i965/fs: Add brw_wm_prog_key bit specifying whether FB reads should be coherent.

Some of the following changes in this series are specific to the
non-coherent path, so I need some way to tell whether the coherent or
non-coherent path is in use.  The flag defaults to the value of the
gl_extensions::MESA_shader_framebuffer_fetch enable so that it can be
overridden easily on hardware that supports both framebuffer fetch
extensions in order to test the non-coherent path, like:

 MESA_EXTENSION_OVERRIDE=-GL_EXT_shader_framebuffer_fetch

(Of course trying to force-enable the coherent framebuffer fetch
extension on hardware without native support won't work and lead to
assertion failures).

Reviewed-by: Kenneth Graunke <[email protected]>

2 files changed, 7 insertions, 0 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_compiler.h b/src/mesa/drivers/dri/i965/brw_compiler.h
index 7d15c281a35..0c300e7cff0 100644
--- a/src/mesa/drivers/dri/i965/brw_compiler.h
+++ b/src/mesa/drivers/dri/i965/brw_compiler.h
@@ -260,6 +260,7 @@ struct brw_wm_prog_key {
    unsigned line_aa:2;
    bool high_quality_derivatives:1;
    bool force_dual_color_blend:1;
+   bool coherent_fb_fetch:1;
 
    uint16_t drawable_height;
    uint64_t input_slots_valid;
diff --git a/src/mesa/drivers/dri/i965/brw_wm.c b/src/mesa/drivers/dri/i965/brw_wm.c
index d725a16eb8b..c513dbcc367 100644
--- a/src/mesa/drivers/dri/i965/brw_wm.c
+++ b/src/mesa/drivers/dri/i965/brw_wm.c
@@ -549,6 +549,9 @@ brw_wm_populate_key(struct brw_context *brw, struct brw_wm_prog_key *key)
 
    /* The unique fragment program ID */
    key->program_string_id = fp->id;
+
+   /* Whether reads from the framebuffer should behave coherently. */
+   key->coherent_fb_fetch = ctx->Extensions.MESA_shader_framebuffer_fetch;
 }
 
 void
@@ -613,6 +616,9 @@ brw_fs_precompile(struct gl_context *ctx,
 
    key.program_string_id = bfp->id;
 
+   /* Whether reads from the framebuffer should behave coherently. */
+   key.coherent_fb_fetch = ctx->Extensions.MESA_shader_framebuffer_fetch;
+
    uint32_t old_prog_offset = brw->wm.base.prog_offset;
    struct brw_wm_prog_data *old_prog_data = brw->wm.prog_data;