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Add UNUSEDLOOP when unused loop is removed (#4926)

This commit is contained in:
Bartłomiej Chmiel 2024-03-07 14:33:49 +01:00 committed by GitHub
parent 6db149c588
commit 32f288084a
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GPG Key ID: B5690EEEBB952194
11 changed files with 396 additions and 21 deletions
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3
src/V3Const.cpp
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@ -3300,6 +3300,9 @@ class ConstVisitor final : public VNVisitor {
if (nodep->precondsp()) {
nodep->replaceWith(nodep->precondsp());
} else {
nodep->v3warn(UNUSEDLOOP,
"Loop condition is always false; body will never execute");
nodep->fileline()->modifyWarnOff(V3ErrorCode::UNUSEDLOOP, true);
nodep->unlinkFrBack();
}
VL_DO_DANGLING(pushDeletep(nodep), nodep);

13
src/V3Error.h
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@ -152,6 +152,7 @@ public:
UNPACKED, // Unsupported unpacked
UNSIGNED, // Comparison is constant due to unsigned arithmetic
UNUSEDGENVAR, // No receivers for genvar
UNUSEDLOOP, // Loop is unused
UNUSEDPARAM, // No receivers for parameters
UNUSEDSIGNAL, // No receivers for signals
USERERROR, // Elaboration time $error
@ -210,7 +211,7 @@ public:
"STATICVAR", "STMTDLY", "SYMRSVDWORD", "SYNCASYNCNET",
"TICKCOUNT", "TIMESCALEMOD",
"UNDRIVEN", "UNOPT", "UNOPTFLAT", "UNOPTTHREADS",
"UNPACKED", "UNSIGNED", "UNUSEDGENVAR", "UNUSEDPARAM", "UNUSEDSIGNAL",
"UNPACKED", "UNSIGNED", "UNUSEDGENVAR", "UNUSEDLOOP" ,"UNUSEDPARAM", "UNUSEDSIGNAL",
"USERERROR", "USERFATAL", "USERINFO", "USERWARN",
"VARHIDDEN", "WAITCONST", "WIDTH", "WIDTHCONCAT", "WIDTHEXPAND", "WIDTHTRUNC", "WIDTHXZEXPAND", "ZERODLY", "ZEROREPL",
" MAX"
@ -254,12 +255,13 @@ public:
|| m_e == BLKSEQ || m_e == DEFPARAM || m_e == DECLFILENAME || m_e == EOFNEWLINE
|| m_e == GENUNNAMED || m_e == IMPORTSTAR || m_e == INCABSPATH
|| m_e == PINCONNECTEMPTY || m_e == PINNOCONNECT || m_e == SYNCASYNCNET
|| m_e == UNDRIVEN || m_e == UNUSEDGENVAR || m_e == UNUSEDPARAM
|| m_e == UNUSEDSIGNAL || m_e == VARHIDDEN);
|| m_e == UNDRIVEN || m_e == UNUSEDGENVAR || m_e == UNUSEDLOOP
|| m_e == UNUSEDPARAM || m_e == UNUSEDSIGNAL || m_e == VARHIDDEN);
}
// Warnings that are unused only
bool unusedError() const VL_MT_SAFE {
return (m_e == UNUSEDGENVAR || m_e == UNUSEDPARAM || m_e == UNUSEDSIGNAL);
return (m_e == UNUSEDGENVAR || m_e == UNUSEDLOOP || m_e == UNUSEDPARAM
|| m_e == UNUSEDSIGNAL);
}
V3ErrorCode renamedTo() const {
@ -275,7 +277,8 @@ public:
return (m_e == WIDTHEXPAND || m_e == WIDTHTRUNC || m_e == WIDTHXZEXPAND);
}
if (other == V3ErrorCode::I_UNUSED) {
return (m_e == UNUSEDGENVAR || m_e == UNUSEDPARAM || m_e == UNUSEDSIGNAL);
return (m_e == UNUSEDGENVAR || m_e == UNUSEDLOOP || m_e == UNUSEDPARAM
|| m_e == UNUSEDSIGNAL);
}
return false;
}

2
src/V3FileLine.cpp
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@ -365,6 +365,7 @@ bool FileLine::warnOff(const string& msg, bool flag) {
// Backward compatibility with msg="UNUSED"
if (V3ErrorCode::unusedMsg(cmsg)) {
warnOff(V3ErrorCode::UNUSEDGENVAR, flag);
warnOff(V3ErrorCode::UNUSEDLOOP, flag);
warnOff(V3ErrorCode::UNUSEDPARAM, flag);
warnOff(V3ErrorCode::UNUSEDSIGNAL, flag);
return true;
@ -394,6 +395,7 @@ void FileLine::warnStyleOff(bool flag) {
void FileLine::warnUnusedOff(bool flag) {
warnOff(V3ErrorCode::UNUSEDGENVAR, flag);
warnOff(V3ErrorCode::UNUSEDLOOP, flag);
warnOff(V3ErrorCode::UNUSEDPARAM, flag);
warnOff(V3ErrorCode::UNUSEDSIGNAL, flag);
}

14
src/V3Gate.cpp
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@ -1312,6 +1312,18 @@ class GateUnused final {
}
}
static void warnUnused(const AstNode* const nodep) {
if (nodep->fileline()->warnIsOff(V3ErrorCode::UNUSEDLOOP)) return;
if (const AstNodeProcedure* const procedurep = VN_CAST(nodep, NodeProcedure)) {
if (procedurep->stmtsp())
procedurep->stmtsp()->foreach([](const AstWhile* const whilep) { //
whilep->v3warn(UNUSEDLOOP, "Loop is not used and will be optimized out");
whilep->fileline()->modifyWarnOff(V3ErrorCode::UNUSEDLOOP, true);
});
}
}
// Remove unused logic
void remove() {
for (V3GraphVertex *vtxp = m_graph.verticesBeginp(), *nextp; vtxp; vtxp = nextp) {
@ -1319,6 +1331,8 @@ class GateUnused final {
if (GateLogicVertex* const lVtxp = vtxp->cast<GateLogicVertex>()) {
if (!lVtxp->consumed() && lVtxp->activep()) { // activep is nullptr under cfunc
AstNode* const nodep = lVtxp->nodep();
warnUnused(nodep);
UINFO(8, " Remove unconsumed " << nodep << endl);
nodep->unlinkFrBack();
VL_DO_DANGLING(nodep->deleteTree(), nodep);

5
src/V3LinkJump.cpp
View File

@ -34,6 +34,7 @@
#include "V3LinkJump.h"
#include "V3AstUserAllocator.h"
#include "V3Error.h"
#include <vector>
@ -228,6 +229,8 @@ class LinkJumpVisitor final : public VNVisitor {
void visit(AstWhile* nodep) override {
// Don't need to track AstRepeat/AstFor as they have already been converted
if (!m_unrollFull.isDefault()) nodep->unrollFull(m_unrollFull);
if (m_modp->hasParameterList() || m_modp->hasGParam())
nodep->fileline()->modifyWarnOff(V3ErrorCode::UNUSEDLOOP, true);
m_unrollFull = VOptionBool::OPT_DEFAULT_FALSE;
VL_RESTORER(m_loopp);
VL_RESTORER(m_loopInc);
@ -254,6 +257,8 @@ class LinkJumpVisitor final : public VNVisitor {
AstWhile* const whilep = new AstWhile{nodep->fileline(), condp, bodyp};
if (!m_unrollFull.isDefault()) whilep->unrollFull(m_unrollFull);
m_unrollFull = VOptionBool::OPT_DEFAULT_FALSE;
// No unused warning for converted AstDoWhile, as body always executes once
nodep->fileline()->modifyWarnOff(V3ErrorCode::UNUSEDLOOP, true);
nodep->replaceWith(whilep);
VL_DO_DANGLING(nodep->deleteTree(), nodep);
if (bodyp) {

2
src/V3Options.cpp
View File

@ -1577,6 +1577,7 @@ void V3Options::parseOptsList(FileLine* fl, const string& optdir, int argc,
});
DECL_OPTION("-Werror-UNUSED", CbCall, []() {
V3Error::pretendError(V3ErrorCode::UNUSEDGENVAR, true);
V3Error::pretendError(V3ErrorCode::UNUSEDLOOP, true);
V3Error::pretendError(V3ErrorCode::UNUSEDPARAM, true);
V3Error::pretendError(V3ErrorCode::UNUSEDSIGNAL, true);
});
@ -1630,6 +1631,7 @@ void V3Options::parseOptsList(FileLine* fl, const string& optdir, int argc,
DECL_OPTION("-Wwarn-UNUSED", CbCall, []() {
FileLine::globalWarnUnusedOff(false);
V3Error::pretendError(V3ErrorCode::UNUSEDGENVAR, false);
V3Error::pretendError(V3ErrorCode::UNUSEDLOOP, false);
V3Error::pretendError(V3ErrorCode::UNUSEDSIGNAL, false);
V3Error::pretendError(V3ErrorCode::UNUSEDPARAM, false);
});

32
test_regress/t/t_lint_misindent_bad.out
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@ -1,27 +1,27 @@
%Warning-MISINDENT: t/t_lint_misindent_bad.v:14:9: Misleading indentation
14 | $display("bad1");
%Warning-MISINDENT: t/t_lint_misindent_bad.v:16:9: Misleading indentation
16 | $display("bad1");
| ^~~~~~~~
t/t_lint_misindent_bad.v:12:7: ... Expected indentation matching this earlier statement's line:
12 | if (0)
t/t_lint_misindent_bad.v:14:7: ... Expected indentation matching this earlier statement's line:
14 | if (0)
| ^~
... For warning description see https://verilator.org/warn/MISINDENT?v=latest
... Use "/* verilator lint_off MISINDENT */" and lint_on around source to disable this message.
%Warning-MISINDENT: t/t_lint_misindent_bad.v:20:9: Misleading indentation
20 | $display("bad2");
%Warning-MISINDENT: t/t_lint_misindent_bad.v:22:9: Misleading indentation
22 | $display("bad2");
| ^~~~~~~~
t/t_lint_misindent_bad.v:16:7: ... Expected indentation matching this earlier statement's line:
16 | if (0)
t/t_lint_misindent_bad.v:18:7: ... Expected indentation matching this earlier statement's line:
18 | if (0)
| ^~
%Warning-MISINDENT: t/t_lint_misindent_bad.v:24:9: Misleading indentation
24 | $display("bad3");
%Warning-MISINDENT: t/t_lint_misindent_bad.v:26:9: Misleading indentation
26 | $display("bad3");
| ^~~~~~~~
t/t_lint_misindent_bad.v:22:7: ... Expected indentation matching this earlier statement's line:
22 | for (;0;)
t/t_lint_misindent_bad.v:24:7: ... Expected indentation matching this earlier statement's line:
24 | for (;0;)
| ^~~
%Warning-MISINDENT: t/t_lint_misindent_bad.v:28:9: Misleading indentation
28 | $display("bad4");
%Warning-MISINDENT: t/t_lint_misindent_bad.v:30:9: Misleading indentation
30 | $display("bad4");
| ^~~~~~~~
t/t_lint_misindent_bad.v:26:7: ... Expected indentation matching this earlier statement's line:
26 | while (0)
t/t_lint_misindent_bad.v:28:7: ... Expected indentation matching this earlier statement's line:
28 | while (0)
| ^~~~~
%Error: Exiting due to

2
test_regress/t/t_lint_misindent_bad.v
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@ -6,6 +6,8 @@
// Do not reindent - spaces are critical to this test
// verilator lint_off UNUSEDLOOP
module t (/*AUTOARG*/);
initial begin

38
test_regress/t/t_lint_removed_unused_loop_bad.out Normal file
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@ -0,0 +1,38 @@
%Warning-UNUSEDLOOP: t/t_lint_removed_unused_loop_bad.v:172:7: Loop condition is always false; body will never execute
: ... note: In instance 't.with_always'
172 | while(0);
| ^~~~~
... For warning description see https://verilator.org/warn/UNUSEDLOOP?v=latest
... Use "/* verilator lint_off UNUSEDLOOP */" and lint_on around source to disable this message.
%Warning-UNUSEDLOOP: t/t_lint_removed_unused_loop_bad.v:155:7: Loop condition is always false; body will never execute
: ... note: In instance 't.non_parametrized_initial'
155 | while(0);
| ^~~~~
%Warning-UNUSEDLOOP: t/t_lint_removed_unused_loop_bad.v:114:7: Loop condition is always false; body will never execute
114 | while(always_zero < 0) begin
| ^~~~~
%Warning-UNUSEDLOOP: t/t_lint_removed_unused_loop_bad.v:156:7: Loop condition is always false; body will never execute
156 | while(always_false);
| ^~~~~
%Warning-UNUSEDLOOP: t/t_lint_removed_unused_loop_bad.v:157:7: Loop condition is always false; body will never execute
157 | while(always_zero < 0);
| ^~~~~
%Warning-UNUSEDLOOP: t/t_lint_removed_unused_loop_bad.v:174:7: Loop condition is always false; body will never execute
174 | while(always_false) begin
| ^~~~~
%Warning-UNUSEDLOOP: t/t_lint_removed_unused_loop_bad.v:184:7: Loop condition is always false; body will never execute
184 | while(always_zero) begin
| ^~~~~
%Warning-UNUSEDLOOP: t/t_lint_removed_unused_loop_bad.v:188:7: Loop condition is always false; body will never execute
188 | for (int i = 0; always_zero; i++)
| ^~~
%Warning-UNUSEDLOOP: t/t_lint_removed_unused_loop_bad.v:193:7: Loop condition is always false; body will never execute
193 | for (int i = 0; i < always_zero; i++)
| ^~~
%Warning-UNUSEDLOOP: t/t_lint_removed_unused_loop_bad.v:136:7: Loop is not used and will be optimized out
136 | while(param_unused_while < always_zero) begin
| ^~~~~
%Warning-UNUSEDLOOP: t/t_lint_removed_unused_loop_bad.v:283:7: Loop is not used and will be optimized out
283 | while (m_2_ticked);
| ^~~~~
%Error: Exiting due to

20
test_regress/t/t_lint_removed_unused_loop_bad.pl Executable file
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@ -0,0 +1,20 @@
#!/usr/bin/env perl
if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
# DESCRIPTION: Verilator: Verilog Test driver/expect definition
#
# Copyright 2024 by Wilson Snyder. This program is free software; you
# can redistribute it and/or modify it under the terms of either the GNU
# Lesser General Public License Version 3 or the Perl Artistic License
# Version 2.0.
# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
scenarios(linter => 1);
lint(
fails => 1,
expect_filename => $Self->{golden_filename},
verilator_flags2 => ["--top-module t", "-Wall"]
);
ok(1);
1;

286
test_regress/t/t_lint_removed_unused_loop_bad.v Normal file
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@ -0,0 +1,286 @@
// DESCRIPTION: Verilator: Verilog Test module
//
// This file ONLY is placed under the Creative Commons Public Domain, for
// any use, without warranty, 2024 by Antmicro.
// SPDX-License-Identifier: CC0-1.0
// verilator lint_off BLKSEQ
// verilator lint_off DECLFILENAME
module t(/*AUTOARG*/
// Inputs
clk, reset_l
);
input clk;
input reset_l;
parametrized_initial#(.REPETITIONS(0)) parametrized_initial0();
parametrized_initial#(.REPETITIONS(1)) parametrized_initial1();
parametrized_initial#(.REPETITIONS(2)) parametrized_initial2();
non_parametrized_initial non_parametrized_initial();
with_always with_always(.clk(clk));
const_condition const_condition();
loop_with_param loop_with_param();
if_with_param if_with_param();
clock_init_race clock_init_race(.clk(clk), .reset_l(reset_l));
endmodule
// module unused - no warning for any of statements inside
module unused(input clk);
reg unused_variable_while = 0;
reg unused_variable_do_while = 0;
reg unused_variable_for = 0;
const logic always_false = 0;
always @(posedge clk) begin
while(unused_variable_while) begin
unused_variable_while <= 1;
end
do begin
unused_variable_do_while <= 1;
end while (unused_variable_do_while);
for (int i = 0; i < 5; i++)
begin
unused_variable_for <= 1;
end
while(always_false) begin
$write("This will not be printed\n");
end
do begin
$write("This will not be printed\n");
end while (always_false);
for (int i = 0; always_false; i++)
begin
$write("This will not be printed\n");
end
end
endmodule
// no warning for loops under parametrized module
module parametrized_initial #(parameter REPETITIONS = 0);
int prints_while = 0;
int prints_do_while = 0;
// loops with evaluation depending on REPETITIONS
initial begin
while(prints_while < REPETITIONS) begin
prints_while = prints_while + 1;
$write("Writing to console to avoid loop being optimized out\n");
end
while(REPETITIONS < 0) begin
$write("Writing to console to avoid loop being optimized out\n");
end
for (int i = 0; i < REPETITIONS; i++) begin
$write("Writing to console to avoid loop being optimized out\n");
end
do begin
prints_do_while = prints_do_while + 1;
$write("Writing to console to avoid loop being optimized out\n");
end while (prints_do_while < REPETITIONS);
end
// loop not changing variable used for output
int param_unused_while = 0;
initial begin
while(param_unused_while < REPETITIONS) begin
param_unused_while = param_unused_while + 1;
end
end
const logic always_false = 0;
// loops with empty bodies
initial begin
while(0);
while(always_false);
while(REPETITIONS < 0);
end
endmodule
module non_parametrized_initial;
int prints_do_while = 0;
const int always_zero = 0;
// loops with evaluation depending on always_zero
initial begin
while(always_zero < 0) begin
$write("This will not be printed\n");
end
// unrolled - no warning
for (int i = 0; i < always_zero; i++) begin
$write("This will not be printed\n");
end
// inlined - no warning
do begin
prints_do_while = prints_do_while + 1;
$write("Writing to console to avoid loop being optimized out\n");
end while (prints_do_while < always_zero);
end
// loop not changing variable used for output
int param_unused_while = 0;
int param_unused_do_while = 0;
int param_unused_for = 0;
initial begin
// warning
while(param_unused_while < always_zero) begin
param_unused_while++;
end
// unrolled - no warning
for (int i = 0; i < 5; i++)
begin
param_unused_for = 1;
end
// inlined - no warning
do begin
param_unused_do_while = 1;
end while (param_unused_do_while > 0);
end
const logic always_false = 0;
// loops with empty bodies - warning
initial begin
while(0);
while(always_false);
while(always_zero < 0);
// inlined - no warning
do begin
end while(0);
// unrolled - no warning
for (int i = 0; i < 1; i++);
end
endmodule
// warning for all unused loops under always
module with_always(input clk);
const logic always_false = 0;
always @(posedge clk) begin
while(0);
while(always_false) begin
$write("Test");
end
end
endmodule
module const_condition;
const logic always_zero = 0;
// loops with const false condition - warning
initial begin
while(always_zero) begin
$write("This will not be printed\n");
end
for (int i = 0; always_zero; i++)
begin
$write("This will not be printed\n");
end
for (int i = 0; i < always_zero; i++)
begin
$write("This will not be printed\n");
end
// inlined - no warning
do begin
$write("This will be printed\n");
end while (always_zero);
end
endmodule
// loop with param - no warning
module loop_with_param;
parameter ZERO_PARAM = 0;
int prints = 2;
initial begin
for (int i = 0; ZERO_PARAM; i++) begin
$write("This will not be printed\n");
end
while (ZERO_PARAM != ZERO_PARAM) begin
$write("This will not be printed\n");
end
while(prints > ZERO_PARAM) begin
prints--;
end
end
endmodule
module if_with_param;
parameter ZERO_PARAM = 0;
parameter ONE_PARAM = 1;
initial begin
if (ZERO_PARAM) begin
// loop under false parametrized if - no warning
int prints = 0;
while(prints < 5) begin
prints++;
end
$write("Prints %d\n", prints);
end else if (!ONE_PARAM) begin
// loop under false parametrized if - no warning
int prints = 0;
while(prints < 5) begin
prints++;
end
$write("Prints %d\n", prints);
end else begin
// loop under true parametrized if - no warning
int prints = 0;
while(prints < 5) begin
prints++;
end
$write("Prints %d\n", prints);
end
end
endmodule
module clock_init_race(input clk, input reset_l);
logic m_2_clock;
logic m_3_clock;
logic m_2_reset = reset_l;
logic m_3_reset = reset_l;
assign m_2_clock = clk;
assign m_3_clock = clk;
int m_3_counter = 0;
initial begin
$write("*-* START TEST *-*\n");
end
always @(posedge clk) begin
if (m_3_counter == 25) begin
$write("*-* All Finished *-*\n");
$finish();
end
end
reg m_2_ticked = 1'b0;
always @(posedge m_2_clock) if (!m_2_reset) begin
m_2_ticked = 1'b1;
end
always @(negedge m_2_clock) m_2_ticked = 1'b0;
always @(posedge m_3_clock) if (!m_3_reset) begin
$write("*-* m_3_clocked *-*\n");
// loop empty - unused loop warning
while (m_2_ticked);
m_3_counter += 1;
end
endmodule