This is quite messy so here are some suggestions and comments.
1) Check your version of the audio slice board and confirm if it matches the following posted and revised schematic - page 1:
Audio Slice Schematics
Assuming they do match, this is the (most) accurate reference point which should be used for your project. Note the PCI Express slot labels and port pins.
2) Noting the above, the webpage for the audio slice which you are referencing in your post is dated / old / out of sync with the revised schematic. This is quite common to XMOS designs and very frustrating and costly in invested time and rework of designs to developers. Note to XMOS - At the very least the work should be cross checked by more than one staff member for accuracy.
3) Moving forward, here is what we observed if you trace the schematic -> working code -> the posted webpage.
#define PORT_I2S_DAC0 XS1_PORT_1D
#define PORT_I2S_DAC1 XS1_PORT_1H ; webpage is incorrect - schematic from 04-2014 was revised & matches port label of working code
#define PORT_I2S_ADC0 XS1_PORT_1K ; webpage is incorrect - schematic from 04-2014 was revised & matches port label of working code
#define PORT_I2S_ADC1 XS1_PORT_1L
#define PORT_I2S_LRCLK XS1_PORT_1I ; webpage is incorrect - schematic from 04-2014 was revised & matches port label of working code
#define PORT_I2S_BCLK XS1_PORT_1A ; webpage is incorrect - schematic from 04-2014 was revised but applies
SCLK label; matches working code
#define PORT_MCLK_IN XS1_PORT_1E
#define PORT_GPIO XS1_PORT_4E
#define PORT_I2C XS1_PORT_4F
There are other errors on the webpage for the audio slice but not relevant to your immediate project. Again, review the schematic for their true pin mappings and definitions as they match the working code.
4) Perhaps a bit less important is the issue that in using the triangle port, you will be applying the use of PCI Express pins B2 and B4.
Download the SliceKit schematic to note how the triangle slice connector differs for these 2 pins:
SliceKit schematics
How to configure the mux so that you may use the shared pins on the Triangle slice port for your project:
Mux configuration logic
Observe that B2 and B4 (both have the EXT suffix in their labels) are being shared via a MUX with the SPI flash device. This multiplexer will allow the GPIO pins to steer the lines to either the SPI flash memory device OR to the Triangle slot. This may be a non-issue as the toolchain will apply small piece of code to allow you to use the B2 & B4 pins as your own after the SPI flash boot. However, will not hurt to confirm if this is indeed the proper configuration for your project. A simple test will be to toggle the respective lines and see if the PCIe slot (triangle) does the same. This auto-inserted mux code is valid when you properly define your Slicekit in the makefile.
Here is a nice discussion on topic for your review:
Discussion of mux on triangle port on SliceKit
Hope you have enough details to move forward on your project.
Disclaimer - have the audio slice kit but have not (yet) attempted to use on the Triangle slot but the above are our observations of the issue.