intel/brw: Add a src array for the common case in fs_inst

In the common case, fs_inst will have up to 4 sources (the HW
instructions have up to 3, and our representation of SENDs have 4).
Embed such array into the fs_inst, and use it whenever applicable
instead of allocating a new array.

Also change the code to reuse the allocated src array when resizing to
a smaller length.

Between the changes above and the reduced amount of initializing
fs_regs, this reduces fossil-db time by around 2% for Borderlands 3
and Rise of the Tomb Raider, and around 1.5% for Total War Warhammer 3.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28379>

src/intel/compiler/brw_fs.cpp

@@ -47,19 +47,22 @@
 
 using namespace brw;
 
+static void
+initialize_sources(fs_inst *inst, const fs_reg src[], uint8_t num_sources);
+
 void
 fs_inst::init(enum opcode opcode, uint8_t exec_size, const fs_reg &dst,
               const fs_reg *src, unsigned sources)
 {
    memset((void*)this, 0, sizeof(*this));
 
-   this->src = new fs_reg[MAX2(sources, 3)];
+   initialize_sources(this, src, sources);
+
    for (unsigned i = 0; i < sources; i++)
       this->src[i] = src[i];
 
    this->opcode = opcode;
    this->dst = dst;
-   this->sources = sources;
    this->exec_size = exec_size;
 
    assert(dst.file != IMM && dst.file != UNIFORM);
@@ -132,31 +135,71 @@ fs_inst::fs_inst(enum opcode opcode, uint8_t exec_width, const fs_reg &dst,
 fs_inst::fs_inst(const fs_inst &that)
 {
    memcpy((void*)this, &that, sizeof(that));
-
-   this->src = new fs_reg[MAX2(that.sources, 3)];
-
-   for (unsigned i = 0; i < that.sources; i++)
-      this->src[i] = that.src[i];
+   initialize_sources(this, that.src, that.sources);
 }
 
 fs_inst::~fs_inst()
 {
-   delete[] this->src;
+   if (this->src != this->builtin_src)
+      delete[] this->src;
+}
+
+static void
+initialize_sources(fs_inst *inst, const fs_reg src[], uint8_t num_sources)
+{
+   if (num_sources > ARRAY_SIZE(inst->builtin_src))
+      inst->src = new fs_reg[num_sources];
+   else
+      inst->src = inst->builtin_src;
+
+   for (unsigned i = 0; i < num_sources; i++)
+      inst->src[i] = src[i];
+
+   inst->sources = num_sources;
 }
 
 void
 fs_inst::resize_sources(uint8_t num_sources)
 {
-   if (this->sources != num_sources) {
-      fs_reg *src = new fs_reg[MAX2(num_sources, 3)];
+   if (this->sources == num_sources)
+      return;
 
-      for (unsigned i = 0; i < MIN2(this->sources, num_sources); ++i)
-         src[i] = this->src[i];
+   fs_reg *old_src = this->src;
+   fs_reg *new_src;
 
-      delete[] this->src;
-      this->src = src;
-      this->sources = num_sources;
+   const unsigned builtin_size = ARRAY_SIZE(this->builtin_src);
+
+   if (old_src == this->builtin_src) {
+      if (num_sources > builtin_size) {
+         new_src = new fs_reg[num_sources];
+         for (unsigned i = 0; i < this->sources; i++)
+            new_src[i] = old_src[i];
+
+      } else {
+         new_src = old_src;
+      }
+   } else {
+      if (num_sources <= builtin_size) {
+         new_src = this->builtin_src;
+         assert(this->sources > num_sources);
+         for (unsigned i = 0; i < num_sources; i++)
+            new_src[i] = old_src[i];
+
+      } else if (num_sources < this->sources) {
+         new_src = old_src;
+
+      } else {
+         new_src = new fs_reg[num_sources];
+         for (unsigned i = 0; i < num_sources; i++)
+            new_src[i] = old_src[i];
+      }
+
+      if (old_src != new_src)
+         delete[] old_src;
    }
+
+   this->sources = num_sources;
+   this->src = new_src;
 }
 
 void

src/intel/compiler/brw_ir_fs.h

@@ -566,6 +566,7 @@ public:
 
    fs_reg dst;
    fs_reg *src;
+   fs_reg builtin_src[4];
 };
 
 /**