[dev.ssa] cmd/compile: getg needs a memory arg

getg reads from memory, so it should really have a
memory arg.  It is critical in functions which call setg
to make sure getg gets ordered correctly with setg.

Change-Id: Ief4875421f741fc49c07b0e1f065ce2535232341
Reviewed-on: https://go-review.googlesource.com/16100
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>

src/cmd/compile/internal/gc/ssa.go

@@ -1870,7 +1870,7 @@ func (s *state) expr(n *Node) *ssa.Value {
 		return s.call(n, callNormal)
 
 	case OGETG:
-		return s.newValue0(ssa.OpGetG, n.Type)
+		return s.newValue1(ssa.OpGetG, n.Type, s.mem())
 
 	case OAPPEND:
 		// append(s, e1, e2, e3).  Compile like:

src/cmd/compile/internal/ssa/gen/AMD64.rules

@@ -287,7 +287,7 @@
 (IsSliceInBounds idx len) -> (SETBE (CMPQ idx len))
 
 (PanicNilCheck ptr mem) -> (LoweredPanicNilCheck ptr mem)
-(GetG) -> (LoweredGetG)
+(GetG mem) -> (LoweredGetG mem)
 (GetClosurePtr) -> (LoweredGetClosurePtr)
 
 (Move [size] dst src mem) -> (REPMOVSB dst src (MOVQconst <config.Frontend().TypeUInt64()> [size]) mem)

src/cmd/compile/internal/ssa/gen/AMD64Ops.go

@@ -423,7 +423,7 @@ func init() {
 
 		// Pseudo-ops
 		{name: "LoweredPanicNilCheck", reg: gp10},
-		{name: "LoweredGetG", reg: gp01},
+		{name: "LoweredGetG", reg: gp01}, // arg0=mem
 		// Scheduler ensures LoweredGetClosurePtr occurs only in entry block,
 		// and sorts it to the very beginning of the block to prevent other
 		// use of DX (the closure pointer)

src/cmd/compile/internal/ssa/gen/generic.rules

@@ -180,7 +180,7 @@
 (Store [size] dst (Load <t> src mem) mem) && !config.fe.CanSSA(t) -> (Move [size] dst src mem)
 (Store [size] dst (Load <t> src mem) (VarDef {x} mem)) && !config.fe.CanSSA(t) -> (Move [size] dst src (VarDef {x} mem))
 
-(If (IsNonNil (GetG)) yes no) -> (First nil yes no)
+(If (IsNonNil (GetG _)) yes no) -> (First nil yes no)
 
 (If (Not cond) yes no) -> (If cond no yes)
 (If (ConstBool [c]) yes no) && c == 1 -> (First nil yes no)

src/cmd/compile/internal/ssa/gen/genericOps.go

@@ -326,7 +326,7 @@ var genericOps = []opData{
 
 	// Pseudo-ops
 	{name: "PanicNilCheck"}, // trigger a dereference fault; arg0=nil ptr, arg1=mem, returns mem
-	{name: "GetG"},          // runtime.getg() (read g pointer)
+	{name: "GetG"},          // runtime.getg() (read g pointer).  arg0=mem
 	{name: "GetClosurePtr"}, // get closure pointer from dedicated register
 
 	// Indexing operations

src/cmd/compile/internal/ssa/regalloc.go

@@ -982,11 +982,6 @@ func (v *Value) rematerializeable() bool {
 		// which can't be moved.
 		return false
 	}
-	if v.Op == OpAMD64LoweredGetG {
-		// It would almost always be ok to rematerialize this op.
-		// The annoying exception is functions that call runtime.setg.
-		return false
-	}
 	if len(v.Args) == 0 {
 		return true
 	}

src/cmd/compile/internal/ssa/rewriteAMD64.go

@@ -2412,18 +2412,20 @@ func rewriteValueAMD64(v *Value, config *Config) bool {
 	end6fd0b53f0acb4d35e7d7fa78d2ca1392:
 		;
 	case OpGetG:
-		// match: (GetG)
+		// match: (GetG mem)
 		// cond:
-		// result: (LoweredGetG)
+		// result: (LoweredGetG mem)
 		{
+			mem := v.Args[0]
 			v.Op = OpAMD64LoweredGetG
 			v.AuxInt = 0
 			v.Aux = nil
 			v.resetArgs()
+			v.AddArg(mem)
 			return true
 		}
-		goto endb17140e71dd641aa4d89e14479160260
+		goto endf543eaaf68c4bef1d4cdc8ba19683723
-	endb17140e71dd641aa4d89e14479160260:
+	endf543eaaf68c4bef1d4cdc8ba19683723:
 		;
 	case OpGoCall:
 		// match: (GoCall [argwid] mem)

src/cmd/compile/internal/ssa/rewritegeneric.go

@@ -1697,16 +1697,16 @@ func rewriteValuegeneric(v *Value, config *Config) bool {
 func rewriteBlockgeneric(b *Block) bool {
 	switch b.Kind {
 	case BlockIf:
-		// match: (If (IsNonNil (GetG)) yes no)
+		// match: (If (IsNonNil (GetG _)) yes no)
 		// cond:
 		// result: (First nil yes no)
 		{
 			v := b.Control
 			if v.Op != OpIsNonNil {
-				goto endafdc4e2525f9933ab0ae7effc3559597
+				goto end41b95d88b4cebdb0ce392bd3c1c89e95
 			}
 			if v.Args[0].Op != OpGetG {
-				goto endafdc4e2525f9933ab0ae7effc3559597
+				goto end41b95d88b4cebdb0ce392bd3c1c89e95
 			}
 			yes := b.Succs[0]
 			no := b.Succs[1]
@@ -1716,8 +1716,8 @@ func rewriteBlockgeneric(b *Block) bool {
 			b.Succs[1] = no
 			return true
 		}
-		goto endafdc4e2525f9933ab0ae7effc3559597
+		goto end41b95d88b4cebdb0ce392bd3c1c89e95
-	endafdc4e2525f9933ab0ae7effc3559597:
+	end41b95d88b4cebdb0ce392bd3c1c89e95:
 		;
 		// match: (If (Not cond) yes no)
 		// cond: