[llvm] 4d1ecf1 - [Transforms] Preserve inbounds attribute of transformed GEPs when flattening loops (#86961)

[via llvm-commits]

Author: AtariDreams
Date: 2024-05-15T10:26:23+09:00
New Revision: 4d1ecf192313b612090d60181937eff03c1a966b

URL: https://github.com/llvm/llvm-project/commit/4d1ecf192313b612090d60181937eff03c1a966b
DIFF: https://github.com/llvm/llvm-project/commit/4d1ecf192313b612090d60181937eff03c1a966b.diff

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

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.

Proof: https://alive2.llvm.org/ce/z/dApMpQ

Added: 
    

Modified: 
    llvm/lib/Transforms/Scalar/LoopFlatten.cpp
    llvm/test/Transforms/LoopFlatten/loop-flatten-gep.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Scalar/LoopFlatten.cpp b/llvm/lib/Transforms/Scalar/LoopFlatten.cpp
index a7f8a22ece277..bb9632ff73a42 100644
--- a/llvm/lib/Transforms/Scalar/LoopFlatten.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopFlatten.cpp
@@ -808,8 +808,10 @@ 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() && InnerGEP->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: