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Rollup merge of #136640 - Zalathar:debuginfo-align-bits, r=compiler-errors

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Debuginfo for function ZSTs should have alignment of 8 bits, not 1 bit

In #116096, function ZSTs were made to have debuginfo that gives them an alignment of “1”. But because alignment in LLVM debuginfo is denoted in *bits*, not bytes, this resulted in an alignment specification of 1 bit instead of 1 byte.

I don't know whether this has any practical consequences, but I noticed that a test started failing when I accidentally fixed the mistake while working on #136632, so I extracted the fix (and the test adjustment) to this PR.
This commit is contained in:
Matthias Krüger 2025-02-08 03:58:45 +01:00 • committed by GitHub
commit 93b194516a
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GPG key ID: B5690EEEBB952194
3 changed files with 10 additions and 11 deletions
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11
compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
View file

@ -319,19 +319,16 @@ fn build_subroutine_type_di_node<'ll, 'tcx>(
// This is actually a function pointer, so wrap it in pointer DI. // This is actually a function pointer, so wrap it in pointer DI.
let name = compute_debuginfo_type_name(cx.tcx, fn_ty, false); let name = compute_debuginfo_type_name(cx.tcx, fn_ty, false);
let (size, align) = match fn_ty.kind() { let (size, align) = match fn_ty.kind() {
ty::FnDef(..) => (0, 1), ty::FnDef(..) => (Size::ZERO, Align::ONE),
ty::FnPtr(..) => ( ty::FnPtr(..) => (cx.tcx.data_layout.pointer_size, cx.tcx.data_layout.pointer_align.abi),
cx.tcx.data_layout.pointer_size.bits(),
cx.tcx.data_layout.pointer_align.abi.bits() as u32,
),
_ => unreachable!(), _ => unreachable!(),
}; };
let di_node = unsafe { let di_node = unsafe {
llvm::LLVMRustDIBuilderCreatePointerType( llvm::LLVMRustDIBuilderCreatePointerType(
DIB(cx), DIB(cx),
fn_di_node, fn_di_node,
size, size.bits(),
align, align.bits() as u32,
0, // Ignore DWARF address space. 0, // Ignore DWARF address space.
name.as_c_char_ptr(), name.as_c_char_ptr(),
name.len(), name.len(),

2
compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
View file

@ -633,7 +633,7 @@ impl<'ll, 'tcx> DebugInfoCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
true, true,
DIFlags::FlagZero, DIFlags::FlagZero,
argument_index, argument_index,
align.bytes() as u32, align.bits() as u32,
) )
} }
} }

8
tests/codegen/debug-fndef-size.rs
View file

@ -1,4 +1,6 @@
// Verify that `i32::cmp` FnDef type is declared with size 0 and align 1 in LLVM debuginfo. // Verify that `i32::cmp` FnDef type is declared with a size of 0 and an
// alignment of 8 bits (1 byte) in LLVM debuginfo.
//@ compile-flags: -O -g -Cno-prepopulate-passes //@ compile-flags: -O -g -Cno-prepopulate-passes
//@ ignore-msvc the types are mangled differently //@ ignore-msvc the types are mangled differently
@ -14,5 +16,5 @@ pub fn main() {
// CHECK: %compare.dbg.spill = alloca [0 x i8], align 1 // CHECK: %compare.dbg.spill = alloca [0 x i8], align 1
// CHECK: dbg{{.}}declare({{(metadata )?}}ptr %compare.dbg.spill, {{(metadata )?}}![[VAR:.*]], {{(metadata )?}}!DIExpression() // CHECK: dbg{{.}}declare({{(metadata )?}}ptr %compare.dbg.spill, {{(metadata )?}}![[VAR:.*]], {{(metadata )?}}!DIExpression()
// CHECK: ![[TYPE:.*]] = !DIDerivedType(tag: DW_TAG_pointer_type, name: "fn(&i32, &i32) -> core::cmp::Ordering", baseType: !{{.*}}, align: 1, dwarfAddressSpace: {{.*}}) // CHECK: ![[TYPE:.*]] = !DIDerivedType(tag: DW_TAG_pointer_type, name: "fn(&i32, &i32) -> core::cmp::Ordering", baseType: !{{.*}}, align: 8, dwarfAddressSpace: {{.*}})
// CHECK: ![[VAR]] = !DILocalVariable(name: "compare", scope: !{{.*}}, file: !{{.*}}, line: {{.*}}, type: ![[TYPE]], align: 1) // CHECK: ![[VAR]] = !DILocalVariable(name: "compare", scope: !{{.*}}, file: !{{.*}}, line: {{.*}}, type: ![[TYPE]], align: 8)