Merge pull request #62332 from tshortli/has-symbol-inhibit-alloc-stack-hoist

Author: tshortli

lib/IRGen/AllocStackHoisting.cpp

@@ -427,13 +427,16 @@ class HoistAllocStack {
 };
 } // end anonymous namespace
 
-bool indicatesDynamicAvailabilityCheckUse(SILInstruction *I) {
+bool inhibitsAllocStackHoisting(SILInstruction *I) {
   if (auto *Apply = dyn_cast<ApplyInst>(I)) {
     return Apply->hasSemantics(semantics::AVAILABILITY_OSVERSION);
   }
   if (auto *bi = dyn_cast<BuiltinInst>(I)) {
     return bi->getBuiltinInfo().ID == BuiltinValueKind::TargetOSVersionAtLeast;
   }
+  if (isa<HasSymbolInst>(I)) {
+    return true;
+  }
   return false;
 }
 
@@ -453,8 +456,10 @@ void HoistAllocStack::collectHoistableInstructions() {
           FunctionExits.push_back(Term);
         continue;
       }
-      // Don't perform alloc_stack hoisting in functions with availability.
-      if (indicatesDynamicAvailabilityCheckUse(&Inst)) {
+      // Don't perform alloc_stack hoisting in functions containing
+      // instructions that indicate hoisting may be unsafe (e.g. `if
+      // #available(...)` or `if #_hasSymbol(...)`.
+      if (inhibitsAllocStackHoisting(&Inst)) {
         AllocStackToHoist.clear();
         return;
       }

test/SILOptimizer/allocstack_hoisting.sil

@@ -257,3 +257,26 @@ bb3:
   return %3 : $()
 }
 
+// CHECK-LABEL: sil @dont_hoist_with_has_symbol_checks
+// CHECK-NOT: alloc_stack
+// CHECK:     cond_br
+// CHECK:   bb1:
+// CHECK:     alloc_stack
+// CHECK: } // end sil function 'dont_hoist_with_has_symbol_checks'
+sil @dont_hoist_with_has_symbol_checks : $@convention(thin) <T> (@in T, Builtin.Int1) -> () {
+bb0(%0 : $*T, %1: $Builtin.Int1):
+  %5 = has_symbol #FixedSize.init
+  cond_br %5, bb1, bb2
+bb1:
+  %2 = alloc_stack $T
+  copy_addr [take] %0 to [init] %2 : $*T
+  destroy_addr %2 : $*T
+  dealloc_stack %2 : $*T
+  br bb3
+bb2:
+  destroy_addr %0 : $*T
+  br bb3
+bb3:
+  %3 = tuple ()
+  return %3 : $()
+}