cmd/gc: handle variable initialization by block move in liveness

Any initialization of a variable by a block copy or block zeroing
or by multiple assignments (componentwise copying or zeroing
of a multiword variable) needs to emit a VARDEF. These cases were not.

Fixes #7205.

TBR=iant
CC=golang-codereviews
https://golang.org/cl/63650044

diff --git a/src/cmd/5g/cgen.c b/src/cmd/5g/cgen.c
index 2d260e72d54cf5803b16b1a975239b0f99e782f7..a5ac6c15bd5a5cf762a8bc7c6eda4c9975b26869 100644 (file)
--- a/src/cmd/5g/cgen.c
+++ b/src/cmd/5g/cgen.c
@@ -1414,6 +1414,7 @@ sgen(Node *n, Node *res, int64 w)
        int32 c, odst, osrc;
        int dir, align, op;
        Prog *p, *ploop;
+       NodeList *l;
 
        if(debug['g']) {
                print("\nsgen w=%lld\n", w);
@@ -1439,6 +1440,17 @@ sgen(Node *n, Node *res, int64 w)
                return;
        }
 
+       // Record site of definition of ns for liveness analysis.
+       if(res->op == ONAME && res->class != PEXTERN)
+               gvardef(res);
+       
+       // If copying .args, that's all the results, so record definition sites
+       // for them for the liveness analysis.
+       if(res->op == ONAME && strcmp(res->sym->name, ".args") == 0)
+               for(l = curfn->dcl; l != nil; l = l->next)
+                       if(l->n->class == PPARAMOUT)
+                               gvardef(l->n);
+
        // Avoid taking the address for simple enough types.
        if(componentgen(n, res))
                return;

diff --git a/src/cmd/6g/cgen.c b/src/cmd/6g/cgen.c
index 76ece93b04cfa157f0258c8c36b12dcbdbb4f214..05cdf54afe83f52b67d91f1223952ee567e20738 100644 (file)
--- a/src/cmd/6g/cgen.c
+++ b/src/cmd/6g/cgen.c
@@ -1337,6 +1337,7 @@ sgen(Node *n, Node *ns, int64 w)
 {
        Node nodl, nodr, nodsi, noddi, cx, oldcx, tmp;
        vlong c, q, odst, osrc;
+       NodeList *l;
 
        if(debug['g']) {
                print("\nsgen w=%lld\n", w);
@@ -1349,6 +1350,17 @@ sgen(Node *n, Node *ns, int64 w)
 
        if(w < 0)
                fatal("sgen copy %lld", w);
+       
+       // Record site of definition of ns for liveness analysis.
+       if(ns->op == ONAME && ns->class != PEXTERN)
+               gvardef(ns);
+       
+       // If copying .args, that's all the results, so record definition sites
+       // for them for the liveness analysis.
+       if(ns->op == ONAME && strcmp(ns->sym->name, ".args") == 0)
+               for(l = curfn->dcl; l != nil; l = l->next)
+                       if(l->n->class == PPARAMOUT)
+                               gvardef(l->n);
 
        // Avoid taking the address for simple enough types.
        if(componentgen(n, ns))

diff --git a/src/cmd/8g/cgen.c b/src/cmd/8g/cgen.c
index cc28a31457990ff56f3b39b0baf08f14f718c2ce..f0630ae4fa0c6e25dc15a807cda9155a02ba76ea 100644 (file)
--- a/src/cmd/8g/cgen.c
+++ b/src/cmd/8g/cgen.c
@@ -1203,6 +1203,7 @@ sgen(Node *n, Node *res, int64 w)
 {
        Node dst, src, tdst, tsrc;
        int32 c, q, odst, osrc;
+       NodeList *l;
 
        if(debug['g']) {
                print("\nsgen w=%lld\n", w);
@@ -1223,6 +1224,17 @@ sgen(Node *n, Node *res, int64 w)
                return;
        }
 
+       // Record site of definition of ns for liveness analysis.
+       if(res->op == ONAME && res->class != PEXTERN)
+               gvardef(res);
+       
+       // If copying .args, that's all the results, so record definition sites
+       // for them for the liveness analysis.
+       if(res->op == ONAME && strcmp(res->sym->name, ".args") == 0)
+               for(l = curfn->dcl; l != nil; l = l->next)
+                       if(l->n->class == PPARAMOUT)
+                               gvardef(l->n);
+
        // Avoid taking the address for simple enough types.
        if(componentgen(n, res))
                return;

diff --git a/src/cmd/gc/pgen.c b/src/cmd/gc/pgen.c
index 8190fc36ff292d0b15f26f8f4942ded487d6d59a..571334e6b78686300ac4f920adf37358c3dd7964 100644 (file)
--- a/src/cmd/gc/pgen.c
+++ b/src/cmd/gc/pgen.c
@@ -34,8 +34,8 @@ makefuncdatasym(char *namefmt, int64 funcdatakind)
 void
 gvardef(Node *n)
 {
-       if(n == N || !isfat(n->type))
-               fatal("gvardef: node is not fat");
+       if(n == N)
+               fatal("gvardef nil");
        switch(n->class) {
        case PAUTO:
        case PPARAM:

diff --git a/src/cmd/gc/plive.c b/src/cmd/gc/plive.c
index 108f89399f67f147db9702dd0f1d302fd24c33da..de868a672a92a4451de9f39cdd46a42ad97865b3 100644 (file)
--- a/src/cmd/gc/plive.c
+++ b/src/cmd/gc/plive.c
@@ -621,7 +621,7 @@ freecfg(Array *cfg)
 static int
 isfunny(Node *node)
 {
-       char *names[] = { ".fp", ".args", "_", nil };
+       char *names[] = { ".fp", ".args", nil };
        int i;
 
        if(node->sym != nil && node->sym->name != nil)
@@ -696,8 +696,8 @@ progeffects(Prog *prog, Array *vars, Bvec *uevar, Bvec *varkill, Bvec *avarinit)
        }
        if(info.flags & (LeftRead | LeftWrite | LeftAddr)) {
                from = &prog->from;
-               if (from->node != nil && !isfunny(from->node) && from->sym != nil) {
-                       switch(prog->from.node->class & ~PHEAP) {
+               if (from->node != nil && from->sym != nil) {
+                       switch(from->node->class & ~PHEAP) {
                        case PAUTO:
                        case PPARAM:
                        case PPARAMOUT:
@@ -710,7 +710,7 @@ progeffects(Prog *prog, Array *vars, Bvec *uevar, Bvec *varkill, Bvec *avarinit)
                                        if(info.flags & (LeftRead | LeftAddr))
                                                bvset(uevar, pos);
                                        if(info.flags & LeftWrite)
-                                               if(from->node != nil && (!isfat(from->node->type) || prog->as == AVARDEF))
+                                               if(from->node != nil && !isfat(from->node->type))
                                                        bvset(varkill, pos);
                                }
                        }
@@ -719,8 +719,8 @@ progeffects(Prog *prog, Array *vars, Bvec *uevar, Bvec *varkill, Bvec *avarinit)
 Next:
        if(info.flags & (RightRead | RightWrite | RightAddr)) {
                to = &prog->to;
-               if (to->node != nil && to->sym != nil && !isfunny(to->node)) {
-                       switch(prog->to.node->class & ~PHEAP) {
+               if (to->node != nil && to->sym != nil) {
+                       switch(to->node->class & ~PHEAP) {
                        case PAUTO:
                        case PPARAM:
                        case PPARAMOUT:
@@ -728,10 +728,9 @@ Next:
                                if(pos == -1)
                                        goto Next1;
                                if(to->node->addrtaken) {
-                                       //if(prog->as == AKILL)
-                                       //      bvset(varkill, pos);
-                                       //else
-                                               bvset(avarinit, pos);
+                                       bvset(avarinit, pos);
+                                       if(prog->as == AVARDEF)
+                                               bvset(varkill, pos);
                                } else {
                                        if(info.flags & (RightRead | RightAddr))
                                                bvset(uevar, pos);

diff --git a/test/live.go b/test/live.go
index c3dbc55c0a209932560e8df04140ccf8e0ececba..ec2df7e5f8f1994a7fef0c75da26180dd24a3915 100644 (file)
--- a/test/live.go
+++ b/test/live.go
@@ -95,3 +95,21 @@ func f7() (x string) {
        return
 }
 
+// ignoring block returns used to cause "live at entry to f8: x, y".
+
+func f8() (x, y string) {
+       return g8()
+}
+
+func g8() (string, string)
+
+// ignoring block assignments used to cause "live at entry to f9: x"
+// issue 7205
+
+var i9 interface{}
+
+func f9() bool {
+       g8()
+       x := i9
+       return x != 99
+}