optimise away OP_KEYS op in scalar/void context

In something like

    if (keys %h) { ... }

the 'keys %h' is implemented as the op sequences

    gv[*h] s
    rv2hv lKRM/1
    keys[t2] sK/1
or
    padhv[%h:1,6] lRM
    keys[t2] sK/1

It turns out that (%h) in scalar and void context now behaves very
similarly to (keys %h) (except that it reset the iterator), so in these
cases, convert the two ops

    rv2hv/padhv, keys

into the single op

    rv2hv/padhv

with a private flag indicating that the op is handling the 'keys' action
by itself.

As well as one less op to execute, this brings the boolean-context
optimisation already present in padhv/rv2sv to keys. So

    if (keys %h) { ... }

is no longer slower than

    if (%h) { ... }

3 files changed, 24 insertions, 30 deletions

diff --git a/ext/B/t/f_map.t b/ext/B/t/f_map.t
index a1cbc38c01..96cea4a495 100644
--- a/ext/B/t/f_map.t
+++ b/ext/B/t/f_map.t
@@ -108,7 +108,7 @@ checkOptree(note   => q{},
 #            goto 7
 # g  <0> pushmark s
 # h  <#> gv[*hash] s
-# i  <1> rv2hv lKRM*/1
+# i  <1> rv2hv lKRM*
 # j  <2> aassign[t10] KS/COM_AGG
 # k  <1> leavesub[1 ref] K/REFC,1
 EOT_EOT
@@ -130,7 +130,7 @@ EOT_EOT
 #            goto 7
 # g  <0> pushmark s
 # h  <$> gv(*hash) s
-# i  <1> rv2hv lKRM*/1
+# i  <1> rv2hv lKRM*
 # j  <2> aassign[t5] KS/COM_AGG
 # k  <1> leavesub[1 ref] K/REFC,1
 EONT_EONT
@@ -157,7 +157,7 @@ checkOptree(note   => q{},
 # 4  <0> pushmark s
 # 5  <0> pushmark s
 # 6  <#> gv[*hash] s
-# 7  <1> rv2hv lKRM*/1
+# 7  <1> rv2hv lKRM*
 # 8  <2> aassign[t3] vKS
 # 9  <;> nextstate(main 476 (eval 10):1) v:{
 # a  <0> pushmark sM
@@ -171,7 +171,7 @@ checkOptree(note   => q{},
 # g      <;> nextstate(main 475 (eval 10):1) v:{
 # h      <#> gvsv[*_] s
 # i      <#> gv[*hash] s
-# j      <1> rv2hv sKR/1
+# j      <1> rv2hv sKR
 # k      <0> pushmark s
 # l      <#> gvsv[*_] s
 # m      <#> gv[*getkey] s/EARLYCV
@@ -190,7 +190,7 @@ EOT_EOT
 # 4  <0> pushmark s
 # 5  <0> pushmark s
 # 6  <$> gv(*hash) s
-# 7  <1> rv2hv lKRM*/1
+# 7  <1> rv2hv lKRM*
 # 8  <2> aassign[t2] vKS
 # 9  <;> nextstate(main 560 (eval 15):1) v:{
 # a  <0> pushmark sM
@@ -204,7 +204,7 @@ EOT_EOT
 # g      <;> nextstate(main 559 (eval 15):1) v:{
 # h      <$> gvsv(*_) s
 # i      <$> gv(*hash) s
-# j      <1> rv2hv sKR/1
+# j      <1> rv2hv sKR
 # k      <0> pushmark s
 # l      <$> gvsv(*_) s
 # m      <$> gv(*getkey) s/EARLYCV
@@ -243,7 +243,7 @@ checkOptree(note   => q{},
 #            goto 7
 # b  <0> pushmark s
 # c  <#> gv[*hash] s
-# d  <1> rv2hv lKRM*/1
+# d  <1> rv2hv lKRM*
 # e  <2> aassign[t10] KS/COM_AGG
 # f  <1> leavesub[1 ref] K/REFC,1
 EOT_EOT
@@ -260,7 +260,7 @@ EOT_EOT
 #            goto 7
 # b  <0> pushmark s
 # c  <$> gv(*hash) s
-# d  <1> rv2hv lKRM*/1
+# d  <1> rv2hv lKRM*
 # e  <2> aassign[t6] KS/COM_AGG
 # f  <1> leavesub[1 ref] K/REFC,1
 EONT_EONT
@@ -289,7 +289,7 @@ checkOptree(note   => q{},
 #            goto 7
 # b  <0> pushmark s
 # c  <#> gv[*hash] s
-# d  <1> rv2hv lKRM*/1
+# d  <1> rv2hv lKRM*
 # e  <2> aassign[t10] KS/COM_AGG
 # f  <1> leavesub[1 ref] K/REFC,1
 EOT_EOT
@@ -306,7 +306,7 @@ EOT_EOT
 #            goto 7
 # b  <0> pushmark s
 # c  <$> gv(*hash) s
-# d  <1> rv2hv lKRM*/1
+# d  <1> rv2hv lKRM*
 # e  <2> aassign[t6] KS/COM_AGG
 # f  <1> leavesub[1 ref] K/REFC,1
 EONT_EONT
@@ -335,7 +335,7 @@ checkOptree(note   => q{},
 #            goto 7
 # b  <0> pushmark s
 # c  <#> gv[*hash] s
-# d  <1> rv2hv lKRM*/1
+# d  <1> rv2hv lKRM*
 # e  <2> aassign[t9] KS/COM_AGG
 # f  <1> leavesub[1 ref] K/REFC,1
 EOT_EOT
@@ -352,7 +352,7 @@ EOT_EOT
 #            goto 7
 # b  <0> pushmark s
 # c  <$> gv(*hash) s
-# d  <1> rv2hv lKRM*/1
+# d  <1> rv2hv lKRM*
 # e  <2> aassign[t5] KS/COM_AGG
 # f  <1> leavesub[1 ref] K/REFC,1
 EONT_EONT
@@ -381,7 +381,7 @@ checkOptree(note   => q{},
 #            goto 7
 # b  <0> pushmark s
 # c  <#> gv[*hash] s
-# d  <1> rv2hv lKRM*/1
+# d  <1> rv2hv lKRM*
 # e  <2> aassign[t8] KS/COM_AGG
 # f  <1> leavesub[1 ref] K/REFC,1
 EOT_EOT
@@ -398,7 +398,7 @@ EOT_EOT
 #            goto 7
 # b  <0> pushmark s
 # c  <$> gv(*hash) s
-# d  <1> rv2hv lKRM*/1
+# d  <1> rv2hv lKRM*
 # e  <2> aassign[t5] KS/COM_AGG
 # f  <1> leavesub[1 ref] K/REFC,1
 EONT_EONT
@@ -426,7 +426,7 @@ checkOptree(note   => q{},
 #            goto 7
 # a  <0> pushmark s
 # b  <#> gv[*hash] s
-# c  <1> rv2hv lKRM*/1
+# c  <1> rv2hv lKRM*
 # d  <2> aassign[t6] KS/COM_AGG
 # e  <#> gv[*array] s
 # f  <1> rv2av[t8] K/1
@@ -445,7 +445,7 @@ EOT_EOT
 #            goto 7
 # a  <0> pushmark s
 # b  <$> gv(*hash) s
-# c  <1> rv2hv lKRM*/1
+# c  <1> rv2hv lKRM*
 # d  <2> aassign[t4] KS/COM_AGG
 # e  <$> gv(*array) s
 # f  <1> rv2av[t5] K/1
diff --git a/ext/B/t/f_sort.t b/ext/B/t/f_sort.t
index fe0927829f..800281fa73 100644
--- a/ext/B/t/f_sort.t
+++ b/ext/B/t/f_sort.t
@@ -280,8 +280,7 @@ checkOptree(note   => q{},
 # 2  <0> pushmark s
 # 3  <0> pushmark s
 # 4  <#> gv[*age] s
-# 5  <1> rv2hv[t9] lKRM/1       < 5.019006
-# 5  <1> rv2hv lKRM/1           >=5.019006
+# 5  <1> rv2hv lKRM
 # 6  <1> keys[t10] lK/1		< 5.019002
 # 6  <1> keys[t10] lKM/1	>=5.019002
 # 7  <@> sort lKS*
@@ -295,8 +294,7 @@ EOT_EOT
 # 2  <0> pushmark s
 # 3  <0> pushmark s
 # 4  <$> gv(*age) s
-# 5  <1> rv2hv[t3] lKRM/1       < 5.019006
-# 5  <1> rv2hv lKRM/1           >=5.019006
+# 5  <1> rv2hv lKRM
 # 6  <1> keys[t4] lK/1		< 5.019002
 # 6  <1> keys[t4] lKM/1		>=5.019002
 # 7  <@> sort lKS*
diff --git a/ext/B/t/optree_samples.t b/ext/B/t/optree_samples.t
index 1330a47302..121fd3eec9 100644
--- a/ext/B/t/optree_samples.t
+++ b/ext/B/t/optree_samples.t
@@ -483,8 +483,7 @@ checkOptree ( name	=> '%h = map { getkey($_) => $_ } @a',
 #            goto 7
 # g  <0> pushmark s
 # h  <#> gv[*h] s
-# i  <1> rv2hv[t2] lKRM*/1         < 5.019006
-# i  <1> rv2hv lKRM*/1             >=5.019006
+# i  <1> rv2hv lKRM*
 # j  <2> aassign[t10] KS/COM_AGG
 # k  <1> leavesub[1 ref] K/REFC,1
 EOT_EOT
@@ -507,8 +506,7 @@ EOT_EOT
 #            goto 7
 # g  <0> pushmark s
 # h  <$> gv(*h) s
-# i  <1> rv2hv[t1] lKRM*/1         < 5.019006
-# i  <1> rv2hv lKRM*/1             >=5.019006
+# i  <1> rv2hv lKRM*
 # j  <2> aassign[t5] KS/COM_AGG
 # k  <1> leavesub[1 ref] K/REFC,1
 EONT_EONT
@@ -521,8 +519,7 @@ checkOptree ( name	=> '%h=(); for $_(@a){$h{getkey($_)} = $_}',
 # 2  <0> pushmark s
 # 3  <0> pushmark s
 # 4  <#> gv[*h] s
-# 5  <1> rv2hv[t2] lKRM*/1         < 5.019006
-# 5  <1> rv2hv lKRM*/1             >=5.019006
+# 5  <1> rv2hv lKRM*
 # 6  <2> aassign[t3] vKS
 # 7  <;> nextstate(main 506 (eval 24):1) v:{
 # 8  <0> pushmark sM
@@ -536,7 +533,7 @@ checkOptree ( name	=> '%h=(); for $_(@a){$h{getkey($_)} = $_}',
 # e      <;> nextstate(main 505 (eval 24):1) v:{
 # f      <#> gvsv[*_] s
 # g      <#> gv[*h] s
-# h      <1> rv2hv sKR/1
+# h      <1> rv2hv sKR
 # i      <0> pushmark s
 # j      <#> gvsv[*_] s
 # k      <#> gv[*getkey] s/EARLYCV
@@ -552,8 +549,7 @@ EOT_EOT
 # 2  <0> pushmark s
 # 3  <0> pushmark s
 # 4  <$> gv(*h) s
-# 5  <1> rv2hv[t1] lKRM*/1         < 5.019006
-# 5  <1> rv2hv lKRM*/1             >=5.019006
+# 5  <1> rv2hv lKRM*
 # 6  <2> aassign[t2] vKS
 # 7  <;> nextstate(main 506 (eval 24):1) v:{
 # 8  <0> pushmark sM
@@ -567,7 +563,7 @@ EOT_EOT
 # e      <;> nextstate(main 505 (eval 24):1) v:{
 # f      <$> gvsv(*_) s
 # g      <$> gv(*h) s
-# h      <1> rv2hv sKR/1
+# h      <1> rv2hv sKR
 # i      <0> pushmark s
 # j      <$> gvsv(*_) s
 # k      <$> gv(*getkey) s/EARLYCV