[InstCombine] Preserve all gep flags in gep of exact div fold

Author: nikic

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

@@ -2941,10 +2941,9 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
                                  m_SpecificInt(countr_zero(TyAllocSize)))))) ||
             match(GEP.getOperand(1),
                   m_Exact(m_IDiv(m_Value(V), m_SpecificInt(TyAllocSize))))) {
-          GetElementPtrInst *NewGEP = GetElementPtrInst::Create(
-              Builder.getInt8Ty(), GEP.getPointerOperand(), V);
-          NewGEP->setIsInBounds(GEP.isInBounds());
-          return NewGEP;
+          return GetElementPtrInst::Create(Builder.getInt8Ty(),
+                                           GEP.getPointerOperand(), V,
+                                           GEP.getNoWrapFlags());
         }
       }
     }

llvm/test/Transforms/InstCombine/getelementptr.ll

@@ -1566,6 +1566,16 @@ define ptr @gep_sdiv_inbounds(ptr %p, i64 %off) {
   ret ptr %ptr
 }
 
+define ptr @gep_sdiv_nuw(ptr %p, i64 %off) {
+; CHECK-LABEL: @gep_sdiv_nuw(
+; CHECK-NEXT:    [[PTR:%.*]] = getelementptr nuw i8, ptr [[P:%.*]], i64 [[OFF:%.*]]
+; CHECK-NEXT:    ret ptr [[PTR]]
+;
+  %index = sdiv exact i64 %off, 7
+  %ptr = getelementptr nuw %struct.C, ptr %p, i64 %index
+  ret ptr %ptr
+}
+
 define ptr @gep_ashr(ptr %p, i64 %off) {
 ; CHECK-LABEL: @gep_ashr(
 ; CHECK-NEXT:    [[PTR:%.*]] = getelementptr i8, ptr [[P:%.*]], i64 [[OFF:%.*]]