[debug-var] When comparing address debug_value against value debug_value remove the diexpr from the address SILDebugVariable.

Otherwise they will never compare the same. Also restore the test that was
updated for the previous commit to its old state. I did this to ensure that each
commit would compile successfully and so that I could show the test associated
with this commit.

Author: gottesmm

include/swift/SIL/SILDebugVariable.h

@@ -62,6 +62,12 @@ struct SILDebugVariable {
            Scope == V.Scope && DIExpr == V.DIExpr;
   }
 
+  SILDebugVariable withoutDIExpr() const {
+    auto result = *this;
+    result.DIExpr = {};
+    return result;
+  }
+
   bool isLet() const { return Name.size() && Constant; }
 
   bool isVar() const { return Name.size() && !Constant; }

lib/SILOptimizer/Transforms/SILMem2Reg.cpp

@@ -167,30 +167,36 @@ static void promoteDebugValueAddr(DebugValueInst *dvai, SILValue value,
   assert(dvai->getOperand()->getType().isLoadable(*dvai->getFunction()) &&
          "Unexpected promotion of address-only type!");
   assert(value && "Expected valid value");
+
   // Avoid inserting the same debug_value twice.
+  //
+  // We remove the di expression when comparing since:
+  //
+  // 1. dvai is on will always have the deref diexpr since it is on addresses.
+  //
+  // 2. We are only trying to delete debug_var that are on values... values will
+  //    never have an op_deref meaning that the comparison will always fail and
+  //    not serve out purpose here.
+  auto dvaiWithoutDIExpr = dvai->getVarInfo()->withoutDIExpr();
   for (auto *use : value->getUses()) {
     if (auto *dvi = dyn_cast<DebugValueInst>(use->getUser())) {
-      // Since we're not comparing di-expression in
-      // SILDebugVariable::operator==(), it's necessary to distinguish
-      // debug_value w/ normal values from that with address-type values.
-      if (!dvi->hasAddrVal() &&
-          *dvi->getVarInfo() == *dvai->getVarInfo()) {
+      if (!dvi->hasAddrVal() && *dvi->getVarInfo() == dvaiWithoutDIExpr) {
         deleter.forceDelete(dvai);
         return;
       }
     }
   }
 
-  auto VarInfo = *dvai->getVarInfo();
   // Drop op_deref if dvai is actually a debug_value instruction
+  auto varInfo = *dvai->getVarInfo();
   if (isa<DebugValueInst>(dvai)) {
-    auto &DIExpr = VarInfo.DIExpr;
-    if (DIExpr)
-      DIExpr.eraseElement(DIExpr.element_begin());
+    auto &diExpr = varInfo.DIExpr;
+    if (diExpr)
+      diExpr.eraseElement(diExpr.element_begin());
   }
 
   SILBuilderWithScope b(dvai, ctx);
-  b.createDebugValue(dvai->getLoc(), value, std::move(VarInfo));
+  b.createDebugValue(dvai->getLoc(), value, std::move(varInfo));
   deleter.forceDelete(dvai);
 }
 

test/SILOptimizer/specialize_unconditional_checked_cast.swift

@@ -97,13 +97,9 @@ ArchetypeToConcreteConvertUInt8(t: c)
 ArchetypeToConcreteConvertUInt8(t: f)
 
 // x -> x where x is not a class.
-//
-// TODO: Why is the optimizer cloning twice here.
-//
 // CHECK-LABEL: sil shared [noinline] @$s37specialize_unconditional_checked_cast31ArchetypeToConcreteConvertUInt8{{[_0-9a-zA-Z]*}}3Not{{.*}}Tg5 : $@convention(thin) (NotUInt8) -> NotUInt8 {
 // CHECK: bb0
 // CHECK-NEXT: debug_value %0
-// CHECK-NEXT: debug_value %0
 // CHECK-NEXT: return %0
 
 // x -> y where y is a class but x is not.
@@ -124,7 +120,6 @@ ArchetypeToConcreteConvertUInt8(t: f)
 // CHECK-LABEL: sil shared [noinline] @$s37specialize_unconditional_checked_cast27ArchetypeToConcreteConvertC{{[_0-9a-zA-Z]*}}Tg5 : $@convention(thin) (@guaranteed C) -> @owned C {
 // CHECK: bb0([[ARG:%.*]] : $C)
 // CHECK-NEXT: debug_value [[ARG]]
-// CHECK-NEXT: debug_value [[ARG]]
 // CHECK-NEXT: strong_retain [[ARG]]
 // CHECK-NEXT: return [[ARG]]