runtime: memory corruption on mips builders

[gopherbot]

#!watchflakes
post <- goarch == "mips64le" && (`SIGILL` || log ~ `SIGILL` || `SIGSEGV` || log ~ `SIGSEGV`)

Issue created automatically to collect these failures.

Example (log):

=== RUN   TestDiagnosticErrorInEditedFile/gopackages/default
SIGILL: illegal instruction
PC=0x120080648 m=12 sigcode=128
instruction bytes: 0x2d 0x50 0x4b 0x1 0xf 0x0 0x0 0x0 0x0 0x0 0x4a 0x8d 0xf 0x0 0x0 0x0

goroutine 0 gp=0x6aadbd8a80 m=12 mp=0x6aae6e5008 [idle]:
runtime.pMask.read(...)
	/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/proc.go:7319
runtime.stealWork(0x2eb5c31547c0)
	/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/proc.go:3860 +0x2a0 fp=0xff91e9a5c8 sp=0xff91e9a540 pc=0x120080648
...
r16  0xff91e9a560	r17  0x6aae6e5008
r18  0x0	r19  0x3558
r20  0x1aac0	r21  0x121efbcc0
r22  0x121e97ed8	r23  0x121f60000
r24  0x582b54e6e9cac6e6	r25  0xfffde80360
r26  0x0	r27  0x0
r28  0x100000000	r29  0xff91e9a540
r30  0x6aadbd8a80	r31  0x12008081c
pc   0x120080648	link 0x12008081c
lo   0x11925196	hi   0x0

— watchflakes

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
default <- pkg == "golang.org/x/tools/gopls/internal/test/integration/diagnostics" && test == "TestDiagnosticErrorInEditedFile/gopackages/default"

2026-02-09 11:50 x_tools-gotip-linux-mips64le tools@c4ec0f5f go@1bb3f4ed x/tools/gopls/internal/test/integration/diagnostics.TestDiagnosticErrorInEditedFile/gopackages/default [SKIP] (log)

=== RUN   TestDiagnosticErrorInEditedFile/gopackages/default
SIGILL: illegal instruction
PC=0x120080648 m=12 sigcode=128
instruction bytes: 0x2d 0x50 0x4b 0x1 0xf 0x0 0x0 0x0 0x0 0x0 0x4a 0x8d 0xf 0x0 0x0 0x0

goroutine 0 gp=0x6aadbd8a80 m=12 mp=0x6aae6e5008 [idle]:
runtime.pMask.read(...)
	/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/proc.go:7319
runtime.stealWork(0x2eb5c31547c0)
	/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/proc.go:3860 +0x2a0 fp=0xff91e9a5c8 sp=0xff91e9a540 pc=0x120080648
...
r16  0xff91e9a560	r17  0x6aae6e5008
r18  0x0	r19  0x3558
r20  0x1aac0	r21  0x121efbcc0
r22  0x121e97ed8	r23  0x121f60000
r24  0x582b54e6e9cac6e6	r25  0xfffde80360
r26  0x0	r27  0x0
r28  0x100000000	r29  0xff91e9a540
r30  0x6aadbd8a80	r31  0x12008081c
pc   0x120080648	link 0x12008081c
lo   0x11925196	hi   0x0

— watchflakes

[cherrymui]

cc @golang/mips