* compile.c (iseq_compile_each): remove redundant trace(line)

  instruction. for example, at the following script
  def m()
  p:xyzzy
  1
  2
  end
  compiler ignores `1' because there is no effect. However,
  `trace(line)' instruction remains in bytecode.
  This modification removes such redundant trace(line) instruction.
* test/ruby/test_iseq.rb: add a test.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39539 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 9 insertions, 0 deletions

diff --git a/compile.c b/compile.c
index fc5229fd9b..8441d97e09 100644
--- a/compile.c
+++ b/compile.c
@@ -3154,6 +3154,7 @@ static int
 iseq_compile_each(rb_iseq_t *iseq, LINK_ANCHOR *ret, NODE * node, int poped)
 {
     enum node_type type;
+    LINK_ELEMENT *saved_last_element = 0;
 
     if (node == 0) {
 	if (!poped) {
@@ -3170,6 +3171,7 @@ iseq_compile_each(rb_iseq_t *iseq, LINK_ANCHOR *ret, NODE * node, int poped)
 
     if (node->flags & NODE_FL_NEWLINE) {
 	ADD_TRACE(ret, nd_line(node), RUBY_EVENT_LINE);
+	saved_last_element = ret->last;
     }
 
     switch (type) {
@@ -5295,6 +5297,13 @@ iseq_compile_each(rb_iseq_t *iseq, LINK_ANCHOR *ret, NODE * node, int poped)
 	return COMPILE_NG;
     }
 
+    /* check & remove redundant trace(line) */
+    if (saved_last_element && ret /* ret can be 0 when error */ &&
+	ret->last == saved_last_element &&
+	((INSN *)saved_last_element)->insn_id == BIN(trace)) {
+	POP_ELEMENT(ret);
+    }
+
     debug_node_end();
     return COMPILE_OK;
 }