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[Loads] Check for overflow when adding MaxPtrDiff + Offset. #11422

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Merged
merged 1 commit into from
Sep 16, 2025
Merged

[Loads] Check for overflow when adding MaxPtrDiff + Offset. #11422

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5 changes: 4 additions & 1 deletion llvm/lib/Analysis/Loads.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -382,7 +382,10 @@ bool llvm::isDereferenceableAndAlignedInLoop(
if (Offset->getAPInt().urem(Alignment.value()) != 0)
return false;

AccessSize = MaxPtrDiff + Offset->getAPInt();
bool Overflow = false;
AccessSize = MaxPtrDiff.uadd_ov(Offset->getAPInt(), Overflow);
if (Overflow)
return false;
AccessSizeSCEV = SE.getAddExpr(PtrDiff, Offset);
Base = NewBase->getValue();
} else
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130 changes: 130 additions & 0 deletions llvm/test/Transforms/LoopVectorize/load-deref-pred-align.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -753,3 +753,133 @@ exit:
call void @llvm.memcpy.p0.p0.i64(ptr %dest, ptr %local_dest, i64 1024, i1 false)
ret void
}

define void @adding_offset_overflows(i32 %n, ptr %A) {
; CHECK-LABEL: @adding_offset_overflows(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[B:%.*]] = alloca [62 x i32], align 4
; CHECK-NEXT: [[C:%.*]] = alloca [144 x i32], align 4
; CHECK-NEXT: call void @init(ptr [[B]])
; CHECK-NEXT: call void @init(ptr [[C]])
; CHECK-NEXT: [[PRE:%.*]] = icmp slt i32 [[N:%.*]], 1
; CHECK-NEXT: br i1 [[PRE]], label [[EXIT:%.*]], label [[PH:%.*]]
; CHECK: ph:
; CHECK-NEXT: [[WIDE_TRIP_COUNT:%.*]] = zext i32 [[N]] to i64
; CHECK-NEXT: [[TMP0:%.*]] = add nsw i64 [[WIDE_TRIP_COUNT]], -1
; CHECK-NEXT: [[MIN_ITERS_CHECK:%.*]] = icmp ult i64 [[TMP0]], 2
; CHECK-NEXT: br i1 [[MIN_ITERS_CHECK]], label [[SCALAR_PH:%.*]], label [[VECTOR_PH:%.*]]
; CHECK: vector.ph:
; CHECK-NEXT: [[N_MOD_VF:%.*]] = urem i64 [[TMP0]], 2
; CHECK-NEXT: [[N_VEC:%.*]] = sub i64 [[TMP0]], [[N_MOD_VF]]
; CHECK-NEXT: [[TMP1:%.*]] = add i64 1, [[N_VEC]]
; CHECK-NEXT: br label [[VECTOR_BODY:%.*]]
; CHECK: vector.body:
; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[PRED_STORE_CONTINUE3:%.*]] ]
; CHECK-NEXT: [[OFFSET_IDX:%.*]] = add i64 1, [[INDEX]]
; CHECK-NEXT: [[TMP2:%.*]] = getelementptr i32, ptr [[A:%.*]], i64 [[OFFSET_IDX]]
; CHECK-NEXT: [[TMP23:%.*]] = getelementptr i32, ptr [[TMP2]], i32 0
; CHECK-NEXT: [[WIDE_LOAD:%.*]] = load <2 x i32>, ptr [[TMP23]], align 4
; CHECK-NEXT: [[TMP3:%.*]] = icmp ne <2 x i32> [[WIDE_LOAD]], zeroinitializer
; CHECK-NEXT: [[TMP4:%.*]] = extractelement <2 x i1> [[TMP3]], i32 0
; CHECK-NEXT: br i1 [[TMP4]], label [[PRED_LOAD_IF:%.*]], label [[PRED_LOAD_CONTINUE:%.*]]
; CHECK: pred.load.if:
; CHECK-NEXT: [[TMP15:%.*]] = add i64 [[OFFSET_IDX]], 0
; CHECK-NEXT: [[TMP16:%.*]] = getelementptr i32, ptr [[B]], i64 [[TMP15]]
; CHECK-NEXT: [[TMP17:%.*]] = load i32, ptr [[TMP16]], align 4
; CHECK-NEXT: [[TMP18:%.*]] = insertelement <2 x i32> poison, i32 [[TMP17]], i32 0
; CHECK-NEXT: br label [[PRED_LOAD_CONTINUE]]
; CHECK: pred.load.continue:
; CHECK-NEXT: [[TMP19:%.*]] = phi <2 x i32> [ poison, [[VECTOR_BODY]] ], [ [[TMP18]], [[PRED_LOAD_IF]] ]
; CHECK-NEXT: [[TMP20:%.*]] = extractelement <2 x i1> [[TMP3]], i32 1
; CHECK-NEXT: br i1 [[TMP20]], label [[PRED_LOAD_IF1:%.*]], label [[PRED_LOAD_CONTINUE2:%.*]]
; CHECK: pred.load.if1:
; CHECK-NEXT: [[TMP21:%.*]] = add i64 [[OFFSET_IDX]], 1
; CHECK-NEXT: [[TMP22:%.*]] = getelementptr i32, ptr [[B]], i64 [[TMP21]]
; CHECK-NEXT: [[TMP13:%.*]] = load i32, ptr [[TMP22]], align 4
; CHECK-NEXT: [[TMP14:%.*]] = insertelement <2 x i32> [[TMP19]], i32 [[TMP13]], i32 1
; CHECK-NEXT: br label [[PRED_LOAD_CONTINUE2]]
; CHECK: pred.load.continue2:
; CHECK-NEXT: [[WIDE_LOAD1:%.*]] = phi <2 x i32> [ [[TMP19]], [[PRED_LOAD_CONTINUE]] ], [ [[TMP14]], [[PRED_LOAD_IF1]] ]
; CHECK-NEXT: [[TMP5:%.*]] = sext <2 x i32> [[WIDE_LOAD1]] to <2 x i64>
; CHECK-NEXT: [[TMP6:%.*]] = extractelement <2 x i1> [[TMP3]], i32 0
; CHECK-NEXT: br i1 [[TMP6]], label [[PRED_STORE_IF:%.*]], label [[PRED_STORE_CONTINUE:%.*]]
; CHECK: pred.store.if:
; CHECK-NEXT: [[TMP7:%.*]] = extractelement <2 x i64> [[TMP5]], i32 0
; CHECK-NEXT: [[TMP8:%.*]] = getelementptr i32, ptr [[C]], i64 [[TMP7]]
; CHECK-NEXT: store i32 0, ptr [[TMP8]], align 4
; CHECK-NEXT: br label [[PRED_STORE_CONTINUE]]
; CHECK: pred.store.continue:
; CHECK-NEXT: [[TMP9:%.*]] = extractelement <2 x i1> [[TMP3]], i32 1
; CHECK-NEXT: br i1 [[TMP9]], label [[PRED_STORE_IF2:%.*]], label [[PRED_STORE_CONTINUE3]]
; CHECK: pred.store.if3:
; CHECK-NEXT: [[TMP10:%.*]] = extractelement <2 x i64> [[TMP5]], i32 1
; CHECK-NEXT: [[TMP11:%.*]] = getelementptr i32, ptr [[C]], i64 [[TMP10]]
; CHECK-NEXT: store i32 0, ptr [[TMP11]], align 4
; CHECK-NEXT: br label [[PRED_STORE_CONTINUE3]]
; CHECK: pred.store.continue4:
; CHECK-NEXT: [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 2
; CHECK-NEXT: [[TMP12:%.*]] = icmp eq i64 [[INDEX_NEXT]], [[N_VEC]]
; CHECK-NEXT: br i1 [[TMP12]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP16:![0-9]+]]
; CHECK: middle.block:
; CHECK-NEXT: [[CMP_N:%.*]] = icmp eq i64 [[TMP0]], [[N_VEC]]
; CHECK-NEXT: br i1 [[CMP_N]], label [[EXIT_LOOPEXIT:%.*]], label [[SCALAR_PH]]
; CHECK: scalar.ph:
; CHECK-NEXT: [[BC_RESUME_VAL:%.*]] = phi i64 [ [[TMP1]], [[MIDDLE_BLOCK]] ], [ 1, [[PH]] ]
; CHECK-NEXT: br label [[LOOP_HEADER:%.*]]
; CHECK: loop.header:
; CHECK-NEXT: [[IV:%.*]] = phi i64 [ [[BC_RESUME_VAL]], [[SCALAR_PH]] ], [ [[IV_NEXT:%.*]], [[LOOP_LATCH:%.*]] ]
; CHECK-NEXT: [[GEP_A:%.*]] = getelementptr i32, ptr [[A]], i64 [[IV]]
; CHECK-NEXT: [[L_A:%.*]] = load i32, ptr [[GEP_A]], align 4
; CHECK-NEXT: [[C_1:%.*]] = icmp eq i32 [[L_A]], 0
; CHECK-NEXT: br i1 [[C_1]], label [[LOOP_LATCH]], label [[IF_THEN:%.*]]
; CHECK: if.then:
; CHECK-NEXT: [[GEP_B:%.*]] = getelementptr i32, ptr [[B]], i64 [[IV]]
; CHECK-NEXT: [[L_IDX:%.*]] = load i32, ptr [[GEP_B]], align 4
; CHECK-NEXT: [[IDX_EXT:%.*]] = sext i32 [[L_IDX]] to i64
; CHECK-NEXT: [[GEP_C:%.*]] = getelementptr i32, ptr [[C]], i64 [[IDX_EXT]]
; CHECK-NEXT: store i32 0, ptr [[GEP_C]], align 4
; CHECK-NEXT: br label [[LOOP_LATCH]]
; CHECK: loop.latch:
; CHECK-NEXT: [[IV_NEXT]] = add i64 [[IV]], 1
; CHECK-NEXT: [[EC:%.*]] = icmp eq i64 [[IV_NEXT]], [[WIDE_TRIP_COUNT]]
; CHECK-NEXT: br i1 [[EC]], label [[EXIT_LOOPEXIT]], label [[LOOP_HEADER]], !llvm.loop [[LOOP17:![0-9]+]]
; CHECK: exit.loopexit:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
entry:
%B = alloca [62 x i32], align 4
%C = alloca [144 x i32], align 4
call void @init(ptr %B)
call void @init(ptr %C)
%pre = icmp slt i32 %n, 1
br i1 %pre, label %exit, label %ph

ph:
%wide.trip.count = zext i32 %n to i64
br label %loop.header

loop.header:
%iv = phi i64 [ 1, %ph ], [ %iv.next, %loop.latch ]
%gep.A = getelementptr i32, ptr %A, i64 %iv
%l.A = load i32, ptr %gep.A, align 4
%c.1 = icmp eq i32 %l.A, 0
br i1 %c.1, label %loop.latch, label %if.then

if.then:
%gep.B = getelementptr i32, ptr %B, i64 %iv
%l.idx = load i32, ptr %gep.B, align 4
%idx.ext = sext i32 %l.idx to i64
%gep.C = getelementptr i32, ptr %C, i64 %idx.ext
store i32 0, ptr %gep.C, align 4
br label %loop.latch

loop.latch:
%iv.next = add i64 %iv, 1
%ec = icmp eq i64 %iv.next, %wide.trip.count
br i1 %ec, label %exit, label %loop.header

exit:
ret void
}