[Mesa-dev] [PATCH v2] glsl: Track initial mask in constant propagation live set

[Ian Romanick]

From: Ian Romanick <ian.d.romanick at intel.com>

The set of values initially available (before any kills) must be
tracked with each constant in the set.  Otherwise the wrong component
can be selected after earlier components have been killed.

NOTE: This is a candidate for the 7.10 and 7.11 branches.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=37383
Cc: Eric Anholt <eric at anholt.net>
Cc: Kenneth Graunke <kenneth at whitecape.org>
Cc: Matthias Bentrup <matthias.bentrup at googlemail.com>
---
v2 fixes some regressions in the previous version.  Instead of
tracking the kill mask in the ACP, the initial value mask is tracked.
A copy constructor is added to make sure the correct initial mask is
propagated to copies.

 src/glsl/opt_constant_propagation.cpp |   17 ++++++++++++++---
 1 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/src/glsl/opt_constant_propagation.cpp b/src/glsl/opt_constant_propagation.cpp
index 4425f42..af77e49 100644
--- a/src/glsl/opt_constant_propagation.cpp
+++ b/src/glsl/opt_constant_propagation.cpp
@@ -51,11 +51,23 @@ public:
       this->var = var;
       this->write_mask = write_mask;
       this->constant = constant;
+      this->initial_values = write_mask;
+   }
+
+   acp_entry(const acp_entry *src)
+   {
+      this->var = src->var;
+      this->write_mask = src->write_mask;
+      this->constant = src->constant;
+      this->initial_values = src->initial_values;
    }
 
    ir_variable *var;
    ir_constant *constant;
    unsigned write_mask;
+
+   /** Mask of values initially available in the constant. */
+   unsigned initial_values;
 };
 
 
@@ -172,7 +184,7 @@ ir_constant_propagation_visitor::handle_rvalue(ir_rvalue **rvalue)
       for (int j = 0; j < 4; j++) {
 	 if (j == channel)
 	    break;
-	 if (found->write_mask & (1 << j))
+	 if (found->initial_values & (1 << j))
 	    rhs_channel++;
       }
 
@@ -285,8 +297,7 @@ ir_constant_propagation_visitor::handle_if_block(exec_list *instructions)
    /* Populate the initial acp with a constant of the original */
    foreach_iter(exec_list_iterator, iter, *orig_acp) {
       acp_entry *a = (acp_entry *)iter.get();
-      this->acp->push_tail(new(this->mem_ctx) acp_entry(a->var, a->write_mask,
-							a->constant));
+      this->acp->push_tail(new(this->mem_ctx) acp_entry(a));
    }
 
    visit_list_elements(this, instructions);
-- 
1.7.4.4