[ConstraintElim] Switch to getBaseObjectSize

Author: dtcxzyw

llvm/lib/Transforms/Scalar/ConstraintElimination.cpp

@@ -1131,9 +1131,9 @@ static bool getConstraintFromMemoryAccess(GetElementPtrInst &GEP,
   // Be conservative since we are not clear on whether an out of bounds access
   // to the padding is UB or not.
   Opts.RoundToAlign = true;
-  ObjectSizeOffsetVisitor Visitor(DL, &TLI, GEP.getContext(), Opts);
-  SizeOffsetAPInt Data = Visitor.compute(Offset.BasePtr);
-  if (!Data.bothKnown() || !Data.Offset.isZero())
+  std::optional<TypeSize> Size =
+      getBaseObjectSize(Offset.BasePtr, DL, &TLI, Opts);
+  if (!Size || Size->isScalable())
     return false;
 
   // Index * Scale + ConstOffset + AccessSize <= AllocSize
@@ -1142,9 +1142,10 @@ static bool getConstraintFromMemoryAccess(GetElementPtrInst &GEP,
   // value for Index.
   uint64_t BitWidth = Offset.ConstantOffset.getBitWidth();
   auto &[Index, Scale] = Offset.VariableOffsets.front();
-  APInt MaxIndex =
-      (Data.Size - APInt(BitWidth, AccessSize) - Offset.ConstantOffset)
-          .udiv(Scale);
+  APInt MaxIndex = (APInt(BitWidth, Size->getFixedValue() - AccessSize,
+                          /*isSigned=*/false, /*implicitTrunc=*/true) -
+                    Offset.ConstantOffset)
+                       .udiv(Scale);
   Pred = ICmpInst::ICMP_ULE;
   A = Index;
   B = ConstantInt::get(Index->getType(), MaxIndex);

llvm/test/Transforms/ConstraintElimination/implied-by-bounded-memory-access.ll

@@ -26,6 +26,25 @@ define i8 @load_global(i64 %idx) {
   ret i8 %add
 }
 
+define i8 @load_global_const_offset(i64 %idx) {
+; CHECK-LABEL: define i8 @load_global_const_offset(
+; CHECK-SAME: i64 [[IDX:%.*]]) {
+; CHECK-NEXT:    [[GEP1:%.*]] = getelementptr nuw i8, ptr @g, i64 1
+; CHECK-NEXT:    [[GEP:%.*]] = getelementptr nuw i8, ptr [[GEP1]], i64 [[IDX]]
+; CHECK-NEXT:    [[LOAD:%.*]] = load i8, ptr [[GEP]], align 1
+; CHECK-NEXT:    [[ZEXT:%.*]] = zext i1 true to i8
+; CHECK-NEXT:    [[ADD:%.*]] = add i8 [[LOAD]], [[ZEXT]]
+; CHECK-NEXT:    ret i8 [[ADD]]
+;
+  %gep1 = getelementptr nuw i8, ptr @g, i64 1
+  %gep = getelementptr nuw i8, ptr %gep1, i64 %idx
+  %load = load i8, ptr %gep
+  %cmp = icmp ult i64 %idx, 4
+  %zext = zext i1 %cmp to i8
+  %add = add i8 %load, %zext
+  ret i8 %add
+}
+
 define i8 @load_global_atomic(i64 %idx) {
 ; CHECK-LABEL: define i8 @load_global_atomic(
 ; CHECK-SAME: i64 [[IDX:%.*]]) {