[Mesa-dev] [PATCH 13/21] glsl: Store short variable names inside ir_variable

[Ian Romanick]

From: Ian Romanick <ian.d.romanick at intel.com>

Most of the overhead of the name allocation is the ralloc tracking,
especially on 64-bit.  The allocation of the variable name "i" is 2
bytes for the name and 40 bytes for the ralloc tracking.

Reduces the peak ir_variable memory usage in a trimmed apitrace of dota2
by 225KiB on 64-bit.

Before: IR MEM: variable usage / name / total: 5746368 1439077 7185445
After:  IR MEM: variable usage / name / total: 5746368 1208630 6954998

Reduces the peak ir_variable memory usage in a trimmed apitrace of dota2
by 70KiB on 32-bit.

Before: IR MEM: variable usage / name / total: 4327584 915817 5243401
After:  IR MEM: variable usage / name / total: 4327584 844096 5171680

Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
---
 src/glsl/ir.cpp              | 11 ++++++++++-
 src/glsl/ir_memory_usage.cpp |  3 ++-
 src/glsl/ir_validate.cpp     |  2 +-
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/src/glsl/ir.cpp b/src/glsl/ir.cpp
index 4907b34..69a0345 100644
--- a/src/glsl/ir.cpp
+++ b/src/glsl/ir.cpp
@@ -1536,7 +1536,16 @@ ir_variable::ir_variable(const struct glsl_type *type, const char *name,
    : ir_instruction(ir_type_variable), max_ifc_array_access(NULL)
 {
    this->type = type;
-   this->name = ralloc_strdup(this, name);
+
+   if (name == NULL) {
+      this->padding[0] = 0;
+      this->name = (char *) this->padding;
+   } else if (strlen(name) < sizeof(this->padding)) {
+      this->name = strcpy((char *) this->padding, name);
+   } else {
+      this->name = ralloc_strdup(this, name);
+   }
+
    this->data.explicit_location = false;
    this->data.has_initializer = false;
    this->data.location = -1;
diff --git a/src/glsl/ir_memory_usage.cpp b/src/glsl/ir_memory_usage.cpp
index 68c0b5c..4918824 100644
--- a/src/glsl/ir_memory_usage.cpp
+++ b/src/glsl/ir_memory_usage.cpp
@@ -63,7 +63,8 @@ ir_memory_usage::visit(ir_variable *ir)
       this->s.variable_usage += (sizeof(ir_state_slot) * ir->num_state_slots)
          + ralloc_header_size;
 
-   this->s.variable_name_usage += strlen(ir->name) + 1 + ralloc_header_size;
+   if (ir->name != (char *) ir->padding)
+      this->s.variable_name_usage += strlen(ir->name) + 1 + ralloc_header_size;
 
    return visit_continue;
 }
diff --git a/src/glsl/ir_validate.cpp b/src/glsl/ir_validate.cpp
index 1cfd0d5..08dd250 100644
--- a/src/glsl/ir_validate.cpp
+++ b/src/glsl/ir_validate.cpp
@@ -634,7 +634,7 @@ ir_validate::visit(ir_variable *ir)
     * in the ir_dereference_variable handler to ensure that a variable is
     * declared before it is dereferenced.
     */
-   if (ir->name)
+   if (ir->name && ir->name != (char *) ir->padding)
       assert(ralloc_parent(ir->name) == ir);
 
    hash_table_insert(ht, ir, ir);
-- 
1.8.1.4