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Rollup merge of #105578 - erikdesjardins:addrspacecast, r=bjorn3

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Fix transmutes between pointers in different address spaces (e.g. fn ptrs on AVR)

Currently, this causes a verifier error (https://godbolt.org/z/YYohed4bj), since it uses `bitcast`, which can't convert between address spaces.

Uncovered due to https://github.com/rust-lang/rust/pull/105545#discussion_r1045269309

r? `@bjorn3`
This commit is contained in:
Matthias Krüger 2022-12-14 17:17:57 +01:00 • committed by GitHub
commit ba71a63fde
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2 changed files with 32 additions and 5 deletions
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13
compiler/rustc_codegen_ssa/src/mir/block.rs
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@ -1802,15 +1802,20 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
match (src.layout.abi, dst.layout.abi) {
(abi::Abi::Scalar(src_scalar), abi::Abi::Scalar(dst_scalar)) => {
// HACK(eddyb) LLVM doesn't like `bitcast`s between pointers and non-pointers.
if (src_scalar.primitive() == abi::Pointer)
== (dst_scalar.primitive() == abi::Pointer)
{
let src_is_ptr = src_scalar.primitive() == abi::Pointer;
let dst_is_ptr = dst_scalar.primitive() == abi::Pointer;
if src_is_ptr == dst_is_ptr {
assert_eq!(src.layout.size, dst.layout.size);
// NOTE(eddyb) the `from_immediate` and `to_immediate_scalar`
// conversions allow handling `bool`s the same as `u8`s.
let src = bx.from_immediate(src.immediate());
let src_as_dst = bx.bitcast(src, bx.backend_type(dst.layout));
// LLVM also doesn't like `bitcast`s between pointers in different address spaces.
let src_as_dst = if src_is_ptr {
bx.pointercast(src, bx.backend_type(dst.layout))
} else {
bx.bitcast(src, bx.backend_type(dst.layout))
};
Immediate(bx.to_immediate_scalar(src_as_dst, dst_scalar)).store(bx, dst);
return;
}