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trans: deal with the fact that ZSTs are always "initialized".

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This commit is contained in:
Eduard Burtescu 2016-05-07 22:59:03 +03:00
parent d460597e33
commit cb3a557e0c
2 changed files with 26 additions and 7 deletions
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23
src/librustc_trans/mir/lvalue.rs
View File

@ -16,11 +16,11 @@ use abi;
use adt;
use base;
use builder::Builder;
use common::{self, BlockAndBuilder, CrateContext, C_uint};
use common::{self, BlockAndBuilder, CrateContext, C_uint, C_undef};
use consts;
use machine;
use type_of::type_of;
use mir::drop;
use llvm;
use Disr;
use std::ptr;
@ -116,10 +116,7 @@ impl<'bcx, 'tcx> MirContext<'bcx, 'tcx> {
// Ergo, we return an undef ValueRef, so we do not have to special-case every
// place using lvalues, and could use it the same way you use a regular
// ReturnPointer LValue (i.e. store into it, load from it etc).
let llty = fcx.fn_ty.ret.original_ty.ptr_to();
unsafe {
llvm::LLVMGetUndef(llty.to_ref())
}
C_undef(fcx.fn_ty.ret.original_ty.ptr_to())
};
let fn_return_ty = bcx.monomorphize(&self.mir.return_ty);
let return_ty = fn_return_ty.unwrap();
@ -228,7 +225,19 @@ impl<'bcx, 'tcx> MirContext<'bcx, 'tcx> {
ret
}
TempRef::Operand(Some(_)) => {
bug!("Lvalue temp already set");
let lvalue_ty = self.mir.lvalue_ty(bcx.tcx(), lvalue);
let lvalue_ty = bcx.monomorphize(&lvalue_ty);
// See comments in TempRef::new_operand as to why
// we always have Some in a ZST TempRef::Operand.
let ty = lvalue_ty.to_ty(bcx.tcx());
if common::type_is_zero_size(bcx.ccx(), ty) {
// Pass an undef pointer as no stores can actually occur.
let llptr = C_undef(type_of(bcx.ccx(), ty).ptr_to());
f(self, LvalueRef::new_sized(llptr, lvalue_ty))
} else {
bug!("Lvalue temp already set");
}
}
}
}

10
src/test/run-pass/mir_trans_calls.rs
View File

@ -138,6 +138,15 @@ fn test_fn_nil_call<F>(f: &F) -> i32
f()
}
#[rustc_mir]
fn test_fn_transmute_zst(x: ()) -> [(); 1] {
fn id<T>(x: T) -> T {x}
id(unsafe {
std::mem::transmute(x)
})
}
fn main() {
assert_eq!(test1(1, (2, 3), &[4, 5, 6]), (1, (2, 3), &[4, 5, 6][..]));
assert_eq!(test2(98), 98);
@ -159,4 +168,5 @@ fn main() {
assert_eq!(test_fn_direct_call(&closure, 100, 4), 324);
assert_eq!(test_fn_nil_call(&(|| 42)), 42);
assert_eq!(test_fn_transmute_zst(()), [()]);
}