i965/fs: Eliminate the magic nature of virtual GRF 0.

This was a debugging aid at one point -- virtual grf 0 should never be
allocated, and it would be used if undefined register access occurred
in codegen.  However, it made the confusing register allocation code
even more confusing by indexing things off of 1 all over.

diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index f55be022f72a6c0fa3bf03abc855c96daafc633d..d57a67cc4fc728327199c9d04f244ea2ea57d2aa 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -181,9 +181,6 @@ fs_visitor::virtual_grf_alloc(int size)
         virtual_grf_array_size *= 2;
       virtual_grf_sizes = reralloc(mem_ctx, virtual_grf_sizes, int,
                                   virtual_grf_array_size);
-
-      /* This slot is always unused. */
-      virtual_grf_sizes[0] = 0;
    }
    virtual_grf_sizes[virtual_grf_next] = size;
    return virtual_grf_next++;
@@ -985,7 +982,7 @@ fs_visitor::calculate_live_intervals()
         }
       } else {
         for (unsigned int i = 0; i < 3; i++) {
-           if (inst->src[i].file == GRF && inst->src[i].reg != 0) {
+           if (inst->src[i].file == GRF) {
               int reg = inst->src[i].reg;
 
               if (!loop_depth) {
@@ -1001,7 +998,7 @@ fs_visitor::calculate_live_intervals()
               }
            }
         }
-        if (inst->dst.file == GRF && inst->dst.reg != 0) {
+        if (inst->dst.file == GRF) {
            int reg = inst->dst.reg;
 
            if (!loop_depth) {
@@ -1715,7 +1712,7 @@ fs_visitor::run()
       if (0) {
         /* Debug of register spilling: Go spill everything. */
         int virtual_grf_count = virtual_grf_next;
-        for (int i = 1; i < virtual_grf_count; i++) {
+        for (int i = 0; i < virtual_grf_count; i++) {
            spill_reg(i);
         }
       }

diff --git a/src/mesa/drivers/dri/i965/brw_fs.h b/src/mesa/drivers/dri/i965/brw_fs.h
index 96e1420038f52e165bafa20dfba38667ed5987c7..0375f672beca1097fa392bea2e6833f7791caa5d 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_fs.h
+++ b/src/mesa/drivers/dri/i965/brw_fs.h
@@ -402,7 +402,7 @@ public:
       this->base_ir = NULL;
 
       this->virtual_grf_sizes = NULL;
-      this->virtual_grf_next = 1;
+      this->virtual_grf_next = 0;
       this->virtual_grf_array_size = 0;
       this->virtual_grf_def = NULL;
       this->virtual_grf_use = NULL;

diff --git a/src/mesa/drivers/dri/i965/brw_fs_reg_allocate.cpp b/src/mesa/drivers/dri/i965/brw_fs_reg_allocate.cpp
index f246ac496605e8be80cc077ae3483e21fb6ed6fe..83dd629aafb4d1b85d492fffb3ec9fabc8b478f8 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_fs_reg_allocate.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_reg_allocate.cpp
@@ -50,7 +50,7 @@ extern "C" {
 static void
 assign_reg(int *reg_hw_locations, fs_reg *reg, int reg_width)
 {
-   if (reg->file == GRF && reg->reg != 0) {
+   if (reg->file == GRF) {
       assert(reg->reg_offset >= 0);
       reg->hw_reg = reg_hw_locations[reg->reg] + reg->reg_offset * reg_width;
       reg->reg = 0;
@@ -60,20 +60,17 @@ assign_reg(int *reg_hw_locations, fs_reg *reg, int reg_width)
 void
 fs_visitor::assign_regs_trivial()
 {
-   int last_grf = 0;
-   int hw_reg_mapping[this->virtual_grf_next];
+   int hw_reg_mapping[this->virtual_grf_next + 1];
    int i;
    int reg_width = c->dispatch_width / 8;
 
-   hw_reg_mapping[0] = 0;
    /* Note that compressed instructions require alignment to 2 registers. */
-   hw_reg_mapping[1] = ALIGN(this->first_non_payload_grf, reg_width);
-   for (i = 2; i < this->virtual_grf_next; i++) {
+   hw_reg_mapping[0] = ALIGN(this->first_non_payload_grf, reg_width);
+   for (i = 1; i <= this->virtual_grf_next; i++) {
       hw_reg_mapping[i] = (hw_reg_mapping[i - 1] +
                           this->virtual_grf_sizes[i - 1] * reg_width);
    }
-   last_grf = hw_reg_mapping[i - 1] + (this->virtual_grf_sizes[i - 1] *
-                                      reg_width);
+   this->grf_used = hw_reg_mapping[this->virtual_grf_next];
 
    foreach_list(node, &this->instructions) {
       fs_inst *inst = (fs_inst *)node;
@@ -83,12 +80,11 @@ fs_visitor::assign_regs_trivial()
       assign_reg(hw_reg_mapping, &inst->src[1], reg_width);
    }
 
-   if (last_grf >= BRW_MAX_GRF) {
+   if (this->grf_used >= BRW_MAX_GRF) {
       fail("Ran out of regs on trivial allocator (%d/%d)\n",
-          last_grf, BRW_MAX_GRF);
+          this->grf_used, BRW_MAX_GRF);
    }
 
-   this->grf_used = last_grf + reg_width;
 }
 
 bool
@@ -101,7 +97,7 @@ fs_visitor::assign_regs()
     * for reg_width == 2.
     */
    int reg_width = c->dispatch_width / 8;
-   int hw_reg_mapping[this->virtual_grf_next + 1];
+   int hw_reg_mapping[this->virtual_grf_next];
    int first_assigned_grf = ALIGN(this->first_non_payload_grf, reg_width);
    int base_reg_count = (BRW_MAX_GRF - first_assigned_grf) / reg_width;
    int class_sizes[base_reg_count];
@@ -125,7 +121,7 @@ fs_visitor::assign_regs()
        */
       class_sizes[class_count++] = 2;
    }
-   for (int r = 1; r < this->virtual_grf_next; r++) {
+   for (int r = 0; r < this->virtual_grf_next; r++) {
       int i;
 
       for (i = 0; i < class_count; i++) {
@@ -195,12 +191,8 @@ fs_visitor::assign_regs()
 
    struct ra_graph *g = ra_alloc_interference_graph(regs,
                                                    this->virtual_grf_next);
-   /* Node 0 is just a placeholder to keep virtual_grf[] mapping 1:1
-    * with nodes.
-    */
-   ra_set_node_class(g, 0, classes[0]);
 
-   for (int i = 1; i < this->virtual_grf_next; i++) {
+   for (int i = 0; i < this->virtual_grf_next; i++) {
       for (int c = 0; c < class_count; c++) {
         if (class_sizes[c] == this->virtual_grf_sizes[i]) {
            if (aligned_pair_class >= 0 &&
@@ -213,7 +205,7 @@ fs_visitor::assign_regs()
         }
       }
 
-      for (int j = 1; j < i; j++) {
+      for (int j = 0; j < i; j++) {
         if (virtual_grf_interferes(i, j)) {
            ra_add_node_interference(g, i, j);
         }
@@ -248,8 +240,7 @@ fs_visitor::assign_regs()
     * numbers.
     */
    this->grf_used = first_assigned_grf;
-   hw_reg_mapping[0] = 0; /* unused */
-   for (int i = 1; i < this->virtual_grf_next; i++) {
+   for (int i = 0; i < this->virtual_grf_next; i++) {
       int reg = ra_get_node_reg(g, i);
       int hw_reg = -1;
 

diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
index 2b769ccbba141033781bbc01e1e3eb0c2d780f91..2e3f9be75b471b1c5b3e62d6d1d83135759131af 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
@@ -142,9 +142,7 @@ fs_visitor::visit(ir_dereference_array *ir)
    this->result.type = brw_type_for_base_type(ir->type);
 
    if (index) {
-      assert(this->result.file == UNIFORM ||
-            (this->result.file == GRF &&
-             this->result.reg != 0));
+      assert(this->result.file == UNIFORM || this->result.file == GRF);
       this->result.reg_offset += index->value.i[0] * element_size;
    } else {
       assert(!"FINISHME: non-constant array element");