From: Ian Romanick Date: Mon, 18 Jul 2011 19:18:19 +0000 (-0700) Subject: glsl: Rework lowering of non-constant array indexing X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=1731ac308631138ca98d34e8b7070c6e3f981939;p=mesa.git glsl: Rework lowering of non-constant array indexing The previous implementation could easily get tricked if the LHS of an assignment included a non-constant index that was "inside" another dereference. For example: mat4 m[2]; m[0][i] = vec4(0.0); Due to the way it tracked whether the array was being assigned, it would think that the non-constant index was in an r-value. The new code fixes that by tracking l-values and r-values differently. The index is also replaced by cloning the IR and replacing the index variable instead of the odd way it was done before. v2: Apply some simplifications suggested by Eric Anholt. Making assignment_generator::rvalue be ir_dereference instead of ir_rvalue simplified the code a bit. Fixes i965 piglit fs-temp-array-mat[234]-index-wr and vs-varying-array-mat[234]-index-wr. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=34691 Reviewed-by: Eric Anholt --- diff --git a/src/glsl/lower_variable_index_to_cond_assign.cpp b/src/glsl/lower_variable_index_to_cond_assign.cpp index c0b69c8f0b1..107bcc67aed 100644 --- a/src/glsl/lower_variable_index_to_cond_assign.cpp +++ b/src/glsl/lower_variable_index_to_cond_assign.cpp @@ -29,6 +29,21 @@ * * Pre-DX10 GPUs often don't have a native way to do this operation, * and this works around that. + * + * The lowering process proceeds as follows. Each non-constant index + * found in an r-value is converted to a canonical form \c array[i]. Each + * element of the array is conditionally assigned to a temporary by comparing + * \c i to a constant index. This is done by cloning the canonical form and + * replacing all occurances of \c i with a constant. Each remaining occurance + * of the canonical form in the IR is replaced with a dereference of the + * temporary variable. + * + * L-values with non-constant indices are handled similarly. In this case, + * the RHS of the assignment is assigned to a temporary. The non-constant + * index is replace with the canonical form (just like for r-values). The + * temporary is conditionally assigned to each element of the canonical form + * by comparing \c i with each index. The same clone-and-replace scheme is + * used. */ #include "ir.h" @@ -43,10 +58,70 @@ is_array_or_matrix(const ir_instruction *ir) return (ir->type->is_array() || ir->type->is_matrix()); } +/** + * Replace a dereference of a variable with a specified r-value + * + * Each time a dereference of the specified value is replaced, the r-value + * tree is cloned. + */ +class deref_replacer : public ir_rvalue_visitor { +public: + deref_replacer(const ir_variable *variable_to_replace, ir_rvalue *value) + : variable_to_replace(variable_to_replace), value(value), + progress(false) + { + assert(this->variable_to_replace != NULL); + assert(this->value != NULL); + } + + virtual void handle_rvalue(ir_rvalue **rvalue) + { + ir_dereference_variable *const dv = (*rvalue)->as_dereference_variable(); + + if ((dv != NULL) && (dv->var == this->variable_to_replace)) { + this->progress = true; + *rvalue = this->value->clone(ralloc_parent(*rvalue), NULL); + } + } + + const ir_variable *variable_to_replace; + ir_rvalue *value; + bool progress; +}; + +/** + * Find a variable index dereference of an array in an rvalue tree + */ +class find_variable_index : public ir_hierarchical_visitor { +public: + find_variable_index() + : deref(NULL) + { + /* empty */ + } + + virtual ir_visitor_status visit_enter(ir_dereference_array *ir) + { + if (is_array_or_matrix(ir->array) + && (ir->array_index->as_constant() == NULL)) { + this->deref = ir; + return visit_stop; + } + + return visit_continue; + } + + /** + * First array dereference found in the tree that has a non-constant index. + */ + ir_dereference_array *deref; +}; + struct assignment_generator { ir_instruction* base_ir; - ir_rvalue* array; + ir_dereference *rvalue; + ir_variable *old_index; bool is_write; unsigned int write_mask; ir_variable* var; @@ -61,18 +136,23 @@ struct assignment_generator * underlying variable. */ void *mem_ctx = ralloc_parent(base_ir); - ir_dereference *element = - new(mem_ctx) ir_dereference_array(this->array->clone(mem_ctx, NULL), - new(mem_ctx) ir_constant(i)); - ir_rvalue *variable = new(mem_ctx) ir_dereference_variable(this->var); - ir_assignment *assignment; - if (is_write) { - assignment = new(mem_ctx) ir_assignment(element, variable, condition, - write_mask); - } else { - assignment = new(mem_ctx) ir_assignment(variable, element, condition); - } + /* Clone the old r-value in its entirety. Then replace any occurances of + * the old variable index with the new constant index. + */ + ir_dereference *element = this->rvalue->clone(mem_ctx, NULL); + ir_constant *const index = new(mem_ctx) ir_constant(i); + deref_replacer r(this->old_index, index); + element->accept(&r); + assert(r.progress); + + /* Generate a conditional assignment to (or from) the constant indexed + * array dereference. + */ + ir_rvalue *variable = new(mem_ctx) ir_dereference_variable(this->var); + ir_assignment *const assignment = (is_write) + ? new(mem_ctx) ir_assignment(element, variable, condition, write_mask) + : new(mem_ctx) ir_assignment(variable, element, condition); list->push_tail(assignment); } @@ -274,7 +354,8 @@ public: } ir_variable *convert_dereference_array(ir_dereference_array *orig_deref, - ir_assignment* orig_assign) + ir_assignment* orig_assign, + ir_dereference *orig_base) { assert(is_array_or_matrix(orig_deref->array)); @@ -320,9 +401,12 @@ public: new(mem_ctx) ir_assignment(lhs, orig_deref->array_index, NULL); base_ir->insert_before(assign); + orig_deref->array_index = lhs->clone(mem_ctx, NULL); + assignment_generator ag; - ag.array = orig_deref->array; + ag.rvalue = orig_base; ag.base_ir = base_ir; + ag.old_index = index; ag.var = var; if (orig_assign) { ag.is_write = true; @@ -342,12 +426,16 @@ public: virtual void handle_rvalue(ir_rvalue **pir) { + if (this->in_assignee) + return; + if (!*pir) return; ir_dereference_array* orig_deref = (*pir)->as_dereference_array(); if (needs_lowering(orig_deref)) { - ir_variable* var = convert_dereference_array(orig_deref, 0); + ir_variable *var = + convert_dereference_array(orig_deref, NULL, orig_deref); assert(var); *pir = new(ralloc_parent(base_ir)) ir_dereference_variable(var); this->progress = true; @@ -359,10 +447,11 @@ public: { ir_rvalue_visitor::visit_leave(ir); - ir_dereference_array *orig_deref = ir->lhs->as_dereference_array(); + find_variable_index f; + ir->lhs->accept(&f); - if (needs_lowering(orig_deref)) { - convert_dereference_array(orig_deref, ir); + if ((f.deref != NULL) && storage_type_needs_lowering(f.deref)) { + convert_dereference_array(f.deref, ir, ir->lhs); ir->remove(); this->progress = true; } @@ -383,7 +472,15 @@ lower_variable_index_to_cond_assign(exec_list *instructions, lower_temp, lower_uniform); - visit_list_elements(&v, instructions); + /* Continue lowering until no progress is made. If there are multiple + * levels of indirection (e.g., non-constant indexing of array elements and + * matrix columns of an array of matrix), each pass will only lower one + * level of indirection. + */ + do { + v.progress = false; + visit_list_elements(&v, instructions); + } while (v.progress); return v.progress; }