Subzero: Control whether deleted instructions are retained.

src/IceCfg.h

@@ -185,6 +185,14 @@ public:
   /// predecessor and successor edges, in the form of CfgNode::InEdges[] and
   /// CfgNode::OutEdges[].
   void computeInOutEdges();
+  /// Renumber the non-deleted instructions in the Cfg.  This needs to be done
+  /// in preparation for live range analysis.  The instruction numbers in a
+  /// block must be monotonically increasing.  The range of instruction numbers
+  /// in a block, from lowest to highest, must not overlap with the range of any
+  /// other block.
+  ///
+  /// Also, if the configuration specifies to do so, remove/unlink all deleted
+  /// instructions from the Cfg, to speed up later passes over the instructions.
   void renumberInstructions();
   void placePhiLoads();
   void placePhiStores();

src/IceCfgNode.cpp

@@ -52,16 +52,25 @@ void CfgNode::appendInst(Inst *Instr) {
   }
 }
 
-// Renumbers the non-deleted instructions in the node. This needs to be done in
-// preparation for live range analysis. The instruction numbers in a block must
-// be monotonically increasing. The range of instruction numbers in a block,
-// from lowest to highest, must not overlap with the range of any other block.
+namespace {
+template <typename List> void removeDeletedAndRenumber(List *L, Cfg *Func) {
+  const bool DoDelete =
+      BuildDefs::minimal() || !GlobalContext::getFlags().getKeepDeletedInsts();
+  auto I = L->begin(), E = L->end(), Next = I;
+  for (++Next; I != E; I = Next++) {
+    if (DoDelete && I->isDeleted()) {
+      L->erase(I);
+    } else {
+      I->renumber(Func);
+    }
+  }
+}
+} // end of anonymous namespace
+
 void CfgNode::renumberInstructions() {
   InstNumberT FirstNumber = Func->getNextInstNumber();
-  for (Inst &I : Phis)
-    I.renumber(Func);
-  for (Inst &I : Insts)
-    I.renumber(Func);
+  removeDeletedAndRenumber(&Phis, Func);
+  removeDeletedAndRenumber(&Insts, Func);
   InstCountEstimate = Func->getNextInstNumber() - FirstNumber;
 }
 

src/IceClFlags.cpp

@@ -136,6 +136,14 @@ cl::opt<bool>
     FunctionSections("ffunction-sections",
                      cl::desc("Emit functions into separate sections"));
 
+/// Retain deleted instructions in the Cfg.  Defaults to true in DUMP-enabled
+/// build, and false in a non-DUMP build, but is ignored in a MINIMAL build.
+/// This flag allows overriding the default primarily for debugging.
+cl::opt<bool>
+    KeepDeletedInsts("keep-deleted-insts",
+                     cl::desc("Retain deleted instructions in the Cfg"),
+                     cl::init(Ice::BuildDefs::dump()));
+
 /// Mock bounds checking on loads/stores.
 cl::opt<bool> MockBoundsCheck("mock-bounds-check",
                               cl::desc("Mock bounds checking on loads/stores"));
@@ -475,6 +483,7 @@ void ClFlags::resetClFlags(ClFlags &OutFlags) {
   OutFlags.ForceMemIntrinOpt = false;
   OutFlags.FunctionSections = false;
   OutFlags.GenerateUnitTestMessages = false;
+  OutFlags.KeepDeletedInsts = Ice::BuildDefs::dump();
   OutFlags.MockBoundsCheck = false;
   OutFlags.PhiEdgeSplit = false;
   OutFlags.RandomNopInsertion = false;
@@ -544,6 +553,7 @@ void ClFlags::getParsedClFlags(ClFlags &OutFlags) {
   OutFlags.setFunctionSections(::FunctionSections);
   OutFlags.setNumTranslationThreads(::NumThreads);
   OutFlags.setOptLevel(::OLevel);
+  OutFlags.setKeepDeletedInsts(::KeepDeletedInsts);
   OutFlags.setMockBoundsCheck(::MockBoundsCheck);
   OutFlags.setPhiEdgeSplit(::EnablePhiEdgeSplit);
   OutFlags.setRandomSeed(::RandomSeed);

src/IceClFlags.h

@@ -164,6 +164,11 @@ public:
     GenerateUnitTestMessages = NewValue;
   }
 
+  /// Get the value of ClFlags::KeepDeletedInsts
+  bool getKeepDeletedInsts() const { return KeepDeletedInsts; }
+  /// Set ClFlags::KeepDeletedInsts to a new value
+  void setKeepDeletedInsts(bool NewValue) { KeepDeletedInsts = NewValue; }
+
   /// Get the value of ClFlags::MockBoundsCheck
   bool getMockBoundsCheck() const { return MockBoundsCheck; }
   /// Set ClFlags::MockBoundsCheck to a new value
@@ -437,6 +442,8 @@ private:
   bool FunctionSections;
   /// Initialized to false; not set by the command line.
   bool GenerateUnitTestMessages;
+  /// see anonymous_namespace{IceClFlags.cpp}::KeepDeletedInsts
+  bool KeepDeletedInsts;
   /// see anonymous_namespace{IceClFlags.cpp}::MockBoundsCheck
   bool MockBoundsCheck;
   /// see anonymous_namespace{IceClFlags.cpp}::EnablePhiEdgeSplit

src/IceDefs.h

@@ -222,7 +222,7 @@ enum VerboseItem {
   IceV_ConstPoolStats = 1 << 23,
   IceV_All = ~IceV_None,
   IceV_Most =
-      IceV_All & ~IceV_LinearScan & ~IceV_GlobalInit & IceV_ConstPoolStats
+      IceV_All & ~IceV_LinearScan & ~IceV_GlobalInit & ~IceV_ConstPoolStats
 };
 using VerboseMask = uint32_t;