From e5a81a130f26b0b2651ad6a22e3748703b11cb46 Mon Sep 17 00:00:00 2001
From: Tim Northover <tnorthover@apple.com>
Date: Sat, 6 Jul 2013 12:58:45 +0000
Subject: [PATCH] Stop putting operations after a tail call.
This prevents the emission of DAG-generated vreg definitions after a
tail call be dropping them entirely (on the grounds that nothing could
use them anyway, and they interfere with O0 CodeGen).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185754 91177308-0d34-0410-b5e6-96231b3b80d8
---
lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp | 4 ++++
test/CodeGen/ARM/fast-tail-call.ll | 16 ++++++++++++++++
2 files changed, 20 insertions(+)
create mode 100644 test/CodeGen/ARM/fast-tail-call.ll
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index fe284f5c0fc..23d83e69cb8 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -5357,6 +5357,10 @@ void SelectionDAGBuilder::LowerCallTo(ImmutableCallSite CS, SDValue Callee,
// As a special case, a null chain means that a tail call has been emitted and
// the DAG root is already updated.
HasTailCall = true;
+
+ // Since there's no actual continuation from this block, nothing can be
+ // relying on us setting vregs for them.
+ PendingExports.clear();
} else {
DAG.setRoot(Result.second);
}
diff --git a/test/CodeGen/ARM/fast-tail-call.ll b/test/CodeGen/ARM/fast-tail-call.ll
new file mode 100644
index 00000000000..9fbdc9d24b0
--- /dev/null
+++ b/test/CodeGen/ARM/fast-tail-call.ll
@@ -0,0 +1,16 @@
+; RUN: llc -mtriple=thumbv7-linux-gnueabi -O0 -arm-tail-calls < %s | FileCheck %s
+
+; Primarily a non-crash test: Thumbv7 Linux does not have FastISel support,
+; which led (via a convoluted route) to DAG nodes after a TC_RETURN that
+; couldn't possibly work.
+
+declare i8* @g(i8*)
+
+define i8* @f(i8* %a) {
+entry:
+ %0 = tail call i8* @g(i8* %a)
+ ret i8* %0
+; CHECK: b g
+; CHECK-NOT: ldr
+; CHECK-NOT: str
+}