3 files changed, 38 insertions, 5 deletions
diff --git a/polly/include/polly/ScopInfo.h b/polly/include/polly/ScopInfo.h
index 9f372388f7f..975bc020b17 100644
--- a/polly/include/polly/ScopInfo.h
+++ b/polly/include/polly/ScopInfo.h
@@ -72,6 +72,7 @@ enum AssumptionKind {
   ALIASING,
   INBOUNDS,
   WRAPPING,
+  ALIGNMENT,
   ERRORBLOCK,
   INFINITELOOP,
   INVARIANTLOAD,
diff --git a/polly/lib/Analysis/ScopInfo.cpp b/polly/lib/Analysis/ScopInfo.cpp
index 43e14bdc0b0..ec90ccb6962 100644
--- a/polly/lib/Analysis/ScopInfo.cpp
+++ b/polly/lib/Analysis/ScopInfo.cpp
@@ -601,6 +601,32 @@ __isl_give isl_map *MemoryAccess::foldAccess(__isl_take isl_map *AccessRelation,
   return AccessRelation;
 }
 
+/// @brief Check if @p Expr is divisible by @p Size.
+static bool isDivisible(const SCEV *Expr, unsigned Size, ScalarEvolution &SE) {
+
+  // Only one factor needs to be divisible.
+  if (auto *MulExpr = dyn_cast<SCEVMulExpr>(Expr)) {
+    for (auto *FactorExpr : MulExpr->operands())
+      if (isDivisible(FactorExpr, Size, SE))
+        return true;
+    return false;
+  }
+
+  // For other n-ary expressions (Add, AddRec, Max,...) all operands need
+  // to be divisble.
+  if (auto *NAryExpr = dyn_cast<SCEVNAryExpr>(Expr)) {
+    for (auto *OpExpr : NAryExpr->operands())
+      if (!isDivisible(OpExpr, Size, SE))
+        return false;
+    return true;
+  }
+
+  auto *SizeSCEV = SE.getConstant(Expr->getType(), Size);
+  auto *UDivSCEV = SE.getUDivExpr(Expr, SizeSCEV);
+  auto *MulSCEV = SE.getMulExpr(UDivSCEV, SizeSCEV);
+  return MulSCEV == Expr;
+}
+
 void MemoryAccess::buildAccessRelation(const ScopArrayInfo *SAI) {
   assert(!AccessRelation && "AccessReltation already built");
 
@@ -620,6 +646,7 @@ void MemoryAccess::buildAccessRelation(const ScopArrayInfo *SAI) {
     return;
   }
 
+  Scop &S = *getStatement()->getParent();
   isl_space *Space = isl_space_alloc(Ctx, 0, Statement->getNumIterators(), 0);
   AccessRelation = isl_map_universe(Space);
 
@@ -634,9 +661,14 @@ void MemoryAccess::buildAccessRelation(const ScopArrayInfo *SAI) {
       // LLVM-IR as something like A[i * elementsize]. This hides the fact that
       // two subsequent values of 'i' index two values that are stored next to
       // each other in memory. By this division we make this characteristic
-      // obvious again.
+      // obvious again. However, if the index is not divisible by the element
+      // size we will bail out.
       isl_val *v = isl_val_int_from_si(Ctx, getElemSizeInBytes());
       Affine = isl_pw_aff_scale_down_val(Affine, v);
+
+      if (!isDivisible(Subscripts[0], getElemSizeInBytes(), *S.getSE()))
+        S.addAssumption(ALIGNMENT, isl_set_empty(S.getParamSpace()),
+                        AccessInstruction->getDebugLoc());
     }
 
     isl_map *SubscriptMap = isl_map_from_pw_aff(Affine);
@@ -2941,6 +2973,8 @@ static std::string toString(AssumptionKind Kind) {
     return "Inbounds";
   case WRAPPING:
     return "No-overflows";
+  case ALIGNMENT:
+    return "Alignment";
   case ERRORBLOCK:
     return "No-error";
   case INFINITELOOP:
diff --git a/polly/test/Isl/CodeGen/invariant_cannot_handle_void.ll b/polly/test/Isl/CodeGen/invariant_cannot_handle_void.ll
index 5497b31d26d..65480d7a4ad 100644
--- a/polly/test/Isl/CodeGen/invariant_cannot_handle_void.ll
+++ b/polly/test/Isl/CodeGen/invariant_cannot_handle_void.ll
@@ -1,11 +1,9 @@
 ; RUN: opt %loadPolly -S -polly-codegen %s | FileCheck %s
 ;
 ; The offset of the %tmp1 load wrt. to %buff (62 bytes) is not divisible
-; by the type size (i32 = 4 bytes), thus the access function build for
-; %tmp1 is empty. As a result the code generation crashed when hoisting
-; %tmp1. This test verifies we do not crash anymore.
+; by the type size (i32 = 4 bytes), thus we will bail out.
 ;
-; CHECK: polly.start
+; CHECK-NOT: polly.start
 ;
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"