From: Stuart Hastings <stuart@apple.com>
Date: Thu, 12 May 2011 23:36:41 +0000 (+0000)
Subject: Non-fast-isel followup to 129634; correctly handle branches controlled
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=5adc64638084c1b8d33ac56e2498b83f1f4bd6e2;p=oota-llvm.git

Non-fast-isel followup to 129634; correctly handle branches controlled
by non-CMP expressions.  The executable test case (129821) would test
this as well, if we had an "-O0 -disable-arm-fast-isel" LLVM-GCC
tester.  Alas, the ARM assembly would be very difficult to check with
FileCheck.

The thumb2-cbnz.ll test is affected; it generates larger code (tst.w
vs. cmp #0), but I believe the new version is correct.
rdar://problem/9298790


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131261 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index e2e6691ba7c..5a833d335c1 100644
--- a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -3535,9 +3535,16 @@ void SelectionDAGLegalize::ExpandNode(SDNode *Node,
                          Tmp2.getOperand(0), Tmp2.getOperand(1),
                          Node->getOperand(2));
     } else {
+      // We test only the i1 bit.  Skip the AND if UNDEF.
+      Tmp3 = (Tmp2.getOpcode() == ISD::UNDEF ||
+              (Tmp2.getOpcode() == ISD::AND &&
+               Tmp2.getConstantOperandVal(1) == 1)) ?
+        Tmp2 :
+        DAG.getNode(ISD::AND, dl, Tmp2.getValueType(), Tmp2,
+                    DAG.getConstant(1, Tmp2.getValueType()));
       Tmp1 = DAG.getNode(ISD::BR_CC, dl, MVT::Other, Tmp1,
-                         DAG.getCondCode(ISD::SETNE), Tmp2,
-                         DAG.getConstant(0, Tmp2.getValueType()),
+                         DAG.getCondCode(ISD::SETNE), Tmp3,
+                         DAG.getConstant(0, Tmp3.getValueType()),
                          Node->getOperand(2));
     }
     Results.push_back(Tmp1);
diff --git a/test/CodeGen/Thumb2/thumb2-cbnz.ll b/test/CodeGen/Thumb2/thumb2-cbnz.ll
index 10a4985d173..0c7f33a6f4a 100644
--- a/test/CodeGen/Thumb2/thumb2-cbnz.ll
+++ b/test/CodeGen/Thumb2/thumb2-cbnz.ll
@@ -20,9 +20,10 @@ bb7:                                              ; preds = %bb3
   br i1 %a, label %bb11, label %bb9
 
 bb9:                                              ; preds = %bb7
-; CHECK:      cmp r0, #0
-; CHECK:      cmp r0, #0
-; CHECK-NEXT: cbnz
+; CHECK:      tst.w	r0, #1
+; CHECK:      tst.w	r0, #1
+; CHECK:      tst.w	r0, #1
+; CHECK:      bne
   %0 = tail call  double @floor(double %b) nounwind readnone ; <double> [#uses=0]
   br label %bb11