[llvm] [InstCombine] Avoid repeated hash lookups (NFC) (PR #124243)

[Kazu Hirata via llvm-commits]

https://github.com/kazutakahirata created https://github.com/llvm/llvm-project/pull/124243

None

>From 9bd0e005c8f3ddd61bc911c8aaf34ac160ef8e0d Mon Sep 17 00:00:00 2001
From: Kazu Hirata <kazu at google.com>
Date: Fri, 24 Jan 2025 01:06:21 -0800
Subject: [PATCH] [InstCombine] Avoid repeated hash lookups (NFC)

---
 .../Transforms/InstCombine/InstCombineVectorOps.cpp  | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
index ce6154fd610eb8..5989c6e6ea30aa 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
@@ -3060,14 +3060,10 @@ Instruction *InstCombinerImpl::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
       unsigned SrcElemsPerTgtElem = TgtElemBitWidth / SrcElemBitWidth;
       assert(SrcElemsPerTgtElem);
       BegIdx /= SrcElemsPerTgtElem;
-      bool BCAlreadyExists = NewBCs.contains(CastSrcTy);
-      auto *NewBC =
-          BCAlreadyExists
-              ? NewBCs[CastSrcTy]
-              : Builder.CreateBitCast(V, CastSrcTy, SVI.getName() + ".bc");
-      if (!BCAlreadyExists)
-        NewBCs[CastSrcTy] = NewBC;
-      auto *Ext = Builder.CreateExtractElement(NewBC, BegIdx,
+      auto [It, Inserted] = NewBCs.try_emplace(CastSrcTy);
+      if (Inserted)
+        It->second = Builder.CreateBitCast(V, CastSrcTy, SVI.getName() + ".bc");
+      auto *Ext = Builder.CreateExtractElement(It->second, BegIdx,
                                                SVI.getName() + ".extract");
       // The shufflevector isn't being replaced: the bitcast that used it
       // is. InstCombine will visit the newly-created instructions.