compile time bug insertion

make BUG=1 -> addsub
make BUG=2 -> muldiv
make BUG=3 -> addsub and muldiv

Author: vtkhatri

Makefile

@@ -33,6 +33,18 @@ ifdef TEST_PRINT
 	vsim_args += +TEST_PRINT
 endif
 
+ifeq ($(BUG), 1)
+	vlog_args += +define+BUG_ADDSUB
+else
+ifeq ($(BUG), 2)
+	vlog_args += +define+BUG_MULDIV
+else
+ifeq ($(BUG), 3)
+	vlog_args += +define+BUG_ADDSUB +define+BUG_MULDIV
+endif
+endif
+endif
+
 build:
 	vlog $(vlog_args) $(SV_TARGET)
 

duv/pfpu32_addsub.v

@@ -112,9 +112,15 @@ module pfpu32_addsub
     addsub_agtb_i ? fract24b_i : fract24a_i;
 
     // shift amount
+`ifdef BUG_ADDSUB
+  wire [9:0] s1t_exp_diff =
+    addsub_agtb_i ? (exp10a_i + exp10b_i) :
+                    (exp10b_i + exp10a_i);
+`else
   wire [9:0] s1t_exp_diff =
     addsub_agtb_i ? (exp10a_i - exp10b_i) :
                     (exp10b_i - exp10a_i);
+`endif
 
   // limiter by 31
   wire [4:0] s1t_shr = s1t_exp_diff[4:0] | {5{|s1t_exp_diff[9:5]}};

duv/pfpu32_muldiv.v

@@ -586,7 +586,11 @@ module pfpu32_muldiv
   // In fact, as the dividend and divisor was normalized
   //   and the result is non-zero
   //   the '1' is maximum number of leading zeros in the quotient.
+`ifdef BUG_MULDIV
+  wire s4t_nlz = s3o_res_qtnt26[25];
+`else
   wire s4t_nlz = ~s3o_res_qtnt26[25];
+`endif
   // left shift flag and corrected exponent
   wire s4t_shlx =
       // shift isn't needed (includes zero result)