From c9166f098ccaec4ce12dd19e64b08b4927ec74c0 Mon Sep 17 00:00:00 2001
From: Chandler Carruth <chandlerc@gmail.com>
Date: Wed, 26 Feb 2014 05:02:19 +0000
Subject: [PATCH] [SROA] Simplify the computing of alignment: we only ever need
 the alignment of the slice being rewritten, not any arbitrary offset.

Every caller is really just trying to compute the alignment for the
whole slice, never for some arbitrary alignment. They are also just
passing a type when they have one to see if we can skip an explicit
alignment in the IR by using the type's alignment. This makes for a much
simpler interface.

Another refactoring inspired by the addrspace patch for SROA, although
only loosely related.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202230 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/SROA.cpp | 46 ++++++++++++----------------------
 1 file changed, 16 insertions(+), 30 deletions(-)

diff --git a/lib/Transforms/Scalar/SROA.cpp b/lib/Transforms/Scalar/SROA.cpp
index d0f2561dd33..ab815fe0600 100644
--- a/lib/Transforms/Scalar/SROA.cpp
+++ b/lib/Transforms/Scalar/SROA.cpp
@@ -2136,22 +2136,16 @@ private:
                           );
   }
 
-  /// \brief Compute suitable alignment to access an offset into the new alloca.
-  unsigned getOffsetAlign(uint64_t Offset) {
+  /// \brief Compute suitable alignment to access this slice of the *new* alloca.
+  ///
+  /// You can optionally pass a type to this routine and if that type's ABI
+  /// alignment is itself suitable, this will return zero.
+  unsigned getSliceAlign(Type *Ty = 0) {
     unsigned NewAIAlign = NewAI.getAlignment();
     if (!NewAIAlign)
       NewAIAlign = DL.getABITypeAlignment(NewAI.getAllocatedType());
-    return MinAlign(NewAIAlign, Offset);
-  }
-
-  /// \brief Compute suitable alignment to access a type at an offset of the
-  /// new alloca.
-  ///
-  /// \returns zero if the type's ABI alignment is a suitable alignment,
-  /// otherwise returns the maximal suitable alignment.
-  unsigned getOffsetTypeAlign(Type *Ty, uint64_t Offset) {
-    unsigned Align = getOffsetAlign(Offset);
-    return Align == DL.getABITypeAlignment(Ty) ? 0 : Align;
+    unsigned Align = MinAlign(NewAIAlign, NewBeginOffset - NewAllocaBeginOffset);
+    return (Ty && Align == DL.getABITypeAlignment(Ty)) ? 0 : Align;
   }
 
   unsigned getIndex(uint64_t Offset) {
@@ -2212,10 +2206,9 @@ private:
                                 LI.isVolatile(), LI.getName());
     } else {
       Type *LTy = TargetTy->getPointerTo();
-      V = IRB.CreateAlignedLoad(
-          getAdjustedAllocaPtr(IRB, NewBeginOffset, LTy),
-          getOffsetTypeAlign(TargetTy, NewBeginOffset - NewAllocaBeginOffset),
-          LI.isVolatile(), LI.getName());
+      V = IRB.CreateAlignedLoad(getAdjustedAllocaPtr(IRB, NewBeginOffset, LTy),
+                                getSliceAlign(TargetTy), LI.isVolatile(),
+                                LI.getName());
       IsPtrAdjusted = true;
     }
     V = convertValue(DL, IRB, V, TargetTy);
@@ -2338,10 +2331,8 @@ private:
     } else {
       Value *NewPtr = getAdjustedAllocaPtr(IRB, NewBeginOffset,
                                            V->getType()->getPointerTo());
-      NewSI = IRB.CreateAlignedStore(
-          V, NewPtr, getOffsetTypeAlign(V->getType(),
-                                        NewBeginOffset - NewAllocaBeginOffset),
-          SI.isVolatile());
+      NewSI = IRB.CreateAlignedStore(V, NewPtr, getSliceAlign(V->getType()),
+                                     SI.isVolatile());
     }
     (void)NewSI;
     Pass.DeadInsts.insert(&SI);
@@ -2396,8 +2387,7 @@ private:
       assert(NewBeginOffset == BeginOffset);
       II.setDest(getAdjustedAllocaPtr(IRB, NewBeginOffset, OldPtr->getType()));
       Type *CstTy = II.getAlignmentCst()->getType();
-      II.setAlignment(ConstantInt::get(
-          CstTy, getOffsetAlign(NewBeginOffset - NewAllocaBeginOffset)));
+      II.setAlignment(ConstantInt::get(CstTy, getSliceAlign()));
 
       deleteIfTriviallyDead(OldPtr);
       return false;
@@ -2409,8 +2399,6 @@ private:
     Type *AllocaTy = NewAI.getAllocatedType();
     Type *ScalarTy = AllocaTy->getScalarType();
 
-    uint64_t SliceOffset = NewBeginOffset - NewAllocaBeginOffset;
-
     // If this doesn't map cleanly onto the alloca type, and that type isn't
     // a single value type, just emit a memset.
     if (!VecTy && !IntTy &&
@@ -2423,7 +2411,7 @@ private:
       Constant *Size = ConstantInt::get(SizeTy, NewEndOffset - NewBeginOffset);
       CallInst *New = IRB.CreateMemSet(
           getAdjustedAllocaPtr(IRB, NewBeginOffset, OldPtr->getType()),
-          II.getValue(), Size, getOffsetAlign(SliceOffset), II.isVolatile());
+          II.getValue(), Size, getSliceAlign(), II.isVolatile());
       (void)New;
       DEBUG(dbgs() << "          to: " << *New << "\n");
       return false;
@@ -2509,11 +2497,9 @@ private:
     APInt RelOffset(IntPtrWidth, NewBeginOffset - BeginOffset);
 
     unsigned Align = II.getAlignment();
-    uint64_t SliceOffset = NewBeginOffset - NewAllocaBeginOffset;
     if (Align > 1)
-      Align =
-          MinAlign(RelOffset.zextOrTrunc(64).getZExtValue(),
-                   MinAlign(II.getAlignment(), getOffsetAlign(SliceOffset)));
+      Align = MinAlign(RelOffset.zextOrTrunc(64).getZExtValue(),
+                       MinAlign(II.getAlignment(), 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