[PATCH] D134705: [clang][DebugInfo] Emit debuginfo for non-constant case value

[Yonghong Song via Phabricator via cfe-commits]

yonghong-song created this revision.
yonghong-song added a reviewer: dblaikie.
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Currently, clang does not emit debuginfo for the switch stmt
case value if it is an enum value. For example,

  $ cat test.c
  enum { AA = 1, BB = 2 };
  int func1(int a) {
    switch(a) {
    case AA: return 10; 
    case BB: return 11; 
    default: break;
    }   
    return 0;
  }
  $ llvm-dwarfdump test.o | grep AA
  $

Note that gcc does emit debuginfo for the same test case.

This patch added such a support with similar implementation
to CodeGenFunction::EmitDeclRefExprDbgValue(). With this patch,

  $ clang -g -c test.c
  $ llvm-dwarfdump test.o | grep AA
                  DW_AT_name    ("AA")
  $   


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D134705

Files:
  clang/lib/CodeGen/CGStmt.cpp
  clang/test/CodeGen/debug-info-enum-case-val.c


Index: clang/test/CodeGen/debug-info-enum-case-val.c
===================================================================
--- /dev/null
+++ clang/test/CodeGen/debug-info-enum-case-val.c
@@ -0,0 +1,27 @@
+// RUN: %clang_cc1 -emit-llvm -debug-info-kind=limited %s -o - | FileCheck %s
+
+enum { A = 1, B = 2 };
+int func1(int a) {
+  switch(a) {
+  case A: return 10;
+  case B: return 11;
+  default: break;
+  }
+  return 0;
+}
+// CHECK:       !DIEnumerator(name: "A", value: 1)
+// CHECK-NEXT:  !DIEnumerator(name: "B", value: 2)
+
+enum { C = 1, D = 2 };
+typedef unsigned long long __t1;
+typedef __t1 __t2;
+int func2(__t2 a) {
+  switch(a) {
+  case C: return 10;
+  case D: return 11;
+  default: break;
+  }
+  return 0;
+}
+// CHECK:       !DIEnumerator(name: "C", value: 1)
+// CHECK-NEXT:  !DIEnumerator(name: "D", value: 2)
Index: clang/lib/CodeGen/CGStmt.cpp
===================================================================
--- clang/lib/CodeGen/CGStmt.cpp
+++ clang/lib/CodeGen/CGStmt.cpp
@@ -1509,6 +1509,21 @@
 
   llvm::ConstantInt *CaseVal =
     Builder.getInt(S.getLHS()->EvaluateKnownConstInt(getContext()));
+
+  // Emit debuginfo for the case value if it is an enum value.
+  const ConstantExpr *CE;
+  if (auto ICE = dyn_cast<ImplicitCastExpr>(S.getLHS()))
+    CE = dyn_cast<ConstantExpr>(ICE->getSubExpr());
+  else
+    CE = dyn_cast<ConstantExpr>(S.getLHS());
+  if (CE) {
+    if (auto DE = dyn_cast<DeclRefExpr>(CE->getSubExpr()))
+      if (CGDebugInfo *Dbg = getDebugInfo())
+        if (CGM.getCodeGenOpts().hasReducedDebugInfo())
+          Dbg->EmitGlobalVariable(DE->getDecl(),
+              APValue(llvm::APSInt(CaseVal->getValue())));
+  }
+
   if (SwitchLikelihood)
     SwitchLikelihood->push_back(Stmt::getLikelihood(Attrs));
 


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