i965/fs: Fix comparisions 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 fs-op-neg-*

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

4 files changed, 49 insertions, 0 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index 738610621b1..c0d93c03a2e 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -1347,6 +1347,19 @@ fs_visitor::register_coalesce()
 	    interfered = true;
 	    break;
 	 }
+
+	 /* The accumulator result appears to get used for the
+	  * conditional modifier generation.  When negating a UD
+	  * value, there is a 33rd bit generated for the sign in the
+	  * accumulator value, so now you can't check, for example,
+	  * equality with a 32-bit value.  See piglit fs-op-neg-uint.
+	  */
+	 if (scan_inst->conditional_mod &&
+	     inst->src[0].negate &&
+	     inst->src[0].type == BRW_REGISTER_TYPE_UD) {
+	    interfered = true;
+	    break;
+	 }
       }
       if (interfered) {
 	 continue;
diff --git a/src/mesa/drivers/dri/i965/brw_fs.h b/src/mesa/drivers/dri/i965/brw_fs.h
index f344330db1d..f5af9ea936a 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.h
+++ b/src/mesa/drivers/dri/i965/brw_fs.h
@@ -535,6 +535,7 @@ public:
 			       fs_inst *last_rhs_inst);
    void emit_assignment_writes(fs_reg &l, fs_reg &r,
 			       const glsl_type *type, bool predicated);
+   void resolve_ud_negate(fs_reg *reg);
 
    struct brw_reg interp_reg(int location, int channel);
    int setup_uniform_values(int loc, const glsl_type *type);
diff --git a/src/mesa/drivers/dri/i965/brw_fs_emit.cpp b/src/mesa/drivers/dri/i965/brw_fs_emit.cpp
index 88a999965a1..0c14baf367d 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_emit.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_emit.cpp
@@ -635,6 +635,16 @@ fs_visitor::generate_code()
 
       for (unsigned int i = 0; i < 3; i++) {
 	 src[i] = brw_reg_from_fs_reg(&inst->src[i]);
+
+	 /* The accumulator result appears to get used for the
+	  * conditional modifier generation.  When negating a UD
+	  * value, there is a 33rd bit generated for the sign in the
+	  * accumulator value, so now you can't check, for example,
+	  * equality with a 32-bit value.  See piglit fs-op-neg-uvec4.
+	  */
+	 assert(!inst->conditional_mod ||
+		inst->src[i].type != BRW_REGISTER_TYPE_UD ||
+		!inst->src[i].negate);
       }
       dst = brw_reg_from_fs_reg(&inst->dst);
 
diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
index e523ae748bc..215cdcdb022 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
@@ -317,6 +317,9 @@ fs_visitor::visit(ir_expression *ir)
       if (intel->gen < 5)
 	 temp.type = op[0].type;
 
+      resolve_ud_negate(&op[0]);
+      resolve_ud_negate(&op[1]);
+
       inst = emit(BRW_OPCODE_CMP, temp, op[0], op[1]);
       inst->conditional_mod = brw_conditional_for_comparison(ir->operation);
       emit(BRW_OPCODE_AND, this->result, this->result, fs_reg(0x1));
@@ -377,6 +380,8 @@ fs_visitor::visit(ir_expression *ir)
       if (intel->gen < 5)
 	 temp.type = op[0].type;
 
+      resolve_ud_negate(&op[0]);
+
       inst = emit(BRW_OPCODE_CMP, temp, op[0], fs_reg(0.0f));
       inst->conditional_mod = BRW_CONDITIONAL_NZ;
       inst = emit(BRW_OPCODE_AND, this->result, this->result, fs_reg(1));
@@ -401,6 +406,9 @@ fs_visitor::visit(ir_expression *ir)
       break;
 
    case ir_binop_min:
+      resolve_ud_negate(&op[0]);
+      resolve_ud_negate(&op[1]);
+
       if (intel->gen >= 6) {
 	 inst = emit(BRW_OPCODE_SEL, this->result, op[0], op[1]);
 	 inst->conditional_mod = BRW_CONDITIONAL_L;
@@ -416,6 +424,9 @@ fs_visitor::visit(ir_expression *ir)
       }
       break;
    case ir_binop_max:
+      resolve_ud_negate(&op[0]);
+      resolve_ud_negate(&op[1]);
+
       if (intel->gen >= 6) {
 	 inst = emit(BRW_OPCODE_SEL, this->result, op[0], op[1]);
 	 inst->conditional_mod = BRW_CONDITIONAL_GE;
@@ -1369,6 +1380,8 @@ fs_visitor::emit_bool_to_cond_code(ir_rvalue *ir)
 
 	 expr->operands[i]->accept(this);
 	 op[i] = this->result;
+
+	 resolve_ud_negate(&op[i]);
       }
 
       switch (expr->operation) {
@@ -1984,3 +1997,15 @@ fs_visitor::emit_fb_writes()
 
    this->current_annotation = NULL;
 }
+
+void
+fs_visitor::resolve_ud_negate(fs_reg *reg)
+{
+   if (reg->type != BRW_REGISTER_TYPE_UD ||
+       !reg->negate)
+      return;
+
+   fs_reg temp = fs_reg(this, glsl_type::uint_type);
+   emit(BRW_OPCODE_MOV, temp, *reg);
+   *reg = temp;
+}