[Mesa-dev] [PATCH] st/mesa: swizzle argument when there's a vector size mismatch

[Ilia Mirkin]

GLSL IR operation arguments can sometimes have an implicit swizzle as a
result of a vector arg and a scalar arg, where the scalar argument is
implicitly expanded to the size of the vector argument.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103955
Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
---

I'm *pretty* sure I looked at all of ir_validate to make sure that this will
be fine, but I wouldn't exclude the possibility that I missed some extremely
odd case. Could use a piglit run.

 src/mesa/state_tracker/st_glsl_to_tgsi.cpp | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
index 0772b736275..8ca337d16ec 100644
--- a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
+++ b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
@@ -1342,9 +1342,30 @@ glsl_to_tgsi_visitor::visit_expression(ir_expression* ir, st_src_reg *op)
 
    int vector_elements = ir->operands[0]->type->vector_elements;
    if (ir->operands[1]) {
+      st_src_reg *swz_op = NULL;
+      if (vector_elements > ir->operands[1]->type->vector_elements) {
+         assert(ir->operands[1]->type->vector_elements == 1);
+         swz_op = &op[1];
+      } else if (vector_elements < ir->operands[1]->type->vector_elements) {
+         assert(ir->operands[0]->type->vector_elements == 1);
+         swz_op = &op[0];
+      }
+      if (swz_op) {
+         uint16_t swizzle_x = GET_SWZ(swz_op->swizzle, 0);
+         swz_op->swizzle = MAKE_SWIZZLE4(swizzle_x, swizzle_x,
+                                         swizzle_x, swizzle_x);
+      }
       vector_elements = MAX2(vector_elements,
                              ir->operands[1]->type->vector_elements);
    }
+   if (ir->operands[2] &&
+       ir->operands[2]->type->vector_elements != vector_elements) {
+      /* This can happen with ir_triop_lrp, i.e. glsl mix */
+      assert(ir->operands[2]->type->vector_elements == 1);
+      uint16_t swizzle_x = GET_SWZ(op[2]->swizzle, 0);
+      op[2].swizzle = MAKE_SWIZZLE4(swizzle_x, swizzle_x,
+                                    swizzle_x, swizzle_x);
+   }
 
    this->result.file = PROGRAM_UNDEFINED;
 
-- 
2.13.6