C++/C#: Remove UnmodeledUse instruction

Author: Dave Bartolomeo

cpp/ql/src/semmle/code/cpp/ir/implementation/Opcode.qll

@@ -61,7 +61,6 @@ private newtype TOpcode =
   TReThrow() or
   TUnwind() or
   TUnmodeledDefinition() or
-  TUnmodeledUse() or
   TAliasedDefinition() or
   TInitializeNonLocal() or
   TAliasedUse() or
@@ -587,12 +586,6 @@ module Opcode {
     }
   }
 
-  class UnmodeledUse extends Opcode, TUnmodeledUse {
-    final override string toString() { result = "UnmodeledUse" }
-
-    final override predicate hasOperandInternal(OperandTag tag) { none() }
-  }
-
   class AliasedDefinition extends Opcode, TAliasedDefinition {
     final override string toString() { result = "AliasedDefinition" }
 

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/IRBlock.qll

@@ -31,10 +31,14 @@ class IRBlockBase extends TIRBlock {
       config.shouldEvaluateDebugStringsForFunction(this.getEnclosingFunction())
     ) and
     this =
-      rank[result + 1](IRBlock funcBlock |
-        funcBlock.getEnclosingFunction() = getEnclosingFunction()
+      rank[result + 1](IRBlock funcBlock, int sortOverride |
+        funcBlock.getEnclosingFunction() = getEnclosingFunction() and
+        // Ensure that the block containing `EnterFunction` always comes first.
+        if funcBlock.getFirstInstruction() instanceof EnterFunctionInstruction
+        then sortOverride = 0
+        else sortOverride = 1
       |
-        funcBlock order by funcBlock.getUniqueId()
+        funcBlock order by sortOverride, funcBlock.getUniqueId()
       )
   }
 

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/IRConsistency.qll

@@ -257,7 +257,6 @@ module InstructionConsistency {
     Operand useOperand, string message, IRFunction func, string funcText
   ) {
     exists(IRBlock useBlock, int useIndex, Instruction defInstr, IRBlock defBlock, int defIndex |
-      not useOperand.getUse() instanceof UnmodeledUseInstruction and
       not defInstr instanceof UnmodeledDefinitionInstruction and
       pointOfEvaluation(useOperand, useBlock, useIndex) and
       defInstr = useOperand.getAnyDef() and

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/IRFunction.qll

@@ -45,11 +45,6 @@ class IRFunction extends TIRFunction {
     result.getEnclosingIRFunction() = this
   }
 
-  pragma[noinline]
-  final UnmodeledUseInstruction getUnmodeledUseInstruction() {
-    result.getEnclosingIRFunction() = this
-  }
-
   /**
    * Gets the single return instruction for this function.
    */

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/Instruction.qll

@@ -320,8 +320,7 @@ class Instruction extends Construction::TInstruction {
   /**
    * Holds if the result of this instruction is precisely modeled in SSA. Always
    * holds for a register result. For a memory result, a modeled result is
-   * connected to its actual uses. An unmodeled result is connected to the
-   * `UnmodeledUse` instruction.
+   * connected to its actual uses. An unmodeled result has no uses.
    *
    * For example:
    * ```
@@ -1248,12 +1247,6 @@ class AliasedUseInstruction extends Instruction {
   AliasedUseInstruction() { getOpcode() instanceof Opcode::AliasedUse }
 }
 
-class UnmodeledUseInstruction extends Instruction {
-  UnmodeledUseInstruction() { getOpcode() instanceof Opcode::UnmodeledUse }
-
-  override string getOperandsString() { result = "mu*" }
-}
-
 /**
  * An instruction representing the choice of one of multiple input values based on control flow.
  *

cpp/ql/src/semmle/code/cpp/ir/implementation/raw/IRBlock.qll

@@ -31,10 +31,14 @@ class IRBlockBase extends TIRBlock {
       config.shouldEvaluateDebugStringsForFunction(this.getEnclosingFunction())
     ) and
     this =
-      rank[result + 1](IRBlock funcBlock |
-        funcBlock.getEnclosingFunction() = getEnclosingFunction()
+      rank[result + 1](IRBlock funcBlock, int sortOverride |
+        funcBlock.getEnclosingFunction() = getEnclosingFunction() and
+        // Ensure that the block containing `EnterFunction` always comes first.
+        if funcBlock.getFirstInstruction() instanceof EnterFunctionInstruction
+        then sortOverride = 0
+        else sortOverride = 1
       |
-        funcBlock order by funcBlock.getUniqueId()
+        funcBlock order by sortOverride, funcBlock.getUniqueId()
       )
   }
 

cpp/ql/src/semmle/code/cpp/ir/implementation/raw/IRConsistency.qll

@@ -257,7 +257,6 @@ module InstructionConsistency {
     Operand useOperand, string message, IRFunction func, string funcText
   ) {
     exists(IRBlock useBlock, int useIndex, Instruction defInstr, IRBlock defBlock, int defIndex |
-      not useOperand.getUse() instanceof UnmodeledUseInstruction and
       not defInstr instanceof UnmodeledDefinitionInstruction and
       pointOfEvaluation(useOperand, useBlock, useIndex) and
       defInstr = useOperand.getAnyDef() and

cpp/ql/src/semmle/code/cpp/ir/implementation/raw/IRFunction.qll

@@ -45,11 +45,6 @@ class IRFunction extends TIRFunction {
     result.getEnclosingIRFunction() = this
   }
 
-  pragma[noinline]
-  final UnmodeledUseInstruction getUnmodeledUseInstruction() {
-    result.getEnclosingIRFunction() = this
-  }
-
   /**
    * Gets the single return instruction for this function.
    */

cpp/ql/src/semmle/code/cpp/ir/implementation/raw/Instruction.qll

@@ -320,8 +320,7 @@ class Instruction extends Construction::TInstruction {
   /**
    * Holds if the result of this instruction is precisely modeled in SSA. Always
    * holds for a register result. For a memory result, a modeled result is
-   * connected to its actual uses. An unmodeled result is connected to the
-   * `UnmodeledUse` instruction.
+   * connected to its actual uses. An unmodeled result has no uses.
    *
    * For example:
    * ```
@@ -1248,12 +1247,6 @@ class AliasedUseInstruction extends Instruction {
   AliasedUseInstruction() { getOpcode() instanceof Opcode::AliasedUse }
 }
 
-class UnmodeledUseInstruction extends Instruction {
-  UnmodeledUseInstruction() { getOpcode() instanceof Opcode::UnmodeledUse }
-
-  override string getOperandsString() { result = "mu*" }
-}
-
 /**
  * An instruction representing the choice of one of multiple input values based on control flow.
  *

cpp/ql/src/semmle/code/cpp/ir/implementation/raw/internal/InstructionTag.qll

@@ -29,7 +29,6 @@ newtype TInstructionTag =
   ReturnTag() or
   ExitFunctionTag() or
   UnmodeledDefinitionTag() or
-  UnmodeledUseTag() or
   AliasedDefinitionTag() or
   InitializeNonLocalTag() or
   AliasedUseTag() or
@@ -129,8 +128,6 @@ string getInstructionTagId(TInstructionTag tag) {
   or
   tag = UnmodeledDefinitionTag() and result = "UnmodeledDef"
   or
-  tag = UnmodeledUseTag() and result = "UnmodeledUse"
-  or
   tag = AliasedDefinitionTag() and result = "AliasedDef"
   or
   tag = InitializeNonLocalTag() and result = "InitNonLocal"