Add some TODOs

src/jit/codegenarmarch.cpp

@@ -1949,6 +1949,13 @@ void CodeGen::genCodeForInitBlkUnroll(GenTreeBlk* node)
     }
     else
     {
+        // TODO-CQ: If the local frame offset is too large to be encoded, the emitter automatically
+        // loads the offset into a reserved register (see CodeGen::rsGetRsvdReg()). If we generate
+        // multiple store instructions we'll also generate multiple offset loading instructions.
+        // We could try to detect such cases, compute the base destination address in this reserved
+        // and use it in all store instructions we generate. Basically this would undo the effect
+        // of local address containment done by lowering.
+
         assert(dstAddr->OperIsLocalAddr());
         dstLclNum = dstAddr->AsLclVarCommon()->GetLclNum();
 
@@ -2078,6 +2085,15 @@ void CodeGen::genCodeForCpBlkUnroll(GenTreeBlk* node)
     }
     else
     {
+        // TODO-CQ: If the local frame offset is too large to be encoded, the emitter automatically
+        // loads the offset into a reserved register (see CodeGen::rsGetRsvdReg()). If we generate
+        // multiple store instructions we'll also generate multiple offset loading instructions.
+        // We could try to detect such cases, compute the base destination address in this reserved
+        // and use it in all store instructions we generate. Basically this would undo the effect
+        // of local address containment done by lowering.
+        //
+        // Same for the local source address case below.
+
         assert(dstAddr->OperIsLocalAddr());
         dstLclNum = dstAddr->AsLclVarCommon()->GetLclNum();
 

src/jit/codegenxarch.cpp

@@ -3083,6 +3083,8 @@ void CodeGen::genCodeForInitBlkUnroll(GenTreeBlk* node)
             emit->emitIns_R_R(INS_punpckldq, EA_16BYTE, srcXmmReg, srcXmmReg);
 #ifdef _TARGET_X86_
             // For x86, we need one more to convert it from 8 bytes to 16 bytes.
+            // TODO-CQ: Instead of 2 punpckldq we could use a single pshufd. This can also be useful
+            // on x64 as it may avoid the need for an 8 byte immediate.
             emit->emitIns_R_R(INS_punpckldq, EA_16BYTE, srcXmmReg, srcXmmReg);
 #endif
         }