From 36734987a59f087ae499c5d0736995007f4af780 Mon Sep 17 00:00:00 2001 From: Jason Ekstrand Date: Sun, 3 Feb 2019 09:32:32 -0600 Subject: [PATCH] nir/deref: Drop zero ptr_as_array derefs They are effectively (&x)[0] or *&x which does nothing. Reviewed-by: Lionel Landwerlin --- src/compiler/nir/nir_deref.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/src/compiler/nir/nir_deref.c b/src/compiler/nir/nir_deref.c index 2f5fda643ca..13aa10c7532 100644 --- a/src/compiler/nir/nir_deref.c +++ b/src/compiler/nir/nir_deref.c @@ -670,6 +670,27 @@ opt_deref_ptr_as_array(nir_builder *b, nir_deref_instr *deref) assert(deref->deref_type == nir_deref_type_ptr_as_array); nir_deref_instr *parent = nir_deref_instr_parent(deref); + + if (nir_src_is_const(deref->arr.index) && + nir_src_as_int(deref->arr.index) == 0) { + /* If it's a ptr_as_array deref with an index of 0, it does nothing + * and we can just replace its uses with its parent. + * + * The source of a ptr_as_array deref always has a deref_type of + * nir_deref_type_array or nir_deref_type_cast. If it's a cast, it + * may be trivial and we may be able to get rid of that too. Any + * trivial cast of trivial cast cases should be handled already by + * opt_deref_cast() above. + */ + if (parent->deref_type == nir_deref_type_cast && + is_trivial_deref_cast(parent)) + parent = nir_deref_instr_parent(parent); + nir_ssa_def_rewrite_uses(&deref->dest.ssa, + nir_src_for_ssa(&parent->dest.ssa)); + nir_instr_remove(&deref->instr); + return true; + } + if (parent->deref_type != nir_deref_type_array && parent->deref_type != nir_deref_type_ptr_as_array) return false; -- 2.30.2