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Make dedup guard optional (#1215)

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This commit is contained in:
Hans Kratz
2021-09-20 18:19:05 +02:00
committed by GitHub
parent 504b0cf68b
commit 26cce19427
11 changed files with 645 additions and 618 deletions
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53
library/stdarch/crates/assert-instr-macro/src/lib.rs
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@@ -41,6 +41,10 @@ pub fn assert_instr(
// testing for.
let disable_assert_instr = std::env::var("STDARCH_DISABLE_ASSERT_INSTR").is_ok();
// Disable dedup guard. Only works if the LLVM MergeFunctions pass is disabled, e.g.
// with `-Z merge-functions=disabled` in RUSTFLAGS.
let disable_dedup_guard = std::env::var("STDARCH_DISABLE_DEDUP_GUARD").is_ok();
// If instruction tests are disabled avoid emitting this shim at all, just
// return the original item without our attribute.
if !cfg!(optimized) || disable_assert_instr {
@@ -128,27 +132,38 @@ pub fn assert_instr(
syn::LitStr::new("C", proc_macro2::Span::call_site())
};
let shim_name_str = format!("{}{}", shim_name, assert_name);
let to_test = quote! {
let to_test = if disable_dedup_guard {
quote! {
#attrs
#[no_mangle]
#[inline(never)]
pub unsafe extern #abi fn #shim_name(#(#inputs),*) #ret {
#name::<#(#const_vals),*>(#(#input_vals),*)
}
}
} else {
quote! {
const #shim_name_ptr : *const u8 = #shim_name_str.as_ptr();
const #shim_name_ptr : *const u8 = #shim_name_str.as_ptr();
#attrs
#[no_mangle]
#[inline(never)]
pub unsafe extern #abi fn #shim_name(#(#inputs),*) #ret {
// The compiler in optimized mode by default runs a pass called
// "mergefunc" where it'll merge functions that look identical.
// Turns out some intrinsics produce identical code and they're
// folded together, meaning that one just jumps to another. This
// messes up our inspection of the disassembly of this function and
// we're not a huge fan of that.
//
// To thwart this pass and prevent functions from being merged we
// generate some code that's hopefully very tight in terms of
// codegen but is otherwise unique to prevent code from being
// folded.
::stdarch_test::_DONT_DEDUP = #shim_name_ptr;
#name::<#(#const_vals),*>(#(#input_vals),*)
#attrs
#[no_mangle]
#[inline(never)]
pub unsafe extern #abi fn #shim_name(#(#inputs),*) #ret {
// The compiler in optimized mode by default runs a pass called
// "mergefunc" where it'll merge functions that look identical.
// Turns out some intrinsics produce identical code and they're
// folded together, meaning that one just jumps to another. This
// messes up our inspection of the disassembly of this function and
// we're not a huge fan of that.
//
// To thwart this pass and prevent functions from being merged we
// generate some code that's hopefully very tight in terms of
// codegen but is otherwise unique to prevent code from being
// folded.
::stdarch_test::_DONT_DEDUP = #shim_name_ptr;
#name::<#(#const_vals),*>(#(#input_vals),*)
}
}
};