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[LoopIdiom] Fix a DL-related crash in optimizeCRCLoop #161509

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Oct 1, 2025
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[LoopIdiom] Fix a DL-related crash in optimizeCRCLoop #161509

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e323dae
[LoopIdom] Add pre-commit crash for crc with DL
artagnon Oct 1, 2025
727ef42
[LoopIdiom] Fix a DL-related crash in optimizeCRCLoop
artagnon Oct 1, 2025
c0ef806
[LoopIdiom] Strip exotic scenario
artagnon Oct 1, 2025
be7f4c8
[LoopIdiom] Fix missed name
artagnon Oct 1, 2025
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17 changes: 9 additions & 8 deletions llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1545,6 +1545,12 @@ bool LoopIdiomRecognize::optimizeCRCLoop(const PolynomialInfo &Info) {
if (TT.getArch() == Triple::hexagon)
return false;

// Check that the DataLayout allows us to index into the new 256-entry CRC
// table.
Type *IdxTy = SE->getDataLayout().getIndexType(M.getContext(), 0);
if (IdxTy->getIntegerBitWidth() < 8)
return false;

// First, create a new GlobalVariable corresponding to the
// Sarwate-lookup-table.
Type *CRCTy = Info.LHS->getType();
Expand Down Expand Up @@ -1598,11 +1604,8 @@ bool LoopIdiomRecognize::optimizeCRCLoop(const PolynomialInfo &Info) {
// crc = (crc << 8) ^ tbl[(iv'th byte of data) ^ (top byte of crc)]
{
auto LoByte = [](IRBuilderBase &Builder, Value *Op, const Twine &Name) {
Type *OpTy = Op->getType();
unsigned OpBW = OpTy->getIntegerBitWidth();
return OpBW > 8
? Builder.CreateAnd(Op, ConstantInt::get(OpTy, 0XFF), Name)
: Op;
return Builder.CreateZExtOrTrunc(
Op, IntegerType::getInt8Ty(Op->getContext()));
};
auto HiIdx = [LoByte, CRCBW](IRBuilderBase &Builder, Value *Op,
const Twine &Name) {
Expand Down Expand Up @@ -1654,9 +1657,7 @@ bool LoopIdiomRecognize::optimizeCRCLoop(const PolynomialInfo &Info) {
: LoByte(Builder, Indexer, "indexer.lo");

// Always index into a GEP using the index type.
Indexer = Builder.CreateZExt(
Indexer, SE->getDataLayout().getIndexType(GV->getType()),
"indexer.ext");
Indexer = Builder.CreateZExt(Indexer, IdxTy, "indexer.ext");

// CRCTableLd = CRCTable[(iv'th byte of data) ^ (top|bottom) byte of CRC].
Value *CRCTableGEP =
Expand Down
70 changes: 70 additions & 0 deletions llvm/test/Transforms/LoopIdiom/cyclic-redundancy-check-dl.ll
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@@ -0,0 +1,70 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals all --version 6
; RUN: opt -passes=loop-idiom -data-layout="p:16:16" -S %s | FileCheck %s --check-prefix=CHECK-i16
; RUN: opt -passes=loop-idiom -data-layout="p:1:8" -S %s | FileCheck %s --check-prefix=CHECK-i1

;.
; CHECK-i16: @.crctable = private constant [256 x i32] zeroinitializer
;.
define void @test_with_dl() {
; CHECK-i16-LABEL: define void @test_with_dl() {
; CHECK-i16-NEXT: [[ENTRY:.*]]:
; CHECK-i16-NEXT: br label %[[PH:.*]]
; CHECK-i16: [[PH_LOOPEXIT:.*]]:
; CHECK-i16-NEXT: [[CRC_NEXT_LCSSA:%.*]] = phi i32 [ [[CRC_NEXT3:%.*]], %[[LOOP:.*]] ]
; CHECK-i16-NEXT: br label %[[PH]]
; CHECK-i16: [[PH]]:
; CHECK-i16-NEXT: [[CRC_USE:%.*]] = phi i32 [ 0, %[[ENTRY]] ], [ [[CRC_NEXT_LCSSA]], %[[PH_LOOPEXIT]] ]
; CHECK-i16-NEXT: br label %[[LOOP]]
; CHECK-i16: [[LOOP]]:
; CHECK-i16-NEXT: [[IV:%.*]] = phi i16 [ 0, %[[PH]] ], [ [[IV_NEXT:%.*]], %[[LOOP]] ]
; CHECK-i16-NEXT: [[CRC2:%.*]] = phi i32 [ 0, %[[PH]] ], [ [[CRC_NEXT3]], %[[LOOP]] ]
; CHECK-i16-NEXT: [[TMP0:%.*]] = trunc i32 [[CRC2]] to i8
; CHECK-i16-NEXT: [[INDEXER_EXT:%.*]] = zext i8 [[TMP0]] to i16
; CHECK-i16-NEXT: [[TBL_PTRADD:%.*]] = getelementptr inbounds i32, ptr @.crctable, i16 [[INDEXER_EXT]]
; CHECK-i16-NEXT: [[TBL_LD:%.*]] = load i32, ptr [[TBL_PTRADD]], align 4
; CHECK-i16-NEXT: [[CRC_LE_SHIFT:%.*]] = lshr i32 [[CRC2]], 8
; CHECK-i16-NEXT: [[CRC_NEXT3]] = xor i32 [[CRC_LE_SHIFT]], [[TBL_LD]]
; CHECK-i16-NEXT: [[IV_NEXT]] = add i16 [[IV]], 1
; CHECK-i16-NEXT: [[EXIT_COND1:%.*]] = icmp ne i16 [[IV]], 0
; CHECK-i16-NEXT: br i1 [[EXIT_COND1]], label %[[LOOP]], label %[[PH_LOOPEXIT]]
;
; CHECK-i1-LABEL: define void @test_with_dl() {
; CHECK-i1-NEXT: [[ENTRY:.*]]:
; CHECK-i1-NEXT: br label %[[PH:.*]]
; CHECK-i1: [[PH_LOOPEXIT:.*]]:
; CHECK-i1-NEXT: [[CRC_NEXT_LCSSA:%.*]] = phi i32 [ [[CRC_NEXT:%.*]], %[[LOOP:.*]] ]
; CHECK-i1-NEXT: br label %[[PH]]
; CHECK-i1: [[PH]]:
; CHECK-i1-NEXT: [[CRC_USE:%.*]] = phi i32 [ 0, %[[ENTRY]] ], [ [[CRC_NEXT_LCSSA]], %[[PH_LOOPEXIT]] ]
; CHECK-i1-NEXT: br label %[[LOOP]]
; CHECK-i1: [[LOOP]]:
; CHECK-i1-NEXT: [[IV:%.*]] = phi i16 [ 0, %[[PH]] ], [ [[IV_NEXT:%.*]], %[[LOOP]] ]
; CHECK-i1-NEXT: [[CRC:%.*]] = phi i32 [ 0, %[[PH]] ], [ [[CRC_NEXT]], %[[LOOP]] ]
; CHECK-i1-NEXT: [[LSHR_CRC_1:%.*]] = lshr i32 [[CRC]], 1
; CHECK-i1-NEXT: [[CRC_AND_1:%.*]] = and i32 [[CRC]], 1
; CHECK-i1-NEXT: [[SB_CHECK:%.*]] = icmp eq i32 [[CRC_AND_1]], 0
; CHECK-i1-NEXT: [[XOR:%.*]] = xor i32 [[LSHR_CRC_1]], 0
; CHECK-i1-NEXT: [[CRC_NEXT]] = select i1 [[SB_CHECK]], i32 [[LSHR_CRC_1]], i32 [[XOR]]
; CHECK-i1-NEXT: [[IV_NEXT]] = add i16 [[IV]], 1
; CHECK-i1-NEXT: [[EXIT_COND:%.*]] = icmp ult i16 [[IV]], 7
; CHECK-i1-NEXT: br i1 [[EXIT_COND]], label %[[LOOP]], label %[[PH_LOOPEXIT]]
;
entry:
br label %ph

ph:
%crc.use = phi i32 [ 0, %entry ], [ %crc.next, %loop ]
br label %loop

loop:
%iv = phi i16 [ 0, %ph ], [ %iv.next, %loop ]
%crc = phi i32 [ 0, %ph ], [ %crc.next, %loop ]
%lshr.crc.1 = lshr i32 %crc, 1
%crc.and.1 = and i32 %crc, 1
%sb.check = icmp eq i32 %crc.and.1, 0
%xor = xor i32 %lshr.crc.1, 0
%crc.next = select i1 %sb.check, i32 %lshr.crc.1, i32 %xor
%iv.next = add i16 %iv, 1
%exit.cond = icmp ult i16 %iv, 7
br i1 %exit.cond, label %loop, label %ph
}
24 changes: 12 additions & 12 deletions llvm/test/Transforms/LoopIdiom/cyclic-redundancy-check.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -118,8 +118,8 @@ define i16 @crc16.le.tc16(i16 %msg, i16 %checksum) {
; CHECK-NEXT: [[IV_INDEXER:%.*]] = zext i8 [[IV_BITS]] to i16
; CHECK-NEXT: [[DATA_INDEXER:%.*]] = lshr i16 [[MSG]], [[IV_INDEXER]]
; CHECK-NEXT: [[CRC_DATA_INDEXER:%.*]] = xor i16 [[DATA_INDEXER]], [[CRC2]]
; CHECK-NEXT: [[INDEXER_LO:%.*]] = and i16 [[CRC_DATA_INDEXER]], 255
; CHECK-NEXT: [[INDEXER_EXT:%.*]] = zext i16 [[INDEXER_LO]] to i64
; CHECK-NEXT: [[TMP0:%.*]] = trunc i16 [[CRC_DATA_INDEXER]] to i8
; CHECK-NEXT: [[INDEXER_EXT:%.*]] = zext i8 [[TMP0]] to i64
; CHECK-NEXT: [[TBL_PTRADD:%.*]] = getelementptr inbounds i16, ptr @.crctable.2, i64 [[INDEXER_EXT]]
; CHECK-NEXT: [[TBL_LD:%.*]] = load i16, ptr [[TBL_PTRADD]], align 2
; CHECK-NEXT: [[CRC_LE_SHIFT:%.*]] = lshr i16 [[CRC2]], 8
Expand Down Expand Up @@ -166,8 +166,8 @@ define i8 @crc8.le.tc16(i16 %msg, i8 %checksum) {
; CHECK-NEXT: [[DATA_INDEXER:%.*]] = lshr i16 [[MSG]], [[IV_INDEXER]]
; CHECK-NEXT: [[CRC_INDEXER_CAST:%.*]] = zext i8 [[CRC2]] to i16
; CHECK-NEXT: [[CRC_DATA_INDEXER:%.*]] = xor i16 [[DATA_INDEXER]], [[CRC_INDEXER_CAST]]
; CHECK-NEXT: [[INDEXER_LO:%.*]] = and i16 [[CRC_DATA_INDEXER]], 255
; CHECK-NEXT: [[INDEXER_EXT:%.*]] = zext i16 [[INDEXER_LO]] to i64
; CHECK-NEXT: [[TMP0:%.*]] = trunc i16 [[CRC_DATA_INDEXER]] to i8
; CHECK-NEXT: [[INDEXER_EXT:%.*]] = zext i8 [[TMP0]] to i64
; CHECK-NEXT: [[TBL_PTRADD:%.*]] = getelementptr inbounds i8, ptr @.crctable.3, i64 [[INDEXER_EXT]]
; CHECK-NEXT: [[TBL_LD]] = load i8, ptr [[TBL_PTRADD]], align 1
; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i8 [[IV]], 1
Expand Down Expand Up @@ -212,8 +212,8 @@ define i16 @crc16.be.tc8.crc.init.li(i16 %checksum, i8 %msg) {
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ 0, %[[ENTRY]] ], [ [[IV_NEXT:%.*]], %[[LOOP]] ]
; CHECK-NEXT: [[CRC2:%.*]] = phi i16 [ [[CRC_INIT]], %[[ENTRY]] ], [ [[CRC_NEXT3:%.*]], %[[LOOP]] ]
; CHECK-NEXT: [[INDEXER_HI:%.*]] = lshr i16 [[CRC2]], 8
; CHECK-NEXT: [[INDEXER_HI_LO_BYTE:%.*]] = and i16 [[INDEXER_HI]], 255
; CHECK-NEXT: [[INDEXER_EXT:%.*]] = zext i16 [[INDEXER_HI_LO_BYTE]] to i64
; CHECK-NEXT: [[TMP0:%.*]] = trunc i16 [[INDEXER_HI]] to i8
; CHECK-NEXT: [[INDEXER_EXT:%.*]] = zext i8 [[TMP0]] to i64
; CHECK-NEXT: [[TBL_PTRADD:%.*]] = getelementptr inbounds i16, ptr @.crctable.4, i64 [[INDEXER_EXT]]
; CHECK-NEXT: [[TBL_LD:%.*]] = load i16, ptr [[TBL_PTRADD]], align 2
; CHECK-NEXT: [[CRC_BE_SHIFT:%.*]] = shl i16 [[CRC2]], 8
Expand Down Expand Up @@ -255,8 +255,8 @@ define i16 @crc16.be.tc8.crc.init.arg(i16 %crc.init) {
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ 0, %[[ENTRY]] ], [ [[IV_NEXT:%.*]], %[[LOOP]] ]
; CHECK-NEXT: [[CRC2:%.*]] = phi i16 [ [[CRC_INIT]], %[[ENTRY]] ], [ [[CRC_NEXT3:%.*]], %[[LOOP]] ]
; CHECK-NEXT: [[INDEXER_HI:%.*]] = lshr i16 [[CRC2]], 8
; CHECK-NEXT: [[INDEXER_HI_LO_BYTE:%.*]] = and i16 [[INDEXER_HI]], 255
; CHECK-NEXT: [[INDEXER_EXT:%.*]] = zext i16 [[INDEXER_HI_LO_BYTE]] to i64
; CHECK-NEXT: [[TMP0:%.*]] = trunc i16 [[INDEXER_HI]] to i8
; CHECK-NEXT: [[INDEXER_EXT:%.*]] = zext i8 [[TMP0]] to i64
; CHECK-NEXT: [[TBL_PTRADD:%.*]] = getelementptr inbounds i16, ptr @.crctable.5, i64 [[INDEXER_EXT]]
; CHECK-NEXT: [[TBL_LD:%.*]] = load i16, ptr [[TBL_PTRADD]], align 2
; CHECK-NEXT: [[CRC_BE_SHIFT:%.*]] = shl i16 [[CRC2]], 8
Expand Down Expand Up @@ -295,8 +295,8 @@ define i16 @crc16.be.tc8.crc.init.arg.flipped.sb.check(i16 %crc.init) {
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ 0, %[[ENTRY]] ], [ [[IV_NEXT:%.*]], %[[LOOP]] ]
; CHECK-NEXT: [[CRC2:%.*]] = phi i16 [ [[CRC_INIT]], %[[ENTRY]] ], [ [[CRC_NEXT3:%.*]], %[[LOOP]] ]
; CHECK-NEXT: [[INDEXER_HI:%.*]] = lshr i16 [[CRC2]], 8
; CHECK-NEXT: [[INDEXER_HI_LO_BYTE:%.*]] = and i16 [[INDEXER_HI]], 255
; CHECK-NEXT: [[INDEXER_EXT:%.*]] = zext i16 [[INDEXER_HI_LO_BYTE]] to i64
; CHECK-NEXT: [[TMP0:%.*]] = trunc i16 [[INDEXER_HI]] to i8
; CHECK-NEXT: [[INDEXER_EXT:%.*]] = zext i8 [[TMP0]] to i64
; CHECK-NEXT: [[TBL_PTRADD:%.*]] = getelementptr inbounds i16, ptr @.crctable.6, i64 [[INDEXER_EXT]]
; CHECK-NEXT: [[TBL_LD:%.*]] = load i16, ptr [[TBL_PTRADD]], align 2
; CHECK-NEXT: [[CRC_BE_SHIFT:%.*]] = shl i16 [[CRC2]], 8
Expand Down Expand Up @@ -406,8 +406,8 @@ define i32 @crc32.le.tc8.data32(i32 %checksum, i32 %msg) {
; CHECK-NEXT: [[IV_INDEXER:%.*]] = zext i8 [[IV_BITS]] to i32
; CHECK-NEXT: [[DATA_INDEXER:%.*]] = lshr i32 [[MSG]], [[IV_INDEXER]]
; CHECK-NEXT: [[CRC_DATA_INDEXER:%.*]] = xor i32 [[DATA_INDEXER]], [[CRC2]]
; CHECK-NEXT: [[INDEXER_LO:%.*]] = and i32 [[CRC_DATA_INDEXER]], 255
; CHECK-NEXT: [[INDEXER_EXT:%.*]] = zext i32 [[INDEXER_LO]] to i64
; CHECK-NEXT: [[TMP0:%.*]] = trunc i32 [[CRC_DATA_INDEXER]] to i8
; CHECK-NEXT: [[INDEXER_EXT:%.*]] = zext i8 [[TMP0]] to i64
; CHECK-NEXT: [[TBL_PTRADD:%.*]] = getelementptr inbounds i32, ptr @.crctable.8, i64 [[INDEXER_EXT]]
; CHECK-NEXT: [[TBL_LD:%.*]] = load i32, ptr [[TBL_PTRADD]], align 4
; CHECK-NEXT: [[CRC_LE_SHIFT:%.*]] = lshr i32 [[CRC2]], 8
Expand Down