[DebugInfo] Remove Expr from debug variables used as DenseMap keys

We do keep the fragment part of the expression as it is important
to identify fragments separately.

A variable with less fragments should be considered a superset of
variables with more fragments, but that would require to change a
lot of code.

(cherry picked from commit b293099)

Author: Snowy1803

include/swift/SIL/SILDebugInfoExpression.h

@@ -296,6 +296,16 @@ class SILDebugInfoExpression {
     return Elements.size() &&
            Elements[0].getAsOperator() == SILDIExprOperator::Dereference;
   }
+
+  /// Return the part of this SILDebugInfoExpression corresponding to fragments
+  SILDebugInfoExpression getFragmentPart() const {
+    for (auto it = element_begin(), end = element_end(); it != end; ++it) {
+      if (it->getAsOperator() == SILDIExprOperator::Fragment
+          || it->getAsOperator() == SILDIExprOperator::TupleFragment)
+        return SILDebugInfoExpression(ArrayRef(it, element_end()));
+    }
+    return {};
+  }
 };
 
 /// Returns the hashcode for the di expr element.

lib/SILOptimizer/Mandatory/DebugInfoCanonicalizer.cpp

@@ -221,6 +221,9 @@ bool DebugInfoCanonicalizer::process() {
           LLVM_DEBUG(llvm::dbgs() << "        Has no var info?! Skipping!\n");
           continue;
         }
+        // Strip things we don't need in the map.
+        debugInfo->DIExpr = debugInfo->DIExpr.getFragmentPart();
+        debugInfo->Type = {};
 
         // Otherwise, we may have a new debug_value to track. Try to begin
         // tracking it...

lib/SILOptimizer/Mandatory/MoveOnlyUtils.cpp

@@ -336,8 +336,7 @@ static bool isLetAllocation(MarkUnresolvedNonCopyableValueInst *mmci) {
   }
 
   if (auto *asi = dyn_cast<AllocStackInst>(mmci->getOperand()))
-    if (auto varInfo = asi->getVarInfo())
-      return varInfo->isLet();
+    return asi->isLet();
 
   return false;
 }

lib/SILOptimizer/Mandatory/MovedAsyncVarDebugInfoPropagator.cpp

@@ -347,8 +347,11 @@ struct DebugInfoPropagator {
     // var with a count already and return that value. If we did not, we insert
     // with the new count before expanding the set (initializing the map with
     // the correct value).
+    auto debugVariable = debugVar;
+    debugVariable.DIExpr = debugVariable.DIExpr.getFragmentPart();
+    debugVariable.Type = {};
     auto iter = dbgVarToDbgVarIndexMap.insert(
-        {debugVar, dbgVarToDbgVarIndexMap.size()});
+        {debugVariable, dbgVarToDbgVarIndexMap.size()});
     LLVM_DEBUG(if (iter.second) llvm::dbgs()
                    << "Mapping: [" << iter.first->second
                    << "] = " << iter.first->first.Name << '\n';);

test/SILOptimizer/debuginfo_canonicalizer.sil

@@ -118,7 +118,7 @@ bb3:
 // CHECK: } // end sil function 'testUndefDiamond'
 sil @testUndefDiamond : $@convention(thin) (@guaranteed Klass) -> () {
 bb0(%0 : $Klass):
-  debug_value [moveable_value_debuginfo] %0 : $Klass, let, name "arg"
+  debug_value [moveable_value_debuginfo] %0 : $Klass, let, (name "arg", loc "debuginfo_canonicalizer.sil":121:3)
   %f = function_ref @yieldOnceCoroutine : $@yield_once @convention(method) (@guaranteed Klass) -> @yields @inout Int64
   (%3, %token) = begin_apply %f(%0) : $@yield_once @convention(method) (@guaranteed Klass) -> @yields @inout Int64
   cond_br undef, bb1, bb2
@@ -128,7 +128,7 @@ bb1:
   br bb3
 
 bb2:
-  debug_value [moveable_value_debuginfo] undef : $Klass, let, name "arg"
+  debug_value [moveable_value_debuginfo] undef : $Klass, let, (name "arg", loc "debuginfo_canonicalizer.sil":121:3)
   abort_apply %token
   br bb3