i965/fs: Create a has_side_effects for fs_inst

When an instruction has a side effect, it impacts the available options when
reordering an instruction. As the EOT flag is an implied write to the render
target in the FS, it can be considered a side effect.

This patch shouldn't actually have any impact on the current code since the EOT
flag implies that the opcode is already one with side effects,
FS_OPCODE_FB_WRITE. The next patch however will introduce an optimization
whereby the EOT flag can occur with an opcode SHADER_OPCODE_TEX, and as that
instruction will perform the same implied write to the render target, it cannot
be reordered.

v2: Remove extra whitespace (Matt)

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>

diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index 8bd8da2389dcfc6cf274fc240fb930ffd0ed8f32..aea1ebb7dea05a98c3a3c00070003a8477f488aa 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -531,6 +531,12 @@ fs_inst::can_do_source_mods(struct brw_context *brw)
    return true;
 }
 
+bool
+fs_inst::has_side_effects() const
+{
+   return this->eot || backend_instruction::has_side_effects();
+}
+
 void
 fs_reg::init()
 {

diff --git a/src/mesa/drivers/dri/i965/brw_ir_fs.h b/src/mesa/drivers/dri/i965/brw_ir_fs.h
index 9ef1261ab3b3b158ba3488f9f20f72841cf5a7ff..30c19f41a319900d38443f1e8c3a1a3b62a30ba7 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_ir_fs.h
+++ b/src/mesa/drivers/dri/i965/brw_ir_fs.h
@@ -225,6 +225,7 @@ public:
    bool is_partial_write() const;
    int regs_read(int arg) const;
    bool can_do_source_mods(struct brw_context *brw);
+   bool has_side_effects() const;
 
    bool reads_flag() const;
    bool writes_flag() const;