Commit fd05620e authored by Yevhenii Kolesnikov's avatar Yevhenii Kolesnikov Committed by Jason Ekstrand
Browse files

nir/from_ssa: consider defs in sibling blocks

If def a and def b are in sibling blocks, the one with higher
parent_instr's index does not necessarily come after the other.

Closes: mesa/mesa#3712
Fixes: 943ddb94

 "nir: Add a better out-of-SSA pass"
Signed-off-by: Yevhenii Kolesnikov's avatarYevhenii Kolesnikov <>
Reviewed-by: Jason Ekstrand's avatarJason Ekstrand <>
Part-of: <mesa/mesa!8246>
parent abdaf5fa
......@@ -45,6 +45,15 @@ struct from_ssa_state {
/* Returns if def @a comes after def @b.
* The core observation that makes the Boissinot algorithm efficient
* is that, given two properly sorted sets, we can check for
* interference in these sets via a linear walk. This is accomplished
* by doing single combined walk over union of the two sets in DFS
* order. It doesn't matter what DFS we do so long as we're
* consistent. Fortunately, the dominance algorithm we ran prior to
* this pass did such a walk and recorded the pre- and post-indices in
* the blocks.
* We treat SSA undefs as always coming before other instruction types.
......@@ -57,7 +66,15 @@ def_after(nir_ssa_def *a, nir_ssa_def *b)
if (b->parent_instr->type == nir_instr_type_ssa_undef)
return true;
return a->parent_instr->index > b->parent_instr->index;
/* If they're in the same block, we can rely on whichever instruction
* comes first in the block.
if (a->parent_instr->block == b->parent_instr->block)
return a->parent_instr->index > b->parent_instr->index;
/* Otherwise, if blocks are distinct, we sort them in DFS pre-order */
return a->parent_instr->block->dom_pre_index >
/* Returns true if a dominates b */
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