[pmo] Change MemoryInst to be an AllocationInst since it will always be so.

Just a part of a series of small cleanups I found over the break in PMO that I
am landing in preparation for landing patches that fix PMO for ownership.

Author: gottesmm

lib/SILOptimizer/Mandatory/PMOMemoryUseCollector.cpp

@@ -39,24 +39,21 @@ static unsigned getElementCountRec(SILModule &Module, SILType T) {
   return 1;
 }
 
-PMOMemoryObjectInfo::PMOMemoryObjectInfo(SingleValueInstruction *MI) {
-  auto &Module = MI->getModule();
+PMOMemoryObjectInfo::PMOMemoryObjectInfo(AllocationInst *allocation)
+    : MemoryInst(allocation) {
+  auto &module = MemoryInst->getModule();
 
-  MemoryInst = MI;
   // Compute the type of the memory object.
-  if (auto *ABI = dyn_cast<AllocBoxInst>(MemoryInst)) {
-    assert(ABI->getBoxType()->getLayout()->getFields().size() == 1 &&
+  if (auto *abi = dyn_cast<AllocBoxInst>(MemoryInst)) {
+    assert(abi->getBoxType()->getLayout()->getFields().size() == 1 &&
            "analyzing multi-field boxes not implemented");
-    MemorySILType = ABI->getBoxType()->getFieldType(Module, 0);
-  } else if (auto *ASI = dyn_cast<AllocStackInst>(MemoryInst)) {
-    MemorySILType = ASI->getElementType();
+    MemorySILType = abi->getBoxType()->getFieldType(module, 0);
   } else {
-    llvm_unreachable(
-        "Predictable Mem Opts should only be analyzing alloc_box/alloc_stack");
+    MemorySILType = cast<AllocStackInst>(MemoryInst)->getElementType();
   }
 
   // Break down the initializer.
-  NumElements = getElementCountRec(Module, MemorySILType);
+  NumElements = getElementCountRec(module, MemorySILType);
 }
 
 SILInstruction *PMOMemoryObjectInfo::getFunctionEntryPoint() const {

lib/SILOptimizer/Mandatory/PMOMemoryUseCollector.h

@@ -70,9 +70,9 @@ class SILBuilder;
 /// not super.init() has been called or not.
 class PMOMemoryObjectInfo {
 public:
-  /// This is the instruction that represents the memory.  It is either an
-  /// allocation (alloc_box, alloc_stack) or a mark_uninitialized.
-  SingleValueInstruction *MemoryInst;
+  /// This is the instruction that represents the memory. It is either an
+  /// alloc_box or alloc_stack.
+  AllocationInst *MemoryInst;
 
   /// This is the base type of the memory allocation.
   SILType MemorySILType;
@@ -87,7 +87,7 @@ class PMOMemoryObjectInfo {
   unsigned NumElements;
 
 public:
-  PMOMemoryObjectInfo(SingleValueInstruction *MemoryInst);
+  PMOMemoryObjectInfo(AllocationInst *MemoryInst);
 
   SILLocation getLoc() const { return MemoryInst->getLoc(); }
   SILFunction &getFunction() const { return *MemoryInst->getFunction(); }