https://github.com/tru updated https://github.com/llvm/llvm-project/pull/156664
>From b4274c3bc8eee764ad048c77b9a4baa12eb708a0 Mon Sep 17 00:00:00 2001
From: David Blaikie <dblai...@gmail.com>
Date: Tue, 2 Sep 2025 14:03:58 -0700
Subject: [PATCH] [DebugInfo] When referencing structured bindings use the
reference's location, not the binding's declaration's location (#153637)
For structured bindings that use custom `get` specializations, the
resulting LLVM IR ascribes the load of the result of `get` to the
binding's declaration, rather than the place where the binding is
referenced - this caused awkward sequencing in the debug info where,
when stepping through the code you'd step back to the binding
declaration every time there was a reference to the binding.
To fix that - when we cross into IRGening a binding - suppress the debug
info location of that subexpression.
I don't represent this as a great bit of API design - certainly open to
ideas, but putting it out here as a place to start.
It's /possible/ this is an incomplete fix, even - if the binding decl
had other subexpressions, those would still get their location applied &
it'd likely be wrong.
So maybe that's a direction to go with to productionize this - add a new
location scoped device that suppresses any overriding - this might be
more robust. How do people feel about that?
(cherry picked from commit 665e875f1a86be650e044bb20744bb272d03e11d)
---
clang/lib/CodeGen/CGCall.cpp | 26 +++++------
clang/lib/CodeGen/CGCall.h | 6 +++
clang/lib/CodeGen/CGExpr.cpp | 9 +++-
.../debug-info-structured-binding.cpp | 44 ++++++++++++++++++-
4 files changed, 69 insertions(+), 16 deletions(-)
diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index c8c3d6b20c496..5344a9710d642 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -4787,19 +4787,6 @@ struct DestroyUnpassedArg final : EHScopeStack::Cleanup {
}
};
-struct DisableDebugLocationUpdates {
- CodeGenFunction &CGF;
- bool disabledDebugInfo;
- DisableDebugLocationUpdates(CodeGenFunction &CGF, const Expr *E) : CGF(CGF) {
- if ((disabledDebugInfo = isa<CXXDefaultArgExpr>(E) && CGF.getDebugInfo()))
- CGF.disableDebugInfo();
- }
- ~DisableDebugLocationUpdates() {
- if (disabledDebugInfo)
- CGF.enableDebugInfo();
- }
-};
-
} // end anonymous namespace
RValue CallArg::getRValue(CodeGenFunction &CGF) const {
@@ -4836,7 +4823,9 @@ void CodeGenFunction::EmitWritebacks(const CallArgList
&args) {
void CodeGenFunction::EmitCallArg(CallArgList &args, const Expr *E,
QualType type) {
- DisableDebugLocationUpdates Dis(*this, E);
+ std::optional<DisableDebugLocationUpdates> Dis;
+ if (isa<CXXDefaultArgExpr>(E))
+ Dis.emplace(*this);
if (const ObjCIndirectCopyRestoreExpr *CRE =
dyn_cast<ObjCIndirectCopyRestoreExpr>(E)) {
assert(getLangOpts().ObjCAutoRefCount);
@@ -6229,3 +6218,12 @@ RValue CodeGenFunction::EmitVAArg(VAArgExpr *VE, Address
&VAListAddr,
return CGM.getABIInfo().EmitMSVAArg(*this, VAListAddr, Ty, Slot);
return CGM.getABIInfo().EmitVAArg(*this, VAListAddr, Ty, Slot);
}
+
+DisableDebugLocationUpdates::DisableDebugLocationUpdates(CodeGenFunction &CGF)
+ : CGF(CGF) {
+ CGF.disableDebugInfo();
+}
+
+DisableDebugLocationUpdates::~DisableDebugLocationUpdates() {
+ CGF.enableDebugInfo();
+}
diff --git a/clang/lib/CodeGen/CGCall.h b/clang/lib/CodeGen/CGCall.h
index 0b4e3f9cb0365..17b2ce558f711 100644
--- a/clang/lib/CodeGen/CGCall.h
+++ b/clang/lib/CodeGen/CGCall.h
@@ -457,6 +457,12 @@ inline FnInfoOpts &operator&=(FnInfoOpts &A, FnInfoOpts B)
{
return A;
}
+struct DisableDebugLocationUpdates {
+ CodeGenFunction &CGF;
+ DisableDebugLocationUpdates(CodeGenFunction &CGF);
+ ~DisableDebugLocationUpdates();
+};
+
} // end namespace CodeGen
} // end namespace clang
diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index 85c768807572f..b5debd93b0f61 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -3314,7 +3314,14 @@ LValue CodeGenFunction::EmitDeclRefLValue(const
DeclRefExpr *E) {
auto *FD = LambdaCaptureFields.lookup(BD);
return EmitCapturedFieldLValue(*this, FD, CXXABIThisValue);
}
- return EmitLValue(BD->getBinding());
+ // Suppress debug location updates when visiting the binding, since the
+ // binding may emit instructions that would otherwise be associated with
the
+ // binding itself, rather than the expression referencing the binding.
(this
+ // leads to jumpy debug stepping behavior where the location/debugger jump
+ // back to the binding declaration, then back to the expression referencing
+ // the binding)
+ DisableDebugLocationUpdates D(*this);
+ return EmitLValue(BD->getBinding(), NotKnownNonNull);
}
// We can form DeclRefExprs naming GUID declarations when reconstituting
diff --git a/clang/test/CodeGenCXX/debug-info-structured-binding.cpp
b/clang/test/CodeGenCXX/debug-info-structured-binding.cpp
index 5fbd54c16382c..4a4a4d8bdfaad 100644
--- a/clang/test/CodeGenCXX/debug-info-structured-binding.cpp
+++ b/clang/test/CodeGenCXX/debug-info-structured-binding.cpp
@@ -7,6 +7,12 @@
// CHECK: #dbg_declare(ptr %{{[0-9]+}}, ![[VAR_4:[0-9]+]],
!DIExpression(DW_OP_deref, DW_OP_plus_uconst, 4),
// CHECK: #dbg_declare(ptr %z1, ![[VAR_5:[0-9]+]], !DIExpression()
// CHECK: #dbg_declare(ptr %z2, ![[VAR_6:[0-9]+]], !DIExpression()
+// CHECK: getelementptr inbounds nuw %struct.A, ptr {{.*}}, i32 0, i32 1, !dbg
![[Y1_DEBUG_LOC:[0-9]+]]
+// CHECK: getelementptr inbounds nuw %struct.A, ptr {{.*}}, i32 0, i32 1, !dbg
![[Y2_DEBUG_LOC:[0-9]+]]
+// CHECK: load ptr, ptr %z2, {{.*}}!dbg ![[Z2_DEBUG_LOC:[0-9]+]]
+// CHECK: getelementptr inbounds [2 x i32], ptr {{.*}}, i64 0, i64 1, !dbg
![[A2_DEBUG_LOC:[0-9]+]]
+// CHECK: getelementptr inbounds nuw { i32, i32 }, ptr {{.*}}, i32 0, i32 1,
!dbg ![[C2_DEBUG_LOC:[0-9]+]]
+// CHECK: extractelement <2 x i32> {{.*}}, i32 1, !dbg ![[V2_DEBUG_LOC:[0-9]+]]
// CHECK: ![[VAR_0]] = !DILocalVariable(name: "a"
// CHECK: ![[VAR_1]] = !DILocalVariable(name: "x1", scope: !{{[0-9]+}}, file:
!{{[0-9]+}}, line: {{[0-9]+}}, type: !{{[0-9]+}})
// CHECK: ![[VAR_2]] = !DILocalVariable(name: "y1", scope: !{{[0-9]+}}, file:
!{{[0-9]+}}, line: {{[0-9]+}}, type: !{{[0-9]+}})
@@ -46,5 +52,41 @@ int f() {
auto [x1, y1] = a;
auto &[x2, y2] = a;
auto [z1, z2] = B{1, 2};
- return x1 + y1 + x2 + y2 + z1 + z2;
+ int array[2] = {3, 4};
+ auto &[a1, a2] = array;
+ _Complex int cmplx = {1, 2};
+ auto &[c1, c2] = cmplx;
+ int vctr __attribute__ ((vector_size (sizeof(int)*2)))= {1, 2};
+ auto &[v1, v2] = vctr;
+ return //
+ x1 //
+ + //
+// CHECK: ![[Y1_DEBUG_LOC]] = !DILocation(line: [[@LINE+1]]
+ y1 //
+ + //
+ x2 //
+ + //
+// CHECK: ![[Y2_DEBUG_LOC]] = !DILocation(line: [[@LINE+1]]
+ y2 //
+ + //
+ z1 //
+ + //
+// CHECK: ![[Z2_DEBUG_LOC]] = !DILocation(line: [[@LINE+1]]
+ z2 //
+ + //
+ a1 //
+ + //
+// CHECK: ![[A2_DEBUG_LOC]] = !DILocation(line: [[@LINE+1]]
+ a2 //
+ + //
+ c1 //
+ + //
+// CHECK: ![[C2_DEBUG_LOC]] = !DILocation(line: [[@LINE+1]]
+ c2 //
+ + //
+ v1 //
+ + //
+// CHECK: ![[V2_DEBUG_LOC]] = !DILocation(line: [[@LINE+1]]
+ v2 //
+ ;
}
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