f295bde84c
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
fnv1a
FNV-1a in avo.
const (
OffsetBasis = 0xcbf29ce484222325
Prime = 0x100000001b3
)
func main() {
TEXT("Hash64", NOSPLIT, "func(data []byte) uint64")
Doc("Hash64 computes the FNV-1a hash of data.")
ptr := Load(Param("data").Base(), GP64())
n := Load(Param("data").Len(), GP64())
h := RAX
MOVQ(Imm(OffsetBasis), h)
p := GP64()
MOVQ(Imm(Prime), p)
Label("loop")
CMPQ(n, Imm(0))
JE(LabelRef("done"))
b := GP64()
MOVBQZX(Mem{Base: ptr}, b)
XORQ(b, h)
MULQ(p)
INCQ(ptr)
DECQ(n)
JMP(LabelRef("loop"))
Label("done")
Store(h, ReturnIndex(0))
RET()
Generate()
}