VM: Remove PushTempInstr, simplify SSA renaming.

runtime/vm/flow_graph_compiler.cc

Index: runtime/vm/flow_graph_compiler.cc
diff --git a/runtime/vm/flow_graph_compiler.cc b/runtime/vm/flow_graph_compiler.cc
index 006053fe3a75998d51f3a4a8b610bece82adcdb0..71fcec4e41b2e9cf97caef81adcf4b6f3d22e581 100644
--- a/runtime/vm/flow_graph_compiler.cc
+++ b/runtime/vm/flow_graph_compiler.cc
@@ -1400,7 +1400,7 @@ void FlowGraphCompiler::AllocateRegistersLocally(Instruction* instr) {
   }
 
   // Allocate all unallocated input locations.
-  const bool should_pop = !instr->IsPushArgument() && !instr->IsPushTemp();
+  const bool should_pop = !instr->IsPushArgument();
   for (intptr_t i = locs->input_count() - 1; i >= 0; i--) {
     Location loc = locs->in(i);
     Register reg = kNoRegister;
@@ -1932,7 +1932,6 @@ void FlowGraphCompiler::FrameStateUpdateWith(Instruction* instr) {
 
   switch (instr->tag()) {
     case Instruction::kPushArgument:
-    case Instruction::kPushTemp:
       // Do nothing.
       break;