Fix >>> sign extension based on expression, bug754.

src/V3Width.cpp

@@ -2232,15 +2232,15 @@ private:
     AstNodeBiop* iterate_shift_final(AstNodeBiop* nodep, AstNUser* vup)  {
 	// Nodep maybe edited
 	if (vup->c()->final()) {
+	    AstNodeDType* expDTypep = vup->c()->dtypeOverridep(nodep->dtypep());
+	    AstNodeDType* subDTypep = expDTypep;
+	    nodep->dtypeFrom(expDTypep);
 	    // ShiftRS converts to ShiftR, but not vice-versa
 	    if (nodep->castShiftRS()) {
 		if (AstNodeBiop* newp=replaceWithUOrSVersion(nodep, nodep->isSigned())) { nodep=NULL;
 		    nodep = newp;  // Process new node instead
 		}
 	    }
-	    AstNodeDType* expDTypep = vup->c()->dtypeOverridep(nodep->dtypep());
-	    AstNodeDType* subDTypep = expDTypep;
-	    nodep->dtypeFrom(expDTypep);
 	    iterateCheck(nodep,"LHS",nodep->lhsp(),CONTEXT,FINAL,subDTypep,EXTEND_EXP);
 	    if (nodep->rhsp()->width()>32) {
 		AstConst* shiftp = nodep->rhsp()->castConst();

test_regress/t/t_math_signed5.pl

@@ -0,0 +1,18 @@
+#!/usr/bin/perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2003 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.
+
+compile (
+    );
+
+execute (
+    check_finished=>1,
+    );
+
+ok(1);
+1;

test_regress/t/t_math_signed5.v

@@ -0,0 +1,111 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed into the Public Domain, for any use,
+// without warranty, 2014 by Wilson Snyder.
+
+`define checkh(gotv,expv) do if ((gotv) !== (expv)) begin $write("%%Error: %s:%0d:  got='h%x exp='h%x\n", `__FILE__,`__LINE__, (gotv), (expv)); fail='1; end while(0)
+`define checkf(gotv,expv) do if ((gotv) !== (expv)) begin $write("%%Error: %s:%0d:  got=%f exp=%f\n", `__FILE__,`__LINE__, (gotv), (expv)); fail='1; end while(0)
+
+  module t (/*AUTOARG*/);
+
+   bit fail;
+
+   reg signed [3:0] w4_s;
+   reg signed [4:0] w5_s;
+   reg [3:0] 	    w4_u;
+   reg [4:0] 	    w5_u;
+   real 	    r;
+
+   reg signed [4:0] bug754_a;
+
+   integer 	    i;
+
+   //verilator lint_off WIDTH
+   wire a = (5'b0 == (5'sb11111 >>> 3'd7));
+   wire b = (5'sb11111 == (5'sb11111 >>> 3'd7));
+   wire c = (1'b0+(5'sb11111 >>> 3'd7));
+   wire d = (1'sb0+(5'sb11111 >>> 3'd7));
+   wire e = (5'b0 == (5'sb11111 / 5'sd3));
+   wire f = (5'sb0 == (5'sb11111 / 5'sd3));
+   wire g = (5'b01010 == (5'b11111 / 5'sd3));
+   initial begin
+      // verilator lint_off STMTDLY
+      #1;
+`ifdef VCS  // I-2014.03
+      `checkh({a, b, c, d, e, f, g}, 7'b1101111);
+`else
+      `checkh({a, b, c, d, e, f, g}, 7'b1101011);
+`endif
+
+      //======================================================================
+
+      if ((-1 >>> 3) != -1) $stop;	// Decimals are signed
+
+      i = 3'sb111 >>> 3;
+      `checkh(i, -1);
+      i = -1 >>> 3;
+      `checkh(i, -1);
+
+      bug754_a = -1;
+      w4_u = |0 != (bug754_a >>> 3'd7);
+      `checkh(w4_u, 4'b0);
+
+      // Sanity check: -1>>7 == -1
+      w5_u = (5'sb11111 >>> 3'd7);
+      `checkh(w5_u, 5'b11111);
+
+      // bug756
+      w4_u = (5'b0 == (5'sb11111 >>> 3'd7));
+      `checkh(w4_u, 4'b0001);
+      w4_u = ((5'b0 == (5'sb11111 >>> 3'd7)));   // Exp 0     Vlt 0
+      `checkh(w4_u, 4'b0001);
+      w4_u = ((5'b01111 == (5'sb11111 / 5'sd2)));    // Strength-reduces to >>>
+`ifdef VCS  // I-2014.03
+      `checkh(w4_u, 4'b0000);  // Wrong, gets 5'b0==..., unsigned does not propagate
+`else
+      `checkh(w4_u, 4'b0001);  // NC-Verilog, Modelsim, XSim, ...
+`endif
+
+      // Does == sign propagate from lhs to rhs?  Yes, but not in VCS
+      w4_u = ((5'b01010 == (5'sb11111 / 5'sd3)));    // Exp 0     Vlt 0  // Must be signed result (-1/3) to make this result zero
+`ifdef VCS  // I-2014.03
+      `checkh(w4_u, 4'b0000);  // Wrong, gets 5'b0==..., unsigned does not propagate
+`else
+      `checkh(w4_u, 4'b0001);  // NC-Verilog, Modelsim, XSim, ...
+`endif
+
+      w4_u = (1'b0+(5'sb11111 >>> 3'd7));        // Exp 00000 Vlt 000000 Actually the signedness of result does NOT matter
+      `checkh(w4_u, 4'b0000);
+
+      w4_u = (5'sb0 == (5'sb11111 / 5'sd3));  // Must be signed result (-1/3) to make this result zero
+      `checkh(w4_u, 4'b0001);
+      // Does == width propagate from lhs to rhs? Yes
+      w4_u = (3'b100==(3'b111 << 2));
+      `checkh(w4_u, 4'b0001);
+      w4_u = (4'b100==(3'b111 << 2));
+      `checkh(w4_u, 4'b0000);
+      w4_u = (4'b1100==(3'b111 << 2));
+      `checkh(w4_u, 4'b0001);
+
+      // Does >>> sign propagate from input same as for +? Yes
+      w4_u = (1'b0+(5'sb11111 >>> 3'd7));
+      `checkh(w4_u, 4'b0000);
+      w4_u = (1'sb0+(5'sb11111 >>> 3'd7));
+      `checkh(w4_u, 4'b1111);
+
+      // Does << width propagate from input same as for +? Yes
+      w4_u = (3'b0+(3'b111 << 2));
+      `checkh(w4_u, 4'b1100);  // width 4 =='s LHS
+      w4_u = (4'b0+(3'b111 << 2));
+      `checkh(w4_u, 4'b1100);
+
+      w4_u = (5'sb11111 == (5'sb11111 >>> 3'd7));  // WHAT? Signedness does propagate across ==?????
+      `checkh(w4_u, 4'b0001);
+      w4_u = ((5'b0 == (5'sb11111 >>> 3'd7)));
+      `checkh(w4_u, 4'b0001);
+
+      if (fail) $stop;
+      $write("*-* All Finished *-*\n");
+      $finish;
+   end
+endmodule