Deref paths may share the same deref instructions in their chains,
e.g.
ssa_100 = deref_var A
ssa_101 = deref_struct "array_field" of ssa_100
ssa_102 = deref_array "[1]" of ssa_101
ssa_103 = deref_struct "field_a" of ssa_102
ssa_104 = deref_struct "field_a" of ssa_103
when comparing the two last deref instructions, their paths will share
a common sequence ssa_100, ssa_101, ssa_102. This patch skips to next
iteration if the deref instructions are the same. Path[0] (the var)
is still handled specially, so in the case above, only ssa_101 and
ssa_102 will be skipped.
---
src/compiler/nir/nir_deref.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/src/compiler/nir/nir_deref.c b/src/compiler/nir/nir_deref.c
index d013b423a8b..c8851688f9d 100644
--- a/src/compiler/nir/nir_deref.c
+++ b/src/compiler/nir/nir_deref.c
@@ -294,6 +294,9 @@ nir_compare_deref_paths(nir_deref_path *a_path,
nir_deref_instr *a_tail = *(a_p++);
nir_deref_instr *b_tail = *(b_p++);
+ if (a_tail == b_tail)
+ continue;
+
switch (a_tail->deref_type) {
case nir_deref_type_array:
case nir_deref_type_array_wildcard: {
--
2.18.0
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