[AddressLowering] Reserve capacity, don't resize.

Resizing a SmallVector of SILValues fills it with invalid SILValues.
THe intent is to reserve space for forthcoming values.

Author: nate-chandler

lib/SILOptimizer/Mandatory/AddressLowering.cpp

@@ -1159,7 +1159,7 @@ void OpaqueStorageAllocation::allocatePhi(PhiValue phi) {
   coalescedPhi.coalesce(phi, pass.valueStorageMap);
 
   SmallVector<SILValue, 4> coalescedValues;
-  coalescedValues.resize(coalescedPhi.getCoalescedOperands().size());
+  coalescedValues.reserve(coalescedPhi.getCoalescedOperands().size());
   for (SILValue value : coalescedPhi.getCoalescedValues())
     coalescedValues.push_back(value);
 

test/SILOptimizer/address_lowering_phi.sil

@@ -500,3 +500,20 @@ merge(%34 : @owned $Value):
   %43 = tuple ()
   return %43 : $()
 }
+
+// CHECK-LABEL: sil [ossa] @f105_phi_into_tuple : {{.*}} {
+// CHECK:         [[STORAGE:%[^,]+]] = alloc_stack $(Self, Builtin.Int1)          
+// CHECK:         [[SELF_ADDR:%[^,]+]] = tuple_element_addr [[STORAGE]]
+// CHECK:         apply {{%[^,]+}}<Self>([[SELF_ADDR]])
+// CHECK-LABEL: } // end sil function 'f105_phi_into_tuple'
+sil [ossa] @f105_phi_into_tuple : $@convention(thin) <Self> () -> () {
+  %getOut = function_ref @getOut : $@convention(thin) <T> () -> @out T
+  %self = apply %getOut<Self>() : $@convention(thin) <τ_0_0> () -> @out τ_0_0
+  br exit(%self : $Self)
+
+exit(%self_2 : @owned $Self):
+  %tuple = tuple (%self_2 : $Self, undef : $Bool)
+  destroy_value %tuple : $(Self, Bool)
+  %retval = tuple ()
+  return %retval : $()
+}