Fix debuginfo for ScalarPair abi parameters

Mark all of these as locals so the debugger does not try to interpret them as being a pointer to the value. This extends the approach used in PR rust-lang#81898.
wesleywiser · Sep 7, 2021 · 68af337 · 68af337
1 parent baf5ea1
commit 68af337
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Showing 2 changed files with 18 additions and 22 deletions.
diff --git a/compiler/rustc_codegen_ssa/src/mir/debuginfo.rs b/compiler/rustc_codegen_ssa/src/mir/debuginfo.rs
@@ -3,9 +3,11 @@ use rustc_index::vec::IndexVec;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::mir;
 use rustc_middle::ty;
+use rustc_middle::ty::layout::LayoutOf;
 use rustc_session::config::DebugInfo;
 use rustc_span::symbol::{kw, Symbol};
 use rustc_span::{BytePos, Span};
+use rustc_target::abi::Abi;
 use rustc_target::abi::Size;
 
 use super::operand::{OperandRef, OperandValue};
@@ -368,21 +370,14 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         {
                             let arg_index = place.local.index() - 1;
                             if target_is_msvc {
-                                // Rust compiler decomposes every &str or slice argument into two components:
-                                // a pointer to the memory address where the data is stored and a usize representing
-                                // the length of the str (or slice). These components will later be used to reconstruct
-                                // the original argument inside the body of the function that owns it (see the
-                                // definition of debug_introduce_local for more details).
-                                //
-                                // Since the original argument is declared inside a function rather than being passed
-                                // in as an argument, it must be marked as a LocalVariable for MSVC debuggers to visualize
-                                // its data correctly. (See issue #81894 for an in-depth description of the problem).
-                                match *var_ty.kind() {
-                                    ty::Ref(_, inner_type, _) => match *inner_type.kind() {
-                                        ty::Slice(_) | ty::Str => VariableKind::LocalVariable,
-                                        _ => VariableKind::ArgumentVariable(arg_index + 1),
-                                    },
-                                    _ => VariableKind::ArgumentVariable(arg_index + 1),
+                                // ScalarPair parameters are spilled to the stack so they need to
+                                // be marked as a `LocalVariable` for MSVC debuggers to visualize
+                                // their data correctly. (See #81894 & #88625)
+                                let var_ty_layout = self.cx.layout_of(var_ty);
+                                if let Abi::ScalarPair(_, _) = var_ty_layout.abi {
+                                    VariableKind::LocalVariable
+                                } else {
+                                    VariableKind::ArgumentVariable(arg_index + 1)
                                 }
                             } else {
                                 // FIXME(eddyb) shouldn't `ArgumentVariable` indices be

diff --git a/src/test/debuginfo/msvc-scalarpair-params.rs b/src/test/debuginfo/msvc-scalarpair-params.rs
@@ -6,14 +6,14 @@
 // cdb-command: dx r1
 // cdb-check:r1               : (0xa..0xc) [Type: core::ops::range::Range<u32>]
 // cdb-command: dx r2
-// cdb-check:r2               : 0x14 [Type: core::ops::range::Range<u64> *]
+// cdb-check:r2               : (0x14..0x1e) [Type: core::ops::range::Range<u64>]
 
 // cdb-command: g
 
 // cdb-command: dx r1
 // cdb-check:r1               : (0x9..0x64) [Type: core::ops::range::Range<u32>]
 // cdb-command: dx r2
-// cdb-check:r2               : 0xc [Type: core::ops::range::Range<u64> *]
+// cdb-check:r2               : (0xc..0x5a) [Type: core::ops::range::Range<u64>]
 
 // cdb-command: g
 
@@ -22,8 +22,9 @@
 // cdb-check:    [variant]        : Some
 // cdb-check:    [+0x004] __0              : 0x4d2 [Type: [...]]
 // cdb-command: dx o2
-// cdb-check:o2               : 0x1 [Type: enum$<core::option::Option<u64> > *]
-// cdb-check:    [variant]
+// cdb-check:o2               : Some [Type: enum$<core::option::Option<u64> >]
+// cdb-check:    [variant]        : Some
+// cdb-check:    [+0x008] __0              : 0x162e [Type: unsigned __int64]
 
 // cdb-command: g
 
@@ -32,9 +33,9 @@
 // cdb-check:    [0]              : 0xa [Type: unsigned int]
 // cdb-check:    [1]              : 0x14 [Type: unsigned int]
 // cdb-command: dx t2
-// cdb-check:t2               : 0x1e [Type: tuple$<u64,u64> *]
-// cdb-check:    [0]              : Unable to read memory at Address 0x1e
-// cdb-check:    [1]              : Unable to read memory at Address 0x26
+// cdb-check:t2               : (0x1e, 0x28) [Type: tuple$<u64,u64>]
+// cdb-check:    [0]              : 0x1e [Type: unsigned __int64]
+// cdb-check:    [1]              : 0x28 [Type: unsigned __int64]
 
 // cdb-command: g