[Assignment Tracking][SelectionDAG] Fix dbg.declare location nullptr deref

Debug intrinsics sometimes end up with empty metadata location operands. The
debug intrinsic interfaces return nullptr when retrieving location operand in
this case.

When assignment tracking is not enabled a dbg.declare with a nullptr location
operand is skipped. Do the same when assignment tracking is enabled (a nullptr
address component of a dbg.assign is already handled correctly.

Reviewed By: jmorse

Differential Revision: https://reviews.llvm.org/D148203

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index d77dfb6..563f14c 100644 (file)
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -1345,6 +1345,11 @@ static bool isFoldedOrDeadInstruction(const Instruction *I,
 static void processDbgDeclare(FunctionLoweringInfo &FuncInfo,
                               const Value *Address, DIExpression *Expr,
                               DILocalVariable *Var, DebugLoc DbgLoc) {
+  if (!Address) {
+    LLVM_DEBUG(dbgs() << "processDbgDeclares skipping " << *Var
+                      << " (bad address)\n");
+    return;
+  }
   MachineFunction *MF = FuncInfo.MF;
   const DataLayout &DL = MF->getDataLayout();
 
@@ -1386,13 +1391,7 @@ static void processDbgDeclares(FunctionLoweringInfo &FuncInfo) {
   for (const BasicBlock &BB : *FuncInfo.Fn) {
     for (const Instruction &I : BB) {
       if (const DbgDeclareInst *DI = dyn_cast<DbgDeclareInst>(&I)) {
-        Value *Address = DI->getAddress();
-        if (!Address) {
-          LLVM_DEBUG(dbgs() << "processDbgDeclares skipping " << *DI
-                            << " (bad address)\n");
-          continue;
-        }
-        processDbgDeclare(FuncInfo, Address, DI->getExpression(),
+        processDbgDeclare(FuncInfo, DI->getAddress(), DI->getExpression(),
                           DI->getVariable(), DI->getDebugLoc());
       }
     }

diff --git a/llvm/test/DebugInfo/assignment-tracking/X86/single-memory-location.ll b/llvm/test/DebugInfo/assignment-tracking/X86/single-memory-location.ll
index 4756d46..1f806e5 100644 (file)
--- a/llvm/test/DebugInfo/assignment-tracking/X86/single-memory-location.ll
+++ b/llvm/test/DebugInfo/assignment-tracking/X86/single-memory-location.ll
@@ -2,7 +2,11 @@
 ; RUN: | FileCheck %s
 
 ;; Check that a dbg.assign for a fully stack-homed variable causes the variable
-;; location to appear in the Machine Function side table.
+;; location to appear in the Machine Function side table (variable 'local').
+;;
+;; The variable 'local2' is tracked using a dbg.declare. Check the variable is
+;; dropped and doesn't cause a crash when the address is an empty metadata
+;; tuple and assignment tracking is enabled for the function.
 ;;
 ;; $ cat test.cpp
 ;; void maybe_writes(int*);
@@ -17,10 +21,13 @@
 
 ; CHECK: ![[VAR:[0-9]+]] = !DILocalVariable(name: "local",
 ; CHECK: stack:
-; CHECK-NEXT: - { id: 0, name: local, type: default, offset: 0, size: 4, alignment: 4, 
-; CHECK-NEXT:     stack-id: default, callee-saved-register: '', callee-saved-restored: true, 
-; CHECK-NEXT:     debug-info-variable: '![[VAR]]', debug-info-expression: '!DIExpression()', 
+; CHECK-NEXT: - { id: 0, name: local, type: default, offset: 0, size: 4, alignment: 4,
+; CHECK-NEXT:     stack-id: default, callee-saved-register: '', callee-saved-restored: true,
+; CHECK-NEXT:     debug-info-variable: '![[VAR]]', debug-info-expression: '!DIExpression()',
 ; CHECK-NEXT:     debug-info-location: '!{{.+}}' }
+; CHECK-NEXT: - { id: 1, name: local2, type: default, offset: 0, size: 4, alignment: 4,
+; CHECK-NEXT:     stack-id: default, callee-saved-register: '', callee-saved-restored: true,
+; CHECK-NEXT:     debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
 
 source_filename = "test.cpp"
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
@@ -30,6 +37,8 @@ define dso_local i32 @_Z7examplev() local_unnamed_addr !dbg !7 {
 entry:
   %local = alloca i32, align 4, !DIAssignID !13
   call void @llvm.dbg.assign(metadata i1 undef, metadata !12, metadata !DIExpression(), metadata !13, metadata ptr %local, metadata !DIExpression()), !dbg !14
+  %local2 = alloca i32, align 4
+  call void @llvm.dbg.declare(metadata !2, metadata !32, metadata !DIExpression()), !dbg !14
   %0 = bitcast ptr %local to ptr, !dbg !15
   call void @llvm.lifetime.start.p0i8(i64 4, ptr nonnull %0), !dbg !15
   call void @_Z12maybe_writesPi(ptr nonnull %local), !dbg !16
@@ -44,6 +53,7 @@ declare !dbg !29 dso_local void @_Z3extiiiiiiiiii(i32, i32, i32, i32, i32, i32,
 declare void @llvm.lifetime.start.p0i8(i64 immarg, ptr nocapture)
 declare void @llvm.lifetime.end.p0i8(i64 immarg, ptr nocapture)
 declare void @llvm.dbg.assign(metadata, metadata, metadata, metadata, metadata, metadata)
+declare void @llvm.dbg.declare(metadata, metadata, metadata)
 
 !llvm.dbg.cu = !{!0}
 !llvm.module.flags = !{!3, !4, !5, !1000}
@@ -77,4 +87,5 @@ declare void @llvm.dbg.assign(metadata, metadata, metadata, metadata, metadata,
 !29 = !DISubprogram(name: "ext", linkageName: "_Z3extiiiiiiiiii", scope: !1, file: !1, line: 2, type: !30, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized, retainedNodes: !2)
 !30 = !DISubroutineType(types: !31)
 !31 = !{null, !10, !10, !10, !10, !10, !10, !10, !10, !10, !10}
+!32 = !DILocalVariable(name: "local2", scope: !7, file: !1, line: 4, type: !10)
 !1000 = !{i32 7, !"debug-info-assignment-tracking", i1 true}