[SelectionDAGBuilder] Replace deprecated calls to MemoryIntrinsic::getAlignment() (NFCI)

Summary:
This change is part of step five in the series of changes to remove alignment argument from
memcpy/memmove/memset in favour of alignment attributes. In particular, this changes the
SelectionDAGBuilder to cease using the old getAlignment() API of MemoryIntrinsic in favour of getting
source & dest specific alignments through the new API.

Steps:
Step 1) Remove alignment parameter and create alignment parameter attributes for
memcpy/memmove/memset. ( rL322965, rC322964, rL322963 )
Step 2) Expand the IRBuilder API to allow creation of memcpy/memmove with differing
source and dest alignments. ( rL323597 )
Step 3) Update Clang to use the new IRBuilder API. ( rC323617 )
Step 4) Update Polly to use the new IRBuilder API. ( rL323618 )
Step 5) Update LLVM passes that create memcpy/memmove calls to use the new IRBuilder API,
and those that use use MemIntrinsicInst::[get|set]Alignment() to use [get|set]DestAlignment()
and [get|set]SourceAlignment() instead. ( rL323886, rL323891, rL324148, rL324273, rL324278,
rL324384, rL324395, rL324402, rL324626, rL324642, rL324653, rL324654, rL324773, rL324774,
rL324781, rL324784, rL324955, rL324960, rL325816, rL327398 )
Step 6) Remove the single-alignment IRBuilder API for memcpy/memmove, and the
MemIntrinsicInst::[get|set]Alignment() methods.

Reference
   http://lists.llvm.org/pipermail/llvm-dev/2015-August/089384.html
   http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20151109/312083.html

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@327421 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -5047,9 +5047,10 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
     SDValue Op1 = getValue(I.getArgOperand(0));
     SDValue Op2 = getValue(I.getArgOperand(1));
     SDValue Op3 = getValue(I.getArgOperand(2));
-    unsigned Align = MCI.getAlignment();
-    if (!Align)
-      Align = 1; // @llvm.memcpy defines 0 and 1 to both mean no alignment.
+    // @llvm.memcpy defines 0 and 1 to both mean no alignment.
+    unsigned DstAlign = std::max<unsigned>(MCI.getDestAlignment(), 1);
+    unsigned SrcAlign = std::max<unsigned>(MCI.getSourceAlignment(), 1);
+    unsigned Align = MinAlign(DstAlign, SrcAlign);
     bool isVol = MCI.isVolatile();
     bool isTC = I.isTailCall() && isInTailCallPosition(&I, DAG.getTarget());
     // FIXME: Support passing different dest/src alignments to the memcpy DAG
@@ -5066,9 +5067,8 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
     SDValue Op1 = getValue(I.getArgOperand(0));
     SDValue Op2 = getValue(I.getArgOperand(1));
     SDValue Op3 = getValue(I.getArgOperand(2));
-    unsigned Align = MSI.getAlignment();
-    if (!Align)
-      Align = 1; // @llvm.memset defines 0 and 1 to both mean no alignment.
+    // @llvm.memset defines 0 and 1 to both mean no alignment.
+    unsigned Align = std::max<unsigned>(MSI.getDestAlignment(), 1);
     bool isVol = MSI.isVolatile();
     bool isTC = I.isTailCall() && isInTailCallPosition(&I, DAG.getTarget());
     SDValue MS = DAG.getMemset(getRoot(), sdl, Op1, Op2, Op3, Align, isVol,
@@ -5081,9 +5081,10 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
     SDValue Op1 = getValue(I.getArgOperand(0));
     SDValue Op2 = getValue(I.getArgOperand(1));
     SDValue Op3 = getValue(I.getArgOperand(2));
-    unsigned Align = MMI.getAlignment();
-    if (!Align)
-      Align = 1; // @llvm.memmove defines 0 and 1 to both mean no alignment.
+    // @llvm.memmove defines 0 and 1 to both mean no alignment.
+    unsigned DstAlign = std::max<unsigned>(MMI.getDestAlignment(), 1);
+    unsigned SrcAlign = std::max<unsigned>(MMI.getSourceAlignment(), 1);
+    unsigned Align = MinAlign(DstAlign, SrcAlign);
     bool isVol = MMI.isVolatile();
     bool isTC = I.isTailCall() && isInTailCallPosition(&I, DAG.getTarget());
     // FIXME: Support passing different dest/src alignments to the memmove DAG