[llvm] [Transforms] Preserve inbounds attribute of transformed GEPs when flattening loops (PR #86961)

[via llvm-commits]

https://github.com/AtariDreams updated https://github.com/llvm/llvm-project/pull/86961

>From 50ebb274101a7dd867d962d6a544d1c7c3da6c0d Mon Sep 17 00:00:00 2001
From: Rose <gfunni234 at gmail.com>
Date: Wed, 27 Mar 2024 17:08:16 -0400
Subject: [PATCH] [Transforms] Preserve inbounds attribute of transformed GEPs
 when flattening loops

When flattening the loop, if the GEP was inbound, it should stay inbound, because the only thing that changed is how the pointers are calculated, not the elements being accessed.
---
 llvm/lib/Transforms/Scalar/LoopFlatten.cpp           | 5 +++--
 llvm/test/Transforms/LoopFlatten/loop-flatten-gep.ll | 6 +++---
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/llvm/lib/Transforms/Scalar/LoopFlatten.cpp b/llvm/lib/Transforms/Scalar/LoopFlatten.cpp
index a7f8a22ece277..f469e8357e5ab 100644
--- a/llvm/lib/Transforms/Scalar/LoopFlatten.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopFlatten.cpp
@@ -808,8 +808,9 @@ static bool DoFlattenLoopPair(FlattenInfo &FI, DominatorTree *DT, LoopInfo *LI,
       // we need to insert the new GEP where the old GEP was.
       if (!DT->dominates(Base, &*Builder.GetInsertPoint()))
         Builder.SetInsertPoint(cast<Instruction>(V));
-      OuterValue = Builder.CreateGEP(GEP->getSourceElementType(), Base,
-                                     OuterValue, "flatten." + V->getName());
+      OuterValue =
+          Builder.CreateGEP(GEP->getSourceElementType(), Base, OuterValue,
+                            "flatten." + V->getName(), GEP->isInBounds());
     }
 
     LLVM_DEBUG(dbgs() << "Replacing: "; V->dump(); dbgs() << "with:      ";
diff --git a/llvm/test/Transforms/LoopFlatten/loop-flatten-gep.ll b/llvm/test/Transforms/LoopFlatten/loop-flatten-gep.ll
index f4b8ea97237fe..e30001670b1e9 100644
--- a/llvm/test/Transforms/LoopFlatten/loop-flatten-gep.ll
+++ b/llvm/test/Transforms/LoopFlatten/loop-flatten-gep.ll
@@ -15,7 +15,7 @@ for.outer.preheader:
   br label %for.inner.preheader
 
 ; CHECK-LABEL: for.inner.preheader:
-; CHECK: %flatten.arrayidx = getelementptr i32, ptr %A, i32 %i
+; CHECK: %flatten.arrayidx = getelementptr inbounds i32, ptr %A, i32 %i
 for.inner.preheader:
   %i = phi i32 [ 0, %for.outer.preheader ], [ %inc2, %for.outer ]
   br label %for.inner
@@ -61,13 +61,13 @@ for.outer.preheader:
   br label %for.inner.preheader
 
 ; CHECK-LABEL: for.inner.preheader:
-; CHECK-NOT: getelementptr i32, ptr %ptr, i32 %i
+; CHECK-NOT: getelementptr inbounds i32, ptr %ptr, i32 %i
 for.inner.preheader:
   %i = phi i32 [ 0, %for.outer.preheader ], [ %inc2, %for.outer ]
   br label %for.inner
 
 ; CHECK-LABEL: for.inner:
-; CHECK: %flatten.arrayidx = getelementptr i32, ptr %ptr, i32 %i
+; CHECK: %flatten.arrayidx = getelementptr inbounds i32, ptr %ptr, i32 %i
 ; CHECK: store i32 0, ptr %flatten.arrayidx, align 4
 ; CHECK: br label %for.outer
 for.inner: