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ir3: Fix the no-emitted-vertex condition emission in geom lowering.

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The if statement we insert would insert a new block before the end block
(and remove the old pre-end-block).  If the new block ended up later in
the HT due to its pointer's hash value, you'd emit another copy of the if
statement after the last one.  I saw this happen up to 4 times in testing.
The worst case would be if all those additions and removals ended up
reallocating the HT, at which point we might use-after-free.

Fixes inconsistent shader-db results with geometry shaders.

Cc: mesa-stable.
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17501>
This commit is contained in:
Emma Anholt 2022-07-12 16:10:17 -07:00 • committed by Marge Bot
parent 2171412c66
commit 43579901be
1 changed files with 25 additions and 22 deletions
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47
src/freedreno/ir3/ir3_nir_lower_tess.c
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@ -1004,31 +1004,34 @@ ir3_nir_lower_gs(nir_shader *shader)
nir_foreach_block_safe (block, impl)
lower_gs_block(block, &b, &state);
set_foreach (impl->end_block->predecessors, block_entry) {
struct nir_block *block = (void *)block_entry->key;
b.cursor = nir_after_block_before_jump(block);
/* Note: returns are lowered, so there should be only one block before the
* end block. If we had real returns, we would probably want to redirect
* them to this new if statement, rather than emitting this code at every
* return statement.
*/
assert(impl->end_block->predecessors->entries == 1);
nir_block *block = nir_impl_last_block(impl);
b.cursor = nir_after_block_before_jump(block);
nir_ssa_def *cond =
nir_ieq_imm(&b, nir_load_var(&b, state.emitted_vertex_var), 0);
/* If we haven't emitted any vertex we need to copy the shadow (old)
* outputs to emit outputs here.
*
* Also some piglit GS tests[1] don't have EndPrimitive() so throw
* in an extra vertex_flags write for good measure. If unneeded it
* will be optimized out.
*
* [1] ex, tests/spec/glsl-1.50/execution/compatibility/clipping/gs-clip-vertex-const-accept.shader_test
*/
nir_ssa_def *cond =
nir_ieq_imm(&b, nir_load_var(&b, state.emitted_vertex_var), 0);
nir_push_if(&b, cond);
nir_store_var(&b, state.vertex_flags_out, nir_imm_int(&b, 4), 0x1);
copy_vars(&b, &state.emit_outputs, &state.old_outputs);
nir_pop_if(&b, NULL);
/* If we haven't emitted any vertex we need to copy the shadow (old)
* outputs to emit outputs here.
*
* Also some piglit GS tests[1] don't have EndPrimitive() so throw
* in an extra vertex_flags write for good measure. If unneeded it
* will be optimized out.
*
* [1] ex, tests/spec/glsl-1.50/execution/compatibility/clipping/gs-clip-vertex-const-accept.shader_test
*/
nir_push_if(&b, cond);
nir_store_var(&b, state.vertex_flags_out, nir_imm_int(&b, 4), 0x1);
copy_vars(&b, &state.emit_outputs, &state.old_outputs);
nir_pop_if(&b, NULL);
nir_discard_if(&b, cond);
nir_discard_if(&b, cond);
copy_vars(&b, &state.new_outputs, &state.emit_outputs);
}
copy_vars(&b, &state.new_outputs, &state.emit_outputs);
exec_list_append(&shader->variables, &state.old_outputs);
exec_list_append(&shader->variables, &state.emit_outputs);