From 8000c6c535c5a1d8515299072b51fd1baa8b632f Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Thu, 22 Oct 2009 00:40:00 +0000
Subject: [PATCH] Don't generate sbfx / ubfx with negative lsb field. Patch by
 David Conrad.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@84813 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/ARM/ARMISelDAGToDAG.cpp |  2 +-
 test/CodeGen/ARM/sbfx.ll           | 10 ++++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/lib/Target/ARM/ARMISelDAGToDAG.cpp b/lib/Target/ARM/ARMISelDAGToDAG.cpp
index 6e976936d98..5c1835b46a2 100644
--- a/lib/Target/ARM/ARMISelDAGToDAG.cpp
+++ b/lib/Target/ARM/ARMISelDAGToDAG.cpp
@@ -1287,7 +1287,7 @@ SDNode *ARMDAGToDAGISel::SelectV6T2BitfieldExtractOp(SDValue Op,
       assert(Srl_imm > 0 && Srl_imm < 32 && "bad amount in shift node!");
       unsigned Width = 32 - Srl_imm;
       int LSB = Srl_imm - Shl_imm;
-      if ((LSB + Width) > 32)
+      if (LSB < 0)
         return NULL;
       SDValue Reg0 = CurDAG->getRegister(0, MVT::i32);
       SDValue Ops[] = { Op.getOperand(0).getOperand(0),
diff --git a/test/CodeGen/ARM/sbfx.ll b/test/CodeGen/ARM/sbfx.ll
index 923f52a8686..6f1d87d2c17 100644
--- a/test/CodeGen/ARM/sbfx.ll
+++ b/test/CodeGen/ARM/sbfx.ll
@@ -35,3 +35,13 @@ entry:
     %tmp2 = lshr i32 %tmp, 29
     ret i32 %tmp2
 }
+
+define i32 @f5(i32 %a) {
+entry:
+; CHECK: f5:
+; CHECK-NOT: sbfx
+; CHECK: bx
+    %tmp = shl i32 %a, 3
+    %tmp2 = ashr i32 %tmp, 1
+    ret i32 %tmp2
+}