LAA: check nusw on GEP in place of inbounds

llvm/lib/Analysis/LoopAccessAnalysis.cpp

@@ -1412,9 +1412,9 @@ static bool isNoWrapAddRec(Value *Ptr, const SCEVAddRecExpr *AR,
   // Look through the potentially overflowing instruction to try to prove
   // non-wrapping for the *specific* value of Ptr.
 
-  // The arithmetic implied by an inbounds GEP can't overflow.
+  // The arithmetic implied by an nusw GEP can't overflow.
   const auto *GEP = dyn_cast<GetElementPtrInst>(Ptr);
-  if (!GEP || !GEP->isInBounds())
+  if (!GEP || !GEP->hasNoUnsignedSignedWrap())
     return false;
 
   // Make sure there is only one non-const index and analyze that.
@@ -1516,12 +1516,12 @@ llvm::getPtrStride(PredicatedScalarEvolution &PSE, Type *AccessTy, Value *Ptr,
   if (isNoWrapAddRec(Ptr, AR, PSE, Lp))
     return Stride;
 
-  // An inbounds getelementptr that is a AddRec with a unit stride
+  // An nusw getelementptr that is a AddRec with a unit stride
   // cannot wrap per definition.  If it did, the result would be poison
   // and any memory access dependent on it would be immediate UB
   // when executed.
   if (auto *GEP = dyn_cast<GetElementPtrInst>(Ptr);
-      GEP && GEP->isInBounds() && (Stride == 1 || Stride == -1))
+      GEP && GEP->hasNoUnsignedSignedWrap() && (Stride == 1 || Stride == -1))
     return Stride;
 
   // If the null pointer is undefined, then a access sequence which would

llvm/test/Analysis/LoopAccessAnalysis/symbolic-stride.ll

@@ -48,6 +48,51 @@ exit:                                          ; preds = %loop
   ret void
 }
 
+; A forwarding in the presence of symbolic strides,
+; with nusw instead of inbounds on the GEPs.
+define void @single_stride_nusw(ptr noalias %A, ptr noalias %B, i64 %N, i64 %stride) {
+; CHECK-LABEL: 'single_stride_nusw'
+; CHECK-NEXT:    loop:
+; CHECK-NEXT:      Report: unsafe dependent memory operations in loop. Use #pragma clang loop distribute(enable) to allow loop distribution to attempt to isolate the offending operations into a separate loop
+; CHECK-NEXT:  Backward loop carried data dependence.
+; CHECK-NEXT:      Dependences:
+; CHECK-NEXT:        Backward:
+; CHECK-NEXT:            %load = load i32, ptr %gep.A, align 4 ->
+; CHECK-NEXT:            store i32 %add, ptr %gep.A.next, align 4
+; CHECK-EMPTY:
+; CHECK-NEXT:      Run-time memory checks:
+; CHECK-NEXT:      Grouped accesses:
+; CHECK-EMPTY:
+; CHECK-NEXT:      Non vectorizable stores to invariant address were not found in loop.
+; CHECK-NEXT:      SCEV assumptions:
+; CHECK-NEXT:      Equal predicate: %stride == 1
+; CHECK-EMPTY:
+; CHECK-NEXT:      Expressions re-written:
+; CHECK-NEXT:      [PSE] %gep.A = getelementptr nusw i32, ptr %A, i64 %mul:
+; CHECK-NEXT:        {%A,+,(4 * %stride)}<%loop>
+; CHECK-NEXT:        --> {%A,+,4}<%loop>
+;
+entry:
+  br label %loop
+
+loop:
+  %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
+  %mul = mul i64 %iv, %stride
+  %gep.A = getelementptr nusw i32, ptr %A, i64 %mul
+  %load = load i32, ptr %gep.A, align 4
+  %gep.B = getelementptr nusw i32, ptr %B, i64 %iv
+  %load_1 = load i32, ptr %gep.B, align 4
+  %add = add i32 %load_1, %load
+  %iv.next = add nuw nsw i64 %iv, 1
+  %gep.A.next = getelementptr nusw i32, ptr %A, i64 %iv.next
+  store i32 %add, ptr %gep.A.next, align 4
+  %exitcond = icmp eq i64 %iv.next, %N
+  br i1 %exitcond, label %exit, label %loop
+
+exit:                                          ; preds = %loop
+  ret void
+}
+
 ; Similar to @single_stride, but with struct types.
 define void @single_stride_struct(ptr noalias %A, ptr noalias %B, i64 %N, i64 %stride) {
 ; CHECK-LABEL: 'single_stride_struct'