Treat INDEX_ADDRs as non-null (#69209)

* Treat INDEX_ADDRs as non-null

If they range check that is.

* Also use IsBoundsChecked in more places

Author: SingleAccretion

src/coreclr/jit/codegenarmarch.cpp

@@ -1796,7 +1796,7 @@ void CodeGen::genCodeForIndexAddr(GenTreeIndexAddr* node)
     const regNumber tmpReg = node->GetSingleTempReg();
 
     // Generate the bounds check if necessary.
-    if ((node->gtFlags & GTF_INX_RNGCHK) != 0)
+    if (node->IsBoundsChecked())
     {
         GetEmitter()->emitIns_R_R_I(INS_ldr, EA_4BYTE, tmpReg, base->GetRegNum(), node->gtLenOffset);
         GetEmitter()->emitIns_R_R(INS_cmp, emitActualTypeSize(index->TypeGet()), index->GetRegNum(), tmpReg);

src/coreclr/jit/codegenloongarch64.cpp

@@ -6744,7 +6744,7 @@ void CodeGen::genCodeForIndexAddr(GenTreeIndexAddr* node)
     assert(index->isUsedFromReg());
 
     // Generate the bounds check if necessary.
-    if ((node->gtFlags & GTF_INX_RNGCHK) != 0)
+    if (node->IsBoundsChecked())
     {
         GetEmitter()->emitIns_R_R_I(INS_ld_w, EA_4BYTE, REG_R21, base->GetRegNum(), node->gtLenOffset);
         // if (index >= REG_R21)

src/coreclr/jit/codegenxarch.cpp

@@ -4893,7 +4893,7 @@ void CodeGen::genCodeForIndexAddr(GenTreeIndexAddr* node)
 #endif
 
     // Generate the bounds check if necessary.
-    if ((node->gtFlags & GTF_INX_RNGCHK) != 0)
+    if (node->IsBoundsChecked())
     {
 #ifdef TARGET_64BIT
         // The CLI Spec allows an array to be indexed by either an int32 or a native int.  In the case that the index

src/coreclr/jit/flowgraph.cpp

@@ -945,6 +945,10 @@ bool Compiler::fgAddrCouldBeNull(GenTree* addr)
     {
         return false;
     }
+    else if (addr->OperIs(GT_INDEX_ADDR))
+    {
+        return !addr->AsIndexAddr()->IsNotNull();
+    }
     else if (addr->OperIs(GT_ARR_ADDR))
     {
         return (addr->gtFlags & GTF_ARR_ADDR_NONNULL) == 0;

src/coreclr/jit/gentree.h

@@ -6169,6 +6169,16 @@ struct GenTreeIndexAddr : public GenTreeOp
     {
     }
 #endif
+
+    bool IsBoundsChecked() const
+    {
+        return (gtFlags & GTF_INX_RNGCHK) != 0;
+    }
+
+    bool IsNotNull() const
+    {
+        return IsBoundsChecked();
+    }
 };
 
 // GenTreeArrAddr - GT_ARR_ADDR, carries information about the array type from morph to VN.