diff --git a/llvm/lib/Target/PowerPC/PPCLoopInstrFormPrep.cpp b/llvm/lib/Target/PowerPC/PPCLoopInstrFormPrep.cpp
--- a/llvm/lib/Target/PowerPC/PPCLoopInstrFormPrep.cpp
+++ b/llvm/lib/Target/PowerPC/PPCLoopInstrFormPrep.cpp
@@ -534,13 +534,6 @@
     return MadeChange;
   }
 
-  // Now we only handle update form for constant increment.
-  // FIXME: add support for non-constant increment UpdateForm.
-  if (!IsConstantInc && Form == UpdateForm) {
-    LLVM_DEBUG(dbgs() << "not a constant incresement for update form!\n");
-    return MadeChange;
-  }
-
   // For some DS form load/store instructions, it can also be an update form,
   // if the stride is a multipler of 4. Use update form if prefer it.
   bool CanPreInc =
@@ -548,10 +541,13 @@
        ((Form == DSForm) && IsConstantInc &&
         !BasePtrIncConstantSCEV->getAPInt().urem(4) && PreferUpdateForm));
   const SCEV *BasePtrStartSCEV = nullptr;
-  if (CanPreInc)
-    BasePtrStartSCEV =
-        SE->getMinusSCEV(BasePtrSCEV->getStart(), BasePtrIncConstantSCEV);
-  else
+  if (CanPreInc) {
+    assert(SE->isLoopInvariant(BasePtrIncSCEV, L) &&
+           "Increment is not loop invariant!\n");
+    BasePtrStartSCEV = SE->getMinusSCEV(BasePtrSCEV->getStart(),
+                                        IsConstantInc ? BasePtrIncConstantSCEV
+                                                      : BasePtrIncSCEV);
+  } else
     BasePtrStartSCEV = BasePtrSCEV->getStart();
 
   if (!isSafeToExpand(BasePtrStartSCEV, *SE))
@@ -589,12 +585,10 @@
   Instruction *PtrInc = nullptr;
   Instruction *NewBasePtr = nullptr;
   if (CanPreInc) {
-    assert(BasePtrIncConstantSCEV &&
-           "update form now only supports constant increment.");
     Instruction *InsPoint = &*Header->getFirstInsertionPt();
-    PtrInc = GetElementPtrInst::Create(
-        I8Ty, NewPHI, BasePtrIncConstantSCEV->getValue(),
-        getInstrName(MemI, GEPNodeIncNameSuffix), InsPoint);
+    PtrInc = GetElementPtrInst::Create(I8Ty, NewPHI, IncNode,
+                                       getInstrName(MemI, GEPNodeIncNameSuffix),
+                                       InsPoint);
     cast<GetElementPtrInst>(PtrInc)->setIsInBounds(IsPtrInBounds(BasePtr));
     for (auto PI : predecessors(Header)) {
       if (PI == LoopPredecessor)
diff --git a/llvm/test/CodeGen/PowerPC/loop-instr-prep-non-const-increasement.ll b/llvm/test/CodeGen/PowerPC/loop-instr-prep-non-const-increasement.ll
--- a/llvm/test/CodeGen/PowerPC/loop-instr-prep-non-const-increasement.ll
+++ b/llvm/test/CodeGen/PowerPC/loop-instr-prep-non-const-increasement.ll
@@ -19,18 +19,18 @@
 ; CHECK-NEXT:    cmpwi r4, 1
 ; CHECK-NEXT:    blt cr0, .LBB0_4
 ; CHECK-NEXT:  # %bb.1: # %for.body.preheader
+; CHECK-NEXT:    extsw r5, r5
+; CHECK-NEXT:    sub r3, r3, r5
 ; CHECK-NEXT:    addi r6, r3, 5
 ; CHECK-NEXT:    clrldi r3, r4, 32
-; CHECK-NEXT:    extsw r5, r5
 ; CHECK-NEXT:    mtctr r3
 ; CHECK-NEXT:    li r3, 0
 ; CHECK-NEXT:    .p2align 5
 ; CHECK-NEXT:  .LBB0_2: # %for.body
 ; CHECK-NEXT:    #
-; CHECK-NEXT:    ld r4, 0(r6)
+; CHECK-NEXT:    ldux r4, r6, r5
 ; CHECK-NEXT:    add r3, r4, r3
 ; CHECK-NEXT:    ld r4, 4(r6)
-; CHECK-NEXT:    add r6, r6, r5
 ; CHECK-NEXT:    add r3, r3, r4
 ; CHECK-NEXT:    bdnz .LBB0_2
 ; CHECK-NEXT:  # %bb.3: # %for.cond.cleanup
@@ -85,18 +85,17 @@
 ; CHECK-NEXT:    cmpwi r4, 1
 ; CHECK-NEXT:    blt cr0, .LBB1_4
 ; CHECK-NEXT:  # %bb.1: # %for.body.preheader
+; CHECK-NEXT:    extsw r5, r5
+; CHECK-NEXT:    sub r3, r3, r5
 ; CHECK-NEXT:    addi r6, r3, 1000
 ; CHECK-NEXT:    clrldi r3, r4, 32
-; CHECK-NEXT:    extsw r5, r5
-; CHECK-NEXT:    li r4, 0
 ; CHECK-NEXT:    mtctr r3
 ; CHECK-NEXT:    li r3, 0
 ; CHECK-NEXT:    .p2align 4
 ; CHECK-NEXT:  .LBB1_2: # %for.body
 ; CHECK-NEXT:    #
-; CHECK-NEXT:    lbzx r7, r6, r4
-; CHECK-NEXT:    add r4, r4, r5
-; CHECK-NEXT:    add r3, r7, r3
+; CHECK-NEXT:    lbzux r4, r6, r5
+; CHECK-NEXT:    add r3, r4, r3
 ; CHECK-NEXT:    bdnz .LBB1_2
 ; CHECK-NEXT:  # %bb.3: # %for.cond.cleanup
 ; CHECK-NEXT:    clrldi r3, r3, 56