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ddc6b64444
Make sure we do any just-before-return cleanup on all paths out of a function, including when recovering. Each exit path should include deferreturn (if there are any defers) and then the exit code (e.g. copying heap-escaping return values back to the stack). Introduce a Defer SSA block type which has two outgoing edges - one the fallthrough edge (the defer was queued successfully) and one which immediately returns (the defer had a successful recover() call and normal execution should resume at the return point). Fixes #14725 Change-Id: Iad035c9fd25ef8b7a74dafbd7461cf04833d981f Reviewed-on: https://go-review.googlesource.com/20486 Reviewed-by: David Chase <drchase@google.com>
86 lines
1.8 KiB
Go
86 lines
1.8 KiB
Go
package ssa
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// phiopt eliminates boolean Phis based on the previous if.
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//
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// Main use case is to transform:
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// x := false
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// if b {
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// x = true
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// }
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// into x = b.
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//
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// In SSA code this appears as
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//
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// b0
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// If b -> b1 b2
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// b1
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// Plain -> b2
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// b2
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// x = (OpPhi (ConstBool [true]) (ConstBool [false]))
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//
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// In this case we can replace x with a copy of b.
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func phiopt(f *Func) {
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for _, b := range f.Blocks {
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if len(b.Preds) != 2 || len(b.Values) == 0 {
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continue
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}
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pb0, b0 := b, b.Preds[0]
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for len(b0.Succs) == 1 && len(b0.Preds) == 1 {
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pb0, b0 = b0, b0.Preds[0]
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}
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if b0.Kind != BlockIf {
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continue
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}
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pb1, b1 := b, b.Preds[1]
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for len(b1.Succs) == 1 && len(b1.Preds) == 1 {
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pb1, b1 = b1, b1.Preds[0]
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}
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if b1 != b0 {
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continue
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}
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// b0 is the if block giving the boolean value.
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var reverse bool
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if b0.Succs[0] == pb0 && b0.Succs[1] == pb1 {
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reverse = false
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} else if b0.Succs[0] == pb1 && b0.Succs[1] == pb0 {
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reverse = true
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} else {
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b.Fatalf("invalid predecessors\n")
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}
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for _, v := range b.Values {
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if v.Op != OpPhi || !v.Type.IsBoolean() || v.Args[0].Op != OpConstBool || v.Args[1].Op != OpConstBool {
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continue
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}
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ok, isCopy := false, false
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if v.Args[0].AuxInt == 1 && v.Args[1].AuxInt == 0 {
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ok, isCopy = true, !reverse
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} else if v.Args[0].AuxInt == 0 && v.Args[1].AuxInt == 1 {
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ok, isCopy = true, reverse
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}
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// (Phi (ConstBool [x]) (ConstBool [x])) is already handled by opt / phielim.
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if ok && isCopy {
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if f.pass.debug > 0 {
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f.Config.Warnl(int(b.Line), "converted OpPhi to OpCopy")
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}
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v.reset(OpCopy)
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v.AddArg(b0.Control)
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continue
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}
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if ok && !isCopy {
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if f.pass.debug > 0 {
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f.Config.Warnl(int(b.Line), "converted OpPhi to OpNot")
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}
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v.reset(OpNot)
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v.AddArg(b0.Control)
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continue
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}
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}
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}
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}
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