[v2] implement constant-folding in __builtin_bswap*()

Message ID	CANeU7QmSd5Zd_H2jDQyTjUMg7C4_6wQOyCR73R=FTdJ=f4+ygg@mail.gmail.com (mailing list archive)
State	Superseded, archived
Headers	show Return-Path: <linux-sparse-owner@kernel.org> MIME-Version: 1.0 In-Reply-To: <20161122131543.GA8370@macbook.local> References: <20161117095503.8754-1-johannes@sipsolutions.net> <CANeU7Q=vFZ2CtMYjMEYSNcJmdEGbg+_f_wYCRwmKZh3Jc76jEA@mail.gmail.com> <1479721551.8662.10.camel@sipsolutions.net> <CANeU7QmSSPT9cq1fNqUxqk5DNWDn7RNLjKnFVdKUdJtCrqfBLg@mail.gmail.com> <20161122131543.GA8370@macbook.local> From: Christopher Li <sparse@chrisli.org> Date: Wed, 23 Nov 2016 00:32:52 +0800 Message-ID: <CANeU7QmSd5Zd_H2jDQyTjUMg7C4_6wQOyCR73R=FTdJ=f4+ygg@mail.gmail.com> Subject: Re: [PATCH v2] implement constant-folding in __builtin_bswap*() To: Luc Van Oostenryck <luc.vanoostenryck@gmail.com> Cc: Johannes Berg <johannes@sipsolutions.net>, Linux-Sparse <linux-sparse@vger.kernel.org>, Nicolai Stange <nicstange@gmail.com> Content-Type: multipart/mixed; boundary=001a1143e56aed0f9b0541e6520b Sender: linux-sparse-owner@vger.kernel.org Precedence: bulk

diff --git a/expand.c b/expand.c index 0f6720c..1ef95ea 100644 --- a/expand.c +++ b/expand.c @@ -802,6 +802,44 @@ int expand_safe_p(struct expression *expr, int cost) return 0; } +/* The arguments are constant if the cost of all of them is zero */ +int expand_bswap(struct expression *expr, int cost) +{ + struct symbol *sym; + struct expression_list *args = expr->args; + long long input; + + if (cost) + return cost; + + sym = expr->fn->ctype; + if (expression_list_size(args) != 1) { + sparse_error(expr->pos, "not enough arguments for function %s", + show_ident(sym->ident)); + return SIDE_EFFECTS; + } + + input = const_expression_value(first_expression(args)); + + if (sym->ident == &__builtin_bswap16_ident) { + expr->value = __builtin_bswap16(input); + expr->ctype = &ushort_ctype; + } else if (sym->ident == &__builtin_bswap32_ident) { + expr->value = __builtin_bswap32(input); + expr->ctype = &uint_ctype; + } else if (sym->ident == &__builtin_bswap64_ident) { + expr->value = __builtin_bswap64(input); + expr->ctype = &ullong_ctype; + } else { + die("Unexpected __builtin_bswap symbol %s\n", show_ident(sym->ident)); + } + + expr->type = EXPR_VALUE; + expr->taint = 0; + return 0; +} + + /* * expand a call expression with a symbol. This * should expand builtins. diff --git a/ident-list.h b/ident-list.h index b65b667..a683f6c 100644 --- a/ident-list.h +++ b/ident-list.h @@ -35,6 +35,9 @@ IDENT_RESERVED(__sizeof_ptr__); IDENT_RESERVED(__builtin_types_compatible_p); IDENT_RESERVED(__builtin_offsetof); IDENT_RESERVED(__label__); +IDENT(__builtin_bswap16); +IDENT(__builtin_bswap32); +IDENT(__builtin_bswap64); /* Attribute names */ IDENT(packed); IDENT(__packed__); diff --git a/lib.c b/lib.c index 2660575..7e35049 100644 --- a/lib.c +++ b/lib.c @@ -819,40 +819,6 @@ void declare_builtin_functions(void) add_pre_buffer("extern int __builtin_popcountl(unsigned long);\n"); add_pre_buffer("extern int __builtin_popcountll(unsigned long long);\n"); - /* And byte swaps.. */ - add_pre_buffer("extern unsigned short ____builtin_bswap16(unsigned short);\n"); - add_pre_buffer("extern unsigned int ____builtin_bswap32(unsigned int);\n"); - add_pre_buffer("extern unsigned long long ____builtin_bswap64(unsigned long long);\n"); - add_pre_buffer("#define __sparse_constant_swab16(x) ((unsigned short)(" - " (((unsigned short)(x) & (unsigned short)0x00ffU) << 8) |" - " (((unsigned short)(x) & (unsigned short)0xff00U) >> 8)))\n"); - add_pre_buffer("#define __sparse_constant_swab32(x) ((unsigned int)(" - " (((unsigned int)(x) & (unsigned int)0x000000ffUL) << 24) |" - " (((unsigned int)(x) & (unsigned int)0x0000ff00UL) << 8) |" - " (((unsigned int)(x) & (unsigned int)0x00ff0000UL) >> 8) |" - " (((unsigned int)(x) & (unsigned int)0xff000000UL) >> 24)))\n"); - add_pre_buffer("#define __sparse_constant_swab64(x) ((unsigned long long)(" - " (((unsigned long long)(x) & (unsigned long long)0x00000000000000ffULL) << 56) |" - " (((unsigned long long)(x) & (unsigned long long)0x000000000000ff00ULL) << 40) |" - " (((unsigned long long)(x) & (unsigned long long)0x0000000000ff0000ULL) << 24) |" - " (((unsigned long long)(x) & (unsigned long long)0x00000000ff000000ULL) << 8) |" - " (((unsigned long long)(x) & (unsigned long long)0x000000ff00000000ULL) >> 8) |" - " (((unsigned long long)(x) & (unsigned long long)0x0000ff0000000000ULL) >> 24) |" - " (((unsigned long long)(x) & (unsigned long long)0x00ff000000000000ULL) >> 40) |" - " (((unsigned long long)(x) & (unsigned long long)0xff00000000000000ULL) >> 56)))\n"); - add_pre_buffer("#define __builtin_bswap16(x)" - " (__builtin_constant_p((unsigned short)(x)) ?" - " __sparse_constant_swab16(x) :" - " ____builtin_bswap16(x))\n"); - add_pre_buffer("#define __builtin_bswap32(x)" - " (__builtin_constant_p((unsigned int)(x)) ?" - " __sparse_constant_swab32(x) :" - " ____builtin_bswap32(x))\n"); - add_pre_buffer("#define __builtin_bswap64(x)" - " (__builtin_constant_p((unsigned long long)(x)) ?" - " __sparse_constant_swab64(x) :" - " ____builtin_bswap64(x))\n"); - /* And atomic memory access functions.. */ add_pre_buffer("extern int __sync_fetch_and_add(void *, ...);\n"); add_pre_buffer("extern int __sync_fetch_and_sub(void *, ...);\n"); diff --git a/lib.h b/lib.h index b778bdc..306ee45 100644 --- a/lib.h +++ b/lib.h @@ -200,6 +200,11 @@ static inline struct instruction *first_instruction(struct instruction_list *hea return first_ptr_list((struct ptr_list *)head); } +static inline struct expression *first_expression(struct expression_list *head) +{ + return first_ptr_list((struct ptr_list *)head); +} + static inline pseudo_t first_pseudo(struct pseudo_list *head) { return first_ptr_list((struct ptr_list *)head); diff --git a/symbol.c b/symbol.c index 92a7a62..e57f207 100644 --- a/symbol.c +++ b/symbol.c @@ -773,6 +773,11 @@ static struct symbol_op choose_op = { .args = arguments_choose, }; +static struct symbol_op bswap_op = { + .evaluate = evaluate_to_integer, + .expand = expand_bswap +}; + /* * Builtin functions */ @@ -788,6 +793,9 @@ static struct sym_init { { "__builtin_warning", &builtin_fn_type, MOD_TOPLEVEL, &warning_op }, { "__builtin_expect", &builtin_fn_type, MOD_TOPLEVEL, &expect_op }, { "__builtin_choose_expr", &builtin_fn_type, MOD_TOPLEVEL, &choose_op }, + { "__builtin_bswap16", &builtin_fn_type, MOD_TOPLEVEL, &bswap_op }, + { "__builtin_bswap32", &builtin_fn_type, MOD_TOPLEVEL, &bswap_op }, + { "__builtin_bswap64", &builtin_fn_type, MOD_TOPLEVEL, &bswap_op }, { NULL, NULL, 0 } }; diff --git a/symbol.h b/symbol.h index 9b3f160..48bbfce 100644 --- a/symbol.h +++ b/symbol.h @@ -130,6 +130,7 @@ struct symbol_op { extern int expand_safe_p(struct expression *expr, int cost); extern int expand_constant_p(struct expression *expr, int cost); +extern int expand_bswap(struct expression *expr, int cost); #define SYM_ATTR_WEAK 0 #define SYM_ATTR_NORMAL 1

[v2] implement constant-folding in __builtin_bswap*()

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