Mesa (master): i965/vs: Fix comparisons with uint negation.

[Eric Anholt]

Module: Mesa
Branch: master
Commit: 31874f074c2eaf2a9421c57f0798c79078d296c4
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=31874f074c2eaf2a9421c57f0798c79078d296c4

Author: Eric Anholt <eric at anholt.net>
Date:   Mon Oct  3 15:31:52 2011 -0700

i965/vs: Fix comparisons with uint negation.

The condmod instruction ends up generating garbage condition codes,
because apparently the comparison happens on the accumulator value (33
bits for UD), not the truncated value that would be written.

Fixes vs-op-neg-*

Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>

---

 src/mesa/drivers/dri/i965/brw_vec4.h               |    1 +
 .../drivers/dri/i965/brw_vec4_copy_propagation.cpp |    9 ++++++++
 src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp     |   22 ++++++++++++++++++++
 3 files changed, 32 insertions(+), 0 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_vec4.h b/src/mesa/drivers/dri/i965/brw_vec4.h
index 848e298..a83a6b2 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4.h
+++ b/src/mesa/drivers/dri/i965/brw_vec4.h
@@ -510,6 +510,7 @@ public:
 				int base_offset);
 
    bool try_emit_sat(ir_expression *ir);
+   void resolve_ud_negate(src_reg *reg);
 
    bool process_move_condition(ir_rvalue *ir);
 
diff --git a/src/mesa/drivers/dri/i965/brw_vec4_copy_propagation.cpp b/src/mesa/drivers/dri/i965/brw_vec4_copy_propagation.cpp
index a5f6f93..c3a9dee 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_copy_propagation.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_copy_propagation.cpp
@@ -205,6 +205,15 @@ try_copy_propagation(struct intel_context *intel,
    if (intel->gen >= 6 && inst->is_math())
       return false;
 
+   /* We can't copy-propagate a UD negation into a condmod
+    * instruction, because the condmod ends up looking at the 33-bit
+    * signed accumulator value instead of the 32-bit value we wanted
+    */
+   if (inst->conditional_mod &&
+       value.negate &&
+       value.type == BRW_REGISTER_TYPE_UD)
+      return false;
+
    /* Don't report progress if this is a noop. */
    if (value.equals(&inst->src[arg]))
       return false;
diff --git a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
index 0ea6d31..02ecdaf 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
@@ -182,6 +182,9 @@ vec4_visitor::IF(src_reg src0, src_reg src1, uint32_t condition)
 
    vec4_instruction *inst;
 
+   resolve_ud_negate(&src0);
+   resolve_ud_negate(&src1);
+
    inst = new(mem_ctx) vec4_instruction(this, BRW_OPCODE_IF, dst_null_d(),
 					src0, src1);
    inst->conditional_mod = condition;
@@ -209,6 +212,9 @@ vec4_visitor::CMP(dst_reg dst, src_reg src0, src_reg src1, uint32_t condition)
 	 dst.fixed_hw_reg.type = dst.type;
    }
 
+   resolve_ud_negate(&src0);
+   resolve_ud_negate(&src1);
+
    inst = new(mem_ctx) vec4_instruction(this, BRW_OPCODE_CMP, dst, src0, src1);
    inst->conditional_mod = condition;
 
@@ -643,6 +649,8 @@ vec4_visitor::emit_bool_to_cond_code(ir_rvalue *ir, uint32_t *predicate)
       for (unsigned int i = 0; i < expr->get_num_operands(); i++) {
 	 expr->operands[i]->accept(this);
 	 op[i] = this->result;
+
+	 resolve_ud_negate(&op[i]);
       }
 
       switch (expr->operation) {
@@ -718,6 +726,8 @@ vec4_visitor::emit_bool_to_cond_code(ir_rvalue *ir, uint32_t *predicate)
 
    ir->accept(this);
 
+   resolve_ud_negate(&this->result);
+
    if (intel->gen >= 6) {
       vec4_instruction *inst = emit(AND(dst_null_d(),
 					this->result, src_reg(1)));
@@ -2329,6 +2339,18 @@ vec4_visitor::move_uniform_array_access_to_pull_constants()
    split_uniform_registers();
 }
 
+void
+vec4_visitor::resolve_ud_negate(src_reg *reg)
+{
+   if (reg->type != BRW_REGISTER_TYPE_UD ||
+       !reg->negate)
+      return;
+
+   src_reg temp = src_reg(this, glsl_type::uvec4_type);
+   emit(BRW_OPCODE_MOV, dst_reg(temp), *reg);
+   *reg = temp;
+}
+
 vec4_visitor::vec4_visitor(struct brw_vs_compile *c,
 			   struct gl_shader_program *prog,
 			   struct brw_shader *shader)