Fix JitOptRepeat (dotnet#94250)

1. Remove an assertion checking assert that can be invalid under JitOptRepeat, where we might
lose information that a constant was ever a handle.
2. Disable JIT/Directed/debugging/debuginfo/tester.csproj under OptRepeat: optimizations
mess with its debug info expectations.
3. Enable JitOptRepeat under stress

src/coreclr/jit/assertionprop.cpp

@@ -866,6 +866,13 @@ void Compiler::optPrintAssertion(AssertionDsc* curAssertion, AssertionIndex asse
                         printf("Exact Type MT(0x%p %s)", dspPtr(iconVal),
                                eeGetClassName((CORINFO_CLASS_HANDLE)iconVal));
                     }
+
+                    // We might want to assert:
+                    //      assert(curAssertion->op2.HasIconFlag());
+                    // However, if we run CSE with shared constant mode, we may end up with an expression instead
+                    // of the original handle value. If we then use JitOptRepeat to re-build value numbers, we lose
+                    // knowledge that the constant was ever a handle, as the expression creating the original value
+                    // was not (and can't be) assigned a handle flag.
                 }
                 else if (curAssertion->op1.kind == O1K_SUBTYPE)
                 {
@@ -1876,7 +1883,6 @@ void Compiler::optDebugCheckAssertion(AssertionDsc* assertion)
             {
                 case O1K_EXACT_TYPE:
                 case O1K_SUBTYPE:
-                    assert(assertion->op2.HasIconFlag());
                     break;
                 case O1K_LCLVAR:
                     assert((lvaGetDesc(assertion->op1.lcl.lclNum)->lvType != TYP_REF) ||
@@ -5428,6 +5434,25 @@ GenTree* Compiler::optAssertionProp_Update(GenTree* newTree, GenTree* tree, Stat
             if (parent != nullptr)
             {
                 parent->ReplaceOperand(useEdge, newTree);
+
+                // If the parent is a GT_IND and we replaced the child with a handle constant, we might need
+                // to mark the GT_IND as invariant. This is the same as what gtNewIndOfIconHandleNode() does.
+                // Review: should some kind of more general morphing take care of this?
+                // Should this share code with gtNewIndOfIconHandleNode()?
+
+                if (parent->OperIs(GT_IND) && newTree->IsIconHandle())
+                {
+                    GenTreeFlags iconFlags = newTree->GetIconHandleFlag();
+                    if (GenTree::HandleKindDataIsInvariant(iconFlags))
+                    {
+                        parent->gtFlags |= GTF_IND_INVARIANT;
+                        if (iconFlags == GTF_ICON_STR_HDL)
+                        {
+                            // String literals are never null
+                            parent->gtFlags |= GTF_IND_NONNULL;
+                        }
+                    }
+                }
             }
             else
             {

src/coreclr/jit/jitconfigvalues.h

@@ -521,7 +521,7 @@ CONFIG_STRING(JitEnableInductionVariableOptsRange, W("JitEnableInductionVariable
 CONFIG_INTEGER(JitDoSsa, W("JitDoSsa"), 1) // Perform Static Single Assignment (SSA) numbering on the variables
 CONFIG_INTEGER(JitDoValueNumber, W("JitDoValueNumber"), 1) // Perform value numbering on method expressions
 
-CONFIG_INTEGER(JitEnableOptRepeat, W("JitEnableOptRepeat"), 0) // If zero, do not allow JitOptRepeat
+CONFIG_INTEGER(JitEnableOptRepeat, W("JitEnableOptRepeat"), 1) // If zero, do not allow JitOptRepeat
 CONFIG_METHODSET(JitOptRepeat, W("JitOptRepeat"))              // Runs optimizer multiple times on specified methods
 CONFIG_INTEGER(JitOptRepeatCount, W("JitOptRepeatCount"), 2)   // Number of times to repeat opts when repeating
 CONFIG_STRING(JitOptRepeatRange, W("JitOptRepeatRange"))       // Enable JitOptRepeat based on method hash range

src/tests/JIT/Directed/debugging/debuginfo/tester.csproj

@@ -14,6 +14,7 @@
     <CLRTestEnvironmentVariable Include="DOTNET_JitNoForwardSub" Value="1" />
     <CLRTestEnvironmentVariable Include="DOTNET_JitEnableHeadTailMerge" Value="0" />
     <CLRTestEnvironmentVariable Include="DOTNET_JitEnableCrossBlockLocalAssertionProp" Value="0" />
+    <CLRTestEnvironmentVariable Include="DOTNET_JitEnableOptRepeat" Value="0" />
 
     <ProjectReference Include="tests_d.ilproj" Aliases="tests_d" />
     <ProjectReference Include="tests_r.ilproj" Aliases="tests_r" />