TableGen: Simplify BitsInit::resolveReferences

Summary:
No functional change intended. The removed code has a loop for
recursive resolving, which is superseded by the recursive
resolving done by the Resolver implementations.

Add a test case which was broken by an earlier version of this
change.

Change-Id: Ib208d037b77a8bbb725977f1388601fc984723d8

Reviewers: arsenm, craig.topper, tra, MartinO

Subscribers: wdng, llvm-commits

Differential Revision: https://reviews.llvm.org/D43655

llvm-svn: 326784

1 files changed, 30 insertions, 1 deletions

diff --git a/llvm/test/TableGen/UnsetBitInit.td b/llvm/test/TableGen/UnsetBitInit.td
index d232293d787..694847358f6 100644
--- a/llvm/test/TableGen/UnsetBitInit.td
+++ b/llvm/test/TableGen/UnsetBitInit.td
@@ -1,5 +1,34 @@
-// RUN: llvm-tblgen %s
+// RUN: llvm-tblgen %s | FileCheck %s
 // XFAIL: vg_leak
+
+// CHECK: --- Defs ---
+
+// Test that P and Q are not replaced by ?. TableGen's codegen emitter backend
+// relies on keeping variable references like this around to describe the
+// structure of instruction encodings.
+//
+// CHECK: def A {
+// CHECK:   bits<8> Inst = { 1, 1, 1, 1, 1, 1, P, Q };
+// CHECK:   bits<2> src = { ?, ? };
+// CHECK:   bit P = ?;
+// CHECK:   bit Q = ?;
+// CHECK: }
+
+def A {
+  bits<8> Inst;
+  bits<2> src;
+
+  bit P;
+  bit Q;
+
+  let Inst{7-2} = 0x3f;
+  let Inst{1} = P;
+  let Inst{0} = Q;
+
+  let P = src{1};
+  let Q = src{0};
+}
+
 class x {
   field bits<32> A;
 }