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

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
ARMFastISel 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 )
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

llvm-svn: 324781

llvm/lib/Target/ARM/ARMFastISel.cpp

@@ -2546,7 +2546,8 @@ bool ARMFastISel::SelectIntrinsicCall(const IntrinsicInst &I) {
         if (!ARMComputeAddress(MTI.getRawDest(), Dest) ||
             !ARMComputeAddress(MTI.getRawSource(), Src))
           return false;
-        unsigned Alignment = MTI.getAlignment();
+        unsigned Alignment = MinAlign(MTI.getDestAlignment(),
+                                      MTI.getSourceAlignment());
         if (ARMTryEmitSmallMemCpy(Dest, Src, Len, Alignment))
           return true;
       }