From c6187dc679a536686afbdeb0999346699df625ce Mon Sep 17 00:00:00 2001
From: Gabriel Dos Reis <GabrielDosReis@users.noreply.github.com>
Date: Tue, 30 Aug 2022 01:54:45 -0700
Subject: Use `LETT` less often (#22)

This patch has the Lisp backend use less often the `LETT` opcode.  In fact, it is no longer used by the Spad compiler codegen.  However, a few cases in the interpreter continues to use it.
---
 src/interp/lisp-backend.boot | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/interp/lisp-backend.boot b/src/interp/lisp-backend.boot
index 8894db4f..722fa9b0 100644
--- a/src/interp/lisp-backend.boot
+++ b/src/interp/lisp-backend.boot
@@ -842,11 +842,14 @@ massageBackendCode x ==
   atomic? x => nil
   -- temporarily have TRACELET report MAKEPROPs.
   if (u := first x) = "MAKEPROP" and $TRACELETFLAG then
-    x.first := "MAKEPROP-SAY"
+    x.op := "MAKEPROP-SAY"
   u in '(DCQ SPADLET SETQ %LET) =>
     if u in '(SPADLET %LET) then
-      append!(x,$FUNNAME__TAIL)
-      x.first := "LETT"
+      if x.args is [y,.] and ident? y then
+        x.op := "SETQ"
+      else
+        x.op := "LETT"
+        append!(x,$FUNNAME__TAIL)
     massageBackendCode CDDR x
     if u ~= "SETQ" then
       ident? second x => pushLocalVariable second x
-- 
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