i965/fs: Fix a bug with dead_code_eliminate on large writes

Previously, if an instruction wrote to more than one register, we
implicitly assumed that it filled the entire register.  We never hit this
before because the only time we did multi-register writes was things like
texturing which always wrote to all of the registers.  However, with the
upcoming ability to do 16-wide instructions in SIMD8 and things of that
nature, we can have multi-register writes at offsets and we'll hit this.

Signed-off-by: Jason Ekstrand <jason.ekstrand@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>

diff --git a/src/mesa/drivers/dri/i965/brw_fs_dead_code_eliminate.cpp b/src/mesa/drivers/dri/i965/brw_fs_dead_code_eliminate.cpp
index 3cb63399d3ef165a777b00d05a38ba173dcac45b..0d26103cc6629bedbd2afce248552ceb4b10785b 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_fs_dead_code_eliminate.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_dead_code_eliminate.cpp
@@ -58,7 +58,7 @@ fs_visitor::dead_code_eliminate()
                int var = live_intervals->var_from_reg(&inst->dst);
                result_live = BITSET_TEST(live, var);
             } else {
-               int var = live_intervals->var_from_vgrf[inst->dst.reg];
+               int var = live_intervals->var_from_reg(&inst->dst);
                for (int i = 0; i < inst->regs_written; i++) {
                   result_live = result_live || BITSET_TEST(live, var + i);
                }