[Mesa-dev] [PATCH 3/6] i965/fs: skip copy-propate for negated logical instructions and 'NOT' src registers

[Abdiel Janulgue]

The negation source modifier on src registers has changed meaning in Broadwell when
used with logical operations.

Make sure copy propagation occurs only for original statements that does not have
negated source registers and destination instruction is not a logical op. In addition,
since we have added 'NOT' as a potentially propagate-able instruction, don't
propagate it either when the destination instruction is not a logical op.

Signed-off-by: Abdiel Janulgue <abdiel.janulgue at linux.intel.com>
---
 src/mesa/drivers/dri/i965/brw_fs_copy_propagation.cpp | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/src/mesa/drivers/dri/i965/brw_fs_copy_propagation.cpp b/src/mesa/drivers/dri/i965/brw_fs_copy_propagation.cpp
index 09d5949..26eda92 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_copy_propagation.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_copy_propagation.cpp
@@ -273,6 +273,15 @@ fs_copy_prop_dataflow::dump_block_data() const
    }
 }
 
+static bool
+is_logic_op(enum opcode opcode)
+{
+   return (opcode == BRW_OPCODE_AND ||
+           opcode == BRW_OPCODE_OR  ||
+           opcode == BRW_OPCODE_XOR ||
+           opcode == BRW_OPCODE_NOT);
+}
+
 bool
 fs_visitor::try_copy_propagate(fs_inst *inst, int arg, acp_entry *entry)
 {
@@ -331,6 +340,11 @@ fs_visitor::try_copy_propagate(fs_inst *inst, int arg, acp_entry *entry)
    if (has_source_modifiers && entry->dst.type != inst->src[arg].type)
       return false;
 
+   if (brw->gen >=8 &&
+       ((entry->src.negate && is_logic_op(inst->opcode)) ||
+        (entry->opcode == BRW_OPCODE_NOT && !is_logic_op(inst->opcode))))
+      return false;
+
    inst->src[arg].file = entry->src.file;
    inst->src[arg].reg = entry->src.reg;
    inst->src[arg].reg_offset = entry->src.reg_offset;
-- 
1.9.1