From bcdc280a873ad369077f446df025d09b28dbead9 Mon Sep 17 00:00:00 2001
From: whitequark <whitequark@whitequark.org>
Date: Sat, 3 Aug 2019 12:44:52 +0000
Subject: [PATCH] hdl.ast, back.rtlil: add source locations to anonymous wires.

This might help with propagation of locations through optimizer
passes, since not all of them take care to preserve cells at all,
but usually wires stay intact when possible.

Also fixes incorrect source location on value.part().
---
 nmigen/back/rtlil.py | 20 +++++++++++---------
 nmigen/hdl/ast.py    |  2 +-
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/nmigen/back/rtlil.py b/nmigen/back/rtlil.py
index 4f6592e..55d15d9 100644
--- a/nmigen/back/rtlil.py
+++ b/nmigen/back/rtlil.py
@@ -227,12 +227,14 @@ class _SyncBuilder(_ProxiedBuilder):
 
 
 def src(src_loc):
+    if src_loc is None:
+        return None
     file, line = src_loc
     return "{}:{}".format(file, line)
 
 
 def srcs(src_locs):
-    return "|".join(sorted(map(src, src_locs)))
+    return "|".join(sorted(filter(lambda x: x, map(src, src_locs))))
 
 
 class LegalizeValue(Exception):
@@ -402,7 +404,7 @@ class _RHSValueCompiler(_ValueCompiler):
             return self.s.anys[value]
 
         res_bits, res_sign = value.shape()
-        res = self.s.rtlil.wire(width=res_bits)
+        res = self.s.rtlil.wire(width=res_bits, src=src(value.src_loc))
         self.s.rtlil.cell("$anyconst", ports={
             "\\Y": res,
         }, params={
@@ -416,7 +418,7 @@ class _RHSValueCompiler(_ValueCompiler):
             return self.s.anys[value]
 
         res_bits, res_sign = value.shape()
-        res = self.s.rtlil.wire(width=res_bits)
+        res = self.s.rtlil.wire(width=res_bits, src=src(value.src_loc))
         self.s.rtlil.cell("$anyseq", ports={
             "\\Y": res,
         }, params={
@@ -433,7 +435,7 @@ class _RHSValueCompiler(_ValueCompiler):
         arg, = value.operands
         arg_bits, arg_sign = arg.shape()
         res_bits, res_sign = value.shape()
-        res = self.s.rtlil.wire(width=res_bits)
+        res = self.s.rtlil.wire(width=res_bits, src=src(value.src_loc))
         self.s.rtlil.cell(self.operator_map[(1, value.op)], ports={
             "\\A": self(arg),
             "\\Y": res,
@@ -452,7 +454,7 @@ class _RHSValueCompiler(_ValueCompiler):
         if new_bits <= value_bits:
             return self(ast.Slice(value, 0, new_bits))
 
-        res = self.s.rtlil.wire(width=new_bits)
+        res = self.s.rtlil.wire(width=new_bits, src=src(value.src_loc))
         self.s.rtlil.cell("$pos", ports={
             "\\A": self(value),
             "\\Y": res,
@@ -476,7 +478,7 @@ class _RHSValueCompiler(_ValueCompiler):
             lhs_wire = self.match_shape(lhs, lhs_bits, lhs_sign)
             rhs_wire = self.match_shape(rhs, rhs_bits, rhs_sign)
         res_bits, res_sign = value.shape()
-        res = self.s.rtlil.wire(width=res_bits)
+        res = self.s.rtlil.wire(width=res_bits, src=src(value.src_loc))
         self.s.rtlil.cell(self.operator_map[(2, value.op)], ports={
             "\\A": lhs_wire,
             "\\B": rhs_wire,
@@ -498,7 +500,7 @@ class _RHSValueCompiler(_ValueCompiler):
         val1_bits = val0_bits = res_bits = max(val1_bits, val0_bits, res_bits)
         val1_wire = self.match_shape(val1, val1_bits, val1_sign)
         val0_wire = self.match_shape(val0, val0_bits, val0_sign)
-        res = self.s.rtlil.wire(width=res_bits)
+        res = self.s.rtlil.wire(width=res_bits, src=src(value.src_loc))
         self.s.rtlil.cell("$mux", ports={
             "\\A": val0_wire,
             "\\B": val1_wire,
@@ -524,7 +526,7 @@ class _RHSValueCompiler(_ValueCompiler):
         if isinstance(value, (ast.Signal, ast.Slice, ast.Cat)):
             sigspec = self(value)
         else:
-            sigspec = self.s.rtlil.wire(len(value))
+            sigspec = self.s.rtlil.wire(len(value), src=src(value.src_loc))
             self.s.rtlil.connect(sigspec, self(value))
         return sigspec
 
@@ -533,7 +535,7 @@ class _RHSValueCompiler(_ValueCompiler):
         lhs_bits, lhs_sign = lhs.shape()
         rhs_bits, rhs_sign = rhs.shape()
         res_bits, res_sign = value.shape()
-        res = self.s.rtlil.wire(width=res_bits)
+        res = self.s.rtlil.wire(width=res_bits, src=src(value.src_loc))
         # Note: Verilog's x[o+:w] construct produces a $shiftx cell, not a $shift cell.
         # However, Migen's semantics defines the out-of-range bits to be zero, so it is correct
         # to use a $shift cell here instead, even though it produces less idiomatic Verilog.
diff --git a/nmigen/hdl/ast.py b/nmigen/hdl/ast.py
index 85310c1..b1d1a7e 100644
--- a/nmigen/hdl/ast.py
+++ b/nmigen/hdl/ast.py
@@ -163,7 +163,7 @@ class Value(metaclass=ABCMeta):
         Part, out
             Selected part of the ``Value``
         """
-        return Part(self, offset, width)
+        return Part(self, offset, width, src_loc_at=1)
 
     def eq(self, value):
         """Assignment.
-- 
2.30.2