When emitting a cmp with 0 for a lowered select, mask out the high

bits of the value carying the boolean condition, as their contents
are undefined. This fixes rdar://10887484.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151310 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/ARM/ARMISelLowering.cpp

@@ -2841,6 +2841,11 @@ SDValue ARMTargetLowering::LowerSELECT(SDValue Op, SelectionDAG &DAG) const {
     }
   }
 
+  // ARM's BooleanContents value is UndefinedBooleanContent. Mask out the
+  // undefined bits before doing a full-word comparison with zero.
+  Cond = DAG.getNode(ISD::AND, dl, Cond.getValueType(), Cond,
+                     DAG.getConstant(1, Cond.getValueType()));
+
   return DAG.getSelectCC(dl, Cond,
                          DAG.getConstant(0, Cond.getValueType()),
                          SelectTrue, SelectFalse, ISD::SETNE);

test/CodeGen/ARM/load_i1_select.ll

@@ -0,0 +1,19 @@
+; RUN: llc < %s | FileCheck %s
+
+target datalayout = "e-p:32:32:32-i1:8:32-i8:8:32-i16:16:32-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:32:64-v128:32:128-a0:0:32-n32-S32"
+target triple = "thumbv7-apple-ios0.0.0"
+
+; Codegen should only compare one bit of the loaded value.
+; rdar://10887484
+
+; CHECK: foo:
+; CHECK: ldrb r[[R0:[0-9]+]], [r0]
+; CHECK: tst.w r[[R0]], #1
+define void @foo(i8* %call, double* %p) nounwind {
+entry:
+  %tmp2 = load i8* %call
+  %tmp3 = trunc i8 %tmp2 to i1
+  %cond = select i1 %tmp3, double 2.000000e+00, double 1.000000e+00
+  store double %cond, double* %p
+  ret void
+}