[SeparateConstOffsetFromGEP] Support multiple indices in reorderGEP (llvm#92339)

The code was essentially already ready to handle multiple indices -- we
only need to adjust the non-negative index check to check all indices,
instead of only the first one.

Change-Id: Icf2ccbd3efea42efd60b6ce47af1e253d104ae60

Author: nikic

llvm/lib/Transforms/Scalar/SeparateConstOffsetFromGEP.cpp

@@ -977,14 +977,9 @@ SeparateConstOffsetFromGEP::lowerToArithmetics(GetElementPtrInst *Variadic,
 
 bool SeparateConstOffsetFromGEP::reorderGEP(GetElementPtrInst *GEP,
                                             TargetTransformInfo &TTI) {
-  if (GEP->getNumIndices() != 1)
-    return false;
-
   auto PtrGEP = dyn_cast<GetElementPtrInst>(GEP->getPointerOperand());
   if (!PtrGEP)
     return false;
-  if (PtrGEP->getNumIndices() != 1)
-    return false;
 
   bool NestedNeedsExtraction;
   int64_t NestedByteOffset =
@@ -1002,14 +997,12 @@ bool SeparateConstOffsetFromGEP::reorderGEP(GetElementPtrInst *GEP,
   bool PtrGEPInBounds = PtrGEP->isInBounds();
   bool IsChainInBounds = GEPInBounds && PtrGEPInBounds;
   if (IsChainInBounds) {
-    auto GEPIdx = GEP->indices().begin();
-    auto KnownGEPIdx = computeKnownBits(GEPIdx->get(), *DL);
-    IsChainInBounds &= KnownGEPIdx.isNonNegative();
-    if (IsChainInBounds) {
-      auto PtrGEPIdx = PtrGEP->indices().begin();
-      auto KnownPtrGEPIdx = computeKnownBits(PtrGEPIdx->get(), *DL);
-      IsChainInBounds &= KnownPtrGEPIdx.isNonNegative();
-    }
+    auto IsKnownNonNegative = [this](Value *V) {
+      return isKnownNonNegative(V, *DL);
+    };
+    IsChainInBounds &= all_of(GEP->indices(), IsKnownNonNegative);
+    if (IsChainInBounds)
+      IsChainInBounds &= all_of(PtrGEP->indices(), IsKnownNonNegative);
   }
 
   IRBuilder<> Builder(GEP);

llvm/test/Transforms/SeparateConstOffsetFromGEP/AMDGPU/reorder-gep.ll

@@ -284,3 +284,29 @@ entry:
   %idx3 = getelementptr i8, ptr addrspace(3) %const3, i64 %in.idx2
   ret void
 }
+
+define void @multiple_index_maybe_neg(ptr %in.ptr, i64 %in.idx1) {
+; CHECK-LABEL: define void @multiple_index_maybe_neg(
+; CHECK-SAME: ptr [[IN_PTR:%.*]], i64 [[IN_IDX1:%.*]]) #[[ATTR0]] {
+; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr [2 x <2 x i8>], ptr [[IN_PTR]], i64 0, i64 [[IN_IDX1]]
+; CHECK-NEXT:    [[TMP2:%.*]] = getelementptr [2 x <2 x i8>], ptr [[TMP1]], i64 0, i64 1
+; CHECK-NEXT:    ret void
+;
+  %const1 = getelementptr inbounds [2 x <2 x i8>], ptr %in.ptr, i64 0, i64 1
+  %idx1 = getelementptr inbounds [2 x <2 x i8>], ptr %const1, i64 0, i64 %in.idx1
+  ret void
+}
+
+define void @multiple_index_nonneg(ptr %in.ptr, i64 %in.idx1) {
+; CHECK-LABEL: define void @multiple_index_nonneg(
+; CHECK-SAME: ptr [[IN_PTR:%.*]], i64 [[IN_IDX1:%.*]]) #[[ATTR0]] {
+; CHECK-NEXT:    [[IN_IDX1_NNEG:%.*]] = and i64 [[IN_IDX1]], 9223372036854775807
+; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr inbounds [2 x <2 x i8>], ptr [[IN_PTR]], i64 0, i64 [[IN_IDX1_NNEG]]
+; CHECK-NEXT:    [[TMP2:%.*]] = getelementptr inbounds [2 x <2 x i8>], ptr [[TMP1]], i64 0, i64 1
+; CHECK-NEXT:    ret void
+;
+  %in.idx1.nneg = and i64 %in.idx1, 9223372036854775807
+  %const1 = getelementptr inbounds [2 x <2 x i8>], ptr %in.ptr, i64 0, i64 1
+  %idx1 = getelementptr inbounds [2 x <2 x i8>], ptr %const1, i64 0, i64 %in.idx1.nneg
+  ret void
+}