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| author | Keith Randall <khr@golang.org> | 2025-05-17 15:05:56 -0700 |
|---|---|---|
| committer | Keith Randall <khr@golang.org> | 2025-10-06 14:11:41 -0700 |
| commit | 719dfcf8a8478d70360bf3c34c0e920be7b32994 (patch) | |
| tree | d58aaf3289de3bb18901e34b336da46b425f8075 /src/runtime/panic.go | |
| parent | f3312124c2370c2f64a7f9ad29732ec30209647a (diff) | |
| download | go-719dfcf8a8478d70360bf3c34c0e920be7b32994.tar.xz | |
cmd/compile: redo arm64 LR/FP save and restore
Instead of storing LR (the return address) at 0(SP) and the FP
(parent's frame pointer) at -8(SP), store them at framesize-8(SP)
and framesize-16(SP), respectively.
We push and pop data onto the stack such that we're never accessing
anything below SP.
The prolog/epilog lengths are unchanged (3 insns for a typical prolog,
2 for a typical epilog).
We use 8 bytes more per frame.
Typical prologue:
STP.W (FP, LR), -16(SP)
MOVD SP, FP
SUB $C, SP
Typical epilogue:
ADD $C, SP
LDP.P 16(SP), (FP, LR)
RET
The previous word where we stored LR, at 0(SP), is now unused.
We could repurpose that slot for storing a local variable.
The new prolog and epilog instructions are recognized by libunwind,
so pc-sampling tools like perf should now be accurate. (TODO: except
maybe after the first RET instruction? Have to look into that.)
Update #73753 (fixes, for arm64)
Update #57302 (Quim thinks this will help on that issue)
Change-Id: I4800036a9a9a08aaaf35d9f99de79a36cf37ebb8
Reviewed-on: https://go-review.googlesource.com/c/go/+/674615
Reviewed-by: David Chase <drchase@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>
Diffstat (limited to 'src/runtime/panic.go')
| -rw-r--r-- | src/runtime/panic.go | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/src/runtime/panic.go b/src/runtime/panic.go index 8c91c9435a..04b3afe168 100644 --- a/src/runtime/panic.go +++ b/src/runtime/panic.go @@ -1379,10 +1379,10 @@ func recovery(gp *g) { // the caller gp.sched.bp = fp - 2*goarch.PtrSize case goarch.IsArm64 != 0: - // on arm64, the architectural bp points one word higher - // than the sp. fp is totally useless to us here, because it - // only gets us to the caller's fp. - gp.sched.bp = sp - goarch.PtrSize + // on arm64, the first two words of the frame are caller's PC + // (the saved LR register) and the caller's BP. + // Coincidentally, the same as amd64. + gp.sched.bp = fp - 2*goarch.PtrSize } gogo(&gp.sched) } |