Merge pull request github#18729 from aschackmull/ssa/deprecate-deadcode

Ssa: Deprecate the unused getALastRead predicate.

Author: aschackmull

cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/SsaInternalsCommon.qll

@@ -769,8 +769,4 @@ module InputSigCommon {
   BasicBlock getImmediateBasicBlockDominator(BasicBlock bb) { result.immediatelyDominates(bb) }
 
   BasicBlock getABasicBlockSuccessor(BasicBlock bb) { result = bb.getASuccessor() }
-
-  class ExitBasicBlock extends BasicBlock {
-    ExitBasicBlock() { this.getLastInstruction() instanceof ExitFunctionInstruction }
-  }
 }

csharp/ql/lib/semmle/code/csharp/controlflow/internal/PreSsa.qll

@@ -90,7 +90,7 @@ module PreSsa {
 
     BasicBlock getABasicBlockSuccessor(BasicBlock bb) { result = bb.getASuccessor() }
 
-    class ExitBasicBlock extends BasicBlock {
+    private class ExitBasicBlock extends BasicBlock {
       ExitBasicBlock() { scopeLast(_, this.getLastElement(), _) }
     }
 

csharp/ql/lib/semmle/code/csharp/dataflow/SSA.qll

@@ -345,7 +345,7 @@ module Ssa {
      * - The read of `this.Field` on line 11 is a last read of the phi node
      *   between lines 9 and 10.
      */
-    final AssignableRead getALastRead() { result = this.getALastReadAtNode(_) }
+    deprecated final AssignableRead getALastRead() { result = this.getALastReadAtNode(_) }
 
     /**
      * Gets a last read of the source variable underlying this SSA definition at
@@ -375,7 +375,7 @@ module Ssa {
      * - The read of `this.Field` on line 11 is a last read of the phi node
      *   between lines 9 and 10.
      */
-    final AssignableRead getALastReadAtNode(ControlFlow::Node cfn) {
+    deprecated final AssignableRead getALastReadAtNode(ControlFlow::Node cfn) {
       SsaImpl::lastReadSameVar(this, cfn) and
       result.getAControlFlowNode() = cfn
     }

csharp/ql/lib/semmle/code/csharp/dataflow/internal/BaseSSA.qll

@@ -55,8 +55,6 @@ module BaseSsa {
 
     BasicBlock getABasicBlockSuccessor(BasicBlock bb) { result = bb.getASuccessor() }
 
-    class ExitBasicBlock extends BasicBlock, ControlFlow::BasicBlocks::ExitBlock { }
-
     class SourceVariable = PreSsa::SimpleLocalScopeVariable;
 
     predicate variableWrite(BasicBlock bb, int i, SourceVariable v, boolean certain) {

csharp/ql/lib/semmle/code/csharp/dataflow/internal/SsaImpl.qll

@@ -17,8 +17,6 @@ private module SsaInput implements SsaImplCommon::InputSig<Location> {
 
   BasicBlock getABasicBlockSuccessor(BasicBlock bb) { result = bb.getASuccessor() }
 
-  class ExitBasicBlock extends BasicBlock, ControlFlow::BasicBlocks::ExitBlock { }
-
   class SourceVariable = Ssa::SourceVariable;
 
   /**
@@ -784,7 +782,9 @@ private predicate adjacentDefReachesUncertainRead(
 
 /** Same as `lastRefRedef`, but skips uncertain reads. */
 pragma[nomagic]
-private predicate lastRefSkipUncertainReads(Definition def, SsaInput::BasicBlock bb, int i) {
+deprecated private predicate lastRefSkipUncertainReads(
+  Definition def, SsaInput::BasicBlock bb, int i
+) {
   Impl::lastRef(def, bb, i) and
   not SsaInput::variableRead(bb, i, def.getSourceVariable(), false)
   or
@@ -794,6 +794,15 @@ private predicate lastRefSkipUncertainReads(Definition def, SsaInput::BasicBlock
   )
 }
 
+pragma[nomagic]
+deprecated predicate lastReadSameVar(Definition def, ControlFlow::Node cfn) {
+  exists(ControlFlow::BasicBlock bb, int i |
+    lastRefSkipUncertainReads(def, bb, i) and
+    variableReadActual(bb, i, _) and
+    cfn = bb.getNode(i)
+  )
+}
+
 cached
 private module Cached {
   cached
@@ -957,15 +966,6 @@ private module Cached {
     )
   }
 
-  cached
-  predicate lastReadSameVar(Definition def, ControlFlow::Node cfn) {
-    exists(ControlFlow::BasicBlock bb, int i |
-      lastRefSkipUncertainReads(def, bb, i) and
-      variableReadActual(bb, i, _) and
-      cfn = bb.getNode(i)
-    )
-  }
-
   cached
   Definition uncertainWriteDefinitionInput(UncertainWriteDefinition def) {
     Impl::uncertainWriteDefinitionInput(def, result)

csharp/ql/test/library-tests/dataflow/ssa/SsaDefLastRead.expected

@@ -240,8 +240,6 @@ module VariableCaptureConfig implements InputSig<js::DbLocation> {
   BasicBlock getImmediateBasicBlockDominator(BasicBlock bb) { result = bb.getImmediateDominator() }
 
   predicate entryBlock(BasicBlock bb) { bb instanceof js::EntryBasicBlock }
-
-  predicate exitBlock(BasicBlock bb) { bb.getLastNode() instanceof js::ControlFlowExitNode }
 }
 
 module VariableCaptureOutput = Flow<js::DbLocation, VariableCaptureConfig>;

csharp/ql/test/library-tests/dataflow/ssa/SsaDefLastRead.ql

@@ -14,10 +14,6 @@ module SsaConfig implements InputSig<js::DbLocation> {
 
   class BasicBlock = js::BasicBlock;
 
-  class ExitBasicBlock extends BasicBlock {
-    ExitBasicBlock() { this.isExitBlock() }
-  }
-
   class SourceVariable extends LocalVariableOrThis {
     SourceVariable() { not this.isCaptured() }
   }

javascript/ql/lib/semmle/javascript/dataflow/internal/VariableCapture.qll

@@ -102,7 +102,7 @@ module Ssa {
      * end
      * ```
      */
-    final VariableReadAccessCfgNode getALastRead() { SsaImpl::lastRead(this, result) }
+    deprecated final VariableReadAccessCfgNode getALastRead() { SsaImpl::lastRead(this, result) }
 
     /**
      * Holds if `read1` and `read2` are adjacent reads of this SSA definition.