Already it saves 2 bytes per call, but also the constant pool
entry may well be shared across multiple calls.
Backports commit 4e45f23943c0bb91588627de3801826546155ad8 from qemu
A new shared header tcg-pool.inc.c adds new_pool_label,
for registering a tcg_target_ulong to be emitted after
the generated code, plus relocation data to install a
pointer to the data.
A new pointer is added to the TCGContext, so that we
dump the constant pool as data, not code.
Backports commit 57a269469dbf70013dab3a176e1735636010a772 from qemu