[PATCH] D26441: Analysis: gep inbounds (gep inbounds (...)) is inbounds.

[Peter Collingbourne via llvm-commits]

pcc created this revision.
pcc added reviewers: sanjoy, efriedma, majnemer.
pcc added a subscriber: llvm-commits.

https://reviews.llvm.org/D26441

Files:
  llvm/lib/Analysis/ConstantFolding.cpp
  llvm/test/Other/constant-fold-gep.ll


Index: llvm/test/Other/constant-fold-gep.ll
===================================================================
--- llvm/test/Other/constant-fold-gep.ll
+++ llvm/test/Other/constant-fold-gep.ll
@@ -106,9 +106,9 @@
 
 ; PLAIN: @Y = global [3 x { i32, i32 }]* getelementptr inbounds ([3 x { i32, i32 }], [3 x { i32, i32 }]* @ext, i64 2)
 ; PLAIN: @Z = global i32* getelementptr inbounds (i32, i32* getelementptr inbounds ([3 x { i32, i32 }], [3 x { i32, i32 }]* @ext, i64 0, i64 1, i32 0), i64 1)
-; OPT: @Y = local_unnamed_addr global [3 x { i32, i32 }]* getelementptr ([3 x { i32, i32 }], [3 x { i32, i32 }]* @ext, i64 2)
+; OPT: @Y = local_unnamed_addr global [3 x { i32, i32 }]* getelementptr inbounds ([3 x { i32, i32 }], [3 x { i32, i32 }]* @ext, i64 2)
 ; OPT: @Z = local_unnamed_addr global i32* getelementptr inbounds ([3 x { i32, i32 }], [3 x { i32, i32 }]* @ext, i64 0, i64 1, i32 1)
-; TO: @Y = local_unnamed_addr global [3 x { i32, i32 }]* getelementptr ([3 x { i32, i32 }], [3 x { i32, i32 }]* @ext, i64 2)
+; TO: @Y = local_unnamed_addr global [3 x { i32, i32 }]* getelementptr inbounds ([3 x { i32, i32 }], [3 x { i32, i32 }]* @ext, i64 2)
 ; TO: @Z = local_unnamed_addr global i32* getelementptr inbounds ([3 x { i32, i32 }], [3 x { i32, i32 }]* @ext, i64 0, i64 1, i32 1)
 
 @ext = external global [3 x { i32, i32 }]
Index: llvm/lib/Analysis/ConstantFolding.cpp
===================================================================
--- llvm/lib/Analysis/ConstantFolding.cpp
+++ llvm/lib/Analysis/ConstantFolding.cpp
@@ -771,6 +771,7 @@
                                   ArrayRef<Constant *> Ops,
                                   const DataLayout &DL,
                                   const TargetLibraryInfo *TLI) {
+  bool InBounds = GEP->isInBounds();
   Type *SrcElemTy = GEP->getSourceElementType();
   Type *ResElemTy = GEP->getResultElementType();
   Type *ResTy = GEP->getType();
@@ -820,6 +821,8 @@
 
   // If this is a GEP of a GEP, fold it all into a single GEP.
   while (auto *GEP = dyn_cast<GEPOperator>(Ptr)) {
+    InBounds &= GEP->isInBounds();
+
     SmallVector<Value *, 4> NestedOps(GEP->op_begin() + 1, GEP->op_end());
 
     // Do not try the incorporate the sub-GEP if some index is not a number.
@@ -926,7 +929,8 @@
     return nullptr;
 
   // Create a GEP.
-  Constant *C = ConstantExpr::getGetElementPtr(SrcElemTy, Ptr, NewIdxs);
+  Constant *C =
+      ConstantExpr::getGetElementPtr(SrcElemTy, Ptr, NewIdxs, InBounds);
   assert(C->getType()->getPointerElementType() == Ty &&
          "Computed GetElementPtr has unexpected type!");
 


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