diff --git a/src/cmd/compile/internal/ssagen/ssa.go b/src/cmd/compile/internal/ssagen/ssa.go
index 48d5e34f46..b4a55c00af 100644
--- a/src/cmd/compile/internal/ssagen/ssa.go
+++ b/src/cmd/compile/internal/ssagen/ssa.go
@@ -7,7 +7,6 @@ package ssagen
 import (
 	"bufio"
 	"bytes"
-	"cmd/compile/internal/abi"
 	"fmt"
 	"go/constant"
 	"html"
@@ -17,6 +16,7 @@ import (
 	"sort"
 	"strings"
 
+	"cmd/compile/internal/abi"
 	"cmd/compile/internal/base"
 	"cmd/compile/internal/ir"
 	"cmd/compile/internal/liveness"
@@ -3521,6 +3521,10 @@ func (s *state) append(n *ir.CallExpr, inplace bool) *ssa.Value {
 		}
 	}
 
+	// The following deletions have no practical effect at this time
+	// because state.vars has been reset by the preceding state.startBlock.
+	// They only enforce the fact that these variables are no longer need in
+	// the current scope.
 	delete(s.vars, ptrVar)
 	delete(s.vars, lenVar)
 	if !inplace {
@@ -6379,7 +6383,7 @@ func (s *state) dottype1(pos src.XPos, src, dst *types.Type, iface, source, targ
 			idata := s.newValue1(ssa.OpIData, byteptr, iface)
 			res = s.newValue2(ssa.OpIMake, dst, s.variable(typVar, byteptr), idata)
 			resok = cond
-			delete(s.vars, typVar)
+			delete(s.vars, typVar) // no practical effect, just to indicate typVar is no longer live.
 			return
 		}
 		// converting to a nonempty interface needs a runtime call.
@@ -6504,12 +6508,12 @@ func (s *state) dottype1(pos src.XPos, src, dst *types.Type, iface, source, targ
 	s.startBlock(bEnd)
 	if tmp == nil {
 		res = s.variable(valVar, dst)
-		delete(s.vars, valVar)
+		delete(s.vars, valVar) // no practical effect, just to indicate typVar is no longer live.
 	} else {
 		res = s.load(dst, addr)
 	}
 	resok = s.variable(okVar, types.Types[types.TBOOL])
-	delete(s.vars, okVar)
+	delete(s.vars, okVar) // ditto
 	return res, resok
 }