[Mesa-dev] [PATCH 3/5] i965/vec4: Fix broken saturate mask check in copy propagation.

[Francisco Jerez]

try_copy_propagate() was checking the bit of the saturate mask for the
arg-th component of the source to decide whether the whole source
should be saturated (WTF?).  We need to swizzle the original saturate
mask and check that for all enabled channels the saturate flag is
either set or unset, as we cannot saturate a subset of destination
components only.
---
This change depends on PATCH 01 of my swizzle clean-up series:
http://lists.freedesktop.org/archives/mesa-dev/2015-March/080003.html

 src/mesa/drivers/dri/i965/brw_vec4_copy_propagation.cpp | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

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 653700e..9437e79 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_copy_propagation.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_copy_propagation.cpp
@@ -331,10 +331,17 @@ try_copy_propagate(struct brw_context *brw, vec4_instruction *inst,
    if (value.equals(inst->src[arg]))
       return false;
 
-   /* Limit saturate propagation only to SEL with src1 bounded within 1.0 and 1.0
-    * otherwise, skip copy propagate altogether
-    */
-   if (entry->saturatemask & (1 << arg)) {
+   const unsigned dst_saturate_mask = inst->dst.writemask &
+      brw_apply_swizzle_to_mask(inst->src[arg].swizzle, entry->saturatemask);
+
+   if (dst_saturate_mask) {
+      /* We either saturate all or nothing. */
+      if (dst_saturate_mask != inst->dst.writemask)
+         return false;
+
+      /* Limit saturate propagation only to SEL with src1 bounded within 1.0
+       * and 1.0 otherwise, skip copy propagate altogether
+       */
       switch(inst->opcode) {
       case BRW_OPCODE_SEL:
          if (inst->src[1].file != IMM ||
-- 
2.1.3