diff options
author | Kristian Høgsberg Kristensen <[email protected]> | 2015-11-04 14:58:54 -0800 |
---|---|---|
committer | Kristian Høgsberg Kristensen <[email protected]> | 2015-11-10 12:02:46 -0800 |
commit | 96b22fb080894ba1840af2372f28a46cc0f40c76 (patch) | |
tree | 197f2454ecfd1778eeea2d81146682ff35fce01e /src/glsl/linker.cpp | |
parent | 60dd5287ff8dbbbe0dbe76bdff6d13c7a5ea9ef0 (diff) |
glsl: Use array deref for access to vector components
We've assumed that we could lower per-component vector access from
vec[i] = scalar
to
vec = ir_triop_vector_insert(vec, scalar, i)
but with SSBOs (and compute shader SLM and tesselation outputs) this is
no longer valid. If a vector is "externally visible", multiple threads
can write independent components simultaneously. With lowering to
ir_triop_vector_insert, each thread read the entire vector, changes one
component, then writes out the entire vector. This is racy.
Instead of generating a ir_binop_vector_extract when we see v[i], we
generate ir_dereference_array. We then add a lowering pass to lower the
ir_dereference_array to ir_binop_vector_extract for rvalues and for to
vector_insert for lvalues in a separate lowering pass.
The resulting IR is the same as before, but we now have a window between
ast->ir conversion and the lowering pass where v[i] appears in the IR as
an array deref. This lets us run lowering passes that lower the vector
access to I/O (eg for SSBO load/store) before we lower the per-component
access to full vector writes.
Reviewed-by: Jordan Justen <[email protected]>
Signed-off-by: Kristian Høgsberg Kristensen <[email protected]>
Diffstat (limited to 'src/glsl/linker.cpp')
-rw-r--r-- | src/glsl/linker.cpp | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/src/glsl/linker.cpp b/src/glsl/linker.cpp index a8baee07f10..db00f8febc6 100644 --- a/src/glsl/linker.cpp +++ b/src/glsl/linker.cpp @@ -4451,6 +4451,8 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog) if (ctx->Const.ShaderCompilerOptions[i].LowerBufferInterfaceBlocks) lower_ubo_reference(prog->_LinkedShaders[i]); + + lower_vector_derefs(prog->_LinkedShaders[i]); } done: |