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Assign from rvalue via temporary register in nowrshmsk CASE

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Avoid repeating complex rvalue expressions for each condition.
This commit is contained in:
Dag Lem 2023-12-08 20:47:43 +01:00
parent dbec704b49
commit 1a2b4759e8
3 changed files with 35 additions and 3 deletions
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16
frontends/ast/simplify.cc
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@ -2932,8 +2932,18 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
long long max_offset = (1ll << (max_width - case_sign_hint)) - 1;
long long min_offset = case_sign_hint ? -(1ll << (max_width - 1)) : 0;
// A temporary register holds the result of the (possibly complex) rvalue expression,
// avoiding repetition in each AST_COND below.
int rvalue_width;
bool rvalue_sign;
children[1]->detectSignWidth(rvalue_width, rvalue_sign);
AstNode *rvalue = mktemp_logic("$bitselwrite$rvalue$", current_ast_mod, true, rvalue_width - 1, 0, rvalue_sign);
AstNode *caseNode = new AstNode(AST_CASE, shift_expr);
newNode = new AstNode(AST_BLOCK,
new AstNode(AST_ASSIGN_EQ, rvalue, children[1]->clone()),
caseNode);
did_something = true;
newNode = new AstNode(AST_CASE, shift_expr);
for (int i = 1 - result_width; i < wire_width; i++) {
// Out of range indexes are handled in genrtlil.cc
int start_bit = wire_offset + i;
@ -2951,8 +2961,8 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
lvalue->set_attribute(ID::wiretype, member_node->clone());
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);
cond->children.push_back(new AstNode(AST_BLOCK, new AstNode(type, lvalue, rvalue->clone())));
caseNode->children.push_back(cond);
}
} else {
// mask and shift operations