cmd/internal/obj/wasm: use 64-bit instructions for indirect calls

Currently, on Wasm, an indirect call is compiled to

	// function index = PC>>16, PC is already on stack
	I32WrapI64
	I32Const $16
	ShrU
	// set PC_B to 0
	...
	// actual call
	CallIndirect

Specifically, the function index is extracted from bits 16-31 of
the "PC". When there are more than 65536 functions, this will
overflow and wrap around, causing wrong function being called.

This CL changes it to use 64-bit operations to extract the
function index from the "PC", so there are enough bits to for it.

For #64856.

Change-Id: I83c11db4b78cf66250e88ac02a82bd13730a8914
Reviewed-on: https://go-review.googlesource.com/c/go/+/567896
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

0 files changed, 0 insertions, 0 deletions