Fix field names in long vector DICompositeType (microsoft#7332)

Fix OOB accesses for debug info vector field names for vectors of length >4.

Author: simoll

tools/clang/lib/CodeGen/CGDebugInfo.cpp

@@ -1047,8 +1047,17 @@ bool CGDebugInfo::TryCollectHLSLRecordElements(const RecordType *Ty,
     unsigned VecSize = hlsl::GetHLSLVecSize(QualTy);
     unsigned ElemSizeInBits = CGM.getContext().getTypeSize(ElemQualTy);
     unsigned CurrentAlignedOffset = 0;
+    SmallString<8> FieldNameBuf;
     for (unsigned ElemIdx = 0; ElemIdx < VecSize; ++ElemIdx) {
-      StringRef FieldName = StringRef(&"xyzw"[ElemIdx], 1);
+      StringRef FieldName;
+      if (VecSize <= 4) {
+        FieldName = StringRef(&"xyzw"[ElemIdx], 1);
+      } else {
+        FieldNameBuf.clear();
+        llvm::raw_svector_ostream OS(FieldNameBuf);
+        OS << 'c' << ElemIdx;
+        FieldName = OS.str();
+      }
       CurrentAlignedOffset =
           llvm::RoundUpToAlignment(CurrentAlignedOffset, AlignBits);
       llvm::DIType *FieldType =

tools/clang/test/CodeGenDXIL/hlsl/types/longvec-field-di.hlsl

@@ -0,0 +1,33 @@
+// RUN: %dxc -Zi -Qembed_debug -T lib_6_9 %s -DNUM=8 | FileCheck %s  --check-prefix=CHECK-LONG
+// RUN: %dxc -Zi -Qembed_debug -T lib_6_9 %s -DNUM=4 | FileCheck %s  --check-prefix=CHECK-SHORT
+
+// Test debug info for short and long vector types
+
+RWByteAddressBuffer buf;
+
+export vector<float, NUM> lv_global_arr_ret() {
+  vector<float, NUM> d = buf.Load<vector<float, NUM> >(0);
+  return d;
+}
+
+// CHECK-LONG:  ![[TYDI:[^ ]+]] = !DICompositeType(tag: DW_TAG_class_type, name: "vector<float, 8>", file: !{{[^ ]+}}, size: 256, align: 32, elements: ![[ELEMDI:[^ ]+]],
+// CHECK-LONG:  ![[ELEMDI]] = !{![[C0:[^ ]+]], ![[C1:[^ ]+]], ![[C2:[^ ]+]], ![[C3:[^ ]+]], ![[C4:[^ ]+]], ![[C5:[^ ]+]], ![[C6:[^ ]+]], ![[C7:[^ ]+]]}
+// CHECK-LONG:  ![[C0]] = !DIDerivedType(tag: DW_TAG_member, name: "c0", scope: !{{[^ ]+}} file: !{{[^ ]+}}, baseType: ![[BASETY:[^ ]+]], size: 32, align: 32, flags: DIFlagPublic)
+// CHECK-LONG:  ![[BASETY]] = !DIBasicType(name: "float", size: 32, align: 32, encoding: DW_ATE_float)
+// CHECK-LONG:  ![[C1]] = !DIDerivedType(tag: DW_TAG_member, name: "c1", scope: !{{[^ ]+}}, file: !{{[^ ]+}}, baseType: ![[BASETY]], size: 32, align: 32, offset: 32, flags: DIFlagPublic)
+// CHECK-LONG:  ![[C2]] = !DIDerivedType(tag: DW_TAG_member, name: "c2", scope: !{{[^ ]+}}, file: !{{[^ ]+}}, baseType: ![[BASETY]], size: 32, align: 32, offset: 64, flags: DIFlagPublic)
+// CHECK-LONG:  ![[C3]] = !DIDerivedType(tag: DW_TAG_member, name: "c3", scope: !{{[^ ]+}}, file: !{{[^ ]+}}, baseType: ![[BASETY]], size: 32, align: 32, offset: 96, flags: DIFlagPublic)
+// CHECK-LONG:  ![[C4]] = !DIDerivedType(tag: DW_TAG_member, name: "c4", scope: !{{[^ ]+}}, file: !{{[^ ]+}}, baseType: ![[BASETY]], size: 32, align: 32, offset: 128, flags: DIFlagPublic)
+// CHECK-LONG:  ![[C5]] = !DIDerivedType(tag: DW_TAG_member, name: "c5", scope: !{{[^ ]+}}, file: !{{[^ ]+}}, baseType: ![[BASETY]], size: 32, align: 32, offset: 160, flags: DIFlagPublic)
+// CHECK-LONG:  ![[C6]] = !DIDerivedType(tag: DW_TAG_member, name: "c6", scope: !{{[^ ]+}}, file: !{{[^ ]+}}, baseType: ![[BASETY]], size: 32, align: 32, offset: 192, flags: DIFlagPublic)
+// CHECK-LONG:  ![[C7]] = !DIDerivedType(tag: DW_TAG_member, name: "c7", scope: !{{[^ ]+}}, file: !{{[^ ]+}}, baseType: ![[BASETY]], size: 32, align: 32, offset: 224, flags: DIFlagPublic)
+// CHECK-LONG:  !{{[^ ]+}} = !DILocalVariable(tag: DW_TAG_auto_variable, name: "d", scope: !{{[^ ]+}}, file: !{{[^ ]+}}, line: 9, type: ![[TYDI]])
+
+// CHECK-SHORT:  ![[TYDI:[^ ]+]] = !DICompositeType(tag: DW_TAG_class_type, name: "vector<float, 4>", file: !{{[^ ]+}}, size: 128, align: 32, elements: ![[ELEMDI:[^ ]+]],
+// CHECK-SHORT:  ![[ELEMDI]] = !{![[X:[^ ]+]], ![[Y:[^ ]+]], ![[Z:[^ ]+]], ![[W:[^ ]+]]}
+// CHECK-SHORT:  ![[X]] = !DIDerivedType(tag: DW_TAG_member, name: "x", scope: !{{[^ ]+}}, file: !{{[^ ]+}}, baseType: ![[BASETY:[^ ]+]], size: 32, align: 32, flags: DIFlagPublic)
+// CHECK-SHORT:  ![[BASETY]] = !DIBasicType(name: "float", size: 32, align: 32, encoding: DW_ATE_float)
+// CHECK-SHORT:  ![[Y]] = !DIDerivedType(tag: DW_TAG_member, name: "y", scope: !{{[^ ]+}}, file: !{{[^ ]+}}, baseType: ![[BASETY]], size: 32, align: 32, offset: 32, flags: DIFlagPublic)
+// CHECK-SHORT:  ![[Z]] = !DIDerivedType(tag: DW_TAG_member, name: "z", scope: !{{[^ ]+}}, file: !{{[^ ]+}}, baseType: ![[BASETY]], size: 32, align: 32, offset: 64, flags: DIFlagPublic)
+// CHECK-SHORT:  ![[W]] = !DIDerivedType(tag: DW_TAG_member, name: "w", scope: !{{[^ ]+}}, file: !{{[^ ]+}}, baseType: ![[BASETY]], size: 32, align: 32, offset: 96, flags: DIFlagPublic)
+// CHECK-SHORT:  !{{[^ ]+}} = !DILocalVariable(tag: DW_TAG_auto_variable, name: "d", scope: !{{[^ ]+}}, file: !{{[^ ]+}}, line: 9, type: ![[TYDI]])