[Mesa-dev] [PATCH 1/2] i965/fs: Fix rendering corruption in unigine tropics.

[Eric Anholt]

We were allocating registers into the MRF hack region, resulting in
sparkly renering in a few of the scenes.  We could do better
allocation by making an MRF class, having MRFs conflict with the
corresponding GRFs, and tracking the live intervals of the "MRF"s and
setting up the conflicts.  But this is way easier for the moment.

NOTE: This is a candidate for the 8.0 branch.
---
 src/mesa/drivers/dri/i965/brw_eu_emit.c           |    2 +-
 src/mesa/drivers/dri/i965/brw_fs.h                |    2 ++
 src/mesa/drivers/dri/i965/brw_fs_reg_allocate.cpp |    6 +++---
 src/mesa/drivers/dri/i965/brw_structs.h           |   11 +++++++++++
 4 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_eu_emit.c b/src/mesa/drivers/dri/i965/brw_eu_emit.c
index 9929739..3347157 100644
--- a/src/mesa/drivers/dri/i965/brw_eu_emit.c
+++ b/src/mesa/drivers/dri/i965/brw_eu_emit.c
@@ -95,7 +95,7 @@ gen7_convert_mrf_to_grf(struct brw_compile *p, struct brw_reg *reg)
    struct intel_context *intel = &p->brw->intel;
    if (intel->gen == 7 && reg->file == BRW_MESSAGE_REGISTER_FILE) {
       reg->file = BRW_GENERAL_REGISTER_FILE;
-      reg->nr += 112;
+      reg->nr += GEN7_MRF_HACK_START;
    }
 }
 
diff --git a/src/mesa/drivers/dri/i965/brw_fs.h b/src/mesa/drivers/dri/i965/brw_fs.h
index d623316..5fdc055 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.h
+++ b/src/mesa/drivers/dri/i965/brw_fs.h
@@ -379,6 +379,7 @@ public:
       this->frag_depth = NULL;
       memset(this->outputs, 0, sizeof(this->outputs));
       this->first_non_payload_grf = 0;
+      this->max_grf = intel->gen >= 7 ? GEN7_MRF_HACK_START : BRW_MAX_GRF;
 
       this->current_annotation = NULL;
       this->base_ir = NULL;
@@ -583,6 +584,7 @@ public:
    ir_variable *frag_depth;
    fs_reg outputs[BRW_MAX_DRAW_BUFFERS];
    int first_non_payload_grf;
+   int max_grf;
    int urb_setup[FRAG_ATTRIB_MAX];
    bool kill_emitted;
 
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 d4dd124..0d1712e 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_reg_allocate.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_reg_allocate.cpp
@@ -63,9 +63,9 @@ fs_visitor::assign_regs_trivial()
       assign_reg(hw_reg_mapping, &inst->src[1], reg_width);
    }
 
-   if (this->grf_used >= BRW_MAX_GRF) {
+   if (this->grf_used >= max_grf) {
       fail("Ran out of regs on trivial allocator (%d/%d)\n",
-	   this->grf_used, BRW_MAX_GRF);
+	   this->grf_used, max_grf);
    }
 
 }
@@ -156,7 +156,7 @@ fs_visitor::assign_regs()
    int reg_width = c->dispatch_width / 8;
    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 base_reg_count = (max_grf - first_assigned_grf) / reg_width;
    int class_sizes[base_reg_count];
    int class_count = 0;
 
diff --git a/src/mesa/drivers/dri/i965/brw_structs.h b/src/mesa/drivers/dri/i965/brw_structs.h
index aef5695..d23ad0d 100644
--- a/src/mesa/drivers/dri/i965/brw_structs.h
+++ b/src/mesa/drivers/dri/i965/brw_structs.h
@@ -37,6 +37,17 @@
 /** Number of general purpose registers (VS, WM, etc) */
 #define BRW_MAX_GRF 128
 
+/**
+ * First GRF used for the MRF hack.
+ *
+ * On gen7, MRFs are no longer used, and contiguous GRFs are used instead.  We
+ * haven't converted our compiler to be aware of this, so it asks for MRFs and
+ * brw_eu_emit.c quietly converts them to be accesses of the top GRFs.  The
+ * register allocators have to be careful of this to avoid corrupting the "MRF"s
+ * with actual GRF allocations.
+ */
+#define GEN7_MRF_HACK_START 112.
+
 /** Number of message register file registers */
 #define BRW_MAX_MRF 16
 
-- 
1.7.7.3