[Mesa-dev] [PATCH v3 6/6] glsl/linker: check for xfb_offset aliasing
Andres Gomez
agomez at igalia.com
Mon Apr 22 00:00:23 UTC 2019
>From page 76 (page 80 of the PDF) of the GLSL 4.60 v.5 spec:
" No aliasing in output buffers is allowed: It is a compile-time or
link-time error to specify variables with overlapping transform
feedback offsets."
Currently, this is expected to fail, but it succeeds:
"
...
layout (xfb_offset = 0) out vec2 a;
layout (xfb_offset = 0) out vec4 b;
...
"
v2:
- Use a data structure to track the used components instead of a
nested loop (Ilia).
v3:
- Take the BITSET_WORD array out from the
gl_transform_feedback_buffer struct and make it local to the
validation process (Timothy).
- Do not use a nested scope for the validation (Timothy).
Cc: Timothy Arceri <tarceri at itsqueeze.com>
Cc: Ilia Mirkin <imirkin at alum.mit.edu>
Signed-off-by: Andres Gomez <agomez at igalia.com>
---
src/compiler/glsl/link_varyings.cpp | 109 ++++++++++++++++++++--------
src/compiler/glsl/link_varyings.h | 6 +-
2 files changed, 84 insertions(+), 31 deletions(-)
diff --git a/src/compiler/glsl/link_varyings.cpp b/src/compiler/glsl/link_varyings.cpp
index 22ec411837d..89874530980 100644
--- a/src/compiler/glsl/link_varyings.cpp
+++ b/src/compiler/glsl/link_varyings.cpp
@@ -1169,8 +1169,10 @@ bool
tfeedback_decl::store(struct gl_context *ctx, struct gl_shader_program *prog,
struct gl_transform_feedback_info *info,
unsigned buffer, unsigned buffer_index,
- const unsigned max_outputs, bool *explicit_stride,
- bool has_xfb_qualifiers) const
+ const unsigned max_outputs,
+ BITSET_WORD *used_components[MAX_FEEDBACK_BUFFERS],
+ bool *explicit_stride, bool has_xfb_qualifiers,
+ const void* mem_ctx) const
{
unsigned xfb_offset = 0;
unsigned size = this->size;
@@ -1197,6 +1199,72 @@ tfeedback_decl::store(struct gl_context *ctx, struct gl_shader_program *prog,
unsigned location = this->location;
unsigned location_frac = this->location_frac;
unsigned num_components = this->num_components();
+
+ /* From GL_EXT_transform_feedback:
+ *
+ * " A program will fail to link if:
+ *
+ * * the total number of components to capture is greater than the
+ * constant MAX_TRANSFORM_FEEDBACK_INTERLEAVED_COMPONENTS_EXT
+ * and the buffer mode is INTERLEAVED_ATTRIBS_EXT."
+ *
+ * From GL_ARB_enhanced_layouts:
+ *
+ * " The resulting stride (implicit or explicit) must be less than or
+ * equal to the implementation-dependent constant
+ * gl_MaxTransformFeedbackInterleavedComponents."
+ */
+ if ((prog->TransformFeedback.BufferMode == GL_INTERLEAVED_ATTRIBS ||
+ has_xfb_qualifiers) &&
+ xfb_offset + num_components >
+ ctx->Const.MaxTransformFeedbackInterleavedComponents) {
+ linker_error(prog,
+ "The MAX_TRANSFORM_FEEDBACK_INTERLEAVED_COMPONENTS "
+ "limit has been exceeded.");
+ return false;
+ }
+
+ /* From the OpenGL 4.60.5 spec, section 4.4.2. Output Layout Qualifiers,
+ * Page 76, (Transform Feedback Layout Qualifiers):
+ *
+ * " No aliasing in output buffers is allowed: It is a compile-time or
+ * link-time error to specify variables with overlapping transform
+ * feedback offsets."
+ */
+ const unsigned max_components =
+ ctx->Const.MaxTransformFeedbackInterleavedComponents;
+ const unsigned first_component = xfb_offset;
+ const unsigned last_component = xfb_offset + num_components - 1;
+ const unsigned start_word = BITSET_BITWORD(first_component);
+ const unsigned end_word = BITSET_BITWORD(last_component);
+ BITSET_WORD *used;
+ assert(last_component < max_components);
+
+ if (!used_components[buffer]) {
+ used_components[buffer] =
+ rzalloc_array(mem_ctx, BITSET_WORD, BITSET_WORDS(max_components));
+ }
+ used = used_components[buffer];
+
+ for (unsigned word = start_word; word <= end_word; word++) {
+ unsigned start_range = 0;
+ unsigned end_range = BITSET_WORDBITS - 1;
+
+ if (word == start_word)
+ start_range = first_component % BITSET_WORDBITS;
+
+ if (word == end_word)
+ end_range = last_component % BITSET_WORDBITS;
+
+ if (used[word] & BITSET_RANGE(start_range, end_range)) {
+ linker_error(prog,
+ "variable '%s', xfb_offset (%d) is causing aliasing.",
+ this->orig_name, xfb_offset * 4);
+ return false;
+ }
+ used[word] |= BITSET_RANGE(start_range, end_range);
+ }
+
while (num_components > 0) {
unsigned output_size = MIN2(num_components, 4 - location_frac);
assert((info->NumOutputs == 0 && max_outputs == 0) ||
@@ -1247,28 +1315,6 @@ tfeedback_decl::store(struct gl_context *ctx, struct gl_shader_program *prog,
info->Buffers[buffer].Stride = xfb_offset;
}
- /* From GL_EXT_transform_feedback:
- * A program will fail to link if:
- *
- * * the total number of components to capture is greater than
- * the constant MAX_TRANSFORM_FEEDBACK_INTERLEAVED_COMPONENTS_EXT
- * and the buffer mode is INTERLEAVED_ATTRIBS_EXT.
- *
- * From GL_ARB_enhanced_layouts:
- *
- * "The resulting stride (implicit or explicit) must be less than or
- * equal to the implementation-dependent constant
- * gl_MaxTransformFeedbackInterleavedComponents."
- */
- if ((prog->TransformFeedback.BufferMode == GL_INTERLEAVED_ATTRIBS ||
- has_xfb_qualifiers) &&
- info->Buffers[buffer].Stride >
- ctx->Const.MaxTransformFeedbackInterleavedComponents) {
- linker_error(prog, "The MAX_TRANSFORM_FEEDBACK_INTERLEAVED_COMPONENTS "
- "limit has been exceeded.");
- return false;
- }
-
store_varying:
info->Varyings[info->NumVarying].Name = ralloc_strdup(prog,
this->orig_name);
@@ -1389,7 +1435,8 @@ cmp_xfb_offset(const void * x_generic, const void * y_generic)
static bool
store_tfeedback_info(struct gl_context *ctx, struct gl_shader_program *prog,
unsigned num_tfeedback_decls,
- tfeedback_decl *tfeedback_decls, bool has_xfb_qualifiers)
+ tfeedback_decl *tfeedback_decls, bool has_xfb_qualifiers,
+ const void *mem_ctx)
{
if (!prog->last_vert_prog)
return true;
@@ -1431,6 +1478,7 @@ store_tfeedback_info(struct gl_context *ctx, struct gl_shader_program *prog,
unsigned num_buffers = 0;
unsigned buffers = 0;
+ BITSET_WORD *used_components[MAX_FEEDBACK_BUFFERS];
if (!has_xfb_qualifiers && separate_attribs_mode) {
/* GL_SEPARATE_ATTRIBS */
@@ -1438,7 +1486,8 @@ store_tfeedback_info(struct gl_context *ctx, struct gl_shader_program *prog,
if (!tfeedback_decls[i].store(ctx, prog,
xfb_prog->sh.LinkedTransformFeedback,
num_buffers, num_buffers, num_outputs,
- NULL, has_xfb_qualifiers))
+ used_components, NULL,
+ has_xfb_qualifiers, mem_ctx))
return false;
buffers |= 1 << num_buffers;
@@ -1475,7 +1524,8 @@ store_tfeedback_info(struct gl_context *ctx, struct gl_shader_program *prog,
if (!tfeedback_decls[i].store(ctx, prog,
xfb_prog->sh.LinkedTransformFeedback,
buffer, num_buffers, num_outputs,
- explicit_stride, has_xfb_qualifiers))
+ used_components, explicit_stride,
+ has_xfb_qualifiers, mem_ctx))
return false;
num_buffers++;
buffer_stream_id = -1;
@@ -1516,7 +1566,8 @@ store_tfeedback_info(struct gl_context *ctx, struct gl_shader_program *prog,
if (!tfeedback_decls[i].store(ctx, prog,
xfb_prog->sh.LinkedTransformFeedback,
buffer, num_buffers, num_outputs,
- explicit_stride, has_xfb_qualifiers))
+ used_components, explicit_stride,
+ has_xfb_qualifiers, mem_ctx))
return false;
}
}
@@ -3002,7 +3053,7 @@ link_varyings(struct gl_shader_program *prog, unsigned first, unsigned last,
}
if (!store_tfeedback_info(ctx, prog, num_tfeedback_decls, tfeedback_decls,
- has_xfb_qualifiers))
+ has_xfb_qualifiers, mem_ctx))
return false;
return true;
diff --git a/src/compiler/glsl/link_varyings.h b/src/compiler/glsl/link_varyings.h
index d0f7ca355b8..b802250819e 100644
--- a/src/compiler/glsl/link_varyings.h
+++ b/src/compiler/glsl/link_varyings.h
@@ -34,7 +34,7 @@
#include "main/glheader.h"
#include "program/prog_parameter.h"
-
+#include "util/bitset.h"
struct gl_shader_program;
struct gl_shader;
@@ -99,7 +99,9 @@ public:
bool store(struct gl_context *ctx, struct gl_shader_program *prog,
struct gl_transform_feedback_info *info, unsigned buffer,
unsigned buffer_index, const unsigned max_outputs,
- bool *explicit_stride, bool has_xfb_qualifiers) const;
+ BITSET_WORD *used_components[MAX_FEEDBACK_BUFFERS],
+ bool *explicit_stride, bool has_xfb_qualifiers,
+ const void *mem_ctx) const;
const tfeedback_candidate *find_candidate(gl_shader_program *prog,
hash_table *tfeedback_candidates);
--
2.20.1
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