verilog: support recursive functions using ternary expressions

This adds a mechanism for marking certain portions of elaboration as
occurring within unevaluated ternary branches. To enable elaboration of
the overall ternary, this also adds width detection for these
unelaborated function calls.

2 files changed, 76 insertions, 0 deletions

diff --git a/tests/various/fib_tern.v b/tests/various/fib_tern.v
new file mode 100644
index 000000000..fefde74ce
--- /dev/null
+++ b/tests/various/fib_tern.v
@@ -0,0 +1,70 @@
+module gate(
+    off, fib0, fib1, fib2, fib3, fib4, fib5, fib6, fib7, fib8, fib9
+);
+    input wire signed [31:0] off;
+
+    function automatic blah(
+        input x
+    );
+        blah = x;
+    endfunction
+
+    function automatic integer fib(
+        input integer k
+    );
+        fib = k == 0
+                ? 0
+                : k == 1
+                    ? 1
+                    : fib(k - 1) + fib(k - 2);
+    endfunction
+
+    function automatic integer fib_wrap(
+        input integer k,
+        output integer o
+    );
+        o = off + fib(k);
+    endfunction
+
+    output integer fib0;
+    output integer fib1;
+    output integer fib2;
+    output integer fib3;
+    output integer fib4;
+    output integer fib5;
+    output integer fib6;
+    output integer fib7;
+    output integer fib8;
+    output integer fib9;
+
+    initial begin : blk
+        integer unused;
+        unused = fib_wrap(0, fib0);
+        unused = fib_wrap(1, fib1);
+        unused = fib_wrap(2, fib2);
+        unused = fib_wrap(3, fib3);
+        unused = fib_wrap(4, fib4);
+        unused = fib_wrap(5, fib5);
+        unused = fib_wrap(6, fib6);
+        unused = fib_wrap(7, fib7);
+        unused = fib_wrap(8, fib8);
+        unused = fib_wrap(9, fib9);
+    end
+endmodule
+
+module gold(
+    off, fib0, fib1, fib2, fib3, fib4, fib5, fib6, fib7, fib8, fib9
+);
+    input wire signed [31:0] off;
+
+    output integer fib0 = off + 0;
+    output integer fib1 = off + 1;
+    output integer fib2 = off + 1;
+    output integer fib3 = off + 2;
+    output integer fib4 = off + 3;
+    output integer fib5 = off + 5;
+    output integer fib6 = off + 8;
+    output integer fib7 = off + 13;
+    output integer fib8 = off + 21;
+    output integer fib9 = off + 34;
+endmodule
diff --git a/tests/various/fib_tern.ys b/tests/various/fib_tern.ys
new file mode 100644
index 000000000..e5bf186e1
--- /dev/null
+++ b/tests/various/fib_tern.ys
@@ -0,0 +1,6 @@
+read_verilog fib_tern.v
+hierarchy
+proc
+equiv_make gold gate equiv
+equiv_simple
+equiv_status -assert