Steps to reproduce:

1. Open the linked project (or set up a project for HDRP usage from https://github.com/Unity-Technologies/ScriptableRenderPipeline)
2. Switch to iOS
3. Build 'BasicProfiling' scene for iOS
4. Run it on device
5. Let it run for a few seconds (up to a minute)
6. Notice the app is killed due to running out of memory

Notes:
This happen with all the scenes I tried to build, though while simpler scenes like 'BasicProfiling' or 'GammaTest' take a bit of time until it crashes, bigger scenes like 'HDRenderLoopTest' or 'ShadowsTest' sometimes fail to render at all and spam the following error until the "ran out of memory" crash happens:

2018-01-22 14:19:20.671095+0200 ProductName[1835:1511362] Execution of the command buffer was aborted due to an error during execution. Ignored (for causing prior/excessi[HDRP][iOS] ve GPU errors) (IOAF code 4)

Devices tested:
iPhone 7 Plus (iOS 11.1.1)
iPhone 8 (iOS 11.0)
iPhone X (iOS 11.2)