Package host assembly into runtime artifact #48
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# Local heap optimizations on Arm64 1. When not required to zero the allocated space for local heap (for sizes up to 64 bytes) - do not emit zeroing sequence. Instead do stack probing and adjust stack pointer: ```diff - stp xzr, xzr, [sp,#-16]! - stp xzr, xzr, [sp,#-16]! - stp xzr, xzr, [sp,#-16]! - stp xzr, xzr, [sp,#-16]! + ldr wzr, [sp],#-64 ``` 2. For sizes less than one `PAGE_SIZE` use `ldr wzr, [sp], #-amount` that does probing at `[sp]` and allocates the space at the same time. This saves one instruction for such local heap allocations: ```diff - ldr wzr, [sp] - sub sp, sp, #208 + ldr wzr, [sp],#-208 ``` Use `ldp tmpReg, xzr, [sp], #-amount` when the offset not encodable by post-index variant of `ldr`: ```diff - ldr wzr, [sp] - sub sp, sp, dotnet#512 + ldp x0, xzr, [sp],#-512 ``` 3. Allow non-loop zeroing (i.e. unrolled sequence) for sizes up to 128 bytes (i.e. up to `LCLHEAP_UNROLL_LIMIT`). This frees up two internal integer registers for such cases: ```diff - mov w11, #128 - ;; bbWeight=0.50 PerfScore 0.25 -G_M44913_IG19: ; gcrefRegs=00F9 {x0 x3 x4 x5 x6 x7}, byrefRegs=0000 {}, byref, isz stp xzr, xzr, [sp,#-16]! - subs x11, x11, #16 - bne G_M44913_IG19 + stp xzr, xzr, [sp,#-112]! + stp xzr, xzr, [sp,#16] + stp xzr, xzr, [sp,#32] + stp xzr, xzr, [sp,#48] + stp xzr, xzr, [sp,#64] + stp xzr, xzr, [sp,#80] + stp xzr, xzr, [sp,#96] ``` 4. Do zeroing in ascending order of the effective address: ```diff - mov w7, #96 -G_M49279_IG13: stp xzr, xzr, [sp,#-16]! - subs x7, x7, #16 - bne G_M49279_IG13 + stp xzr, xzr, [sp,#-80]! + stp xzr, xzr, [sp,#16] + stp xzr, xzr, [sp,#32] + stp xzr, xzr, [sp,#48] + stp xzr, xzr, [sp,#64] ``` In the example, the zeroing is done at `[initialSp-16], [initialSp-96], [initialSp-80], [initialSp-64], [initialSp-48], [initialSp-32]` addresses. The idea here is to allow a CPU to detect the sequential `memset` to `0` pattern and switch into write streaming mode.
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Avoid an extra artifact as the runtimes need this to function in Unity anyway.
This will require changes to the Unity integration once this lands.