cmd/gc: fix crash in -live debugging output

R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/53930043

diff --git a/src/cmd/gc/plive.c b/src/cmd/gc/plive.c
index 73699956daac4f55b7958b87ed012f4163acec13..96437488ad8edb9bc63184d9cbf58c61efe6a4c8 100644 (file)
--- a/src/cmd/gc/plive.c
+++ b/src/cmd/gc/plive.c
@@ -635,7 +635,9 @@ isfunny(Node *node)
 //
 // The output vectors give bits for variables:
 //     uevar - used by this instruction
-//     varkill - set by this instruction
+//     varkill - killed by this instruction
+//             for variables without address taken, means variable was set
+//             for variables with address taken, means variable was marked dead
 //     avarinit - initialized or referred to by this instruction,
 //             only for variables with address taken but not escaping to heap
 //
@@ -694,13 +696,15 @@ progeffects(Prog *prog, Array *vars, Bvec *uevar, Bvec *varkill, Bvec *avarinit)
                                pos = arrayindexof(vars, from->node);
                                if(pos == -1)
                                        goto Next;
-                               if(from->node->addrtaken)
+                               if(from->node->addrtaken) {
                                        bvset(avarinit, pos);
-                               if(info.flags & (LeftRead | LeftAddr))
-                                       bvset(uevar, pos);
-                               if(info.flags & LeftWrite)
-                                       if(from->node != nil && (!isfat(from->node->type) || prog->as == AFATVARDEF))
-                                               bvset(varkill, pos);
+                               } else {
+                                       if(info.flags & (LeftRead | LeftAddr))
+                                               bvset(uevar, pos);
+                                       if(info.flags & LeftWrite)
+                                               if(from->node != nil && (!isfat(from->node->type) || prog->as == AFATVARDEF))
+                                                       bvset(varkill, pos);
+                               }
                        }
                }
        }
@@ -715,13 +719,18 @@ Next:
                                pos = arrayindexof(vars, to->node);
                                if(pos == -1)
                                        goto Next1;
-                               if(to->node->addrtaken)
-                                       bvset(avarinit, pos);
-                               if(info.flags & (RightRead | RightAddr))
-                                       bvset(uevar, pos);
-                               if(info.flags & RightWrite)
-                                       if(to->node != nil && (!isfat(to->node->type) || prog->as == AFATVARDEF))
+                               if(to->node->addrtaken) {
+                                       if(prog->as == AKILL)
                                                bvset(varkill, pos);
+                                       else
+                                               bvset(avarinit, pos);
+                               } else {
+                                       if(info.flags & (RightRead | RightAddr))
+                                               bvset(uevar, pos);
+                                       if(info.flags & RightWrite)
+                                               if(to->node != nil && (!isfat(to->node->type) || prog->as == AFATVARDEF))
+                                                       bvset(varkill, pos);
+                               }
                        }
                }
        }
@@ -1589,8 +1598,10 @@ livenessepilogue(Liveness *lv)
                                if(debuglive >= 1) {
                                        fmtstrinit(&fmt);
                                        fmtprint(&fmt, "%L: live at ", p->lineno);
-                                       if(p->as == ACALL)
+                                       if(p->as == ACALL && p->to.node)
                                                fmtprint(&fmt, "call to %s:", p->to.node->sym->name);
+                                       else if(p->as == ACALL)
+                                               fmtprint(&fmt, "indirect call:");
                                        else
                                                fmtprint(&fmt, "entry to %s:", p->from.node->sym->name);
                                        numlive = 0;