[PATCH] D151393: [CodeGen] Make __clang_call_terminate have an unwind table entry

[Shoaib Meenai via Phabricator via cfe-commits]

smeenai created this revision.
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This enables debuggers to step past that frame on architectures that
don't use DWARF unwinding (such as armv7) even without debug info. The
problem should theoretically be architecture-agnostic, but according to
https://discourse.llvm.org/t/51633/2 it gets masked on architectures
that use DWARF unwind info.

Fixes https://github.com/llvm/llvm-project/issues/40696


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D151393

Files:
  clang/lib/CodeGen/ItaniumCXXABI.cpp
  clang/test/CodeGenCXX/clang-call-terminate.uwtable.cpp


Index: clang/test/CodeGenCXX/clang-call-terminate.uwtable.cpp
===================================================================
--- /dev/null
+++ clang/test/CodeGenCXX/clang-call-terminate.uwtable.cpp
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 -triple=x86_64-linux-gnu -fexceptions -fcxx-exceptions 
-emit-llvm -o - %s | \
+// RUN:   FileCheck --check-prefixes=CHECK,NOUNWIND %s
+// RUN: %clang_cc1 -triple=x86_64-linux-gnu -fexceptions -fcxx-exceptions 
-funwind-tables=1 -emit-llvm -o - %s | \
+// RUN:   FileCheck --check-prefixes=CHECK,SYNCUNWIND %s
+// RUN: %clang_cc1 -triple=x86_64-linux-gnu -fexceptions -fcxx-exceptions 
-funwind-tables=2 -emit-llvm -o - %s | \
+// RUN:   FileCheck --check-prefixes=CHECK,ASYNCUNWIND %s
+
+void caller(void callback()) noexcept { callback(); }
+
+// CHECK: define {{.*}}void @__clang_call_terminate({{[^)]*}}) #[[#ATTRNUM:]]
+// CHECK: attributes #[[#ATTRNUM]] = {
+// NOUNWIND-NOT: uwtable
+// NOUNWIND-SAME: }
+// SYNCUNWIND-SAME: uwtable(sync)
+// ASYNCUNWIND-SAME: uwtable{{ }}
Index: clang/lib/CodeGen/ItaniumCXXABI.cpp
===================================================================
--- clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -4692,6 +4692,11 @@
     fn->setDoesNotThrow();
     fn->setDoesNotReturn();
 
+    // Ensure stack traces can progress past this frame (e.g. for debuggers).
+    const CodeGenOptions &CodeGenOpts = CGM.getCodeGenOpts();
+    if (CodeGenOpts.UnwindTables)
+      fn->setUWTableKind(llvm::UWTableKind(CodeGenOpts.UnwindTables));
+
     // What we really want is to massively penalize inlining without
     // forbidding it completely.  The difference between that and
     // 'noinline' is negligible.



Index: clang/test/CodeGenCXX/clang-call-terminate.uwtable.cpp
===================================================================
--- /dev/null
+++ clang/test/CodeGenCXX/clang-call-terminate.uwtable.cpp
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 -triple=x86_64-linux-gnu -fexceptions -fcxx-exceptions -emit-llvm -o - %s | \
+// RUN:   FileCheck --check-prefixes=CHECK,NOUNWIND %s
+// RUN: %clang_cc1 -triple=x86_64-linux-gnu -fexceptions -fcxx-exceptions -funwind-tables=1 -emit-llvm -o - %s | \
+// RUN:   FileCheck --check-prefixes=CHECK,SYNCUNWIND %s
+// RUN: %clang_cc1 -triple=x86_64-linux-gnu -fexceptions -fcxx-exceptions -funwind-tables=2 -emit-llvm -o - %s | \
+// RUN:   FileCheck --check-prefixes=CHECK,ASYNCUNWIND %s
+
+void caller(void callback()) noexcept { callback(); }
+
+// CHECK: define {{.*}}void @__clang_call_terminate({{[^)]*}}) #[[#ATTRNUM:]]
+// CHECK: attributes #[[#ATTRNUM]] = {
+// NOUNWIND-NOT: uwtable
+// NOUNWIND-SAME: }
+// SYNCUNWIND-SAME: uwtable(sync)
+// ASYNCUNWIND-SAME: uwtable{{ }}
Index: clang/lib/CodeGen/ItaniumCXXABI.cpp
===================================================================
--- clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -4692,6 +4692,11 @@
     fn->setDoesNotThrow();
     fn->setDoesNotReturn();
 
+    // Ensure stack traces can progress past this frame (e.g. for debuggers).
+    const CodeGenOptions &CodeGenOpts = CGM.getCodeGenOpts();
+    if (CodeGenOpts.UnwindTables)
+      fn->setUWTableKind(llvm::UWTableKind(CodeGenOpts.UnwindTables));
+
     // What we really want is to massively penalize inlining without
     // forbidding it completely.  The difference between that and
     // 'noinline' is negligible.

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