[llvm] [DSE] Make iter order deterministic in removePartiallyOverlappedStores. NFC (PR #127678)

[Björn Pettersson via llvm-commits]

https://github.com/bjope created https://github.com/llvm/llvm-project/pull/127678

In removePartiallyOverlappedStores we iterate over InstOverlapIntervalsTy which is a DenseMap. Change that map into using MapVector to ensure that we apply the transforms in a deterministic order. I've only seen that the order matters if starting to use names for the instructions created when doing the transforms. But such things are a bit annoying when debugging etc.

>From 024594af6f7bef91d763dad33faf4d7b9cdc48e9 Mon Sep 17 00:00:00 2001
From: Bjorn Pettersson <bjorn.a.pettersson at ericsson.com>
Date: Tue, 18 Feb 2025 19:23:37 +0100
Subject: [PATCH] [DSE] Make iteration order deterministic in
 removePartiallyOverlappedStores. NFCI

In removePartiallyOverlappedStores we iterate over
InstOverlapIntervalsTy which is a DenseMap. Change that map into
using MapVector to ensure that we apply the transforms in a
deterministic order. I've only seen that the order matters if
starting to use names for the instructions created when doing the
transforms. But such things are a bit annoying when debugging etc.
---
 llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
index a1649c276de83..f3b53e05c519e 100644
--- a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
@@ -174,7 +174,7 @@ static cl::opt<bool> EnableInitializesImprovement(
 // Helper functions
 //===----------------------------------------------------------------------===//
 using OverlapIntervalsTy = std::map<int64_t, int64_t>;
-using InstOverlapIntervalsTy = DenseMap<Instruction *, OverlapIntervalsTy>;
+using InstOverlapIntervalsTy = MapVector<Instruction *, OverlapIntervalsTy>;
 
 /// Returns true if the end of this instruction can be safely shortened in
 /// length.