From: David Chase <drchase@google.com>
Date: Mon, 10 Aug 2020 17:33:15 +0000 (-0400)
Subject: cmd/compile: some minor cleanups
X-Git-Tag: go1.16beta1~799
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=51690f777c9e842e7693f8713e9686aab380ef31;p=gostls13.git

cmd/compile: some minor cleanups

Change-Id: Icdf3320814ad4a86a5ae532f4fcb899da3f46ae3
Reviewed-on: https://go-review.googlesource.com/c/go/+/248186
Trust: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
---

diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index 7bde7f7c65..90ce9e54f8 100644
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -4375,9 +4375,7 @@ func (s *state) call(n *Node, k callKind, returnResultAddr bool) *ssa.Value {
 
 	switch n.Op {
 	case OCALLFUNC:
-		if k != callDeferStack && ssa.LateCallExpansionEnabledWithin(s.f) {
-			testLateExpansion = true
-		}
+		testLateExpansion = k != callDeferStack && ssa.LateCallExpansionEnabledWithin(s.f)
 		if k == callNormal && fn.Op == ONAME && fn.Class() == PFUNC {
 			sym = fn.Sym
 			break
@@ -4392,9 +4390,7 @@ func (s *state) call(n *Node, k callKind, returnResultAddr bool) *ssa.Value {
 		if fn.Op != ODOTMETH {
 			s.Fatalf("OCALLMETH: n.Left not an ODOTMETH: %v", fn)
 		}
-		if k != callDeferStack && ssa.LateCallExpansionEnabledWithin(s.f) {
-			testLateExpansion = true
-		}
+		testLateExpansion = k != callDeferStack && ssa.LateCallExpansionEnabledWithin(s.f)
 		if k == callNormal {
 			sym = fn.Sym
 			break
@@ -4406,9 +4402,7 @@ func (s *state) call(n *Node, k callKind, returnResultAddr bool) *ssa.Value {
 		if fn.Op != ODOTINTER {
 			s.Fatalf("OCALLINTER: n.Left not an ODOTINTER: %v", fn.Op)
 		}
-		if k != callDeferStack && ssa.LateCallExpansionEnabledWithin(s.f) {
-			testLateExpansion = true
-		}
+		testLateExpansion = k != callDeferStack && ssa.LateCallExpansionEnabledWithin(s.f)
 		var iclosure *ssa.Value
 		iclosure, rcvr = s.getClosureAndRcvr(fn)
 		if k == callNormal {
diff --git a/src/cmd/compile/internal/ssa/expand_calls.go b/src/cmd/compile/internal/ssa/expand_calls.go
index 8c06040542..bbd9aeee51 100644
--- a/src/cmd/compile/internal/ssa/expand_calls.go
+++ b/src/cmd/compile/internal/ssa/expand_calls.go
@@ -39,7 +39,9 @@ func expandCalls(f *Func) {
 		hiOffset = 4
 	}
 
-	pairTypes := func(et types.EType) (tHi, tLo *types.Type) {
+	// intPairTypes returns the pair of 32-bit int types needed to encode a 64-bit integer type on a target
+	// that has no 64-bit integer registers.
+	intPairTypes := func(et types.EType) (tHi, tLo *types.Type) {
 		tHi = tUint32
 		if et == types.TINT64 {
 			tHi = tInt32
@@ -147,8 +149,8 @@ func expandCalls(f *Func) {
 		}
 	}
 
-	// storeArg converts stores of SSA-able aggregates into a series of stores of smaller types into
-	// individual parameter slots.
+	// storeArg converts stores of SSA-able aggregate arguments (passed to a call) into a series of stores of
+	// smaller types into individual parameter slots.
 	// TODO when registers really arrive, must also decompose anything split across two registers or registers and memory.
 	var storeArg func(pos src.XPos, b *Block, a *Value, t *types.Type, offset int64, mem *Value) *Value
 	storeArg = func(pos src.XPos, b *Block, a *Value, t *types.Type, offset int64, mem *Value) *Value {
@@ -165,7 +167,7 @@ func expandCalls(f *Func) {
 			return storeArg(pos, b, a.Args[0], t.Elem(), offset, mem)
 
 		case OpInt64Make:
-			tHi, tLo := pairTypes(t.Etype)
+			tHi, tLo := intPairTypes(t.Etype)
 			mem = storeArg(pos, b, a.Args[0], tHi, offset+hiOffset, mem)
 			return storeArg(pos, b, a.Args[1], tLo, offset+lowOffset, mem)
 		}
@@ -207,7 +209,7 @@ func expandCalls(f *Func) {
 			if t.Width == regSize {
 				break
 			}
-			tHi, tLo := pairTypes(t.Etype)
+			tHi, tLo := intPairTypes(t.Etype)
 			sel := src.Block.NewValue1(pos, OpInt64Hi, tHi, src)
 			mem = splitStore(dst, sel, mem, v, tHi, offset+hiOffset, firstStorePos)
 			firstStorePos = firstStorePos.WithNotStmt()
@@ -261,6 +263,9 @@ func expandCalls(f *Func) {
 		return x
 	}
 
+	// rewriteArgs removes all the Args from a call and converts the call args into appropriate
+	// stores (or later, register movement).  Extra args for interface and closure calls are ignored,
+	// but removed.
 	rewriteArgs := func(v *Value, firstArg int) *Value {
 		// Thread the stores on the memory arg
 		aux := v.Aux.(*AuxCall)