[LVA] Don't invalidate reads/writes that don't alias any tracked values.

In DSE and RLE any unkown read/write often causes most if not all tracked values to be invalidated. This doesn't need to be the case. If the tracked value doesn't alias any of the operands of the unkown instruction, then we can safely keep the tracked value validated.

Author: zoecarver

lib/SILOptimizer/Transforms/DeadStoreElimination.cpp

@@ -1087,7 +1087,12 @@ void DSEContext::processUnknownReadInstForGenKillSet(SILInstruction *I) {
   for (unsigned i = 0; i < S->LocationNum; ++i) {
     if (!S->BBMaxStoreSet.test(i))
       continue;
-    if (!AA->mayReadFromMemory(I, LocationVault[i].getBase()))
+    auto val = LocationVault[i].getBase();
+    if (!AA->mayReadFromMemory(I, val))
+      continue;
+    if (llvm::all_of(I->getAllOperands(), [&AA = AA, &val](Operand &op) {
+          return AA->isNoAlias(op.get(), val);
+        }))
       continue;
     // Update the genset and kill set.
     S->startTrackingLocation(S->BBKillSet, i);
@@ -1100,7 +1105,12 @@ void DSEContext::processUnknownReadInstForDSE(SILInstruction *I) {
   for (unsigned i = 0; i < S->LocationNum; ++i) {
     if (!S->isTrackingLocation(S->BBWriteSetMid, i))
       continue;
-    if (!AA->mayReadFromMemory(I, LocationVault[i].getBase()))
+    auto val = LocationVault[i].getBase();
+    if (!AA->mayReadFromMemory(I, val))
+      continue;
+    if (llvm::all_of(I->getAllOperands(), [&AA = AA, &val](Operand &op) {
+          return AA->isNoAlias(op.get(), val);
+        }))
       continue;
     S->stopTrackingLocation(S->BBWriteSetMid, i);
   }

lib/SILOptimizer/Transforms/RedundantLoadElimination.cpp

@@ -977,6 +977,10 @@ void BlockState::processUnknownWriteInstForGenKillSet(RLEContext &Ctx,
     LSLocation &R = Ctx.getLocation(i);
     if (!AA->mayWriteToMemory(I, R.getBase()))
       continue;
+    if (llvm::all_of(I->getAllOperands(), [&AA, &R](Operand &op) {
+          return AA->isNoAlias(op.get(), R.getBase());
+        }))
+      continue;
     // MayAlias.
     stopTrackingLocation(BBGenSet, i);
     startTrackingLocation(BBKillSet, i);
@@ -996,6 +1000,10 @@ void BlockState::processUnknownWriteInstForRLE(RLEContext &Ctx,
     LSLocation &R = Ctx.getLocation(i);
     if (!AA->mayWriteToMemory(I, R.getBase()))
       continue;
+    if (llvm::all_of(I->getAllOperands(), [&AA, &R](Operand &op) {
+          return AA->isNoAlias(op.get(), R.getBase());
+        }))
+      continue;
     // MayAlias.
     stopTrackingLocation(ForwardSetIn, i);
     stopTrackingValue(ForwardValIn, i);

test/SILOptimizer/dead_store_elim.sil

@@ -1501,3 +1501,43 @@ bb0(%0 : $*foo):
   %20 = tuple()
   return %20 : $()
 }
+
+class Foo {
+  @_hasStorage @_hasInitialValue var x: Int { get set }
+  deinit
+  init()
+}
+
+class Bar {
+  @_hasStorage @_hasInitialValue var x: Int { get set }
+  deinit
+  init()
+}
+
+// CHECK-LABEL: @unknown_unrelated_read
+// CHECK: store
+// CHECK-NOT: store
+// CHECK-LABEL: end sil function 'unknown_unrelated_read'
+sil hidden @unknown_unrelated_read : $@convention(thin) (@inout Int) -> () {
+bb0(%0 : $*Int):
+  %1 = alloc_ref $Foo
+  %3 = integer_literal $Builtin.Int64, 0
+  %4 = struct $Int (%3 : $Builtin.Int64)
+  %5 = ref_element_addr %1 : $Foo, #Foo.x
+  store %4 to %5 : $*Int
+
+  %10 = alloc_ref [stack] $Bar
+  %12 = ref_element_addr %10 : $Bar, #Bar.x
+  %15 = integer_literal $Builtin.Int64, 1
+  %16 = struct $Int (%15 : $Builtin.Int64)
+  store %16 to %12 : $*Int
+
+  set_deallocating %10 : $Bar
+  dealloc_ref %10 : $Bar
+  dealloc_ref [stack] %10 : $Bar
+
+  copy_addr %5 to %0 : $*Int
+
+  %20 = tuple()
+  return %20 : $()
+}