Mesa (7.10): i965/fs: Avoid register coalescing away gen6 MATH workarounds.

[Ian Romanick]

Module: Mesa
Branch: 7.10
Commit: ec4822a316d63a45e3084753359b757d96c3917d
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=ec4822a316d63a45e3084753359b757d96c3917d

Author: Kenneth Graunke <kenneth at whitecape.org>
Date:   Sat Feb 19 01:05:11 2011 -0800

i965/fs: Avoid register coalescing away gen6 MATH workarounds.

The code that generates MATH instructions attempts to work around
the hardware ignoring source modifiers (abs and negate) by emitting
moves into temporaries.  Unfortunately, this pass coalesced those
registers, restoring the original problem.  Avoid doing that.

Fixes several OpenGL ES2 conformance failures on Sandybridge.

NOTE: This is a candidate for the 7.10 branch.

Reviewed-by: Eric Anholt <eric at anholt.net>
(cherry picked from commit 2c2686b912de19a430aba9f5ea5fa679eabdc5c6)

---

 src/mesa/drivers/dri/i965/brw_fs.cpp |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index b7425a0..eaa9ae6 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -2980,6 +2980,8 @@ fs_visitor::register_coalesce()
 	  inst->dst.type != inst->src[0].type)
 	 continue;
 
+      bool has_source_modifiers = inst->src[0].abs || inst->src[0].negate;
+
       /* Found a move of a GRF to a GRF.  Let's see if we can coalesce
        * them: check for no writes to either one until the exit of the
        * program.
@@ -3012,6 +3014,14 @@ fs_visitor::register_coalesce()
 	       break;
 	    }
 	 }
+
+	 /* The gen6 MATH instruction can't handle source modifiers, so avoid
+	  * coalescing those for now.  We should do something more specific.
+	  */
+	 if (intel->gen == 6 && scan_inst->is_math() && has_source_modifiers) {
+	    interfered = true;
+	    break;
+	 }
       }
       if (interfered) {
 	 continue;