From 4711fea6c085e773d65f10c630f8d7a698f5b323 Mon Sep 17 00:00:00 2001 From: Claire Wolf Date: Wed, 1 Apr 2020 12:43:42 +0200 Subject: [PATCH] Improved rewrite code for writing to bit slice (disabled for now) This adds the new rewrite rule. But it's still missing a check that makes sure the new rewrite rule is actually a valid substitute in the always block being processed. Therefore the new rewrite rule is just disabled for now. Signed-off-by: Claire Wolf --- frontends/ast/simplify.cc | 76 ++++++++++++++++++++++++++++++++------- 1 file changed, 64 insertions(+), 12 deletions(-) diff --git a/frontends/ast/simplify.cc b/frontends/ast/simplify.cc index cb89f58ba..e181af140 100644 --- a/frontends/ast/simplify.cc +++ b/frontends/ast/simplify.cc @@ -1721,8 +1721,10 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage, } // replace dynamic ranges in left-hand side expressions (e.g. "foo[bar] <= 1'b1;") with - // a big case block that selects the correct single-bit assignment. - if (type == AST_ASSIGN_EQ || type == AST_ASSIGN_LE) { + // either a big case block that selects the correct single-bit assignment, or mask and + // shift operations. + if (type == AST_ASSIGN_EQ || type == AST_ASSIGN_LE) + { if (children[0]->type != AST_IDENTIFIER || children[0]->children.size() == 0) goto skip_dynamic_range_lvalue_expansion; if (children[0]->children[0]->range_valid || did_something) @@ -1731,10 +1733,13 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage, goto skip_dynamic_range_lvalue_expansion; if (!children[0]->id2ast->range_valid) goto skip_dynamic_range_lvalue_expansion; + int source_width = children[0]->id2ast->range_left - children[0]->id2ast->range_right + 1; int result_width = 1; + AstNode *shift_expr = NULL; AstNode *range = children[0]->children[0]; + if (range->children.size() == 1) { shift_expr = range->children[0]->clone(); } else { @@ -1747,19 +1752,66 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage, log_file_error(filename, location.first_line, "Unsupported expression on dynamic range select on signal `%s'!\n", str.c_str()); result_width = abs(int(left_at_zero_ast->integer - right_at_zero_ast->integer)) + 1; } - did_something = true; - newNode = new AstNode(AST_CASE, shift_expr); - for (int i = 0; i < source_width; i++) { - int start_bit = children[0]->id2ast->range_right + i; - AstNode *cond = new AstNode(AST_COND, mkconst_int(start_bit, true)); + + if (1) + { + // big case block + + did_something = true; + newNode = new AstNode(AST_CASE, shift_expr); + for (int i = 0; i < source_width; i++) { + int start_bit = children[0]->id2ast->range_right + i; + AstNode *cond = new AstNode(AST_COND, mkconst_int(start_bit, true)); + AstNode *lvalue = children[0]->clone(); + lvalue->delete_children(); + int end_bit = std::min(start_bit+result_width,source_width) - 1; + lvalue->children.push_back(new AstNode(AST_RANGE, + mkconst_int(end_bit, true), mkconst_int(start_bit, true))); + cond->children.push_back(new AstNode(AST_BLOCK, new AstNode(type, lvalue, children[1]->clone()))); + newNode->children.push_back(cond); + } + } + else + { + // mask and shift operations, disabled for now + + AstNode *wire_mask = new AstNode(AST_WIRE, new AstNode(AST_RANGE, mkconst_int(source_width-1, true), mkconst_int(0, true))); + wire_mask->str = stringf("$bitselwrite$mask$%s:%d$%d", filename.c_str(), location.first_line, autoidx++); + wire_mask->attributes["\\nosync"] = AstNode::mkconst_int(1, false); + wire_mask->is_logic = true; + while (wire_mask->simplify(true, false, false, 1, -1, false, false)) { } + current_ast_mod->children.push_back(wire_mask); + + AstNode *wire_data = new AstNode(AST_WIRE, new AstNode(AST_RANGE, mkconst_int(source_width-1, true), mkconst_int(0, true))); + wire_data->str = stringf("$bitselwrite$data$%s:%d$%d", filename.c_str(), location.first_line, autoidx++); + wire_data->attributes["\\nosync"] = AstNode::mkconst_int(1, false); + wire_data->is_logic = true; + while (wire_data->simplify(true, false, false, 1, -1, false, false)) { } + current_ast_mod->children.push_back(wire_data); + + did_something = true; + newNode = new AstNode(AST_BLOCK); + AstNode *lvalue = children[0]->clone(); lvalue->delete_children(); - int end_bit = std::min(start_bit+result_width,source_width) - 1; - lvalue->children.push_back(new AstNode(AST_RANGE, - mkconst_int(end_bit, true), mkconst_int(start_bit, true))); - cond->children.push_back(new AstNode(AST_BLOCK, new AstNode(type, lvalue, children[1]->clone()))); - newNode->children.push_back(cond); + + AstNode *ref_mask = new AstNode(AST_IDENTIFIER); + ref_mask->str = wire_mask->str; + ref_mask->was_checked = true; + + AstNode *ref_data = new AstNode(AST_IDENTIFIER); + ref_data->str = wire_data->str; + ref_data->was_checked = true; + + AstNode *shamt = shift_expr; + + newNode->children.push_back(new AstNode(AST_ASSIGN_EQ, ref_mask->clone(), + new AstNode(AST_SHIFT_LEFT, mkconst_bits(std::vector(result_width, State::S1), false), shamt->clone()))); + newNode->children.push_back(new AstNode(AST_ASSIGN_EQ, ref_data->clone(), + new AstNode(AST_SHIFT_LEFT, new AstNode(AST_BIT_AND, mkconst_bits(std::vector(result_width, State::S1), false), children[1]->clone()), shamt))); + newNode->children.push_back(new AstNode(type, lvalue, new AstNode(AST_BIT_OR, new AstNode(AST_BIT_AND, lvalue->clone(), new AstNode(AST_BIT_NOT, ref_mask)), ref_data))); } + goto apply_newNode; } skip_dynamic_range_lvalue_expansion:; -- 2.30.2