Merge pull request #5390 from eeckstein/fix-simplify-cfg

SIL: fix a bug which can cause the stack nesting to get broken by SimplifyCFG's jump threading

Author: eeckstein

lib/SIL/LoopInfo.cpp

@@ -76,8 +76,6 @@ bool SILLoop::canDuplicate(SILInstruction *I) const {
     return false;
   }
 
-  assert(I->isTriviallyDuplicatable() &&
-         "Code here must match isTriviallyDuplicatable in SILInstruction");
   return true;
 }
 

lib/SIL/SILInstruction.cpp

@@ -983,6 +983,10 @@ bool SILInstruction::isTriviallyDuplicatable() const {
   if (isa<AllocStackInst>(this) || isa<DeallocStackInst>(this)) {
     return false;
   }
+  if (auto *ARI = dyn_cast<AllocRefInst>(this)) {
+    if (ARI->canAllocOnStack())
+      return false;
+  }
 
   if (isa<OpenExistentialAddrInst>(this) ||
       isa<OpenExistentialRefInst>(this) ||

test/SILOptimizer/simplify_cfg.sil

@@ -1246,6 +1246,48 @@ bb7:
   br bb1
 }
 
+sil @unknown2 : $@convention(thin) () -> ()
+
+// CHECK-LABEL: no_checked_cast_br_threading_with_alloc_ref_stack
+// CHECK: checked_cast_br
+// CHECK: apply
+// CHECK: apply
+// CHECK: checked_cast_br
+// CHECK: apply
+// CHECK: apply
+// CHECK: return
+sil @no_checked_cast_br_threading_with_alloc_ref_stack : $@convention(method) (@guaranteed Base) -> () {
+bb0(%0 : $Base):
+  %fu = function_ref @unknown : $@convention(thin) () -> ()
+  %fu2 = function_ref @unknown2 : $@convention(thin) () -> ()
+  checked_cast_br [exact] %0 : $Base to $Base, bb1, bb2
+
+bb1(%1 : $Base):
+  apply %fu() : $@convention(thin) () -> ()
+  br bb3
+
+bb2:
+  apply %fu2() : $@convention(thin) () -> ()
+  br bb3
+
+bb3:
+  %a = alloc_ref [stack] $Base
+  checked_cast_br [exact] %0 : $Base to $Base, bb4, bb5
+
+bb4(%2 : $Base):
+  apply %fu() : $@convention(thin) () -> ()
+  br bb6
+
+bb5:
+  apply %fu2() : $@convention(thin) () -> ()
+  br bb6
+
+bb6:
+  dealloc_ref [stack] %a : $Base
+  %r = tuple()
+  return %r : $()
+}
+
 
 // CHECK-LABEL: sil @jumpthread_switch_enum
 // CHECK-NOT: switch_enum