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101 lines
3.1 KiB
Go
101 lines
3.1 KiB
Go
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// Copyright 2020 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package ssa
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import "cmd/compile/internal/types"
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// expandCalls converts LE (Late Expansion) calls that act like they receive value args into a lower-level form
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// that is more oriented to a platform's ABI. The SelectN operations that extract results are also rewritten into
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// more appropriate forms.
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func expandCalls(f *Func) {
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canSSAType := f.fe.CanSSA
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sp, _ := f.spSb()
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// Calls that need lowering have some number of inputs, including a memory input,
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// and produce a tuple of (value1, value2, ..., mem) where valueK may or may not be SSA-able.
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// With the current ABI those inputs need to be converted into stores to memory,
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// rethreading the call's memory input to the first, and the new call now receiving the last.
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// With the current ABI, the outputs need to be converted to loads, which will all use the call's
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// memory output as their input.
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// Step 1: find all references to calls as values and rewrite those.
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for _, b := range f.Blocks {
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for _, v := range b.Values {
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switch v.Op {
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case OpSelectN:
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call := v.Args[0]
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aux := call.Aux.(*AuxCall)
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which := v.AuxInt
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t := v.Type
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if which == aux.NResults() { // mem is after the results.
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// rewrite v as a Copy of call -- the replacement call will produce a mem.
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v.copyOf(call)
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} else {
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pt := types.NewPtr(t)
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if canSSAType(t) {
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off := f.ConstOffPtrSP(pt, aux.OffsetOfResult(which), sp)
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v.reset(OpLoad)
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v.SetArgs2(off, call)
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} else {
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panic("Should not have non-SSA-able OpSelectN")
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}
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}
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v.Type = t // not right for the mem operand yet, but will be when call is rewritten.
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case OpSelectNAddr:
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call := v.Args[0]
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which := v.AuxInt
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aux := call.Aux.(*AuxCall)
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pt := v.Type
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off := f.ConstOffPtrSP(pt, aux.OffsetOfResult(which), sp)
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v.copyOf(off)
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}
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}
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}
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// Step 2: rewrite the calls
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for _, b := range f.Blocks {
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for _, v := range b.Values {
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switch v.Op {
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case OpStaticLECall:
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// Thread the stores on the memory arg
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m0 := v.Args[len(v.Args)-1]
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mem := m0
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pos := v.Pos.WithNotStmt()
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aux := v.Aux.(*AuxCall)
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auxInt := v.AuxInt
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for i, a := range v.Args {
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if a == m0 {
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break
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}
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if a.Op == OpDereference {
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// "Dereference" of addressed (probably not-SSA-eligible) value becomes Move
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src := a.Args[0]
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dst := f.ConstOffPtrSP(src.Type, aux.OffsetOfArg(int64(i)), sp)
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a.reset(OpMove)
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a.Pos = pos
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a.Type = types.TypeMem
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a.Aux = aux.TypeOfArg(int64(i))
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a.AuxInt = aux.SizeOfArg(int64(i))
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a.SetArgs3(dst, src, mem)
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mem = a
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} else {
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// Add a new store.
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t := aux.TypeOfArg(int64(i))
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dst := f.ConstOffPtrSP(types.NewPtr(t), aux.OffsetOfArg(int64(i)), sp)
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mem = b.NewValue3A(pos, OpStore, types.TypeMem, t, dst, a, mem)
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}
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}
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v.reset(OpStaticCall)
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v.Type = types.TypeMem
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v.Aux = aux
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v.AuxInt = auxInt
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v.SetArgs1(mem)
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}
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}
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}
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}
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