JIT: remove single-def restriction from escape analysis type refinement (#113808)

Instead, model all assignments to unescaped locals in the connection graph,
and deduce the new type via graph analysis.

Update the INDEX_ADDR expansion to handle cases where the array is stack
allocated (interior pointers are now TYP_I_IMPL, not TYP_BYREF).

Also use the new "unknown source" to do a more accurate analysis with OSR;
only OSR locals have unknown values.

Author: AndyAyersMS

src/coreclr/jit/gentree.cpp

@@ -7291,6 +7291,7 @@ bool GenTree::OperSupportsOrderingSideEffect() const
 
     switch (OperGet())
     {
+        case GT_ARR_ADDR:
         case GT_BOUNDS_CHECK:
         case GT_IND:
         case GT_BLK:

src/coreclr/jit/gentree.h

@@ -450,6 +450,7 @@ enum GenTreeFlags : unsigned int
     GTF_VAR_MOREUSES      = 0x00800000, // GT_LCL_VAR -- this node has additional uses, for example due to cloning
     GTF_VAR_CONTEXT       = 0x00400000, // GT_LCL_VAR -- this node is part of a runtime lookup
     GTF_VAR_EXPLICIT_INIT = 0x00200000, // GT_LCL_VAR -- this node is an "explicit init" store. Valid until rationalization.
+    GTF_VAR_CONNECTED     = 0x00100000, // GT_STORE_LCL_VAR -- this store was modelled in the connection graph during escape analysis
 
     // For additional flags for GT_CALL node see GTF_CALL_M_*
 

src/coreclr/jit/morph.cpp

@@ -3181,17 +3181,21 @@ GenTree* Compiler::fgMorphIndexAddr(GenTreeIndexAddr* indexAddr)
     }
 #endif
 
+    // Note the array reference may now be TYP_I_IMPL, TYP_BYREF, or TYP_REF
+    //
+    var_types const arrPtrType = arrRef->TypeIs(TYP_I_IMPL) ? TYP_I_IMPL : TYP_BYREF;
+
     // First element's offset
     GenTree* elemOffset = gtNewIconNode(elemOffs, TYP_I_IMPL);
     if (groupArrayRefWithElemOffset)
     {
-        GenTree* basePlusOffset = gtNewOperNode(GT_ADD, TYP_BYREF, arrRef, elemOffset);
-        addr                    = gtNewOperNode(GT_ADD, TYP_BYREF, basePlusOffset, addr);
+        GenTree* basePlusOffset = gtNewOperNode(GT_ADD, arrPtrType, arrRef, elemOffset);
+        addr                    = gtNewOperNode(GT_ADD, arrPtrType, basePlusOffset, addr);
     }
     else
     {
         addr = gtNewOperNode(GT_ADD, TYP_I_IMPL, addr, elemOffset);
-        addr = gtNewOperNode(GT_ADD, TYP_BYREF, arrRef, addr);
+        addr = gtNewOperNode(GT_ADD, arrPtrType, arrRef, addr);
     }
 
     // TODO-Throughput: bash the INDEX_ADDR to ARR_ADDR here instead of creating a new node.