[InstCombine] Preserve all gep flags in another select of gep fold

Author: nikic

llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp

@@ -3712,9 +3712,8 @@ Instruction *InstCombinerImpl::visitSelectInst(SelectInst &SI) {
       std::swap(NewT, NewF);
     Value *NewSI =
         Builder.CreateSelect(CondVal, NewT, NewF, SI.getName() + ".idx", &SI);
-    if (Gep->isInBounds())
-      return GetElementPtrInst::CreateInBounds(ElementType, Ptr, {NewSI});
-    return GetElementPtrInst::Create(ElementType, Ptr, {NewSI});
+    return GetElementPtrInst::Create(ElementType, Ptr, NewSI,
+                                     Gep->getNoWrapFlags());
   };
   if (auto *TrueGep = dyn_cast<GetElementPtrInst>(TrueVal))
     if (auto *NewGep = SelectGepWithBase(TrueGep, FalseVal, false))

llvm/test/Transforms/InstCombine/select-gep.ll

@@ -84,6 +84,32 @@ define ptr @test2a(ptr %p, i64 %x, i64 %y) {
   ret ptr %select
 }
 
+define ptr @test2a_nusw(ptr %p, i64 %x, i64 %y) {
+; CHECK-LABEL: @test2a_nusw(
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt i64 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[SELECT_IDX:%.*]] = select i1 [[CMP]], i64 [[X]], i64 0
+; CHECK-NEXT:    [[SELECT:%.*]] = getelementptr nusw i32, ptr [[P:%.*]], i64 [[SELECT_IDX]]
+; CHECK-NEXT:    ret ptr [[SELECT]]
+;
+  %gep = getelementptr nusw i32, ptr %p, i64 %x
+  %cmp = icmp ugt i64 %x, %y
+  %select = select i1 %cmp, ptr %gep, ptr %p
+  ret ptr %select
+}
+
+define ptr @test2a_nuw(ptr %p, i64 %x, i64 %y) {
+; CHECK-LABEL: @test2a_nuw(
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt i64 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[SELECT_IDX:%.*]] = select i1 [[CMP]], i64 [[X]], i64 0
+; CHECK-NEXT:    [[SELECT:%.*]] = getelementptr nuw i32, ptr [[P:%.*]], i64 [[SELECT_IDX]]
+; CHECK-NEXT:    ret ptr [[SELECT]]
+;
+  %gep = getelementptr nuw i32, ptr %p, i64 %x
+  %cmp = icmp ugt i64 %x, %y
+  %select = select i1 %cmp, ptr %gep, ptr %p
+  ret ptr %select
+}
+
 ; PR50183
 define ptr @test2b(ptr %p, i64 %x, i64 %y) {
 ; CHECK-LABEL: @test2b(