i965/fs: When doing no work for live interval calculation, do no allocation.

When I had a bug causing the backend to never finish optimizing, it
also sent me deep into swap.  This avoids extra memory allocation per
trip through optimization, and thus may reduce the peak memory
allocation of the driver even in the success case.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

diff --git a/src/mesa/drivers/dri/i965/brw_fs_live_variables.cpp b/src/mesa/drivers/dri/i965/brw_fs_live_variables.cpp
index c6f0fbc..c7ee582 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_fs_live_variables.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_live_variables.cpp
@@ -163,12 +163,17 @@ void
 fs_visitor::calculate_live_intervals()
 {
    int num_vars = this->virtual_grf_next;
-   int *def = ralloc_array(mem_ctx, int, num_vars);
-   int *use = ralloc_array(mem_ctx, int, num_vars);
 
    if (this->live_intervals_valid)
       return;
 
+   int *def = ralloc_array(mem_ctx, int, num_vars);
+   int *use = ralloc_array(mem_ctx, int, num_vars);
+   ralloc_free(this->virtual_grf_def);
+   ralloc_free(this->virtual_grf_use);
+   this->virtual_grf_def = def;
+   this->virtual_grf_use = use;
+
    for (int i = 0; i < num_vars; i++) {
       def[i] = MAX_INSTRUCTION;
       use[i] = -1;
@@ -215,11 +220,6 @@ fs_visitor::calculate_live_intervals()
       }
    }
 
-   ralloc_free(this->virtual_grf_def);
-   ralloc_free(this->virtual_grf_use);
-   this->virtual_grf_def = def;
-   this->virtual_grf_use = use;
-
    this->live_intervals_valid = true;
 }