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pass: ensure frame pointer register is saved (#174)

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Currently `avo` uses `BP` as a standard general-purpose register. However, `BP` is used for the frame pointer and should be callee-save. Under some circumstances, the Go assembler will do this automatically, but not always. At the moment `avo` can produce code that clobbers the `BP` register. Since Go 1.16 this code will also fail a new `go vet` check.

This PR provides a (currently sub-optimal) fix for the issue. It introduces an `EnsureBasePointerCalleeSaved` pass which will check if the base pointer is written to by a function, and if so will artificially ensure that the function has a non-zero frame size. This will trigger the Go assembler to automatically save and restore the BP register.

In addition, we update the `asmdecl` tool to `asmvet`, which includes the `framepointer` vet check.

Updates #156
This commit is contained in:
Michael McLoughlin
2021-04-18 18:37:56 -07:00
committed by GitHub
parent 4592e16ebb
commit f295bde84c
16 changed files with 154 additions and 28 deletions
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1
pass/pass.go
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@@ -21,6 +21,7 @@ var Compile = Concat(
FunctionPass(AllocateRegisters),
FunctionPass(BindRegisters),
FunctionPass(VerifyAllocation),
FunctionPass(EnsureBasePointerCalleeSaved),
Func(IncludeTextFlagHeader),
FunctionPass(PruneSelfMoves),
FunctionPass(RequiredISAExtensions),