Subzero: Fix JumpTable lowering on x86-64.

src/IceTargetLoweringX86BaseImpl.h

Index: src/IceTargetLoweringX86BaseImpl.h
diff --git a/src/IceTargetLoweringX86BaseImpl.h b/src/IceTargetLoweringX86BaseImpl.h
index a6bc892ffe1b1f352accf80f243963f09aaade75..b056ea4dbf0f89e0d8c4f652370e811248af217f 100644
--- a/src/IceTargetLoweringX86BaseImpl.h
+++ b/src/IceTargetLoweringX86BaseImpl.h
@@ -5853,7 +5853,12 @@ void TargetX86Base<TraitsType>::lowerCaseCluster(const CaseCluster &Case,
     const Type PointerType = getPointerType();
     if (RangeIndex->getType() != PointerType) {
       Index = makeReg(PointerType);
-      _movzx(Index, RangeIndex);
+      if (RangeIndex->getType() == IceType_i64) {

[John, 2016/02/29 15:34:09]

How do you feel about:

if (typeSizeInByes(PointerType) > typSizeInBytes(RangeIndex.getType()) {
  Index = makeReg(PointerType);
  _movzx(Index, RangeIndex);
} else if (typeSizeInByes(PointerType) < typSizeInBytes(RangeIndex.getType()) {
  Index = makeReg(PointerType);
  _mov(Index, RangeIndex);
} else {
  Index = legalizeToReg(RangeIndex);
}

This is "moar" future-proof should we ever need a non-ILP32 target.

+        assert(Traits::Is64Bit);
+        _mov(Index, RangeIndex); // trunc
+      } else {
+        _movzx(Index, RangeIndex);
+      }
     } else {
       Index = legalizeToReg(RangeIndex);
     }