C++: respond to technical nits

rdmarsh2 · rdmarsh2 · commit 7ef0d5e98d3e · 2018-11-26T15:47:47.000-08:00
diff --git a/cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/SSAConstruction.qll b/cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/SSAConstruction.qll
@@ -183,7 +183,7 @@ cached private module Cached {
     result  instanceof UnmodeledDefinitionInstruction and
     instruction.getFunction() = result.getFunction()
     or
-    result = getChiInstructionTotalOperand(instruction.(ChiInstruction), tag.(ChiTotalOperandTag))
+    result = getChiInstructionTotalOperand(instruction)
   }
 
   cached Instruction getPhiInstructionOperandDefinition(PhiInstruction instr,
@@ -203,7 +203,7 @@ cached private module Cached {
     )
   }
 
-  cached Instruction getChiInstructionTotalOperand(ChiInstruction chiInstr, ChiTotalOperandTag tag) {
+  cached Instruction getChiInstructionTotalOperand(ChiInstruction chiInstr) {
     exists(Alias::VirtualVariable vvar, OldIR::Instruction oldInstr, OldIR::IRBlock defBlock,
       int defRank, int defIndex, OldIR::IRBlock useBlock, int useRank |
       ChiTag(oldInstr) = chiInstr.getTag() and
@@ -233,6 +233,11 @@ cached private module Cached {
     result = getOldInstruction(instruction).getUnconvertedResultExpression()
   }
 
+  /*
+   * This adds Chi nodes to the instruction successor relation; if an instruction has a Chi node,
+   * that node is its successor in the new successor relation, and the Chi node's successors are
+   * the new instructions generated from the successors of the old instruction
+   */
   cached Instruction getInstructionSuccessor(Instruction instruction, EdgeKind kind) {
     if(hasChiNode(_, getOldInstruction(instruction)))
     then
@@ -331,6 +336,10 @@ cached private module Cached {
       (
         access = Alias::getOperandMemoryAccess(use.getAnOperand())
         or
+        /*
+         * a partial write to a virtual variable is going to generate a use of that variable when
+         * Chi nodes are inserted, so we need to mark it as a use in the old IR
+         */
         access = Alias::getResultMemoryAccess(use) and
         access.isPartialMemoryAccess()
       ) and
@@ -471,8 +480,7 @@ cached private module Cached {
       ma = Alias::getResultMemoryAccess(def) and
       ma.isPartialMemoryAccess() and
       ma.getVirtualVariable() = vvar
-    ) and
-    not def instanceof OldIR::UnmodeledDefinitionInstruction
+    )
   }
 }
 
diff --git a/cpp/ql/src/semmle/code/cpp/ir/implementation/raw/internal/InstructionTag.qll b/cpp/ql/src/semmle/code/cpp/ir/implementation/raw/internal/InstructionTag.qll
@@ -94,6 +94,7 @@ string getInstructionTagId(TInstructionTag tag) {
   tag = OnlyInstructionTag() and result = "Only" or  // Single instruction (not including implicit Load)
   tag = InitializerVariableAddressTag() and result = "InitVarAddr" or
   tag = InitializerStoreTag() and result = "InitStore" or
+  tag = InitializerUninitializedTag() and result = "InitUninit" or
   tag = ZeroPadStringConstantTag() and result = "ZeroPadConst" or
   tag = ZeroPadStringElementIndexTag() and result = "ZeroPadElemIndex" or
   tag = ZeroPadStringElementAddressTag() and result = "ZeroPadElemAddr" or
@@ -113,6 +114,7 @@ string getInstructionTagId(TInstructionTag tag) {
   tag = ExitFunctionTag() and result = "ExitFunc" or
   tag = UnmodeledDefinitionTag() and result = "UnmodeledDef" or
   tag = UnmodeledUseTag() and result = "UnmodeledUse" or
+  tag = AliasedDefinitionTag() and result = "AliasedDef" or
   tag = SwitchBranchTag() and result = "SwitchBranch" or
   tag = CallTargetTag() and result = "CallTarget" or
   tag = CallTag() and result = "Call" or
