[HashRecognize] Strip excess-TC check #157479
Merged
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Checking if trip-count exceeds 256 is no longer necessary, as we have moved away from KnownBits computations to pattern-matching, which is very cheap and independent of TC.
llvmbot
added
the
llvm:analysis
Member
|
@llvm/pr-subscribers-llvm-analysis Author: Ramkumar Ramachandra (artagnon) ChangesChecking if trip-count exceeds 256 is no longer necessary, as we have moved away from KnownBits computations to pattern-matching, which is very cheap and independent of TC. Full diff: https://github.com/llvm/llvm-project/pull/157479.diff 2 Files Affected:
diff --git a/llvm/lib/Analysis/HashRecognize.cpp b/llvm/lib/Analysis/HashRecognize.cpp
index 5b3448f5df35d..1b608870d28a8 100644
--- a/llvm/lib/Analysis/HashRecognize.cpp
+++ b/llvm/lib/Analysis/HashRecognize.cpp
@@ -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);
diff --git a/llvm/test/Analysis/HashRecognize/cyclic-redundancy-check.ll b/llvm/test/Analysis/HashRecognize/cyclic-redundancy-check.ll
index 432a4d72fafb4..7dec2f8f96906 100644
--- a/llvm/test/Analysis/HashRecognize/cyclic-redundancy-check.ll
+++ b/llvm/test/Analysis/HashRecognize/cyclic-redundancy-check.ll
@@ -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
@@ -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
|
Collaborator
|
LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/181/builds/27441 Here is the relevant piece of the build log for the reference |
Collaborator
|
LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/116/builds/18047 Here is the relevant piece of the build log for the reference |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
4 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Checking if trip-count exceeds 256 is no longer necessary, as we have moved away from KnownBits computations to pattern-matching, which is very cheap and independent of TC.