122 lines
4.7 KiB
Rust
122 lines
4.7 KiB
Rust
// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// Information concerning the machine representation of various types.
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use lib::llvm::{ValueRef};
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use lib::llvm::False;
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use lib::llvm::llvm;
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use middle::trans::common::*;
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use middle::trans::type_::Type;
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// ______________________________________________________________________
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// compute sizeof / alignof
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// Returns the number of bytes clobbered by a Store to this type.
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pub fn llsize_of_store(cx: &CrateContext, ty: Type) -> uint {
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unsafe {
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return llvm::LLVMStoreSizeOfType(cx.td.lltd, ty.to_ref()) as uint;
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}
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}
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// Returns the number of bytes between successive elements of type T in an
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// array of T. This is the "ABI" size. It includes any ABI-mandated padding.
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pub fn llsize_of_alloc(cx: &CrateContext, ty: Type) -> uint {
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unsafe {
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return llvm::LLVMABISizeOfType(cx.td.lltd, ty.to_ref()) as uint;
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}
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}
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// Returns, as near as we can figure, the "real" size of a type. As in, the
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// bits in this number of bytes actually carry data related to the datum
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// with the type. Not junk, padding, accidentally-damaged words, or
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// whatever. Rounds up to the nearest byte though, so if you have a 1-bit
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// value, we return 1 here, not 0. Most of rustc works in bytes. Be warned
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// that LLVM *does* distinguish between e.g. a 1-bit value and an 8-bit value
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// at the codegen level! In general you should prefer `llbitsize_of_real`
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// below.
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pub fn llsize_of_real(cx: &CrateContext, ty: Type) -> uint {
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unsafe {
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let nbits = llvm::LLVMSizeOfTypeInBits(cx.td.lltd, ty.to_ref()) as uint;
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if nbits & 7u != 0u {
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// Not an even number of bytes, spills into "next" byte.
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1u + (nbits >> 3)
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} else {
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nbits >> 3
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}
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}
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}
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/// Returns the "real" size of the type in bits.
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pub fn llbitsize_of_real(cx: &CrateContext, ty: Type) -> uint {
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unsafe {
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llvm::LLVMSizeOfTypeInBits(cx.td.lltd, ty.to_ref()) as uint
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}
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}
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/// Returns the size of the type as an LLVM constant integer value.
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pub fn llsize_of(cx: &CrateContext, ty: Type) -> ValueRef {
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// Once upon a time, this called LLVMSizeOf, which does a
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// getelementptr(1) on a null pointer and casts to an int, in
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// order to obtain the type size as a value without requiring the
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// target data layout. But we have the target data layout, so
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// there's no need for that contrivance. The instruction
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// selection DAG generator would flatten that GEP(1) node into a
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// constant of the type's alloc size, so let's save it some work.
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return C_uint(cx, llsize_of_alloc(cx, ty));
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}
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// Returns the "default" size of t (see above), or 1 if the size would
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// be zero. This is important for things like vectors that expect
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// space to be consumed.
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pub fn nonzero_llsize_of(cx: &CrateContext, ty: Type) -> ValueRef {
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if llbitsize_of_real(cx, ty) == 0 {
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unsafe { llvm::LLVMConstInt(cx.int_type.to_ref(), 1, False) }
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} else {
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llsize_of(cx, ty)
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}
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}
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// Returns the preferred alignment of the given type for the current target.
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// The preferred alignment may be larger than the alignment used when
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// packing the type into structs. This will be used for things like
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// allocations inside a stack frame, which LLVM has a free hand in.
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pub fn llalign_of_pref(cx: &CrateContext, ty: Type) -> uint {
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unsafe {
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return llvm::LLVMPreferredAlignmentOfType(cx.td.lltd, ty.to_ref()) as uint;
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}
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}
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// Returns the minimum alignment of a type required by the platform.
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// This is the alignment that will be used for struct fields, arrays,
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// and similar ABI-mandated things.
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pub fn llalign_of_min(cx: &CrateContext, ty: Type) -> uint {
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unsafe {
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return llvm::LLVMABIAlignmentOfType(cx.td.lltd, ty.to_ref()) as uint;
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}
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}
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// Returns the "default" alignment of t, which is calculated by casting
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// null to a record containing a single-bit followed by a t value, then
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// doing gep(0,1) to get at the trailing (and presumably padded) t cell.
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pub fn llalign_of(cx: &CrateContext, ty: Type) -> ValueRef {
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unsafe {
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return llvm::LLVMConstIntCast(
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llvm::LLVMAlignOf(ty.to_ref()), cx.int_type.to_ref(), False);
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}
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}
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pub fn llelement_offset(cx: &CrateContext, struct_ty: Type, element: uint) -> uint {
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unsafe {
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return llvm::LLVMOffsetOfElement(cx.td.lltd, struct_ty.to_ref(), element as u32) as uint;
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}
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}
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