Fix unsafe peephole optimization

Reported by https://hackerone.com/dkasak

Fix unsafe peephole optimization
Reported by https://hackerone.com/dkasak
964427f8 · Francis Bogsanyi · Bouke van der Bijl · a630c4f4 · 964427f8 · 964427f8
Unverified Commit 964427f8 authored Nov 17, 2016 by Francis Bogsanyi Committed by Bouke van der Bijl Nov 24, 2016
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mrbgems/mruby-compiler/core/codegen.c mrbgems/mruby-compiler/core/codegen.c +4 -2

test/t/codegen.rb test/t/codegen.rb +11 -0

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--- a/mrbgems/mruby-compiler/core/codegen.c
+++ b/mrbgems/mruby-compiler/core/codegen.c
@@ -1798,8 +1798,10 @@ codegen(codegen_scope *s, node *tree, int val)
        int pos;
        pop();
-        if (val && vsp >= 0) {
+        if (val) {
-          genop(s, MKOP_AB(OP_MOVE, vsp, cursp()));
+          if (vsp >= 0) {
+            genop(s, MKOP_AB(OP_MOVE, vsp, cursp()));
+          }
          pos = genop(s, MKOP_AsBx(name[0]=='|'?OP_JMPIF:OP_JMPNOT, cursp(), 0));
        }
        else {

--- a/test/t/codegen.rb
+++ b/test/t/codegen.rb
+##
+# Codegen tests
+assert('peephole optimization does not eliminate move whose result is reused') do
+  assert_raise LocalJumpError do
+    def method
+      yield
+    end
+    method(&a &&= 0)
+  end
+end