nir: fix dangling ssadef->name ptrs

In many places, the convention is to pass an existing ssadef name ptr
when construction/initializing a new nir_ssa_def.  But that goes badly
(as noticed by garbage in nir_print output) when the original string
gets freed.

Just use ralloc_strdup() instead, and add ralloc_free() in the two
places that would care (not that the strings wouldn't eventually get
freed anyways).

Also fixup the nir_search code which was directly setting ssadef->name
to use the parent instruction as memctx.

Signed-off-by: Rob Clark <robclark@freedesktop.org>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/compiler/nir/nir.c

@@ -1317,12 +1317,13 @@ nir_instr_rewrite_dest(nir_instr *instr, nir_dest *dest, nir_dest new_dest)
       src_add_all_uses(dest->reg.indirect, instr, NULL);
 }
 
+/* note: does *not* take ownership of 'name' */
 void
 nir_ssa_def_init(nir_instr *instr, nir_ssa_def *def,
                  unsigned num_components,
                  unsigned bit_size, const char *name)
 {
-   def->name = name;
+   def->name = ralloc_strdup(instr, name);
    def->parent_instr = instr;
    list_inithead(&def->uses);
    list_inithead(&def->if_uses);
@@ -1339,6 +1340,7 @@ nir_ssa_def_init(nir_instr *instr, nir_ssa_def *def,
    }
 }
 
+/* note: does *not* take ownership of 'name' */
 void
 nir_ssa_dest_init(nir_instr *instr, nir_dest *dest,
                  unsigned num_components, unsigned bit_size,

src/compiler/nir/nir_search.c

@@ -469,7 +469,7 @@ construct_value(const nir_search_value *value,
 
       switch (c->type) {
       case nir_type_float:
-         load->def.name = ralloc_asprintf(mem_ctx, "%f", c->data.d);
+         load->def.name = ralloc_asprintf(load, "%f", c->data.d);
          switch (bitsize->dest_size) {
          case 32:
             load->value.f32[0] = c->data.d;
@@ -483,7 +483,7 @@ construct_value(const nir_search_value *value,
          break;
 
       case nir_type_int:
-         load->def.name = ralloc_asprintf(mem_ctx, "%ld", c->data.i);
+         load->def.name = ralloc_asprintf(load, "%ld", c->data.i);
          switch (bitsize->dest_size) {
          case 32:
             load->value.i32[0] = c->data.i;
@@ -497,7 +497,7 @@ construct_value(const nir_search_value *value,
          break;
 
       case nir_type_uint:
-         load->def.name = ralloc_asprintf(mem_ctx, "%lu", c->data.u);
+         load->def.name = ralloc_asprintf(load, "%lu", c->data.u);
          switch (bitsize->dest_size) {
          case 32:
             load->value.u32[0] = c->data.u;

src/compiler/nir/nir_to_ssa.c

@@ -221,6 +221,7 @@ rewrite_def_forwards(nir_dest *dest, void *_state)
    list_del(&dest->reg.def_link);
    nir_ssa_dest_init(state->parent_instr, dest, reg->num_components,
                      reg->bit_size, name);
+   ralloc_free(name);
 
    /* push our SSA destination on the stack */
    state->states[index].index++;
@@ -274,6 +275,7 @@ rewrite_alu_instr_forward(nir_alu_instr *instr, rewrite_state *state)
       list_del(&instr->dest.dest.reg.def_link);
       nir_ssa_dest_init(&instr->instr, &instr->dest.dest, num_components,
                         reg->bit_size, name);
+      ralloc_free(name);
 
       if (nir_op_infos[instr->op].output_size == 0) {
          /*