Fix icmp lowering

Summary:
During icmp lowering it can happen that a constant value can be larger than expected (see the code around the change).
APInt::getMinSignedBits() must be checked again as the shift before can change the constant sign to positive.
I'm not sure it is the best fix possible though.

Test Plan: Regression test included.

Reviewers: resistor, chandlerc, spatel, hfinkel

Reviewed By: hfinkel

Subscribers: hfinkel, llvm-commits

Differential Revision: http://reviews.llvm.org/D9147

llvm-svn: 237812

llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp

@@ -1730,7 +1730,8 @@ TargetLowering::SimplifySetCC(EVT VT, SDValue N0, SDValue N1,
           ShiftBits = C1.countTrailingZeros();
         }
         NewC = NewC.lshr(ShiftBits);
-        if (ShiftBits && isLegalICmpImmediate(NewC.getSExtValue())) {
+        if (ShiftBits && NewC.getMinSignedBits() <= 64 &&
+          isLegalICmpImmediate(NewC.getSExtValue())) {
           EVT ShiftTy = DCI.isBeforeLegalize() ?
             getPointerTy() : getShiftAmountTy(N0.getValueType());
           EVT CmpTy = N0.getValueType();

llvm/test/CodeGen/Generic/icmp-illegal.ll

@@ -0,0 +1,50 @@
+
+; RUN: llc < %s | FileCheck %s
+
+; CHECK-LABEL: test_ult
+define i1 @test_ult(i256 %a) nounwind {
+  %1 = icmp ult i256 %a, -6432394258550908438
+  ret i1 %1
+}
+
+; CHECK-LABEL: test_ule
+define i1 @test_ule(i256 %a) nounwind {
+  %1 = icmp ule i256 %a, -6432394258550908438
+  ret i1 %1
+}
+
+; CHECK-LABEL: test_ugt
+define i1 @test_ugt(i256 %a) nounwind {
+  %1 = icmp ugt i256 %a, -6432394258550908438
+  ret i1 %1
+}
+
+; CHECK-LABEL: test_uge
+define i1 @test_uge(i256 %a) nounwind {
+  %1 = icmp uge i256 %a, -6432394258550908438
+  ret i1 %1
+}
+
+; CHECK-LABEL: test_slt
+define i1 @test_slt(i256 %a) nounwind {
+  %1 = icmp slt i256 %a, -6432394258550908438
+  ret i1 %1
+}
+
+; CHECK-LABEL: test_sle
+define i1 @test_sle(i256 %a) nounwind {
+  %1 = icmp sle i256 %a, -6432394258550908438
+  ret i1 %1
+}
+
+; CHECK-LABEL: test_sgt
+define i1 @test_sgt(i256 %a) nounwind {
+  %1 = icmp sgt i256 %a, -6432394258550908438
+  ret i1 %1
+}
+
+; CHECK-LABEL: test_sge
+define i1 @test_sge(i256 %a) nounwind {
+  %1 = icmp sge i256 %a, -6432394258550908438
+  ret i1 %1
+}