implement unwinding abi's (RFC 2945)
### Changes
This commit implements unwind ABI's, specified in RFC 2945.
We adjust the `rustc_middle::ty::layout::fn_can_unwind` function,
used to compute whether or not a `FnAbi` object represents a
function that should be able to unwind when `panic=unwind` is in
use.
Changes are also made to
`rustc_mir_build::build::should_abort_on_panic` so that the
function ABI is used to determind whether it should abort, assuming
that the `panic=unwind` strategy is being used, and no explicit
unwind attribute was provided.
### Tests
Unit tests, checking that the behavior is correct for `C-unwind`,
`stdcall-unwind`, `system-unwind`, and `thiscall-unwind`, are
included. These alternative `unwind` ABI strings are specified in
RFC 2945, in the "_Other `unwind` ABI strings_" section.
Additionally, a test case is included to assert that the LLVM IR
generated for an external function defined with the `C-unwind` ABI
will be appropriately labeled with the `nounwind` LLVM attribute
when the `panic=abort` compilation flag is used.
### Ignore Directives
This commit uses `ignore-*` directives in two of our `*-unwind` ABI
test cases.
Specifically, the `stdcall-unwind` and `thiscall-unwind` test cases
ignore architectures that do not support `stdcall` and `thiscall`,
respectively.
These directives are cribbed from
`src/test/ui/c-variadic/variadic-ffi-1.rs` for `stdcall`, and
`src/test/ui/extern/extern-thiscall.rs` for `thiscall`.
2020-09-10 12:38:39 -05:00
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// compile-flags: -C opt-level=0
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2022-08-17 21:13:37 -05:00
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// Test that `nounwind` attributes are correctly applied to exported `system` and `system-unwind`
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implement unwinding abi's (RFC 2945)
### Changes
This commit implements unwind ABI's, specified in RFC 2945.
We adjust the `rustc_middle::ty::layout::fn_can_unwind` function,
used to compute whether or not a `FnAbi` object represents a
function that should be able to unwind when `panic=unwind` is in
use.
Changes are also made to
`rustc_mir_build::build::should_abort_on_panic` so that the
function ABI is used to determind whether it should abort, assuming
that the `panic=unwind` strategy is being used, and no explicit
unwind attribute was provided.
### Tests
Unit tests, checking that the behavior is correct for `C-unwind`,
`stdcall-unwind`, `system-unwind`, and `thiscall-unwind`, are
included. These alternative `unwind` ABI strings are specified in
RFC 2945, in the "_Other `unwind` ABI strings_" section.
Additionally, a test case is included to assert that the LLVM IR
generated for an external function defined with the `C-unwind` ABI
will be appropriately labeled with the `nounwind` LLVM attribute
when the `panic=abort` compilation flag is used.
### Ignore Directives
This commit uses `ignore-*` directives in two of our `*-unwind` ABI
test cases.
Specifically, the `stdcall-unwind` and `thiscall-unwind` test cases
ignore architectures that do not support `stdcall` and `thiscall`,
respectively.
These directives are cribbed from
`src/test/ui/c-variadic/variadic-ffi-1.rs` for `stdcall`, and
`src/test/ui/extern/extern-thiscall.rs` for `thiscall`.
2020-09-10 12:38:39 -05:00
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// extern functions. `system-unwind` functions MUST NOT have this attribute. We disable
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// optimizations above to prevent LLVM from inferring the attribute.
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#![crate_type = "lib"]
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#![feature(c_unwind)]
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// CHECK: @rust_item_that_cannot_unwind() unnamed_addr #0 {
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#[no_mangle]
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pub extern "system" fn rust_item_that_cannot_unwind() {
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}
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// CHECK: @rust_item_that_can_unwind() unnamed_addr #1 {
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#[no_mangle]
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pub extern "system-unwind" fn rust_item_that_can_unwind() {
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}
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// Now, make some assertions that the LLVM attributes for these functions are correct. First, make
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// sure that the first item is correctly marked with the `nounwind` attribute:
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//
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// CHECK: attributes #0 = { {{.*}}nounwind{{.*}} }
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//
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// Next, let's assert that the second item, which CAN unwind, does not have this attribute.
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//
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// CHECK: attributes #1 = {
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// CHECK-NOT: nounwind
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// CHECK: }
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