[llvm] [Analysis] Avoid repeated hash lookups (NFC) (PR #133045)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-analysis

Author: Kazu Hirata (kazutakahirata)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/133045.diff


1 Files Affected:

- (modified) llvm/lib/Analysis/ScalarEvolution.cpp (+3-3) 


``````````diff
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 314baa7c7aee1..69561472dc663 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -15443,9 +15443,9 @@ void ScalarEvolution::LoopGuards::collectFromBlock(
       // Bail out, unless we have a non-wrapping, monotonic range.
       if (ExactRegion.isWrappedSet() || ExactRegion.isFullSet())
         return false;
-      auto I = RewriteMap.find(LHSUnknown);
-      const SCEV *RewrittenLHS = I != RewriteMap.end() ? I->second : LHSUnknown;
-      RewriteMap[LHSUnknown] = SE.getUMaxExpr(
+      auto [I, Inserted] = RewriteMap.try_emplace(LHSUnknown);
+      const SCEV *RewrittenLHS = Inserted ? LHSUnknown : I->second;
+      I->second = SE.getUMaxExpr(
           SE.getConstant(ExactRegion.getUnsignedMin()),
           SE.getUMinExpr(RewrittenLHS,
                          SE.getConstant(ExactRegion.getUnsignedMax())));

``````````

</details>


https://github.com/llvm/llvm-project/pull/133045