[clang] [CIR] Fix a crash when source location is unknown (PR #185059)
Andy Kaylor via cfe-commits
cfe-commits at lists.llvm.org
Fri Mar 6 09:40:08 PST 2026
https://github.com/andykaylor created https://github.com/llvm/llvm-project/pull/185059
When we call `getLoc()` with an invalid `SourceLocation` and `currSrcLoc` is also invalid, we were crashing or asserting. I tracked down one case where this was happening (generating an argument in a vtable thunk) and fixed that to provide a location. I also am updating the `getLoc()` implementation so that it will use an unknown location in release builds rather than crashing because the location isn't critical for correct compilation.
>From 6269662dca4d5b3328a13aaddc2a1fbbb08e7b20 Mon Sep 17 00:00:00 2001
From: Andy Kaylor <akaylor at nvidia.com>
Date: Fri, 6 Mar 2026 09:29:16 -0800
Subject: [PATCH] [CIR] Fix a crash when source location is unknown
When we call `getLoc()` with an invalid `SourceLocation` and
`currSrcLoc` is also invalid, we were crashing or asserting. I tracked
down one case where this was happening (generating an argument in a
vtable thunk) and fixed that to provide a location. I also am updating
the `getLoc()` implementation so that it will use an unknown location
in release builds rather than crashing because the location isn't critical
for correct compilation.
---
clang/lib/CIR/CodeGen/CIRGenFunction.cpp | 16 ++++--
clang/lib/CIR/CodeGen/CIRGenVTables.cpp | 4 +-
clang/test/CIR/CodeGen/thunks.cpp | 64 ++++++++++++++++++++++++
3 files changed, 78 insertions(+), 6 deletions(-)
diff --git a/clang/lib/CIR/CodeGen/CIRGenFunction.cpp b/clang/lib/CIR/CodeGen/CIRGenFunction.cpp
index c64630db08965..71a647e37ea52 100644
--- a/clang/lib/CIR/CodeGen/CIRGenFunction.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenFunction.cpp
@@ -113,9 +113,14 @@ mlir::Location CIRGenFunction::getLoc(SourceLocation srcLoc) {
return mlir::FileLineColLoc::get(builder.getStringAttr(filename),
pLoc.getLine(), pLoc.getColumn());
}
- // Do our best...
+ // We expect to have a currSrcLoc set, so we assert here, but it isn't
+ // critical for the correctness of compilation, so in non-assert builds
+ // we fallback on using an unknown location.
assert(currSrcLoc && "expected to inherit some source location");
- return *currSrcLoc;
+ if (currSrcLoc)
+ return *currSrcLoc;
+ // We're brave, but time to give up.
+ return builder.getUnknownLoc();
}
mlir::Location CIRGenFunction::getLoc(SourceRange srcLoc) {
@@ -128,9 +133,12 @@ mlir::Location CIRGenFunction::getLoc(SourceRange srcLoc) {
mlir::Attribute metadata;
return mlir::FusedLoc::get(locs, metadata, &getMLIRContext());
}
- if (currSrcLoc) {
+ // We expect to have a currSrcLoc set, so we assert here, but it isn't
+ // critical for the correctness of compilation, so in non-assert builds
+ // we fallback on using an unknown location.
+ assert(currSrcLoc && "expected to inherit some source location");
+ if (currSrcLoc)
return *currSrcLoc;
- }
// We're brave, but time to give up.
return builder.getUnknownLoc();
}
diff --git a/clang/lib/CIR/CodeGen/CIRGenVTables.cpp b/clang/lib/CIR/CodeGen/CIRGenVTables.cpp
index 1453765cc3078..00f3adfb1757f 100644
--- a/clang/lib/CIR/CodeGen/CIRGenVTables.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenVTables.cpp
@@ -766,8 +766,8 @@ void CIRGenFunction::generateThunk(cir::FuncOp fn,
// Create lexical scope - must stay alive for entire thunk generation.
// startFunction() requires currLexScope to be set.
- mlir::Location unknownLoc = builder.getUnknownLoc();
- LexicalScope lexScope{*this, unknownLoc, entryBb};
+ SourceLocRAIIObject locRAII(*this, fn.getLoc());
+ LexicalScope lexScope{*this, fn.getLoc(), entryBb};
startThunk(fn, gd, fnInfo, isUnprototyped);
assert(!cir::MissingFeatures::generateDebugInfo());
diff --git a/clang/test/CIR/CodeGen/thunks.cpp b/clang/test/CIR/CodeGen/thunks.cpp
index 5a27eb373746d..15c4810738420 100644
--- a/clang/test/CIR/CodeGen/thunks.cpp
+++ b/clang/test/CIR/CodeGen/thunks.cpp
@@ -69,6 +69,28 @@ D::~D() {}
} // namespace Test3
+namespace Test4 {
+// Non-virtual this-adjusting thunk for a method with a by-value parameter.
+// This exercises the case where emitDelegateCallArg is called with an invalid
+// SourceLocation during thunk generation, which requires getLoc to handle
+// a null currSrcLoc gracefully.
+
+struct A {
+ virtual void f();
+};
+
+struct B {
+ virtual void g(int x);
+};
+
+struct C : A, B {
+ void g(int x) override;
+};
+
+void C::g(int x) {}
+
+} // namespace Test4
+
// In CIR, all globals are emitted before functions.
// Test1 vtable: C's vtable references the thunk for B's entry.
@@ -81,6 +103,11 @@ D::~D() {}
// CIR-DAG: #cir.global_view<@_ZN5Test21C1gEv> : !cir.ptr<!u8i>
// CIR-DAG: #cir.global_view<@_ZThn8_N5Test21C1gEv> : !cir.ptr<!u8i>
+// Test4 vtable: C's vtable references the thunk for B's entry.
+// CIR-DAG: cir.global "private" external @_ZTVN5Test41CE = #cir.vtable<{
+// CIR-DAG: #cir.global_view<@_ZN5Test41C1gEi> : !cir.ptr<!u8i>
+// CIR-DAG: #cir.global_view<@_ZThn8_N5Test41C1gEi> : !cir.ptr<!u8i>
+
// Test3 vtable: D's vtable references D1, D0, and their thunks.
// CIR-DAG: cir.global "private" external @_ZTVN5Test31DE = #cir.vtable<{
// CIR-DAG: #cir.global_view<@_ZN5Test31DD1Ev> : !cir.ptr<!u8i>
@@ -141,6 +168,21 @@ D::~D() {}
// CIR: cir.call @_ZN5Test31DD0Ev(%[[T3B_RESULT]])
// CIR: cir.return
+// --- Test4: by-value parameter thunk ---
+
+// CIR: cir.func {{.*}} @_ZN5Test41C1gEi
+
+// The thunk adjusts 'this' by -8 bytes, forwards the int arg, and calls C::g().
+// CIR: cir.func {{.*}} @_ZThn8_N5Test41C1gEi(%arg0: !cir.ptr<
+// CIR: %[[T4_THIS:.*]] = cir.load
+// CIR: %[[T4_CAST:.*]] = cir.cast bitcast %[[T4_THIS]] : !cir.ptr<{{.*}}> -> !cir.ptr<!u8i>
+// CIR: %[[T4_OFFSET:.*]] = cir.const #cir.int<-8> : !s64i
+// CIR: %[[T4_ADJUSTED:.*]] = cir.ptr_stride %[[T4_CAST]], %[[T4_OFFSET]] : (!cir.ptr<!u8i>, !s64i) -> !cir.ptr<!u8i>
+// CIR: %[[T4_RESULT:.*]] = cir.cast bitcast %[[T4_ADJUSTED]] : !cir.ptr<!u8i> -> !cir.ptr<
+// CIR: %[[T4_ARG:.*]] = cir.load
+// CIR: cir.call @_ZN5Test41C1gEi(%[[T4_RESULT]], %[[T4_ARG]])
+// CIR: cir.return
+
// --- LLVM checks ---
// LLVM: @_ZTVN5Test11CE = global { [3 x ptr], [3 x ptr] } {
@@ -158,6 +200,11 @@ D::~D() {}
// LLVM-SAME: [4 x ptr] [ptr inttoptr (i64 -8 to ptr), ptr null, ptr @_ZThn8_N5Test31DD1Ev, ptr @_ZThn8_N5Test31DD0Ev]
// LLVM-SAME: }
+// LLVM: @_ZTVN5Test41CE = global { [4 x ptr], [3 x ptr] } {
+// LLVM-SAME: [4 x ptr] [ptr null, ptr null, ptr @_ZN5Test41A1fEv, ptr @_ZN5Test41C1gEi],
+// LLVM-SAME: [3 x ptr] [ptr inttoptr (i64 -8 to ptr), ptr null, ptr @_ZThn8_N5Test41C1gEi]
+// LLVM-SAME: }
+
// LLVM: define {{.*}} void @_ZThn8_N5Test11C1fEv(ptr{{.*}})
// LLVM: %[[L1_THIS:.*]] = load ptr, ptr
// LLVM: %[[L1_ADJ:.*]] = getelementptr i8, ptr %[[L1_THIS]], i64 -8
@@ -178,6 +225,12 @@ D::~D() {}
// LLVM: %[[L3B_ADJ:.*]] = getelementptr i8, ptr %[[L3B_THIS]], i64 -8
// LLVM: call void @_ZN5Test31DD0Ev(ptr{{.*}} %[[L3B_ADJ]])
+// LLVM: define {{.*}} void @_ZThn8_N5Test41C1gEi(ptr{{.*}}, i32{{.*}})
+// LLVM: %[[L4_THIS:.*]] = load ptr, ptr
+// LLVM: %[[L4_ADJ:.*]] = getelementptr i8, ptr %[[L4_THIS]], i64 -8
+// LLVM: %[[L4_ARG:.*]] = load i32, ptr
+// LLVM: call void @_ZN5Test41C1gEi(ptr{{.*}} %[[L4_ADJ]], i32{{.*}} %[[L4_ARG]])
+
// --- OGCG checks ---
// OGCG: @_ZTVN5Test11CE = unnamed_addr constant { [3 x ptr], [3 x ptr] } {
@@ -195,6 +248,11 @@ D::~D() {}
// OGCG-SAME: [4 x ptr] [ptr inttoptr (i64 -8 to ptr), ptr null, ptr @_ZThn8_N5Test31DD1Ev, ptr @_ZThn8_N5Test31DD0Ev]
// OGCG-SAME: }
+// OGCG: @_ZTVN5Test41CE = unnamed_addr constant { [4 x ptr], [3 x ptr] } {
+// OGCG-SAME: [4 x ptr] [ptr null, ptr null, ptr @_ZN5Test41A1fEv, ptr @_ZN5Test41C1gEi],
+// OGCG-SAME: [3 x ptr] [ptr inttoptr (i64 -8 to ptr), ptr null, ptr @_ZThn8_N5Test41C1gEi]
+// OGCG-SAME: }
+
// OGCG: define {{.*}} void @_ZThn8_N5Test11C1fEv(ptr{{.*}})
// OGCG: %[[O1_THIS:.*]] = load ptr, ptr
// OGCG: %[[O1_ADJ:.*]] = getelementptr inbounds i8, ptr %[[O1_THIS]], i64 -8
@@ -214,3 +272,9 @@ D::~D() {}
// OGCG: %[[O3B_THIS:.*]] = load ptr, ptr
// OGCG: %[[O3B_ADJ:.*]] = getelementptr inbounds i8, ptr %[[O3B_THIS]], i64 -8
// OGCG: call void @_ZN5Test31DD0Ev(ptr{{.*}} %[[O3B_ADJ]])
+
+// OGCG: define {{.*}} void @_ZThn8_N5Test41C1gEi(ptr{{.*}}, i32{{.*}})
+// OGCG: %[[O4_THIS:.*]] = load ptr, ptr
+// OGCG: %[[O4_ADJ:.*]] = getelementptr inbounds i8, ptr %[[O4_THIS]], i64 -8
+// OGCG: %[[O4_ARG:.*]] = load i32, ptr
+// OGCG: {{.*}}call void @_ZN5Test41C1gEi(ptr{{.*}} %[[O4_ADJ]], i32{{.*}} %[[O4_ARG]])
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