[PATCH] D159468: [AsmPrinter][DwarfDebug] Skip vars with fragments in different location kinds

[Felipe de Azevedo Piovezan via Phabricator via llvm-commits]

fdeazeve created this revision.
fdeazeve added a reviewer: aprantl.
Herald added a subscriber: hiraditya.
Herald added a project: All.
fdeazeve requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

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.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D159468

Files:
  llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
  llvm/test/DebugInfo/AArch64/dbg-entry-value-swiftasync.mir


Index: llvm/test/DebugInfo/AArch64/dbg-entry-value-swiftasync.mir
===================================================================
--- llvm/test/DebugInfo/AArch64/dbg-entry-value-swiftasync.mir
+++ 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
@@ -45,6 +53,11 @@
 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' }
@@ -52,6 +65,8 @@
       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
Index: llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
===================================================================
--- llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1570,10 +1570,13 @@
                       << "\n");
 
     if (DbgVariable *DbgVar = MFVars.lookup(Var)) {
-      if (DbgVar->hasFrameIndexExprs())
+      if (DbgVar->hasFrameIndexExprs() && RegVar->hasFrameIndexExprs())
         DbgVar->addMMIEntry(*RegVar);
-      else
+      else if (VI.inEntryValueRegister())
         DbgVar->getEntryValue()->addExpr(VI.getEntryValueRegister(), *VI.Expr);
+      else
+        LLVM_DEBUG(dbgs() << "Dropping debug info for " << VI.Var->getName()
+                          << ", conflicting fragment types\n");
     } else if (InfoHolder.addScopeVariable(Scope, RegVar.get())) {
       MFVars.insert({Var, RegVar.get()});
       ConcreteEntities.push_back(std::move(RegVar));


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D159468.556053.patch
Type: text/x-patch
Size: 4440 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20230906/508d4644/attachment.bin>