[dev.ssa] cmd/compile/internal/ssa: handle dead code a different way
Instead of trying to delete dead code as soon as we find it, just
mark it as dead using a PlainAndDead block kind. The deadcode pass
will do the real removal.
This way is somewhat more efficient because we don't need to mess
with successor and predecessor lists of all the dead blocks.
Fixes #12347
Change-Id: Ia42d6b5f9cdb3215a51737b3eb117c00bd439b13
Reviewed-on: https://go-review.googlesource.com/14033
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
diff --git a/src/cmd/compile/internal/ssa/rewritegeneric.go b/src/cmd/compile/internal/ssa/rewritegeneric.go
index b14ed9c..3ec4118 100644
--- a/src/cmd/compile/internal/ssa/rewritegeneric.go
+++ b/src/cmd/compile/internal/ssa/rewritegeneric.go
@@ -1574,27 +1574,25 @@
case BlockIf:
// match: (If (IsNonNil (GetG)) yes no)
// cond:
- // result: (Plain nil yes)
+ // result: (First nil yes no)
{
v := b.Control
if v.Op != OpIsNonNil {
- goto end0f2bb0111a86be0436b44210dbd83a90
+ goto endafdc4e2525f9933ab0ae7effc3559597
}
if v.Args[0].Op != OpGetG {
- goto end0f2bb0111a86be0436b44210dbd83a90
+ goto endafdc4e2525f9933ab0ae7effc3559597
}
yes := b.Succs[0]
no := b.Succs[1]
- b.Func.removePredecessor(b, no)
- b.Kind = BlockPlain
+ b.Kind = BlockFirst
b.Control = nil
- b.Succs = b.Succs[:1]
b.Succs[0] = yes
- b.Likely = BranchUnknown
+ b.Succs[1] = no
return true
}
- goto end0f2bb0111a86be0436b44210dbd83a90
- end0f2bb0111a86be0436b44210dbd83a90:
+ goto endafdc4e2525f9933ab0ae7effc3559597
+ endafdc4e2525f9933ab0ae7effc3559597:
;
// match: (If (Not cond) yes no)
// cond:
@@ -1619,53 +1617,50 @@
;
// match: (If (ConstBool {c}) yes no)
// cond: c.(bool)
- // result: (Plain nil yes)
+ // result: (First nil yes no)
{
v := b.Control
if v.Op != OpConstBool {
- goto end9ff0273f9b1657f4afc287562ca889f0
+ goto end7a20763049489cdb40bb1eaa57d113d8
}
c := v.Aux
yes := b.Succs[0]
no := b.Succs[1]
if !(c.(bool)) {
- goto end9ff0273f9b1657f4afc287562ca889f0
+ goto end7a20763049489cdb40bb1eaa57d113d8
}
- b.Func.removePredecessor(b, no)
- b.Kind = BlockPlain
+ b.Kind = BlockFirst
b.Control = nil
- b.Succs = b.Succs[:1]
b.Succs[0] = yes
- b.Likely = BranchUnknown
+ b.Succs[1] = no
return true
}
- goto end9ff0273f9b1657f4afc287562ca889f0
- end9ff0273f9b1657f4afc287562ca889f0:
+ goto end7a20763049489cdb40bb1eaa57d113d8
+ end7a20763049489cdb40bb1eaa57d113d8:
;
// match: (If (ConstBool {c}) yes no)
// cond: !c.(bool)
- // result: (Plain nil no)
+ // result: (First nil no yes)
{
v := b.Control
if v.Op != OpConstBool {
- goto endf401a4553c3c7c6bed64801da7bba076
+ goto end3ecbf5b2cc1f0a08444d8ab1871a829c
}
c := v.Aux
yes := b.Succs[0]
no := b.Succs[1]
if !(!c.(bool)) {
- goto endf401a4553c3c7c6bed64801da7bba076
+ goto end3ecbf5b2cc1f0a08444d8ab1871a829c
}
- b.Func.removePredecessor(b, yes)
- b.Kind = BlockPlain
+ b.Kind = BlockFirst
b.Control = nil
- b.Succs = b.Succs[:1]
b.Succs[0] = no
- b.Likely = BranchUnknown
+ b.Succs[1] = yes
+ b.Likely *= -1
return true
}
- goto endf401a4553c3c7c6bed64801da7bba076
- endf401a4553c3c7c6bed64801da7bba076:
+ goto end3ecbf5b2cc1f0a08444d8ab1871a829c
+ end3ecbf5b2cc1f0a08444d8ab1871a829c:
}
return false
}
