cmd/6g, cmd/8g, cmd/5g: make the undefined instruction have no successors

The UNDEF instruction was listed in the instruction data as having the next instruction in the stream as its successor. This confused the optimizer into adding a load where it wasn't needed, in turn confusing the liveness analysis pass for GC bitmaps into thinking that the variable was live.

Fixes #7229.

LGTM=iant, rsc
R=golang-codereviews, bradfitz, iant, dave, rsc
CC=golang-codereviews
https://golang.org/cl/56910045

diff --git a/src/cmd/5g/prog.c b/src/cmd/5g/prog.c
index e5b8fbd279703c2cb4934250c9454a9a560bd380..3e42721365ee0db7c350d0dc819e08d4e10bacda 100644 (file)
--- a/src/cmd/5g/prog.c
+++ b/src/cmd/5g/prog.c
@@ -26,7 +26,7 @@ static ProgInfo progtable[ALAST] = {
        [ATEXT]=        {Pseudo},
        [AFUNCDATA]=    {Pseudo},
        [APCDATA]=      {Pseudo},
-       [AUNDEF]=       {OK},
+       [AUNDEF]=       {Break},
        [AUSEFIELD]=    {OK},
        [ACHECKNIL]=    {LeftRead},
        [AFATVARDEF]=   {Pseudo | RightWrite},

diff --git a/src/cmd/6g/prog.c b/src/cmd/6g/prog.c
index 657cc9f7710222a3976c0cfdb14cf5a2e4596a17..71f44a3e20f50945d0a9abebb99f645bbe3a3f8f 100644 (file)
--- a/src/cmd/6g/prog.c
+++ b/src/cmd/6g/prog.c
@@ -38,7 +38,7 @@ static ProgInfo progtable[ALAST] = {
        [ATEXT]=        {Pseudo},
        [AFUNCDATA]=    {Pseudo},
        [APCDATA]=      {Pseudo},
-       [AUNDEF]=       {OK},
+       [AUNDEF]=       {Break},
        [AUSEFIELD]=    {OK},
        [ACHECKNIL]=    {LeftRead},
        [AFATVARDEF]=   {Pseudo | RightWrite},

diff --git a/src/cmd/8g/prog.c b/src/cmd/8g/prog.c
index 7745d503b82194f30e1fd186ee307227b63e1e3c..0162b02881c3870d3160de2a04c272a24abcaf34 100644 (file)
--- a/src/cmd/8g/prog.c
+++ b/src/cmd/8g/prog.c
@@ -38,7 +38,7 @@ static ProgInfo progtable[ALAST] = {
        [ATEXT]=        {Pseudo},
        [AFUNCDATA]=    {Pseudo},
        [APCDATA]=      {Pseudo},
-       [AUNDEF]=       {OK},
+       [AUNDEF]=       {Break},
        [AUSEFIELD]=    {OK},
        [ACHECKNIL]=    {LeftRead},
        [AFATVARDEF]=   {Pseudo | RightWrite},