improve folding of expressions that move a single bit around

Message ID	1480198964-143031-1-git-send-email-bonzini@gnu.org
State	New
Headers	show Return-Path: <gcc-patches-return-442714-incoming=patchwork.ozlabs.org@gcc.gnu.org> DomainKey-Signature: a=rsa-sha1; c=nofws; d=gcc.gnu.org; h=list-id :list-unsubscribe:list-archive:list-post:list-help:sender:from :to:subject:date:message-id; q=dns; s=default; b=WyPMWfHJFIgBKZt dWb8fpDIBbjzCVNLqVyu0ZnLfcgBzRfcS67+wkXegj0da4zidRv9T8bCIqXB6DoU kJ48UfCjxzMRYLxdTalXjg3Vz9ItckeuEZmYEQxy0RTPTYWee57WbHOnd4aovRSn FwXZkKZsLy5Y7TNWvZI/TJDNtE2E= Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk Sender: gcc-patches-owner@gcc.gnu.org From: Paolo Bonzini <bonzini@gnu.org> To: gcc-patches@gcc.gnu.org Subject: [PATCH] improve folding of expressions that move a single bit around Date: Sat, 26 Nov 2016 23:22:44 +0100 Message-Id: <1480198964-143031-1-git-send-email-bonzini@gnu.org>

Index: combine.c =================================================================== --- combine.c (revision 242742) +++ combine.c (working copy) @@ -6522,14 +6522,22 @@ simplify_shift_const (NULL_RTX, ASHIFT, mode, gen_lowpart (mode, XEXP (cond, 0)), i); - /* (IF_THEN_ELSE (NE REG 0) (0) (8)) is REG for nonzero_bits (REG) == 8. */ + /* (IF_THEN_ELSE (NE A 0) C1 0) is A or a zero-extend of A if the only + non-zero bit in A is C1. */ if (true_code == NE && XEXP (cond, 1) == const0_rtx && false_rtx == const0_rtx && CONST_INT_P (true_rtx) - && GET_MODE (XEXP (cond, 0)) == mode + && INTEGRAL_MODE_P (GET_MODE (XEXP (cond, 0))) && (UINTVAL (true_rtx) & GET_MODE_MASK (mode)) - == nonzero_bits (XEXP (cond, 0), mode) + == nonzero_bits (XEXP (cond, 0), GET_MODE (XEXP (cond, 0))) && (i = exact_log2 (UINTVAL (true_rtx) & GET_MODE_MASK (mode))) >= 0) - return XEXP (cond, 0); + { + rtx val = XEXP (cond, 0); + enum machine_mode val_mode = GET_MODE (val); + if (val_mode == mode) + return val; + else if (GET_MODE_PRECISION (val_mode) < GET_MODE_PRECISION (mode)) + return simplify_gen_unary (ZERO_EXTEND, mode, val, val_mode); + } return x; } Index: match.pd =================================================================== --- match.pd (revision 242742) +++ match.pd (working copy) @@ -2554,6 +2554,19 @@ (cmp (bit_and@2 @0 integer_pow2p@1) @1) (icmp @2 { build_zero_cst (TREE_TYPE (@0)); }))) +/* If we have (A & C) != 0 ? D : 0 where C and D are powers of 2, + convert this into a shift of (A & C). */ +(simplify + (cond + (ne (bit_and@2 @0 integer_pow2p@1) integer_zerop) + integer_pow2p@3 integer_zerop) + (with { + int shift = wi::exact_log2 (@3) - wi::exact_log2 (@1); + } + (if (shift > 0) + (lshift (convert @2) { build_int_cst (integer_type_node, shift); }) + (convert (rshift @2 { build_int_cst (integer_type_node, -shift); }))))) + /* If we have (A & C) != 0 where C is the sign bit of A, convert this into A < 0. Similarly for (A & C) == 0 into A >= 0. */ (for cmp (eq ne) @@ -2568,6 +2581,19 @@ (with { tree stype = signed_type_for (TREE_TYPE (@0)); } (ncmp (convert:stype @0) { build_zero_cst (stype); }))))) +/* If we have A < 0 ? C : 0 where C and D are powers of 2, + convert this into a right shift and AND. */ +(simplify + (cond + (lt @0 integer_zerop) + integer_pow2p@1 integer_zerop) + (with { + int shift = element_precision (@0) - wi::exact_log2 (@1) - 1; + } + (bit_and + (convert (rshift @0 { build_int_cst (integer_type_node, shift); })) + @1))) + /* When the addresses are not directly of decls compare base and offset. This implements some remaining parts of fold_comparison address comparisons but still no complete part of it. Still it is good Index: testsuite/gcc.dg/fold-and-lshift.c =================================================================== --- testsuite/gcc.dg/fold-and-lshift.c (revision 0) +++ testsuite/gcc.dg/fold-and-lshift.c (working copy) @@ -0,0 +1,35 @@ +/* { dg-do compile } */ +/* { dg-options "-O -fdump-tree-original" } */ + +int f(int x) +{ + return (x << 2) & 128; +} + +int g(int x) +{ + return !!(x & 32) << 7; +} + +int h(int x) +{ + return ((x >> 5) & 1) << 7; +} + +int i(int x) +{ + return (x & 32) >> 5 << 7; +} + +int j(int x) +{ + return ((x >> 5) & 1) ? 128 : 0; +} + +int k(int x) +{ + return (x & 32) ? 128 : 0; +} + +/* { dg-final { scan-tree-dump-not " \\? " "original" } } */ +/* { dg-final { scan-assembler-not "sarl" { target i?86-*-* x86_64-*-* } } }" */ Index: testsuite/gcc.dg/fold-and-rshift-1.c =================================================================== --- testsuite/gcc.dg/fold-and-rshift-1.c (revision 0) +++ testsuite/gcc.dg/fold-and-rshift-1.c (working copy) @@ -0,0 +1,35 @@ +/* { dg-do compile } */ +/* { dg-options "-O -fdump-tree-original" } */ + +int f(int x) +{ + return (x >> 2) & 128; +} + +int g(int x) +{ + return !!(x & 512) << 7; +} + +int h(int x) +{ + return ((x >> 9) & 1) << 7; +} + +int i(int x) +{ + return (x & 512) >> 9 << 7; +} + +int j(int x) +{ + return ((x >> 9) & 1) ? 128 : 0; +} + +int k(int x) +{ + return (x & 512) ? 128 : 0; +} + +/* { dg-final { scan-tree-dump-not " \\? " "original" } } */ +/* { dg-final { scan-assembler-not "sall" { target i?86-*-* x86_64-*-* } } }" */ Index: testsuite/gcc.dg/fold-and-rshift-2.c =================================================================== --- testsuite/gcc.dg/fold-and-rshift-2.c (revision 0) +++ testsuite/gcc.dg/fold-and-rshift-2.c (working copy) @@ -0,0 +1,25 @@ +/* { dg-do compile } */ +/* { dg-options "-O -fdump-tree-original" } */ + +unsigned f(unsigned x) +{ + return (x >> 29) & 32; +} + +unsigned g(unsigned x) +{ + return !!(x & 0x80000000) << 5; +} + +unsigned j(unsigned x) +{ + return ((x >> 31) & 1) ? 32 : 0; +} + +unsigned k(unsigned x) +{ + return (x & 0x80000000) ? 32 : 0; +} + +/* { dg-final { scan-tree-dump-not " \\? " "original" } } */ +/* { dg-final { scan-assembler-not "sall" { target i?86-*-* x86_64-*-* } } }" */

improve folding of expressions that move a single bit around

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