0473a4f1d8
Initially MIR differentiated between arguments and locals, which introduced a need to add extra copies assigning the argument to a local, even for simple bindings. This differentiation no longer exists, but we're still creating those copies, bloating the MIR and LLVM IR we emit. Additionally, the current approach means that we create debug info for both the incoming argument (marking it as an argument), and then immediately shadow it a local that goes by the same name. This can be confusing when using e.g. "info args" in gdb, or when e.g. a debugger with a GUI displays the function arguments separately from the local variables, especially when the binding is mutable, because the argument doesn't change, while the local variable does.
48 lines
1.7 KiB
Rust
48 lines
1.7 KiB
Rust
// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// compile-flags: -C no-prepopulate-passes
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#![crate_type = "lib"]
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pub struct Bytes {
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a: u8,
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b: u8,
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c: u8,
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d: u8,
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}
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// CHECK-LABEL: small_array_alignment
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// The array is stored as i32, but its alignment is lower, go with 1 byte to avoid target
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// dependent alignment
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#[no_mangle]
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pub fn small_array_alignment(x: &mut [i8; 4], y: [i8; 4]) {
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// CHECK: [[TMP:%.+]] = alloca i32
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// CHECK: %y = alloca [4 x i8]
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// CHECK: store i32 %0, i32* [[TMP]]
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// CHECK: [[Y8:%[0-9]+]] = bitcast [4 x i8]* %y to i8*
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// CHECK: [[TMP8:%[0-9]+]] = bitcast i32* [[TMP]] to i8*
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// CHECK: call void @llvm.memcpy.{{.*}}(i8* [[Y8]], i8* [[TMP8]], i{{[0-9]+}} 4, i32 1, i1 false)
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*x = y;
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}
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// CHECK-LABEL: small_struct_alignment
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// The struct is stored as i32, but its alignment is lower, go with 1 byte to avoid target
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// dependent alignment
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#[no_mangle]
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pub fn small_struct_alignment(x: &mut Bytes, y: Bytes) {
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// CHECK: [[TMP:%.+]] = alloca i32
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// CHECK: %y = alloca %Bytes
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// CHECK: store i32 %0, i32* [[TMP]]
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// CHECK: [[Y8:%[0-9]+]] = bitcast %Bytes* %y to i8*
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// CHECK: [[TMP8:%[0-9]+]] = bitcast i32* [[TMP]] to i8*
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// CHECK: call void @llvm.memcpy.{{.*}}(i8* [[Y8]], i8* [[TMP8]], i{{[0-9]+}} 4, i32 1, i1 false)
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*x = y;
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}
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