jit(arm64): support call instruction

wasm/jit/jit_amd64.go

@@ -4729,8 +4729,8 @@ func (c *amd64Compiler) callFunction(addr wasm.FunctionAddress, addrReg int16, f
 
 	// 2) Set engine.valueStackContext.stackBasePointer for the next function.
 	{
-		// At this point, tmpRegister holds the OLD stack base pointer. We could get the new frame's
-		// stack base pointer by "OLD stack base pointer + OLD stack pointer - # of function params"
+		// At this point, tmpRegister holds the old stack base pointer. We could get the new frame's
+		// stack base pointer by "old stack base pointer + old stack pointer - # of function params"
 		// See the comments in engine.pushCallFrame which does exactly the same calculation in Go.
 		calculateNextStackBasePointer := c.newProg()
 		calculateNextStackBasePointer.As = x86.AADDQ
@@ -4870,8 +4870,7 @@ func (c *amd64Compiler) returnFunction() error {
 	// Obtain the temporary registers to be used in the followings.
 	regs, found := c.locationStack.takeFreeRegisters(generalPurposeRegisterTypeInt, 3)
 	if !found {
-		// This in theory never happen as all the registers must be free except addrReg.
-		return fmt.Errorf("could not find enough free registers")
+		return fmt.Errorf("BUG: all the registers should be free at this point")
 	}
 	c.locationStack.markRegisterUsed(regs...)