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[HashRecognize] Strip excess-TC check #157479

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Merged
artagnon merged 1 commit into from
Sep 8, 2025
Merged

[HashRecognize] Strip excess-TC check #157479

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2 changes: 1 addition & 1 deletion llvm/lib/Analysis/HashRecognize.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -446,7 +446,7 @@ std::variant<PolynomialInfo, StringRef> HashRecognize::recognizeCRC() const {
if (!Latch || !Exit || !IndVar || L.getNumBlocks() != 1)
return "Loop not in canonical form";
unsigned TC = SE.getSmallConstantTripCount(&L);
if (!TC || TC > 256 || TC % 8)
if (!TC || TC % 8)
return "Unable to find a small constant byte-multiple trip count";

auto R = getRecurrences(Latch, IndVar, L);
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8 changes: 4 additions & 4 deletions llvm/test/Analysis/HashRecognize/cyclic-redundancy-check.ll
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Expand Up @@ -574,10 +574,10 @@ exit: ; preds = %loop
ret i16 %crc.next
}

define i16 @not.crc.tc.limit(i16 %crc.init) {
; CHECK-LABEL: 'not.crc.tc.limit'
define i16 @not.crc.tc.exceeds.data.bw(i16 %crc.init) {
; CHECK-LABEL: 'not.crc.tc.exceeds.data.bw'
; CHECK-NEXT: Did not find a hash algorithm
; CHECK-NEXT: Reason: Unable to find a small constant byte-multiple trip count
; CHECK-NEXT: Reason: Loop iterations exceed bitwidth of data
;
entry:
br label %loop
Expand All @@ -590,7 +590,7 @@ loop: ; preds = %loop, %entry
%check.sb = icmp slt i16 %crc, 0
%crc.next = select i1 %check.sb, i16 %crc.xor, i16 %crc.shl
%iv.next = add nuw nsw i32 %iv, 1
%exit.cond = icmp samesign ult i32 %iv, 512
%exit.cond = icmp samesign ult i32 %iv, 511
br i1 %exit.cond, label %loop, label %exit

exit: ; preds = %loop
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