From 38e90e3de1c05ccfd469275c08d403f638cdcce1 Mon Sep 17 00:00:00 2001
From: Chandler Carruth <chandlerc@gmail.com>
Date: Wed, 26 Feb 2014 07:29:54 +0000
Subject: [SROA] Split the alignment computation complete for the memcpy
 rewriting to work independently for the slice side and the other side.

This allows us to only compute the minimum of the two when we actually
rewrite to a memcpy that needs to take the minimum, and preserve higher
alignment for one side or the other when rewriting to loads and stores.

This fix was inspired by seeing the result of some refactoring that
makes addrspace handling better.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202242 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/SROA.cpp | 32 ++++++++++++++++----------------
 1 file changed, 16 insertions(+), 16 deletions(-)

(limited to 'lib')

diff --git a/lib/Transforms/Scalar/SROA.cpp b/lib/Transforms/Scalar/SROA.cpp
index 9b81949909..859e3a79b7 100644
--- a/lib/Transforms/Scalar/SROA.cpp
+++ b/lib/Transforms/Scalar/SROA.cpp
@@ -2494,10 +2494,7 @@ private:
     assert((IsDest && II.getRawDest() == OldPtr) ||
            (!IsDest && II.getRawSource() == OldPtr));
 
-    unsigned MinAlignment = II.getAlignment();
-    if (MinAlignment == 0)
-      MinAlignment = 1; // Fix the '0' alignment used by memcpy and memmove.
-    MinAlignment = MinAlign(MinAlignment, getSliceAlign());
+    unsigned SliceAlign = getSliceAlign();
 
     // For unsplit intrinsics, we simply modify the source and destination
     // pointers in place. This isn't just an optimization, it is a matter of
@@ -2513,9 +2510,10 @@ private:
       else
         II.setSource(AdjustedPtr);
 
-      if (II.getAlignment() > MinAlignment) {
+      if (II.getAlignment() > SliceAlign) {
         Type *CstTy = II.getAlignmentCst()->getType();
-        II.setAlignment(ConstantInt::get(CstTy, MinAlignment));
+        II.setAlignment(
+            ConstantInt::get(CstTy, MinAlign(II.getAlignment(), SliceAlign)));
       }
 
       DEBUG(dbgs() << "          to: " << II << "\n");
@@ -2564,10 +2562,8 @@ private:
     // Compute the relative offset for the other pointer within the transfer.
     unsigned IntPtrWidth = DL.getPointerSizeInBits();
     APInt OtherOffset(IntPtrWidth, NewBeginOffset - BeginOffset);
-
-    // Factor the offset other pointer's alignment into the requinerd minimum.
-    MinAlignment =
-        MinAlign(MinAlignment, OtherOffset.zextOrTrunc(64).getZExtValue());
+    unsigned OtherAlign = MinAlign(II.getAlignment() ? II.getAlignment() : 1,
+                                   OtherOffset.zextOrTrunc(64).getZExtValue());
 
     if (EmitMemCpy) {
       Type *OtherPtrTy = OtherPtr->getType();
@@ -2581,9 +2577,9 @@ private:
       Type *SizeTy = II.getLength()->getType();
       Constant *Size = ConstantInt::get(SizeTy, NewEndOffset - NewBeginOffset);
 
-      CallInst *New = IRB.CreateMemCpy(IsDest ? OurPtr : OtherPtr,
-                                       IsDest ? OtherPtr : OurPtr,
-                                       Size, MinAlignment, II.isVolatile());
+      CallInst *New = IRB.CreateMemCpy(
+          IsDest ? OurPtr : OtherPtr, IsDest ? OtherPtr : OurPtr, Size,
+          MinAlign(SliceAlign, OtherAlign), II.isVolatile());
       (void)New;
       DEBUG(dbgs() << "          to: " << *New << "\n");
       return false;
@@ -2612,9 +2608,13 @@ private:
 
     Value *SrcPtr = getAdjustedPtr(IRB, DL, OtherPtr, OtherOffset, OtherPtrTy,
                                    OtherPtr->getName() + ".");
+    unsigned SrcAlign = OtherAlign;
     Value *DstPtr = &NewAI;
-    if (!IsDest)
+    unsigned DstAlign = SliceAlign;
+    if (!IsDest) {
       std::swap(SrcPtr, DstPtr);
+      std::swap(SrcAlign, DstAlign);
+    }
 
     Value *Src;
     if (VecTy && !IsWholeAlloca && !IsDest) {
@@ -2628,7 +2628,7 @@ private:
       uint64_t Offset = NewBeginOffset - NewAllocaBeginOffset;
       Src = extractInteger(DL, IRB, Src, SubIntTy, Offset, "extract");
     } else {
-      Src = IRB.CreateAlignedLoad(SrcPtr, MinAlignment, II.isVolatile(),
+      Src = IRB.CreateAlignedLoad(SrcPtr, SrcAlign, II.isVolatile(),
                                   "copyload");
     }
 
@@ -2646,7 +2646,7 @@ private:
     }
 
     StoreInst *Store = cast<StoreInst>(
-        IRB.CreateAlignedStore(Src, DstPtr, MinAlignment, II.isVolatile()));
+        IRB.CreateAlignedStore(Src, DstPtr, DstAlign, II.isVolatile()));
     (void)Store;
     DEBUG(dbgs() << "          to: " << *Store << "\n");
     return !II.isVolatile();
-- 
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