Suppress unused warnings using attribute

git-svn-id: file://localhost/svn/verilator/trunk/verilator@821 77ca24e4-aefa-0310-84f0-b9a241c72d87

bin/verilator

@@ -1279,7 +1279,7 @@ appropriate width.
 $display and friends must have a constant format string as the first
 argument (as with C's printf), you cannot simply list variables standalone.
 
-=head1 ERRORS
+=head1 ERRORS AND WARNINGS
 
 Warnings may be disabled in two ways.  First, when the warning is
 printed it will include a warning code.  Simply surround the offending
@@ -1289,13 +1289,13 @@ line with a warn_off/warn_on pair:
 	if (`DEF_THAT_IS_EQ_ZERO <= 3) $stop;
 	// verilator lint_on UNSIGNED
 
-They may also be globally disabled by invoking Verilator with the
+Warnings may also be globally disabled by invoking Verilator with the
-C<-Wno-I<warning>> switch.  This should be avoided, as it removes
+C<-Wno-I<warning>> switch.  This should be avoided, as it removes all
-all checking across the designs, and prevents other users from
+checking across the designs, and prevents other users from compiling your
-compiling your code without knowing the magic set of disables needed
+code without knowing the magic set of disables needed to successfully
-to successfully compile your design.
+compile your design.
 
-Warnings:
+List of all warnings:
 
 =over 4
 
@@ -1389,11 +1389,11 @@ may be only one particular usage of a multiply instantiated block.  The
 construct should be cleaned up to improve runtime; two times better
 performance may be possible by fixing these warnings.
 
-Unlike UNOPT this occurs after netlist flattening, and indicates a more
+Unlike the UNOPT warning, this occurs after netlist flattening, and
-basic problem, as the less obvious case described under UNOPT does not
+indicates a more basic problem, as the less obvious case described under
-apply.
+UNOPT does not apply.
 
-Often this is caused by logic that isn't truly circular as viewed by
+Often UNOPTFLAT is caused by logic that isn't truly circular as viewed by
 synthesis which analyzes interconnection per-bit, but is circular to
 simulation which analyzes per-bus:
 
@@ -1401,12 +1401,25 @@ simulation which analyzes per-bus:
 
 This statement needs to be evaluated multiple times, as a change in
 "shift_in" requires "x" to be computed 3 times before it becomes stable.
-For significantly better performance, split this into 2 separate signals:
+For significantly better performance, split this into 2 separate signals,
+and then if necessary generate the original signal:
 
       wire [2:1] x_21 = x[1:0];
       wire [0:0] x_0  = shift_in;
+      wire [2:0] x = {x_21, x_0};
 
-This warning may also be due to clock enables.  To fix these, use the
+This logic needs to be evaluated only once.  These sort of changes may also
+speed up your traditional event driven simulator, as it will result in
+fewer events per cycle.
+
+The most complicated UNOPTFLAT path we've seen was due to low bits of a bus
+being generated from an always statement that consumed high bits of the
+same bus processed by another series of always blocks.  The fix is the
+same; split it into two separate signals, then create the bus from the two
+separate signals.
+
+The UNOPTFLAT warning may also be due to clock enables, identified from the
+reported path going through a clock gating cell.  To fix these, use the
 clock_enable meta comment described above.
 
 =item UNSIGNED
@@ -1464,8 +1477,8 @@ that is not yet supported in Verilator.  See the Limitations chapter.
 =item Verilated model didn't converge
 
 Verilator sometimes has to evaluate combinatorial logic multiple times,
-usually around code where a UNOPT warning was issued, but disabled.  For
+usually around code where a UNOPTFLAT warning was issued, but disabled.
-example:
+For example:
 
    always @ (a)  b=~a;
    always @ (b)  a=b

src/V3EmitCBase.h

@@ -109,7 +109,7 @@ public:
     bool optSystemPerl() { return v3Global.opt.systemPerl(); }
     static string symClassName() { return v3Global.opt.prefix()+"__Syms"; }
     static string symClassVar()  { return symClassName()+"* __restrict vlSymsp"; }
-    static string symTopAssign() { return v3Global.opt.prefix()+"* __restrict vlTOPp = vlSymsp->TOPp;"; }
+    static string symTopAssign() { return v3Global.opt.prefix()+"* __restrict vlTOPp VL_ATTR_UNUSED = vlSymsp->TOPp;"; }
     static string modClassName(AstModule* modp) {	// Return name of current module being processed
 	if (modp->isTop()) {
 	    return v3Global.opt.prefix();

test_c/Makefile_obj

@@ -20,8 +20,8 @@ include Vtop.mk
 CPPFLAGS += -DVL_DEBUG=1
 ifeq ($(VERILATOR_AUTHOR_SITE),1)	# Local... Else don't burden users
 CPPFLAGS += -DVL_THREADED=1
-CPPFLAGS += -W
+CPPFLAGS += -W -Werror -Wall
-CPPFLAGS += -Werror
+#CPPFLAGS += -Wno-unused-variable	# Instead, add VL_ATTR_UNUSED in gen'ed code
 #CPPFLAGS += -pedantic-errors
 endif
 

test_sp/Makefile_obj

@@ -21,6 +21,9 @@ CPPFLAGS += -DUTIL_PRINTF=sp_log_printf
 CPPFLAGS += -Wno-deprecated
 CPPFLAGS += $(SYSTEMC_CXX_FLAGS)
 CPPFLAGS += $(OPT)
+ifeq ($(VERILATOR_AUTHOR_SITE),1)	# Local... Else don't burden users
+CPPFLAGS += -W -Wall -Wno-char-subscripts -Wno-unused-parameter -Wno-unused-variable -Wno-uninitialized -Werror
+endif
 
 LDFLAGS += $(SYSTEMC_CXX_FLAGS)