rust/src/librustc_codegen_llvm/allocator.rs

use crate::attributes;
use libc::c_uint;
use rustc::bug;
use rustc::ty::TyCtxt;
use rustc_ast::expand::allocator::{AllocatorKind, AllocatorTy, ALLOCATOR_METHODS};

use crate::llvm::{self, False, True};
use crate::ModuleLlvm;

pub(crate) unsafe fn codegen(tcx: TyCtxt<'_>, mods: &mut ModuleLlvm, kind: AllocatorKind) {
    let llcx = &*mods.llcx;
    let llmod = mods.llmod();
    let usize = match &tcx.sess.target.target.target_pointer_width[..] {
        "16" => llvm::LLVMInt16TypeInContext(llcx),
        "32" => llvm::LLVMInt32TypeInContext(llcx),
        "64" => llvm::LLVMInt64TypeInContext(llcx),
        tws => bug!("Unsupported target word size for int: {}", tws),
    };
    let i8 = llvm::LLVMInt8TypeInContext(llcx);
    let i8p = llvm::LLVMPointerType(i8, 0);
    let void = llvm::LLVMVoidTypeInContext(llcx);

    for method in ALLOCATOR_METHODS {
        let mut args = Vec::with_capacity(method.inputs.len());
        for ty in method.inputs.iter() {
            match *ty {
                AllocatorTy::Layout => {
                    args.push(usize); // size
                    args.push(usize); // align
                }
                AllocatorTy::Ptr => args.push(i8p),
                AllocatorTy::Usize => args.push(usize),

                AllocatorTy::ResultPtr | AllocatorTy::Unit => panic!("invalid allocator arg"),
            }
        }
        let output = match method.output {
            AllocatorTy::ResultPtr => Some(i8p),
            AllocatorTy::Unit => None,

            AllocatorTy::Layout | AllocatorTy::Usize | AllocatorTy::Ptr => {
                panic!("invalid allocator output")
            }
        };
        let ty = llvm::LLVMFunctionType(
            output.unwrap_or(void),
            args.as_ptr(),
            args.len() as c_uint,
            False,
        );
        let name = format!("__rust_{}", method.name);
        let llfn = llvm::LLVMRustGetOrInsertFunction(llmod, name.as_ptr().cast(), name.len(), ty);

        if tcx.sess.target.target.options.default_hidden_visibility {
            llvm::LLVMRustSetVisibility(llfn, llvm::Visibility::Hidden);
        }
        if tcx.sess.target.target.options.requires_uwtable {
            attributes::emit_uwtable(llfn, true);
        }

        let callee = kind.fn_name(method.name);
        let callee =
            llvm::LLVMRustGetOrInsertFunction(llmod, callee.as_ptr().cast(), callee.len(), ty);
        llvm::LLVMRustSetVisibility(callee, llvm::Visibility::Hidden);

        let llbb = llvm::LLVMAppendBasicBlockInContext(llcx, llfn, "entry\0".as_ptr().cast());

        let llbuilder = llvm::LLVMCreateBuilderInContext(llcx);
        llvm::LLVMPositionBuilderAtEnd(llbuilder, llbb);
        let args = args
            .iter()
            .enumerate()
            .map(|(i, _)| llvm::LLVMGetParam(llfn, i as c_uint))
            .collect::<Vec<_>>();
        let ret =
            llvm::LLVMRustBuildCall(llbuilder, callee, args.as_ptr(), args.len() as c_uint, None);
        llvm::LLVMSetTailCall(ret, True);
        if output.is_some() {
            llvm::LLVMBuildRet(llbuilder, ret);
        } else {
            llvm::LLVMBuildRetVoid(llbuilder);
        }
        llvm::LLVMDisposeBuilder(llbuilder);
    }
}