From 880afa1c5d1b099eed5034340a67e56b9dda4c09 Mon Sep 17 00:00:00 2001
From: Jay Foad <jay.foad@amd.com>
Date: Tue, 13 Feb 2024 13:44:31 +0000
Subject: [TableGen] Use vectors instead of sets for testing intersection. NFC.
 (#81602)

In a few places we test whether sets (i.e. sorted ranges) intersect by
computing the set_intersection and then testing whether it is empty. For
this purpose it should be more efficient to use a std:vector instead of
a std::set to hold the result of the set_intersection, since insertion
is simpler.
---
 llvm/utils/TableGen/AsmMatcherEmitter.cpp |  7 +++----
 llvm/utils/TableGen/CodeGenRegisters.cpp  | 11 +++++------
 2 files changed, 8 insertions(+), 10 deletions(-)

diff --git a/llvm/utils/TableGen/AsmMatcherEmitter.cpp b/llvm/utils/TableGen/AsmMatcherEmitter.cpp
index 9065885..a212265 100644
--- a/llvm/utils/TableGen/AsmMatcherEmitter.cpp
+++ b/llvm/utils/TableGen/AsmMatcherEmitter.cpp
@@ -242,11 +242,10 @@ public:
       if (!isRegisterClass() || !RHS.isRegisterClass())
         return false;
 
-      RegisterSet Tmp;
-      std::insert_iterator<RegisterSet> II(Tmp, Tmp.begin());
+      std::vector<Record *> Tmp;
       std::set_intersection(Registers.begin(), Registers.end(),
-                            RHS.Registers.begin(), RHS.Registers.end(), II,
-                            LessRecordByID());
+                            RHS.Registers.begin(), RHS.Registers.end(),
+                            std::back_inserter(Tmp), LessRecordByID());
 
       return !Tmp.empty();
     }
diff --git a/llvm/utils/TableGen/CodeGenRegisters.cpp b/llvm/utils/TableGen/CodeGenRegisters.cpp
index 25f3864..5c74a6f 100644
--- a/llvm/utils/TableGen/CodeGenRegisters.cpp
+++ b/llvm/utils/TableGen/CodeGenRegisters.cpp
@@ -2034,12 +2034,11 @@ void CodeGenRegBank::computeRegUnitSets() {
     // Compare new sets with all original classes.
     for (unsigned SearchIdx = (Idx >= NumRegUnitSubSets) ? 0 : Idx + 1;
          SearchIdx != EndIdx; ++SearchIdx) {
-      std::set<unsigned> Intersection;
-      std::set_intersection(RegUnitSets[Idx].Units.begin(),
-                            RegUnitSets[Idx].Units.end(),
-                            RegUnitSets[SearchIdx].Units.begin(),
-                            RegUnitSets[SearchIdx].Units.end(),
-                            std::inserter(Intersection, Intersection.begin()));
+      std::vector<unsigned> Intersection;
+      std::set_intersection(
+          RegUnitSets[Idx].Units.begin(), RegUnitSets[Idx].Units.end(),
+          RegUnitSets[SearchIdx].Units.begin(),
+          RegUnitSets[SearchIdx].Units.end(), std::back_inserter(Intersection));
       if (Intersection.empty())
         continue;
 
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