[dev.ssa] cmd/compile: optimize phi ops
Redo how we keep track of forward references when building SSA.
When the forward reference is resolved, update the Value node
in place.
Improve the phi elimination pass so it can simplify phis of phis.
Give SSA package access to decoded line numbers. Fix line numbers
for constant booleans.
Change-Id: I3dc9896148d260be2f3dd14cbe5db639ec9fa6b7
Reviewed-on: https://go-review.googlesource.com/18674
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
diff --git a/src/cmd/compile/internal/ssa/gen/genericOps.go b/src/cmd/compile/internal/ssa/gen/genericOps.go
index d17f558..5c1a7af 100644
--- a/src/cmd/compile/internal/ssa/gen/genericOps.go
+++ b/src/cmd/compile/internal/ssa/gen/genericOps.go
@@ -371,6 +371,9 @@
// Used during ssa construction. Like Copy, but the arg has not been specified yet.
{name: "FwdRef"},
+ // Unknown value. Used for Values whose values don't matter because they are dead code.
+ {name: "Unknown"},
+
{name: "VarDef", typ: "Mem"}, // aux is a *gc.Node of a variable that is about to be initialized. arg0=mem, returns mem
{name: "VarKill"}, // aux is a *gc.Node of a variable that is known to be dead. arg0=mem, returns mem
{name: "VarLive"}, // aux is a *gc.Node of a variable that must be kept live. arg0=mem, returns mem
