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1 // Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
4 //
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
10
11 // Information concerning the machine representation of various types.
12
13 #![allow(non_camel_case_types)]
14
15 use llvm::{self, ValueRef};
16 use common::*;
17
18 use type_::Type;
19
20 pub type llbits = u64;
21 pub type llsize = u64;
22 pub type llalign = u32;
23
24 // ______________________________________________________________________
25 // compute sizeof / alignof
26
27 // Returns the number of bytes clobbered by a Store to this type.
28 pub fn llsize_of_store(cx: &CrateContext, ty: Type) -> llsize {
29 unsafe {
30 return llvm::LLVMStoreSizeOfType(cx.td(), ty.to_ref());
31 }
32 }
33
34 // Returns the number of bytes between successive elements of type T in an
35 // array of T. This is the "ABI" size. It includes any ABI-mandated padding.
36 pub fn llsize_of_alloc(cx: &CrateContext, ty: Type) -> llsize {
37 unsafe {
38 return llvm::LLVMABISizeOfType(cx.td(), ty.to_ref());
39 }
40 }
41
42 // Returns, as near as we can figure, the "real" size of a type. As in, the
43 // bits in this number of bytes actually carry data related to the datum
44 // with the type. Not junk, accidentally-damaged words, or whatever.
45 // Note that padding of the type will be included for structs, but not for the
46 // other types (i.e. SIMD types).
47 // Rounds up to the nearest byte though, so if you have a 1-bit
48 // value, we return 1 here, not 0. Most of rustc works in bytes. Be warned
49 // that LLVM *does* distinguish between e.g. a 1-bit value and an 8-bit value
50 // at the codegen level! In general you should prefer `llbitsize_of_real`
51 // below.
52 pub fn llsize_of_real(cx: &CrateContext, ty: Type) -> llsize {
53 unsafe {
54 let nbits = llvm::LLVMSizeOfTypeInBits(cx.td(), ty.to_ref());
55 if nbits & 7 != 0 {
56 // Not an even number of bytes, spills into "next" byte.
57 1 + (nbits >> 3)
58 } else {
59 nbits >> 3
60 }
61 }
62 }
63
64 /// Returns the "real" size of the type in bits.
65 pub fn llbitsize_of_real(cx: &CrateContext, ty: Type) -> llbits {
66 unsafe {
67 llvm::LLVMSizeOfTypeInBits(cx.td(), ty.to_ref())
68 }
69 }
70
71 /// Returns the size of the type as an LLVM constant integer value.
72 pub fn llsize_of(cx: &CrateContext, ty: Type) -> ValueRef {
73 // Once upon a time, this called LLVMSizeOf, which does a
74 // getelementptr(1) on a null pointer and casts to an int, in
75 // order to obtain the type size as a value without requiring the
76 // target data layout. But we have the target data layout, so
77 // there's no need for that contrivance. The instruction
78 // selection DAG generator would flatten that GEP(1) node into a
79 // constant of the type's alloc size, so let's save it some work.
80 return C_uint(cx, llsize_of_alloc(cx, ty));
81 }
82
83 // Returns the preferred alignment of the given type for the current target.
84 // The preferred alignment may be larger than the alignment used when
85 // packing the type into structs. This will be used for things like
86 // allocations inside a stack frame, which LLVM has a free hand in.
87 pub fn llalign_of_pref(cx: &CrateContext, ty: Type) -> llalign {
88 unsafe {
89 return llvm::LLVMPreferredAlignmentOfType(cx.td(), ty.to_ref());
90 }
91 }
92
93 // Returns the minimum alignment of a type required by the platform.
94 // This is the alignment that will be used for struct fields, arrays,
95 // and similar ABI-mandated things.
96 pub fn llalign_of_min(cx: &CrateContext, ty: Type) -> llalign {
97 unsafe {
98 return llvm::LLVMABIAlignmentOfType(cx.td(), ty.to_ref());
99 }
100 }
101
102 pub fn llelement_offset(cx: &CrateContext, struct_ty: Type, element: usize) -> u64 {
103 unsafe {
104 return llvm::LLVMOffsetOfElement(cx.td(),
105 struct_ty.to_ref(),
106 element as u32);
107 }
108 }