Merge pull request #1402 from larsclausen/real-unary-minus-opcode

vvp: Add opcode for unary real minus

Documentation/developer/guide/vvp/opcodes.rst

@@ -812,6 +812,10 @@ result is pushed back on the vec4 stack.
 
 This opcode multiplies two real words together.
 
+* %neg/wr
+
+This opcode negates the real value on top of the real stack.
+
 * %nand
 
 Perform the bitwise NAND of two vec4 vectors, and push the result. Each

ivtest/ivltests/real_unary_minus_inf.v

@@ -0,0 +1,31 @@
+// Check that unary real minus preserves infinities.
+
+module test;
+
+  reg failed;
+  real inf;
+  real result;
+
+  `define check(val, exp) \
+    if (val !== exp) begin \
+      $display("FAILED(%0d). '%s' expected %h, got %h", `__LINE__, \
+               `"val`", exp, val); \
+      failed = 1'b1; \
+    end
+
+  initial begin
+    failed = 1'b0;
+    inf = $bitstoreal(64'h7ff0000000000000);
+
+    result = -inf;
+    `check($realtobits(result), 64'hfff0000000000000);
+
+    result = -result;
+    `check($realtobits(result), 64'h7ff0000000000000);
+
+    if (!failed) begin
+      $display("PASSED");
+    end
+  end
+
+endmodule

ivtest/ivltests/real_unary_minus_nan.v

@@ -0,0 +1,31 @@
+// Check that unary real minus preserves NaN bits.
+
+module test;
+
+  reg failed;
+  real nan;
+  real result;
+
+  `define check(val, exp) \
+    if (val !== exp) begin \
+      $display("FAILED(%0d). '%s' expected %h, got %h", `__LINE__, \
+               `"val`", exp, val); \
+      failed = 1'b1; \
+    end
+
+  initial begin
+    failed = 1'b0;
+    nan = $bitstoreal(64'h7ff8000000000001);
+
+    result = -nan;
+    `check($realtobits(result), 64'hfff8000000000001);
+
+    result = -result;
+    `check($realtobits(result), 64'h7ff8000000000001);
+
+    if (!failed) begin
+      $display("PASSED");
+    end
+  end
+
+endmodule

ivtest/ivltests/real_unary_minus_zero.v

@@ -0,0 +1,31 @@
+// Check that unary real minus preserves the sign of zero.
+
+module test;
+
+  reg failed;
+  real zero;
+  real result;
+
+  `define check(val, exp) \
+    if (val !== exp) begin \
+      $display("FAILED(%0d). '%s' expected %h, got %h", `__LINE__, \
+               `"val`", exp, val); \
+      failed = 1'b1; \
+    end
+
+  initial begin
+    failed = 1'b0;
+    zero = 0.0;
+
+    result = -zero;
+    `check($realtobits(result), 64'h8000000000000000);
+
+    result = -result;
+    `check($realtobits(result), 64'h0000000000000000);
+
+    if (!failed) begin
+      $display("PASSED");
+    end
+  end
+
+endmodule

ivtest/regress-vvp.list

@@ -214,6 +214,9 @@ pv_wr_fn_vec4			vvp_tests/pv_wr_fn_vec4.json
 queue_fail			vvp_tests/queue_fail.json
 readmem-invalid			vvp_tests/readmem-invalid.json
 real_negative_zero		vvp_tests/real_negative_zero.json
+real_unary_minus_inf		vvp_tests/real_unary_minus_inf.json
+real_unary_minus_nan		vvp_tests/real_unary_minus_nan.json
+real_unary_minus_zero		vvp_tests/real_unary_minus_zero.json
 scaled_real			vvp_tests/scaled_real.json
 scan-invalid			vvp_tests/scan-invalid.json
 sdf_interconnect1		vvp_tests/sdf_interconnect1.json

ivtest/vvp_tests/real_unary_minus_inf.json

@@ -0,0 +1,4 @@
+{
+    "type"   : "normal",
+    "source" : "real_unary_minus_inf.v"
+}

ivtest/vvp_tests/real_unary_minus_nan.json

@@ -0,0 +1,4 @@
+{
+    "type"   : "normal",
+    "source" : "real_unary_minus_nan.v"
+}

ivtest/vvp_tests/real_unary_minus_zero.json

@@ -0,0 +1,4 @@
+{
+    "type"   : "normal",
+    "source" : "real_unary_minus_zero.v"
+}

tgt-vvp/eval_real.c

@@ -453,9 +453,8 @@ static void draw_unary_real(ivl_expr_t expr)
       }
 
       if (ivl_expr_opcode(expr) == '-') {
-	    fprintf(vvp_out, "    %%pushi/real 0, 0; load 0.0\n");
 	    draw_eval_real(sube);
-	    fprintf(vvp_out, "    %%sub/wr;\n");
+	    fprintf(vvp_out, "    %%neg/wr;\n");
 	    return;
       }
 

vvp/codes.h

@@ -164,6 +164,7 @@ extern bool of_MOD_WR(vthread_t thr, vvp_code_t code);
 extern bool of_MUL(vthread_t thr, vvp_code_t code);
 extern bool of_MULI(vthread_t thr, vvp_code_t code);
 extern bool of_MUL_WR(vthread_t thr, vvp_code_t code);
+extern bool of_NEG_WR(vthread_t thr, vvp_code_t code);
 extern bool of_NAND(vthread_t thr, vvp_code_t code);
 extern bool of_NANDR(vthread_t thr, vvp_code_t code);
 extern bool of_NEW_COBJ(vthread_t thr, vvp_code_t code);

vvp/compile.cc

@@ -219,6 +219,7 @@ static const struct opcode_table_s opcode_table[] = {
       { "%muli",   of_MULI,   3,  {OA_BIT1,     OA_BIT2,     OA_NUMBER} },
       { "%nand",   of_NAND,   0,  {OA_NONE,     OA_NONE,     OA_NONE} },
       { "%nand/r", of_NANDR,  0,  {OA_NONE,     OA_NONE,     OA_NONE} },
+      { "%neg/wr", of_NEG_WR, 0,  {OA_NONE,     OA_NONE,     OA_NONE} },
       { "%new/cobj",  of_NEW_COBJ,  1, {OA_VPI_PTR,OA_NONE,  OA_NONE} },
       { "%new/darray",of_NEW_DARRAY,2, {OA_BIT1,   OA_STRING,OA_NONE} },
       { "%noop",   of_NOOP,   0,  {OA_NONE,     OA_NONE,     OA_NONE} },

vvp/vthread.cc

@@ -4288,6 +4288,15 @@ bool of_MOD_WR(vthread_t thr, vvp_code_t)
       return true;
 }
 
+/*
+ * %neg/wr
+ */
+bool of_NEG_WR(vthread_t thr, vvp_code_t)
+{
+      thr->poke_real(0, -thr->peek_real(0));
+      return true;
+}
+
 /*
  * %pad/s <wid>
  */