[llvm] LoopIdiomRecognize: update comment about ctpop (NFC) (PR #70812)
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Tue Oct 31 07:39:28 PDT 2023
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-transforms
Author: Ramkumar Ramachandra (artagnon)
<details>
<summary>Changes</summary>
Ever since 95de7c3, LoopIdiomRecognize has been able to recognize the ctpop idiom, with target-specific lowering information. However, the comment in the header about ctpop not being recognized is outdated. Remove it.
---
Full diff: https://github.com/llvm/llvm-project/pull/70812.diff
1 Files Affected:
- (modified) llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp (-6)
``````````diff
diff --git a/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp b/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
index b85178585e0ada0..3b2a7b03dd6d34e 100644
--- a/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
@@ -24,12 +24,6 @@
// memcmp, strlen, etc.
// Future floating point idioms to recognize in -ffast-math mode:
// fpowi
-// Future integer operation idioms to recognize:
-// ctpop
-//
-// Beware that isel's default lowering for ctpop is highly inefficient for
-// i64 and larger types when i64 is legal and the value has few bits set. It
-// would be good to enhance isel to emit a loop for ctpop in this case.
//
// This could recognize common matrix multiplies and dot product idioms and
// replace them with calls to BLAS (if linked in??).
``````````
</details>
https://github.com/llvm/llvm-project/pull/70812
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