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[dslx] Convert if-else-if chains into PrioritySelects #3163

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55 changes: 37 additions & 18 deletions xls/codegen/testdata/assertions_comb_multiple_ifdef_guards.svtxt
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Expand Up @@ -2,26 +2,45 @@ module assertions_top(
input wire [31:0] y,
output wire [31:0] out
);
wire [30:0] add_197;
wire ult_204;
wire [31:0] literal_202;
wire [30:0] add_211;
wire ult_208;
wire nand_213;
wire nand_214;
assign add_197 = y[31:1] + 31'h7fff_fffb;
assign ult_204 = y < 32'h0000_0014;
assign literal_202 = 32'h0000_0004;
assign add_211 = y[31:1] + 31'h0000_000f;
assign ult_208 = y < 32'h0000_000a;
assign nand_213 = ~(y > 32'h0000_0009 & ult_204 & {add_197, y[0]} > literal_202);
assign nand_214 = ~(ult_208 & y > literal_202);
assign out = ult_208 ? {add_211, y[0]} : y & {32{ult_204}};
function automatic [30:0] priority_sel_31b_2way (input reg [1:0] sel, input reg [30:0] case0, input reg [30:0] case1, input reg [30:0] default_value);
begin
unique casez (sel)
2'b?1: begin
priority_sel_31b_2way = case0;
end
2'b10: begin
priority_sel_31b_2way = case1;
end
2'b00: begin
priority_sel_31b_2way = default_value;
end
default: begin
// Propagate X
priority_sel_31b_2way = 'X;
end
endcase
end
endfunction
wire [30:0] add_189;
wire ult_196;
wire ult_197;
wire [31:0] literal_193;
wire [30:0] add_203;
wire nand_206;
wire nand_207;
assign add_189 = y[31:1] + 31'h7fff_fffb;
assign ult_196 = y < 32'h0000_0014;
assign ult_197 = y < 32'h0000_000a;
assign literal_193 = 32'h0000_0004;
assign add_203 = y[31:1] + 31'h0000_000f;
assign nand_206 = ~(ult_197 & y > literal_193);
assign nand_207 = ~(ult_196 & y > 32'h0000_0009 & {add_189, y[0]} > literal_193);
assign out = {priority_sel_31b_2way({ult_196, ult_197}, add_203, y[31:1], 31'h0000_0000), ult_196 & y[0]};
`ifdef ASSERT_ON
`ifndef SYNTHESIS
y_ge_than_21: assert final ($isunknown(ult_204) || ult_204) else $fatal(0, "Assertion failure via fail! @ xls/examples/assertions/assertions.x:32:14-32:37");
__assertions__main_0___itok__assertions__main___itok__assertions__main_0___itok__assertions__func_0__32_x_less_than_5: assert final ($isunknown(nand_213) || nand_213) else $fatal(0, "Assertion failure via assert! @ xls/examples/assertions/assertions.x:21:12-21:40");
__assertions__main_0___itok__assertions__main___itok__assertions__main_1___itok__assertions__func_0__32_x_less_than_5: assert final ($isunknown(nand_214) || nand_214) else $fatal(0, "Assertion failure via assert! @ xls/examples/assertions/assertions.x:21:12-21:40");
y_ge_than_21: assert final ($isunknown(ult_196) || ult_196) else $fatal(0, "Assertion failure via fail! @ xls/examples/assertions/assertions.x:32:14-32:37");
__assertions__main_0___itok__assertions__main___itok__assertions__main_0___itok__assertions__func_0__32_x_less_than_5: assert final ($isunknown(nand_206) || nand_206) else $fatal(0, "Assertion failure via assert! @ xls/examples/assertions/assertions.x:21:12-21:40");
__assertions__main_0___itok__assertions__main___itok__assertions__main_1___itok__assertions__func_0__32_x_less_than_5: assert final ($isunknown(nand_207) || nand_207) else $fatal(0, "Assertion failure via assert! @ xls/examples/assertions/assertions.x:21:12-21:40");
`endif // SYNTHESIS
`endif // ASSERT_ON
endmodule
55 changes: 37 additions & 18 deletions xls/codegen/testdata/assertions_comb_no_ifdef_guards.svtxt
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Original file line number Diff line number Diff line change
Expand Up @@ -2,22 +2,41 @@ module assertions_top(
input wire [31:0] y,
output wire [31:0] out
);
wire [30:0] add_197;
wire ult_204;
wire [31:0] literal_202;
wire [30:0] add_211;
wire ult_208;
wire nand_213;
wire nand_214;
assign add_197 = y[31:1] + 31'h7fff_fffb;
assign ult_204 = y < 32'h0000_0014;
assign literal_202 = 32'h0000_0004;
assign add_211 = y[31:1] + 31'h0000_000f;
assign ult_208 = y < 32'h0000_000a;
assign nand_213 = ~(y > 32'h0000_0009 & ult_204 & {add_197, y[0]} > literal_202);
assign nand_214 = ~(ult_208 & y > literal_202);
assign out = ult_208 ? {add_211, y[0]} : y & {32{ult_204}};
y_ge_than_21: assert final ($isunknown(ult_204) || ult_204) else $fatal(0, "Assertion failure via fail! @ xls/examples/assertions/assertions.x:32:14-32:37");
__assertions__main_0___itok__assertions__main___itok__assertions__main_0___itok__assertions__func_0__32_x_less_than_5: assert final ($isunknown(nand_213) || nand_213) else $fatal(0, "Assertion failure via assert! @ xls/examples/assertions/assertions.x:21:12-21:40");
__assertions__main_0___itok__assertions__main___itok__assertions__main_1___itok__assertions__func_0__32_x_less_than_5: assert final ($isunknown(nand_214) || nand_214) else $fatal(0, "Assertion failure via assert! @ xls/examples/assertions/assertions.x:21:12-21:40");
function automatic [30:0] priority_sel_31b_2way (input reg [1:0] sel, input reg [30:0] case0, input reg [30:0] case1, input reg [30:0] default_value);
begin
unique casez (sel)
2'b?1: begin
priority_sel_31b_2way = case0;
end
2'b10: begin
priority_sel_31b_2way = case1;
end
2'b00: begin
priority_sel_31b_2way = default_value;
end
default: begin
// Propagate X
priority_sel_31b_2way = 'X;
end
endcase
end
endfunction
wire [30:0] add_189;
wire ult_196;
wire ult_197;
wire [31:0] literal_193;
wire [30:0] add_203;
wire nand_206;
wire nand_207;
assign add_189 = y[31:1] + 31'h7fff_fffb;
assign ult_196 = y < 32'h0000_0014;
assign ult_197 = y < 32'h0000_000a;
assign literal_193 = 32'h0000_0004;
assign add_203 = y[31:1] + 31'h0000_000f;
assign nand_206 = ~(ult_197 & y > literal_193);
assign nand_207 = ~(ult_196 & y > 32'h0000_0009 & {add_189, y[0]} > literal_193);
assign out = {priority_sel_31b_2way({ult_196, ult_197}, add_203, y[31:1], 31'h0000_0000), ult_196 & y[0]};
y_ge_than_21: assert final ($isunknown(ult_196) || ult_196) else $fatal(0, "Assertion failure via fail! @ xls/examples/assertions/assertions.x:32:14-32:37");
__assertions__main_0___itok__assertions__main___itok__assertions__main_0___itok__assertions__func_0__32_x_less_than_5: assert final ($isunknown(nand_206) || nand_206) else $fatal(0, "Assertion failure via assert! @ xls/examples/assertions/assertions.x:21:12-21:40");
__assertions__main_0___itok__assertions__main___itok__assertions__main_1___itok__assertions__func_0__32_x_less_than_5: assert final ($isunknown(nand_207) || nand_207) else $fatal(0, "Assertion failure via assert! @ xls/examples/assertions/assertions.x:21:12-21:40");
endmodule
1 change: 1 addition & 0 deletions xls/dslx/ir_convert/BUILD
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Expand Up @@ -353,6 +353,7 @@ cc_library(
"//xls/ir:value_utils",
"//xls/ir:verifier",
"//xls/ir:xls_ir_interface_cc_proto",
"@com_google_absl//absl/algorithm:container",
"@com_google_absl//absl/container:btree",
"@com_google_absl//absl/container:flat_hash_map",
"@com_google_absl//absl/container:flat_hash_set",
Expand Down
73 changes: 73 additions & 0 deletions xls/dslx/ir_convert/function_converter.cc
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Expand Up @@ -26,6 +26,7 @@
#include <variant>
#include <vector>

#include "absl/algorithm/container.h"
#include "absl/container/btree_set.h"
#include "absl/container/flat_hash_map.h"
#include "absl/log/check.h"
Expand Down Expand Up @@ -4129,7 +4130,79 @@ absl::Status FunctionConverter::HandleStatement(const Statement* node) {
return absl::OkStatus();
}

absl::Status FunctionConverter::HandleConditionalChain(
const Conditional* node) {
XLS_RET_CHECK(std::holds_alternative<Conditional*>(node->alternate()));

std::vector<BValue> tests;
std::vector<BValue> results;
const Conditional* cond = node;
std::optional<BValue> higher_priority_true = std::nullopt;
while (true) {
XLS_RETURN_IF_ERROR(Visit(cond->test()));
XLS_ASSIGN_OR_RETURN(BValue test, Use(cond->test()));
{
ScopedControlPredicate scp(
this, [&](const PredicateFun& orig_control_predicate) {
BValue activated = orig_control_predicate();
CHECK_EQ(activated.GetType()->AsBitsOrDie()->bit_count(), 1);
if (higher_priority_true.has_value()) {
return function_builder_->And(
{activated, test,
function_builder_->Not(*higher_priority_true)});
} else {
return function_builder_->And(activated, test);
}
});
XLS_RETURN_IF_ERROR(Visit(cond->consequent()));
}
XLS_ASSIGN_OR_RETURN(BValue result, Use(cond->consequent()));
tests.push_back(test);
results.push_back(result);

if (higher_priority_true.has_value()) {
higher_priority_true = function_builder_->Or(*higher_priority_true, test);
} else {
higher_priority_true = test;
}

if (!std::holds_alternative<Conditional*>(cond->alternate())) {
break;
}
cond = std::get<Conditional*>(cond->alternate());
};

// We finished the final conditional in the chain, so what's left in the
// alternate is what we return if none of the tests are true.
{
ScopedControlPredicate scp(
this, [&](const PredicateFun& orig_control_predicate) {
BValue activated = orig_control_predicate();
CHECK_EQ(activated.GetType()->AsBitsOrDie()->bit_count(), 1);
return function_builder_->And(
activated, function_builder_->Not(*higher_priority_true));
});
XLS_RETURN_IF_ERROR(Visit(ToExprNode(cond->alternate())));
}
XLS_ASSIGN_OR_RETURN(BValue default_result,
Use(ToExprNode(cond->alternate())));

// Reverse the tests, since priority-select goes in LSB-first order.
absl::c_reverse(tests);
Def(node, [&](const SourceInfo& loc) -> BValue {
BValue selector = function_builder_->Concat(tests, loc);
return function_builder_->PrioritySelect(
selector, /*cases=*/results, /*default_value=*/default_result, loc);
});
return absl::OkStatus();
}

absl::Status FunctionConverter::HandleConditional(const Conditional* node) {
if (std::holds_alternative<Conditional*>(node->alternate())) {
// This is a chained conditional.
return HandleConditionalChain(node);
}

XLS_RETURN_IF_ERROR(Visit(node->test()));
XLS_ASSIGN_OR_RETURN(BValue arg0, Use(node->test()));

Expand Down
3 changes: 3 additions & 0 deletions xls/dslx/ir_convert/function_converter.h
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Expand Up @@ -426,6 +426,9 @@ class FunctionConverter {
absl::Status HandleConditional(const Conditional* node);
absl::Status HandleTupleIndex(const TupleIndex* node);

// Handles a conditional chain (where the alternate is another conditional).
absl::Status HandleConditionalChain(const Conditional* node);

// Handles invocation of a user-defined function (UDF).
absl::Status HandleUdfInvocation(const Invocation* node, xls::Function* f,
std::vector<BValue> args);
Expand Down