aco: reduce memory usage of live_var_analysis

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Georg Lehmann <dadschoorse@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/39408>

src/amd/compiler/aco_live_var_analysis.cpp

@@ -193,6 +193,8 @@ get_demand_for_reg(live_ctx& ctx, T op_or_def)
 void
 process_live_temps_per_block(live_ctx& ctx, Block* block)
 {
+   ctx.m.release_reallocate();
+
    RegisterDemand new_demand;
    unsigned num_linear_vgprs = 0;
    block->register_demand = RegisterDemand();

src/amd/compiler/aco_util.h

@@ -298,6 +298,38 @@ public:
       buffer->current_idx = 0;
    }
 
+   /* Release all memory, with the expectation that a similar amount will be allocated again. */
+   void release_reallocate()
+   {
+      size_t size = 0;
+      for (Buffer* buf = buffer; buf; buf = buf->next)
+         size += buf->current_idx;
+
+      if (buffer->data_size >= size) {
+         Buffer* buf = buffer->next;
+         while (buf) {
+            Buffer* next = buf->next;
+            free(buf);
+            buf = next;
+         }
+         buffer->next = NULL;
+         buffer->current_idx = 0;
+         return;
+      }
+
+      release();
+      free(buffer);
+
+      size_t total_size = initial_size;
+      do {
+         total_size *= 2;
+      } while (total_size - sizeof(Buffer) < size);
+      buffer = (Buffer*)malloc(total_size);
+      buffer->next = NULL;
+      buffer->data_size = total_size - sizeof(Buffer);
+      buffer->current_idx = 0;
+   }
+
    bool operator==(const monotonic_buffer_resource& other) const { return buffer == other.buffer; }
 
 private: