Subzero: Improve usability of liveness-related tools.

src/IceTargetLowering.cpp

Index: src/IceTargetLowering.cpp
diff --git a/src/IceTargetLowering.cpp b/src/IceTargetLowering.cpp
index 69207889b7e349b2a10a5561088f6699e1d431a3..eb4a54d4fb7ea915198113554503fa6178ba361b 100644
--- a/src/IceTargetLowering.cpp
+++ b/src/IceTargetLowering.cpp
@@ -246,17 +246,21 @@ void TargetLowering::regAlloc(RegAllocKind Kind) {
   LinearScan.scan(RegMask, Ctx->getFlags().shouldRandomizeRegAlloc());
 }
 
-void TargetLowering::inferTwoAddress() {
-  // Find two-address non-SSA instructions where Dest==Src0, and set the
-  // DestNonKillable flag to keep liveness analysis consistent.
+void TargetLowering::markRedefinitions() {
+  // Find (non-SSA) instructions where the Dest variable appears in some source
+  // operand, and set the IsDestRedefined flag to keep liveness analysis
+  // consistent.
   for (auto Inst = Context.getCur(), E = Context.getNext(); Inst != E; ++Inst) {
     if (Inst->isDeleted())
       continue;
-    if (Variable *Dest = Inst->getDest()) {
-      // TODO(stichnot): We may need to consider all source operands, not just
-      // the first one, if using 3-address instructions.
-      if (Inst->getSrcSize() > 0 && Inst->getSrc(0) == Dest)
-        Inst->setDestNonKillable();
+    Variable *Dest = Inst->getDest();
+    if (Dest == nullptr)
+      continue;
+    FOREACH_VAR_IN_INST(Var, *Inst) {
+      if (Var == Dest) {
+        Inst->setDestRedefined();
+        break;
+      }
     }
   }
 }