[dev.ssa] cmd/compile: start arguments as spilled

Declare a function's arguments as having already been
spilled so their use just requires a restore.

Allow spill locations to be portions of larger objects the stack.
Required to load portions of compound input arguments.

Rename the memory input to InputMem.  Use Arg for the
pre-spilled argument values.

Change-Id: I8fe2a03ffbba1022d98bfae2052b376b96d32dda
Reviewed-on: https://go-review.googlesource.com/16536
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/cmd/compile/internal/ssa/tighten.go b/src/cmd/compile/internal/ssa/tighten.go
index 4fa26d2d18..6726c06e76 100644
--- a/src/cmd/compile/internal/ssa/tighten.go
+++ b/src/cmd/compile/internal/ssa/tighten.go
@@ -54,8 +54,8 @@ func tighten(f *Func) {
 		for _, b := range f.Blocks {
 			for i := 0; i < len(b.Values); i++ {
 				v := b.Values[i]
-				if v.Op == OpPhi || v.Op == OpGetClosurePtr || v.Op == OpConvert {
-					// GetClosurePtr must stay in entry block.
+				if v.Op == OpPhi || v.Op == OpGetClosurePtr || v.Op == OpConvert || v.Op == OpArg {
+					// GetClosurePtr & Arg must stay in entry block.
 					// OpConvert must not float over call sites.
 					// TODO do we instead need a dependence edge of some sort for OpConvert?
 					// Would memory do the trick, or do we need something else that relates