Large loadable types peepholes and address assignment

Contract some load store patterns and assign addresses to (non-address)
SIL SSA values.

rdar://115571407

Author: aschwaighofer

include/swift/AST/IRGenOptions.h

@@ -404,6 +404,9 @@ class IRGenOptions {
   /// using TypeInfo entries.
   unsigned ForceStructTypeLayouts : 1;
 
+  /// Run a reg2Mem pass after large loadable type lowering.
+  unsigned EnableLargeLoadableTypesReg2Mem : 1;
+
   /// Enable generation and use of layout string based value witnesses
   unsigned EnableLayoutStringValueWitnesses : 1;
 
@@ -537,6 +540,7 @@ class IRGenOptions {
         CompactAbsoluteFunctionPointer(false), DisableLegacyTypeInfo(false),
         PrespecializeGenericMetadata(false), UseIncrementalLLVMCodeGen(true),
         UseTypeLayoutValueHandling(true), ForceStructTypeLayouts(false),
+        EnableLargeLoadableTypesReg2Mem(true),
         EnableLayoutStringValueWitnesses(false),
         EnableLayoutStringValueWitnessesInstantiation(false),
         EnableObjectiveCProtocolSymbolicReferences(true),

include/swift/Option/FrontendOptions.td

@@ -1070,6 +1070,12 @@ def force_struct_type_layouts : Flag<["-"], "force-struct-type-layouts">,
 def enable_layout_string_value_witnesses : Flag<["-"], "enable-layout-string-value-witnesses">,
   HelpText<"Enable layout string based value witnesses">;
 
+def enable_large_loadable_types_reg2mem : Flag<["-"], "enable-large-loadable-types-reg2mem">,
+  HelpText<"Enable large loadable types register to memory pass">;
+
+def disable_large_loadable_types_reg2mem : Flag<["-"], "disable-large-loadable-types-reg2mem">,
+  HelpText<"Disable large loadable types register to memory pass">;
+
 let Flags = [FrontendOption, NoDriverOption, HelpHidden, ModuleInterfaceOptionIgnorable] in {
   def enable_pack_metadata_stack_promotion :
     Joined<["-"], "enable-pack-metadata-stack-promotion=">,

lib/Frontend/CompilerInvocation.cpp

@@ -3009,7 +3009,10 @@ static bool ParseIRGenArgs(IRGenOptions &Opts, ArgList &Args,
     Args.hasFlag(OPT_enable_relative_protocol_witness_tables,
                  OPT_disable_relative_protocol_witness_tables,
                  Opts.UseRelativeProtocolWitnessTables);
-
+  Opts.EnableLargeLoadableTypesReg2Mem =
+      Args.hasFlag(OPT_enable_large_loadable_types_reg2mem,
+                   OPT_disable_large_loadable_types_reg2mem,
+                   Opts.EnableLargeLoadableTypesReg2Mem);
   Opts.EnableLayoutStringValueWitnesses = Args.hasFlag(OPT_enable_layout_string_value_witnesses,
                                                        OPT_disable_layout_string_value_witnesses,
                                                        Opts.EnableLayoutStringValueWitnesses);