[MemoryLifetimeVerifier] Permit leaks in dead-ends

Author: nate-chandler

include/swift/SIL/SILFunction.h

@@ -1676,7 +1676,8 @@ class SILFunction
   }
 
   /// Verifies the lifetime of memory locations in the function.
-  void verifyMemoryLifetime(CalleeCache *calleeCache);
+  void verifyMemoryLifetime(CalleeCache *calleeCache,
+                            DeadEndBlocks *deadEndBlocks);
 
   /// Verifies ownership of the function.
   /// Since we don't have complete lifetimes everywhere, computes DeadEndBlocks

lib/SIL/Verifier/MemoryLifetimeVerifier.cpp

@@ -12,13 +12,14 @@
 
 #define DEBUG_TYPE "sil-memory-lifetime-verifier"
 #include "swift/Basic/Assertions.h"
-#include "swift/SIL/MemoryLocations.h"
+#include "swift/SIL/ApplySite.h"
+#include "swift/SIL/BasicBlockDatastructures.h"
+#include "swift/SIL/BasicBlockUtils.h"
 #include "swift/SIL/BitDataflow.h"
 #include "swift/SIL/CalleeCache.h"
+#include "swift/SIL/MemoryLocations.h"
 #include "swift/SIL/SILBasicBlock.h"
 #include "swift/SIL/SILFunction.h"
-#include "swift/SIL/ApplySite.h"
-#include "swift/SIL/BasicBlockDatastructures.h"
 #include "llvm/Support/CommandLine.h"
 
 using namespace swift;
@@ -43,6 +44,7 @@ class MemoryLifetimeVerifier {
 
   SILFunction *function;
   CalleeCache *calleeCache;
+  DeadEndBlocks *deadEndBlocks;
   MemoryLocations locations;
 
   /// alloc_stack memory locations which are used for store_borrow.
@@ -140,11 +142,12 @@ class MemoryLifetimeVerifier {
   }
 
 public:
-  MemoryLifetimeVerifier(SILFunction *function, CalleeCache *calleeCache) :
-    function(function),
-    calleeCache(calleeCache),
-    locations(/*handleNonTrivialProjections*/ true,
-              /*handleTrivialLocations*/ true) {}
+  MemoryLifetimeVerifier(SILFunction *function, CalleeCache *calleeCache,
+                         DeadEndBlocks *deadEndBlocks)
+      : function(function), calleeCache(calleeCache),
+        deadEndBlocks(deadEndBlocks),
+        locations(/*handleNonTrivialProjections*/ true,
+                  /*handleTrivialLocations*/ true) {}
 
   /// The main entry point to verify the lifetime of all memory locations in
   /// the function.
@@ -883,7 +886,12 @@ void MemoryLifetimeVerifier::checkBlock(SILBasicBlock *block, Bits &bits) {
       }
       case SILInstructionKind::DeallocStackInst: {
         SILValue opVal = cast<DeallocStackInst>(&I)->getOperand();
-        requireBitsClear(bits & nonTrivialLocations, opVal, &I);
+        if (!deadEndBlocks->isDeadEnd(I.getParent())) {
+          // TODO: rdar://159311784: Maybe at some point the invariant will be
+          //                         enforced that values stored into addresses
+          //                         don't leak in dead-ends.
+          requireBitsClear(bits & nonTrivialLocations, opVal, &I);
+        }
         // Needed to clear any bits of trivial locations (which are not required
         // to be zero).
         locations.clearBits(bits, opVal);
@@ -973,7 +981,8 @@ void MemoryLifetimeVerifier::verify() {
 
 } // anonymous namespace
 
-void SILFunction::verifyMemoryLifetime(CalleeCache *calleeCache) {
-  MemoryLifetimeVerifier verifier(this, calleeCache);
+void SILFunction::verifyMemoryLifetime(CalleeCache *calleeCache,
+                                       DeadEndBlocks *deadEndBlocks) {
+  MemoryLifetimeVerifier verifier(this, calleeCache, deadEndBlocks);
   verifier.verify();
 }

lib/SIL/Verifier/SILVerifier.cpp

@@ -7380,7 +7380,7 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
 
     if (F->hasOwnership() && F->shouldVerifyOwnership() &&
         !mod.getASTContext().hadError()) {
-      F->verifyMemoryLifetime(calleeCache);
+      F->verifyMemoryLifetime(calleeCache, &getDeadEndBlocks());
     }
   }
 

test/SIL/memory_lifetime.sil

@@ -864,3 +864,11 @@ bb0:
   %10 = tuple ()                                  
   return %10                                      
 } 
+
+sil [ossa] @storage_leaked_into_dead_ends : $@convention(thin) () -> () {
+  %t = apply undef() : $@convention(thin) () -> (@owned T)
+  %t_addr = alloc_stack $T
+  store %t to [init] %t_addr
+  dealloc_stack %t_addr
+  unreachable
+}

test/SILOptimizer/allocbox_to_stack_ownership.sil

@@ -1205,39 +1205,6 @@ bb0(%0 : $*T, %1 : $*T, %2 : $*T):
   return %15 : $()
 }
 
-// CHECK-LABEL: sil [ossa] @alloc_box_in_specialized_callee :
-// CHECK-NOT:     alloc_box
-// CHECK-LABEL: } // end sil function 'alloc_box_in_specialized_callee'
-sil [ossa] @alloc_box_in_specialized_callee : $@convention(thin) (Int) -> () {
-bb0(%0 : $Int):
-  %1 = alloc_box ${ var Int }
-  %2 = project_box %1, 0
-  store %0 to [trivial] %2
-  %4 = function_ref @callee_with_allocbox : $@convention(thin) (@guaranteed { var Int }) -> ()
-  %5 = apply %4(%1) : $@convention(thin) (@guaranteed { var Int }) -> ()
-  destroy_value %1
-  %r = tuple ()
-  return %r
-}
-
-// CHECK-LABEL: sil shared [ossa] @$s20callee_with_allocboxTf0s_n :
-// CHECK-NOT:     alloc_box
-// CHECK-LABEL: } // end sil function '$s20callee_with_allocboxTf0s_n'
-
-// CHECK-LABEL: sil [ossa] @callee_with_allocbox :
-// CHECK-NOT:     alloc_box
-// CHECK-LABEL: } // end sil function 'callee_with_allocbox'
-sil [ossa] @callee_with_allocbox : $@convention(thin) (@guaranteed { var Int }) -> () {
-bb0(%0 : @guaranteed ${ var Int }):
-  %1 = alloc_box ${ var Int }
-  %2 = project_box %1 : ${ var Int }, 0
-  %3 = project_box %0 : ${ var Int }, 0
-  copy_addr %3 to %2
-  destroy_value %1
-  %r = tuple ()
-  return %r
-}
-
 sil @getC : $@convention(thin) () -> (@owned C)
 
 // CHECK-LABEL: sil [ossa] @leak_to_inf_loop_1 : {{.*}} {