:M2) C) C2)) we can write it instead as (and:M1 (lshiftrt:M1 (truncate:M1 (x:M2)) C) C2) (if that is valid, of course), which has smaller modes for the binary ops, and the truncate can often simplify further (if "x" is a register, for example). * gcc/simplify-rtx.c (simplify_truncation): Simplify TRUNCATE of AND of [LA]SHIFTRT. From-SVN: r230164 --- gcc/ChangeLog | 5 +++++ gcc/simplify-rtx.c | 28 ++++++++++++++++++++++++++++ 2 files changed, 33 insertions(+) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index fb7e4f071f0..eb556d05957 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,8 @@ +2015-11-11 Segher Boessenkool + + * gcc/simplify-rtx.c (simplify_truncation): Simplify TRUNCATE + of AND of [LA]SHIFTRT. + 2015-11-11 Martin Liska Richard Biener diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c index 17568baa8b0..c4fc42aebcf 100644 --- a/gcc/simplify-rtx.c +++ b/gcc/simplify-rtx.c @@ -714,6 +714,34 @@ simplify_truncation (machine_mode mode, rtx op, return simplify_gen_binary (ASHIFT, mode, XEXP (XEXP (op, 0), 0), XEXP (op, 1)); + /* Likewise (truncate:QI (and:SI (lshiftrt:SI (x:SI) C) C2)) into + (and:QI (lshiftrt:QI (truncate:QI (x:SI)) C) C2) for suitable C + and C2. */ + if (GET_CODE (op) == AND + && (GET_CODE (XEXP (op, 0)) == LSHIFTRT + || GET_CODE (XEXP (op, 0)) == ASHIFTRT) + && CONST_INT_P (XEXP (XEXP (op, 0), 1)) + && CONST_INT_P (XEXP (op, 1))) + { + rtx op0 = (XEXP (XEXP (op, 0), 0)); + rtx shift_op = XEXP (XEXP (op, 0), 1); + rtx mask_op = XEXP (op, 1); + unsigned HOST_WIDE_INT shift = UINTVAL (shift_op); + unsigned HOST_WIDE_INT mask = UINTVAL (mask_op); + + if (shift < precision + /* If doing this transform works for an X with all bits set, + it works for any X. */ + && ((GET_MODE_MASK (mode) >> shift) & mask) + == ((GET_MODE_MASK (op_mode) >> shift) & mask) + && (op0 = simplify_gen_unary (TRUNCATE, mode, op0, op_mode)) + && (op0 = simplify_gen_binary (LSHIFTRT, mode, op0, shift_op))) + { + mask_op = GEN_INT (trunc_int_for_mode (mask, mode)); + return simplify_gen_binary (AND, mode, op0, mask_op); + } + } + /* Recognize a word extraction from a multi-word subreg. */ if ((GET_CODE (op) == LSHIFTRT || GET_CODE (op) == ASHIFTRT) -- 2.30.2