[arm fast-isel] Make the fast-isel implementation of memcpy respect alignment.

rdar://12821569

llvm-svn: 169460

1 files changed, 22 insertions, 11 deletions

diff --git a/llvm/lib/Target/ARM/ARMFastISel.cpp b/llvm/lib/Target/ARM/ARMFastISel.cpp
index 23d372cceae..21bb1476440 100644
--- a/llvm/lib/Target/ARM/ARMFastISel.cpp
+++ b/llvm/lib/Target/ARM/ARMFastISel.cpp
@@ -186,7 +186,8 @@ class ARMFastISel : public FastISel {
     bool ARMComputeAddress(const Value *Obj, Address &Addr);
     void ARMSimplifyAddress(Address &Addr, EVT VT, bool useAM3);
     bool ARMIsMemCpySmall(uint64_t Len);
-    bool ARMTryEmitSmallMemCpy(Address Dest, Address Src, uint64_t Len);
+    bool ARMTryEmitSmallMemCpy(Address Dest, Address Src, uint64_t Len,
+                               unsigned Alignment);
     unsigned ARMEmitIntExt(EVT SrcVT, unsigned SrcReg, EVT DestVT, bool isZExt);
     unsigned ARMMaterializeFP(const ConstantFP *CFP, EVT VT);
     unsigned ARMMaterializeInt(const Constant *C, EVT VT);
@@ -2422,21 +2423,30 @@ bool ARMFastISel::ARMIsMemCpySmall(uint64_t Len) {
 }
 
 bool ARMFastISel::ARMTryEmitSmallMemCpy(Address Dest, Address Src,
-                                        uint64_t Len) {
+                                        uint64_t Len, unsigned Alignment) {
   // Make sure we don't bloat code by inlining very large memcpy's.
   if (!ARMIsMemCpySmall(Len))
     return false;
 
-  // We don't care about alignment here since we just emit integer accesses.
   while (Len) {
     MVT VT;
-    if (Len >= 4)
-      VT = MVT::i32;
-    else if (Len >= 2)
-      VT = MVT::i16;
-    else {
-      assert(Len == 1);
-      VT = MVT::i8;
+    if (!Alignment || Alignment >= 4) {
+      if (Len >= 4)
+        VT = MVT::i32;
+      else if (Len >= 2)
+        VT = MVT::i16;
+      else {
+        assert (Len == 1 && "Expected a length of 1!");
+        VT = MVT::i8;
+      }
+    } else {
+      // Bound based on alignment.
+      if (Len >= 2 && Alignment == 2)
+        VT = MVT::i16;
+      else {
+        assert (Alignment == 1 && "Expected an alignment of 1!");
+        VT = MVT::i8;
+      }
     }
 
     bool RV;
@@ -2515,7 +2525,8 @@ bool ARMFastISel::SelectIntrinsicCall(const IntrinsicInst &I) {
         if (!ARMComputeAddress(MTI.getRawDest(), Dest) ||
             !ARMComputeAddress(MTI.getRawSource(), Src))
           return false;
-        if (ARMTryEmitSmallMemCpy(Dest, Src, Len))
+        unsigned Alignment = MTI.getAlignment();
+        if (ARMTryEmitSmallMemCpy(Dest, Src, Len, Alignment))
           return true;
       }
     }