[dev.ssa] cmd/compile/ssa: place for loop incr in a separate block
This is a prerequisite for implementing break and continue;
blocks ending in break or continue need to have
the increment block as a successor.
While we're here, implement for loops with no condition.
Change-Id: I85d8ba020628d805bfd0bd583dfd16e1be6f6fae
Reviewed-on: https://go-review.googlesource.com/11941
Reviewed-by: Keith Randall <khr@golang.org>
diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index 866db61..96ae49a 100644
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -379,8 +379,10 @@
addEdge(b, s.exit)
case OFOR:
+ // OFOR: for Ninit; Left; Right { Nbody }
bCond := s.f.NewBlock(ssa.BlockPlain)
bBody := s.f.NewBlock(ssa.BlockPlain)
+ bIncr := s.f.NewBlock(ssa.BlockPlain)
bEnd := s.f.NewBlock(ssa.BlockPlain)
// first, jump to condition test
@@ -388,13 +390,14 @@
addEdge(b, bCond)
// generate code to test condition
- // TODO(khr): Left == nil exception
- if n.Left == nil {
- s.Unimplementedf("cond n.Left == nil: %v", n)
- }
s.startBlock(bCond)
- s.stmtList(n.Left.Ninit)
- cond := s.expr(n.Left)
+ var cond *ssa.Value
+ if n.Left != nil {
+ s.stmtList(n.Left.Ninit)
+ cond = s.expr(n.Left)
+ } else {
+ cond = s.entryNewValue0A(ssa.OpConst, Types[TBOOL], true)
+ }
b = s.endBlock()
b.Kind = ssa.BlockIf
b.Control = cond
@@ -405,13 +408,16 @@
// generate body
s.startBlock(bBody)
s.stmtList(n.Nbody)
+ if b := s.endBlock(); b != nil {
+ addEdge(b, bIncr)
+ }
+
+ // generate incr
+ s.startBlock(bIncr)
if n.Right != nil {
s.stmt(n.Right)
}
- b = s.endBlock()
- // If the body ends in a return statement,
- // the condition check and loop are unreachable.
- if b != nil {
+ if b := s.endBlock(); b != nil {
addEdge(b, bCond)
}
s.startBlock(bEnd)
