Also respect -mergeable-traps when merging cond_fails in SILOptimizer

SwiftCompilerSources/Sources/Optimizer/FunctionPasses/MergeCondFails.swift

@@ -39,10 +39,12 @@ private func runMergeCondFails(function: Function, context: FunctionPassContext)
 
     for inst in block.instructions {
       if let cfi = inst as? CondFailInst {
+        let messageIsSame = condFailToMerge.isEmpty || cfi.message == condFailToMerge.first!.message
+        let forceAllowMerge = context.options.enableMergeableTraps
+
         // Do not process arithmetic overflow checks. We typically generate more
         // efficient code with separate jump-on-overflow.
-        if !hasOverflowConditionOperand(cfi) &&
-           (condFailToMerge.isEmpty || cfi.message == condFailToMerge.first!.message) {
+        if !hasOverflowConditionOperand(cfi) && (messageIsSame || forceAllowMerge) {
           condFailToMerge.push(cfi)
         }
       } else if inst.mayHaveSideEffects || inst.mayReadFromMemory {

SwiftCompilerSources/Sources/Optimizer/PassManager/Options.swift

@@ -40,6 +40,10 @@ struct Options {
     _bridged.hasFeature(.Embedded)
   }
 
+  var enableMergeableTraps: Bool {
+    _bridged.enableMergeableTraps()
+  }
+
   func hasFeature(_ feature: BridgedFeature) -> Bool {
     _bridged.hasFeature(feature)
   }

include/swift/AST/SILOptions.h

@@ -335,6 +335,9 @@ public:
   /// Temporarily used to bootstrap the AddressableParameters feature.
   bool EnableAddressDependencies = true;
 
+  // Whether to allow merging traps and cond_fails.
+  bool MergeableTraps = false;
+
   SILOptions() {}
 
   /// Return a hash code of any components from these options that should

include/swift/SILOptimizer/OptimizerBridging.h

@@ -376,6 +376,7 @@ struct BridgedPassContext {
 
   BRIDGED_INLINE bool useAggressiveReg2MemForCodeSize() const;
   BRIDGED_INLINE bool enableStackProtection() const;
+  BRIDGED_INLINE bool enableMergeableTraps() const;
   BRIDGED_INLINE bool hasFeature(BridgedFeature feature) const;
   BRIDGED_INLINE bool enableMoveInoutStackProtection() const;
   BRIDGED_INLINE AssertConfiguration getAssertConfiguration() const;

include/swift/SILOptimizer/OptimizerBridgingImpl.h

@@ -543,6 +543,11 @@ bool BridgedPassContext::enableStackProtection() const {
   return mod->getOptions().EnableStackProtection;
 }
 
+bool BridgedPassContext::enableMergeableTraps() const {
+  swift::SILModule *mod = invocation->getPassManager()->getModule();
+  return mod->getOptions().MergeableTraps;
+}
+
 bool BridgedPassContext::hasFeature(BridgedFeature feature) const {
   swift::SILModule *mod = invocation->getPassManager()->getModule();
   return mod->getASTContext().LangOpts.hasFeature((swift::Feature)feature);

lib/Frontend/CompilerInvocation.cpp

@@ -3109,11 +3109,11 @@ static bool ParseSILArgs(SILOptions &Opts, ArgList &Args,
     Opts.ShouldFunctionsBePreservedToDebugger &=
         LTOKind.value() == IRGenLLVMLTOKind::None;
 
-  
-  Opts.EnableAddressDependencies =
+    Opts.EnableAddressDependencies =
     Args.hasFlag(OPT_enable_address_dependencies,
                  OPT_disable_address_dependencies,
                  Opts.EnableAddressDependencies);
+  Opts.MergeableTraps = Args.hasArg(OPT_mergeable_traps);
 
   return false;
 }