[InstCombine] Preserve all flags in select of gep fold

Preserve the flag intersection.

Author: nikic

llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp

@@ -486,9 +486,8 @@ Instruction *InstCombinerImpl::foldSelectOpOp(SelectInst &SI, Instruction *TI,
   if (auto *TGEP = dyn_cast<GetElementPtrInst>(TI)) {
     auto *FGEP = cast<GetElementPtrInst>(FI);
     Type *ElementType = TGEP->getSourceElementType();
-    return TGEP->isInBounds() && FGEP->isInBounds()
-               ? GetElementPtrInst::CreateInBounds(ElementType, Op0, {Op1})
-               : GetElementPtrInst::Create(ElementType, Op0, {Op1});
+    return GetElementPtrInst::Create(
+        ElementType, Op0, Op1, TGEP->getNoWrapFlags() & FGEP->getNoWrapFlags());
   }
   llvm_unreachable("Expected BinaryOperator or GEP");
   return nullptr;

llvm/test/Transforms/InstCombine/opaque-ptr.ll

@@ -639,6 +639,30 @@ define ptr @select_of_gep(i1 %c, ptr %p) {
   ret ptr %s
 }
 
+define ptr @select_of_gep_flags_1(i1 %c, ptr %p) {
+; CHECK-LABEL: @select_of_gep_flags_1(
+; CHECK-NEXT:    [[S_V:%.*]] = select i1 [[C:%.*]], i64 4, i64 8
+; CHECK-NEXT:    [[S:%.*]] = getelementptr nusw i8, ptr [[P:%.*]], i64 [[S_V]]
+; CHECK-NEXT:    ret ptr [[S]]
+;
+  %gep1 = getelementptr inbounds i32, ptr %p, i64 1
+  %gep2 = getelementptr nusw nuw i32, ptr %p, i64 2
+  %s = select i1 %c, ptr %gep1, ptr %gep2
+  ret ptr %s
+}
+
+define ptr @select_of_gep_flags_2(i1 %c, ptr %p) {
+; CHECK-LABEL: @select_of_gep_flags_2(
+; CHECK-NEXT:    [[S_V:%.*]] = select i1 [[C:%.*]], i64 4, i64 8
+; CHECK-NEXT:    [[S:%.*]] = getelementptr nuw i8, ptr [[P:%.*]], i64 [[S_V]]
+; CHECK-NEXT:    ret ptr [[S]]
+;
+  %gep1 = getelementptr nuw i32, ptr %p, i64 1
+  %gep2 = getelementptr nusw nuw i32, ptr %p, i64 2
+  %s = select i1 %c, ptr %gep1, ptr %gep2
+  ret ptr %s
+}
+
 define ptr @select_of_gep_different_type(i1 %c, ptr %p) {
 ; CHECK-LABEL: @select_of_gep_different_type(
 ; CHECK-NEXT:    [[S_V:%.*]] = select i1 [[C:%.*]], i64 4, i64 16