[Mesa-dev] [PATCH 39/78] i965/nir/vec4: Add swizzle utility method for vector ops

[Eduardo Lima Mitev]

From: Antia Puentes <apuentes at igalia.com>

For operations that have a predefined operand size > 0, defined in
glsl/nir/nir_opcodes.c, NIR returns a swizzle containing zeros in the
components from outside the source vector. However, the driver
expects those components to have a swizzle value equal to the swizzle
of the component in (number of vector elements - 1). For example,

   for a vec2 operation with an identity swizzle (.xy):
      - (NIR -> XYXX, driver ->XYYYY)

   for a vec3 operation with swizzle (.zxy)
      - (NIR-> ZXYX, driver -> ZXYY)

This method handles that.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89580
---
 src/mesa/drivers/dri/i965/brw_vec4_nir.cpp | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/src/mesa/drivers/dri/i965/brw_vec4_nir.cpp b/src/mesa/drivers/dri/i965/brw_vec4_nir.cpp
index cf74693..6beb95d 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_nir.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_nir.cpp
@@ -734,6 +734,28 @@ brw_conditional_for_nir_comparison(nir_op op)
    }
 }
 
+static src_reg
+fix_swizzle_for_input_fixed_size(nir_op op, src_reg src)
+{
+   /* For operations that have a predefined operand size > 0, defined in
+    * glsl/nir/nir_opcodes.c, NIR returns a swizzle containing zeros in the
+    * components from outside the source vector. However, the driver
+    * expects those components to have a swizzle value equal to the swizzle
+    * of the component in (number of vector elements - 1). For example,
+    * for a vec2 operation with an identity swizzle (.xy):
+    *         - (NIR -> XYXX, driver ->XYYYY)
+    * for a vec3 operation with swizzle (.zxy)
+    *         - (NIR-> ZXYX, driver -> ZXYY)
+    */
+   unsigned size = nir_op_infos[op].input_sizes[0];
+   assert(size > 0);
+
+   src.swizzle = brw_compose_swizzle(brw_swizzle_for_size(size),
+                                     src.swizzle);
+
+   return src;
+}
+
 void
 vec4_visitor::nir_emit_alu(nir_alu_instr *instr)
 {
-- 
2.1.4