| commit | 4ea7aa7cf3755533634904d934c89f93d461d642 | [log] [tgz] |
|---|---|---|
| author | Cherry Zhang <cherryyz@google.com> | Tue Jun 25 14:48:04 2019 -0400 |
| committer | Cherry Zhang <cherryyz@google.com> | Wed Jun 26 16:01:47 2019 +0000 |
| tree | c2bbd74b1f9f4d4e5b131b0afb881039b5818722 | |
| parent | 24f7d89a73b7bd77127a56e8a8552c48278d251b [diff] |
cmd/compile, runtime: use R20, R21 in ARM64's Duff's devices Currently we use R16 and R17 for ARM64's Duff's devices. According to ARM64 ABI, R16 and R17 can be used by the (external) linker as scratch registers in trampolines. So don't use these registers to pass information across functions. It seems unlikely that calling Duff's devices would need a trampoline in normal cases. But it could happen if the call target is out of the 128 MB direct jump limit. The choice of R20 and R21 is kind of arbitrary. The register allocator allocates from low-numbered registers. High numbered registers are chosen so it is unlikely to hold a live value and forces a spill. Fixes #32773. Change-Id: Id22d555b5afeadd4efcf62797d1580d641c39218 Reviewed-on: https://go-review.googlesource.com/c/go/+/183842 Run-TryBot: Cherry Zhang <cherryyz@google.com> Reviewed-by: Keith Randall <khr@golang.org>
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