[llvm] d7c84d7 - [LAA] Collect loop guards only once in MemoryDepChecker (NFCI).

[Florian Hahn via llvm-commits]

Author: Florian Hahn
Date: 2024-08-21T08:28:52+01:00
New Revision: d7c84d7b71fc5ea89b87480ff5d727496288799c

URL: https://github.com/llvm/llvm-project/commit/d7c84d7b71fc5ea89b87480ff5d727496288799c
DIFF: https://github.com/llvm/llvm-project/commit/d7c84d7b71fc5ea89b87480ff5d727496288799c.diff

LOG: [LAA] Collect loop guards only once in MemoryDepChecker (NFCI).

This on its own gives small compile-time improvements in some configs
and enables using loop guards at more places in the future while keeping
compile-time impact low.

https://llvm-compile-time-tracker.com/compare.php?from=c44202574ff9a8c0632aba30c2765b134557435f&to=55ffc3dd920fa9af439fd39f8f9cc13509531420&stat=instructions:u

Added: 
    

Modified: 
    llvm/include/llvm/Analysis/LoopAccessAnalysis.h
    llvm/lib/Analysis/LoopAccessAnalysis.cpp

Removed: 
    


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diff  --git a/llvm/include/llvm/Analysis/LoopAccessAnalysis.h b/llvm/include/llvm/Analysis/LoopAccessAnalysis.h
index 87c70abba30fcd..73d9c26ed6b1b7 100644
--- a/llvm/include/llvm/Analysis/LoopAccessAnalysis.h
+++ b/llvm/include/llvm/Analysis/LoopAccessAnalysis.h
@@ -334,6 +334,9 @@ class MemoryDepChecker {
            std::pair<const SCEV *, const SCEV *>>
       PointerBounds;
 
+  /// Cache for the loop guards of InnermostLoop.
+  std::optional<ScalarEvolution::LoopGuards> LoopGuards;
+
   /// Check whether there is a plausible dependence between the two
   /// accesses.
   ///

diff  --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
index 872bc52b82cca7..980f142f113265 100644
--- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
@@ -2054,8 +2054,12 @@ MemoryDepChecker::isDependent(const MemAccessInfo &A, unsigned AIdx,
       LLVM_DEBUG(dbgs() << "LAA: Strided accesses are independent\n");
       return Dependence::NoDep;
     }
-  } else
-    Dist = SE.applyLoopGuards(Dist, InnermostLoop);
+  } else {
+    if (!LoopGuards)
+      LoopGuards.emplace(
+          ScalarEvolution::LoopGuards::collect(InnermostLoop, SE));
+    Dist = SE.applyLoopGuards(Dist, *LoopGuards);
+  }
 
   // Negative distances are not plausible dependencies.
   if (SE.isKnownNonPositive(Dist)) {