[dev.ssa] cmd/compile/internal/ssa: handle returns correctly
Make sure that return blocks take a store as their control. Without
this, code was getting inserted between the return and exit blocks.
Use AEND to mark the end of code. The live variable analysis gets
confused when routines end like:
JMP earlier
RET
because the RET is unreachable. The RET was incorrectly added to the
last basic block, rendering the JMP invisible to the CFG builder.
Change-Id: I91b32c8b37075347243ff039b4e4385856fba7cd
Reviewed-on: https://go-review.googlesource.com/14398
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
diff --git a/src/cmd/compile/internal/gc/plive.go b/src/cmd/compile/internal/gc/plive.go
index fa8bc20..2ac6396 100644
--- a/src/cmd/compile/internal/gc/plive.go
+++ b/src/cmd/compile/internal/gc/plive.go
@@ -425,7 +425,7 @@
bb := newblock(firstp)
cfg = append(cfg, bb)
- for p := firstp; p != nil; p = p.Link {
+ for p := firstp; p != nil && p.As != obj.AEND; p = p.Link {
Thearch.Proginfo(p)
if p.To.Type == obj.TYPE_BRANCH {
if p.To.Val == nil {
@@ -453,7 +453,7 @@
// contained instructions until a label is reached. Add edges
// for branches and fall-through instructions.
for _, bb := range cfg {
- for p := bb.last; p != nil; p = p.Link {
+ for p := bb.last; p != nil && p.As != obj.AEND; p = p.Link {
if p.Opt != nil && p != bb.last {
break
}
@@ -462,6 +462,8 @@
// Stop before an unreachable RET, to avoid creating
// unreachable control flow nodes.
if p.Link != nil && p.Link.As == obj.ARET && p.Link.Mode == 1 {
+ // TODO: remove after SSA is done. SSA does not
+ // generate any unreachable RET instructions.
break
}
diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index 96d6204..9791967 100644
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -116,8 +116,11 @@
s.stmtList(fn.Nbody)
// fallthrough to exit
- if b := s.endBlock(); b != nil {
+ if s.curBlock != nil {
+ m := s.mem()
+ b := s.endBlock()
b.Kind = ssa.BlockRet
+ b.Control = m
b.AddEdgeTo(s.exit)
}
@@ -575,8 +578,10 @@
case ORETURN:
s.stmtList(n.List)
+ m := s.mem()
b := s.endBlock()
b.Kind = ssa.BlockRet
+ b.Control = m
b.AddEdgeTo(s.exit)
case OCONTINUE, OBREAK:
@@ -2631,8 +2636,6 @@
p.To.Val = s.deferTarget
}
- Pc.As = obj.ARET // overwrite AEND
-
if logProgs {
for p := ptxt; p != nil; p = p.Link {
var s string
diff --git a/src/cmd/compile/internal/ssa/check.go b/src/cmd/compile/internal/ssa/check.go
index 4b38bec..b860f63 100644
--- a/src/cmd/compile/internal/ssa/check.go
+++ b/src/cmd/compile/internal/ssa/check.go
@@ -63,8 +63,11 @@
if len(b.Succs) != 1 {
f.Fatalf("ret block %s len(Succs)==%d, want 1", b, len(b.Succs))
}
- if b.Control != nil {
- f.Fatalf("ret block %s has non-nil control %s", b, b.Control.LongString())
+ if b.Control == nil {
+ f.Fatalf("ret block %s has nil control %s", b)
+ }
+ if !b.Control.Type.IsMemory() {
+ f.Fatalf("ret block %s has non-memory control value %s", b, b.Control.LongString())
}
if b.Succs[0].Kind != BlockExit {
f.Fatalf("ret block %s has successor %s, not Exit", b, b.Succs[0].Kind)
diff --git a/src/cmd/compile/internal/ssa/gen/genericOps.go b/src/cmd/compile/internal/ssa/gen/genericOps.go
index 042d34e..9bc7790 100644
--- a/src/cmd/compile/internal/ssa/gen/genericOps.go
+++ b/src/cmd/compile/internal/ssa/gen/genericOps.go
@@ -369,9 +369,11 @@
// kind control successors
// ------------------------------------------
// Exit return mem []
+// Ret return mem [exit]
// Plain nil [next]
// If a boolean Value [then, else]
-// Call mem [nopanic, panic] (control opcode should be OpCall or OpStaticCall)
+// Call mem [nopanic, exit] (control opcode should be OpCall or OpStaticCall)
+// First nil [always,never]
var genericBlocks = []blockData{
{name: "Exit"}, // no successors. There should only be 1 of these.
