cmd/compile: linux/arm stalls during bootstrap at tip as of "use tail calls for wrappers for embedded interfaces"

[dmitshur]

CL 751465 fixed #77781 but caused linux/arm to run into a https://ci.chromium.org/b/8687988093932136273 failure mode. As of CL 752560, the failure mode of linux/arm is different, namely make.bash runs for 3 hrs+ and times out before completing.

See https://ci.chromium.org/b/8687731122429485201 for example, or other recent builds.

CC @randall77.

[gabyhelp]

Related Issues

• x/build: frequent "unexpected stale targets" on linux-arm-arm5spacemonkey after bootstrapping is complete #35740 (closed)

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[randall77]

Found the immediate problem, in the archive/zip test binary:

TEXT archive/zip.(*ReadCloser).Open(SB) <autogenerated>
  <autogenerated>:1     0x219a1c                e59d0004                MOVW 0x4(R13), R0       
  <autogenerated>:1     0x219a20                e1d0b0d0                MOVBS (R0), R11         
  <autogenerated>:1     0x219a24                e28d1000                ADD $0, R13, R1         
  <autogenerated>:1     0x219a28                e2800004                ADD $4, R0, R0          
  <autogenerated>:1     0x219a2c                e5810004                MOVW R0, 0x4(R1)        
  <autogenerated>:1     0x219a30                e59d0008                MOVW 0x8(R13), R0       
  <autogenerated>:1     0x219a34                e5810008                MOVW R0, 0x8(R1)        
  <autogenerated>:1     0x219a38                e59d000c                MOVW 0xc(R13), R0       
  <autogenerated>:1     0x219a3c                e581000c                MOVW R0, 0xc(R1)        
  <autogenerated>:1     0x219a40                eafffffe                B 0x219a40              

Notice the last branch branches to itself. I think a relocation is missing or not being applied correctly. That branch should go somewhere else.
Instead it infinite loops.

[gopherbot]

Change https://go.dev/cl/753840 mentions this issue: cmd/compile: fix arm direct tail call