[AsmPrinter][DwarfDebug] Skip vars with fragments in different location kinds

The AsmPrinter currently assumes that a Debug Variable will have all of its
fragments with the same "kind" of location (i.e. all in the stack or all in
entry values). This is not enforced by the verifier, so it needs to be handled
properly. Until we do so, we conservatively drop one of the fragments.

Differential Revision: https://reviews.llvm.org/D159468

Author: felipepiovezan

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -1546,12 +1546,27 @@ void DwarfDebug::collectVariableInfoFromMFTable(
 
     ensureAbstractEntityIsCreatedIfScoped(TheCU, Var.first, Scope->getScopeNode());
 
-    if (DbgVariable *DbgVar = MFVars.lookup(Var)) {
-      if (auto *MMI = std::get_if<Loc::MMI>(DbgVar))
-        MMI->addFrameIndexExpr(VI.Expr, VI.getStackSlot());
-      else
-        DbgVar->get<Loc::EntryValue>().addExpr(VI.getEntryValueRegister(),
-                                               *VI.Expr);
+    // If we have already seen information for this variable, add to what we
+    // already know.
+    if (DbgVariable *PreviousLoc = MFVars.lookup(Var)) {
+      auto *PreviousMMI = std::get_if<Loc::MMI>(PreviousLoc);
+      auto *PreviousEntryValue = std::get_if<Loc::EntryValue>(PreviousLoc);
+      // Previous and new locations are both stack slots (MMI).
+      if (PreviousMMI && VI.inStackSlot())
+        PreviousMMI->addFrameIndexExpr(VI.Expr, VI.getStackSlot());
+      // Previous and new locations are both entry values.
+      else if (PreviousEntryValue && VI.inEntryValueRegister())
+        PreviousEntryValue->addExpr(VI.getEntryValueRegister(), *VI.Expr);
+      else {
+        // Locations differ, this should (rarely) happen in optimized async
+        // coroutines.
+        // Prefer whichever location has an EntryValue.
+        if (PreviousLoc->holds<Loc::MMI>())
+          PreviousLoc->emplace<Loc::EntryValue>(VI.getEntryValueRegister(),
+                                                *VI.Expr);
+        LLVM_DEBUG(dbgs() << "Dropping debug info for " << VI.Var->getName()
+                          << ", conflicting fragment location types\n");
+      }
       continue;
     }
 

llvm/test/DebugInfo/AArch64/dbg-entry-value-swiftasync.mir

@@ -8,16 +8,23 @@
 # CHECK-SAME:     DW_OP_GNU_entry_value(DW_OP_reg22 W22), DW_OP_piece 0x8,
 # CHECK-SAME:     DW_OP_GNU_entry_value(DW_OP_reg22 W22), DW_OP_plus_uconst 0x2a, DW_OP_piece 0x8)
 # CHECK-NEXT:   DW_AT_name    ("fragmented_var")
+# CHECK:      DW_TAG_variable
+# CHECK-NEXT:   DW_AT_location       (DW_OP_piece 0x8, DW_OP_GNU_entry_value(DW_OP_reg22 W22), DW_OP_piece 0x8)
+# CHECK-NEXT:   DW_AT_name    ("multi_type_fragmented_var")
 
 
 --- |
   target triple = "aarch64--"
   define void @foo(ptr %unused_arg, ptr swiftasync %async_arg) !dbg !4 {
+    %storage = alloca i64
     call void @llvm.dbg.declare(metadata ptr %async_arg, metadata !10, metadata !DIExpression(DW_OP_LLVM_entry_value, 1)), !dbg !12
     ; A two fragment variable.
     ; Fragments intentionally out of order to ensure the code can handle this.
     call void @llvm.dbg.declare(metadata ptr %async_arg, metadata !10, metadata !DIExpression(DW_OP_LLVM_entry_value, 1, DW_OP_plus_uconst, 42, DW_OP_LLVM_fragment, 64, 64)), !dbg !12
     call void @llvm.dbg.declare(metadata ptr %async_arg, metadata !11, metadata !DIExpression(DW_OP_LLVM_entry_value, 1, DW_OP_LLVM_fragment, 0, 64)), !dbg !12
+    ; A fragmented variable mixing entry values and stack slot locations.
+    call void @llvm.dbg.declare(metadata ptr %async_arg, metadata !13, metadata !DIExpression(DW_OP_LLVM_entry_value, 1, DW_OP_LLVM_fragment, 64, 64)), !dbg !12
+    call void @llvm.dbg.declare(metadata ptr %storage, metadata !13, metadata !DIExpression(DW_OP_LLVM_fragment, 0, 64)), !dbg !12
     ret void, !dbg !12
   }
   declare void @llvm.dbg.declare(metadata, metadata, metadata)
@@ -36,6 +43,7 @@
   !10 = !DILocalVariable(name: "a", scope: !4, file: !1, line: 1, type: !7)
   !11 = !DILocalVariable(name: "fragmented_var", scope: !4, file: !1, line: 1, type: !7)
   !12 = !DILocation(line: 1, column: 37, scope: !4)
+  !13 = !DILocalVariable(name: "multi_type_fragmented_var", scope: !4, file: !1, line: 1, type: !7)
 ...
 ---
 name:            foo
@@ -45,13 +53,20 @@ liveins:
 stack:
   - { id: 0, name: '', type: spill-slot, offset: -16, size: 8, alignment: 16,
       stack-id: default, callee-saved-register: '$lr', callee-saved-restored: true }
+  - { id: 1, name: '', type: default, offset: 0, size: 1, alignment: 8,
+      stack-id: default, callee-saved-register: '', callee-saved-restored: true,
+      debug-info-variable: '!13', debug-info-expression: '!DIExpression(DW_OP_LLVM_fragment, 0, 64)',
+      debug-info-location: '!12' }
+
 entry_values:
   - { entry-value-register: '$x22', debug-info-variable: '!10', debug-info-expression: '!DIExpression(DW_OP_LLVM_entry_value, 1, DW_OP_deref)',
       debug-info-location: '!12' }
   - { entry-value-register: '$x22', debug-info-variable: '!11', debug-info-expression: '!DIExpression(DW_OP_LLVM_entry_value, 1, DW_OP_plus_uconst, 42, DW_OP_deref, DW_OP_LLVM_fragment, 64, 64)',
       debug-info-location: '!12' }
   - { entry-value-register: '$x22', debug-info-variable: '!11', debug-info-expression: '!DIExpression(DW_OP_LLVM_entry_value, 1,  DW_OP_deref, DW_OP_LLVM_fragment, 0, 64)',
       debug-info-location: '!12' }
+  - { entry-value-register: '$x22', debug-info-variable: '!13', debug-info-expression: '!DIExpression(DW_OP_LLVM_entry_value, 1, DW_OP_deref, DW_OP_LLVM_fragment, 64, 64)',
+      debug-info-location: '!12' }
 body:             |
   bb.0 (%ir-block.0):
     liveins: $x0, $x22, $lr