Add a SILOption to control whether we should use an aggressive form of

keeping large values indirect

Author: aschwaighofer

include/swift/AST/SILOptions.h

@@ -318,6 +318,10 @@ class SILOptions {
   /// for the debugger?
   bool ShouldFunctionsBePreservedToDebugger = true;
 
+  /// Block expanding and register promotion more aggressively throughout the
+  /// optimizer.
+  bool UseAggressiveReg2MemForCodeSize = false;
+
   SILOptions() {}
 
   /// Return a hash code of any components from these options that should

include/swift/Option/FrontendOptions.td

@@ -1294,6 +1294,13 @@ def disable_lifetime_dependence_diagnostics :
   Flag<["-"], "disable-lifetime-dependence-diagnostics">,
   HelpText<"Disable lifetime dependence diagnostics for Nonescapable types.">;
 
+def enable_aggressive_reg2mem :
+  Flag<["-"], "enable-aggressive-reg2mem">,
+  HelpText<"Enable a more aggresive reg2mem heuristic">;
+def disable_aggressive_reg2mem :
+  Flag<["-"], "disable-aggresive-reg2mem">,
+  HelpText<"Disable a more aggresive reg2mem heuristic">;
+
 def enable_collocate_metadata_functions :
   Flag<["-"], "enable-collocate-metadata-functions">,
   HelpText<"Enable collocate metadata functions">;

lib/Frontend/CompilerInvocation.cpp

@@ -3738,6 +3738,7 @@ bool CompilerInvocation::parseArgs(
     SILOpts.SkipFunctionBodies = FunctionBodySkipping::None;
     SILOpts.CMOMode = CrossModuleOptimizationMode::Everything;
     SILOpts.EmbeddedSwift = true;
+    SILOpts.UseAggressiveReg2MemForCodeSize = true;
     // OSSA modules are required for deinit de-virtualization.
     SILOpts.EnableOSSAModules = true;
     // -g is promoted to -gdwarf-types in embedded Swift
@@ -3751,6 +3752,11 @@ bool CompilerInvocation::parseArgs(
     }
   }
 
+  SILOpts.UseAggressiveReg2MemForCodeSize =
+    ParsedArgs.hasFlag(OPT_enable_aggressive_reg2mem,
+                       OPT_disable_aggressive_reg2mem,
+                       SILOpts.UseAggressiveReg2MemForCodeSize);
+
   // With Swift 6, enable @_spiOnly by default. This also enables proper error
   // reporting of ioi references from spi decls.
   if (LangOpts.EffectiveLanguageVersion.isVersionAtLeast(6)) {