Index: lib/CodeGen/IslNodeBuilder.cpp
===================================================================
--- lib/CodeGen/IslNodeBuilder.cpp
+++ lib/CodeGen/IslNodeBuilder.cpp
@@ -1107,6 +1107,28 @@
     ExecutionCtx = isl_set_intersect(ExecutionCtx, BaseExecutionCtx);
   }
 
+  // If the size of a dimension is dependent on another class, make sure it is
+  // preloaded.
+  for (unsigned i = 1, e = SAI->getNumberOfDimensions(); i < e; ++i) {
+    const SCEV *Dim = SAI->getDimensionSize(i);
+    // This special case parallels the special case for loads in
+    // ScopDetection::hasValidArraySizes.
+    if (const SCEVUnknown *Unknown = dyn_cast<SCEVUnknown>(Dim)) {
+      if (auto *BaseIAClass =
+              S.lookupInvariantEquivClass(Unknown->getValue())) {
+        if (!preloadInvariantEquivClass(*BaseIAClass))
+          return false;
+
+        // After we preloaded the BaseIAClass we adjusted the BaseExecutionCtx
+        // and we need to refine the ExecutionCtx.
+        isl_set *BaseExecutionCtx = isl_set_copy(BaseIAClass->ExecutionContext);
+        ExecutionCtx = isl_set_intersect(ExecutionCtx, BaseExecutionCtx);
+      }
+    } else {
+      assert(!hasScalarDepsInsideRegion(Dim, &S.getRegion(), nullptr, false));
+    }
+  }
+
   Instruction *AccInst = MA->getAccessInstruction();
   Type *AccInstTy = AccInst->getType();
 
Index: test/Isl/CodeGen/invariant-load-dimension.ll
===================================================================
--- /dev/null
+++ test/Isl/CodeGen/invariant-load-dimension.ll
@@ -0,0 +1,36 @@
+; RUN: opt -S < %s -polly-codegen -polly-process-unprofitable -polly-invariant-load-hoisting | FileCheck %s
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n8:16:32-S64"
+
+%S = type { i32, i32, [12 x %L] }
+%L = type { i32, i32, double, i32, i32, i32, i32, i32 }
+
+define void @test(%S* %cpi, i1 %b) {
+; CHECK-LABEL: @test(
+; CHECK: polly.start
+entry:
+  %nt = getelementptr inbounds %S, %S* %cpi, i32 0, i32 1
+  br i1 %b, label %if.then14, label %exit
+
+if.then14:
+  %ns = getelementptr inbounds %S, %S* %cpi, i32 0, i32 0
+  %l0 = load i32, i32* %ns, align 8
+  %cmp12.i = icmp sgt i32 %l0, 0
+  br i1 %cmp12.i, label %for.body.lr.ph.i, label %exit
+
+for.body.lr.ph.i:
+  %l1 = load i32, i32* %nt, align 4
+  br label %for.body.i
+
+for.body.i:
+  %phi = phi i32 [ 0, %for.body.lr.ph.i ], [ %inc, %for.body.i ]
+  %mul.i163 = mul nsw i32 %phi, %l1
+  %cv = getelementptr inbounds %S, %S* %cpi, i32 0, i32 2, i32 %mul.i163, i32 0
+  store i32 0, i32* %cv, align 8
+  %inc = add nuw nsw i32 %phi, 1
+  %l2 = load i32, i32* %ns, align 8
+  %cmp.i164 = icmp slt i32 %inc, %l2
+  br i1 %cmp.i164, label %for.body.i, label %exit
+
+exit:
+  ret void
+}