[InstSimplify] Don't lose inbounds when simplifying a GEP

I noticed this while working on a (ptrtoint (gep null, x)) -> x fold. Reviewed By: nikic Differential Revision: https://reviews.llvm.org/D110168
llvm · Sep 23, 2021 · 05663dc · 05663dc
1 parent 8b87c3d
commit 05663dc
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Showing 6 changed files with 21 additions and 17 deletions.
diff --git a/llvm/include/llvm/Analysis/InstructionSimplify.h b/llvm/include/llvm/Analysis/InstructionSimplify.h
@@ -248,7 +248,7 @@ Value *SimplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal,
                           const SimplifyQuery &Q);
 
 /// Given operands for a GetElementPtrInst, fold the result or return null.
-Value *SimplifyGEPInst(Type *SrcTy, ArrayRef<Value *> Ops,
+Value *SimplifyGEPInst(Type *SrcTy, ArrayRef<Value *> Ops, bool InBounds,
                        const SimplifyQuery &Q);
 
 /// Given operands for an InsertValueInst, fold the result or return null.

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -70,8 +70,8 @@ static Value *SimplifyOrInst(Value *, Value *, const SimplifyQuery &, unsigned);
 static Value *SimplifyXorInst(Value *, Value *, const SimplifyQuery &, unsigned);
 static Value *SimplifyCastInst(unsigned, Value *, Type *,
                                const SimplifyQuery &, unsigned);
-static Value *SimplifyGEPInst(Type *, ArrayRef<Value *>, const SimplifyQuery &,
-                              unsigned);
+static Value *SimplifyGEPInst(Type *, ArrayRef<Value *>, bool,
+                              const SimplifyQuery &, unsigned);
 static Value *SimplifySelectInst(Value *, Value *, Value *,
                                  const SimplifyQuery &, unsigned);
 
@@ -3983,7 +3983,8 @@ static Value *simplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp,
 
     if (auto *GEP = dyn_cast<GetElementPtrInst>(I))
       return PreventSelfSimplify(SimplifyGEPInst(GEP->getSourceElementType(),
-                                                 NewOps, Q, MaxRecurse - 1));
+                                                 NewOps, GEP->isInBounds(), Q,
+                                                 MaxRecurse - 1));
 
     if (isa<SelectInst>(I))
       return PreventSelfSimplify(
@@ -4328,7 +4329,7 @@ Value *llvm::SimplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal,
 
 /// Given operands for an GetElementPtrInst, see if we can fold the result.
 /// If not, this returns null.
-static Value *SimplifyGEPInst(Type *SrcTy, ArrayRef<Value *> Ops,
+static Value *SimplifyGEPInst(Type *SrcTy, ArrayRef<Value *> Ops, bool InBounds,
                               const SimplifyQuery &Q, unsigned) {
   // The type of the GEP pointer operand.
   unsigned AS =
@@ -4448,13 +4449,13 @@ static Value *SimplifyGEPInst(Type *SrcTy, ArrayRef<Value *> Ops,
     return nullptr;
 
   auto *CE = ConstantExpr::getGetElementPtr(SrcTy, cast<Constant>(Ops[0]),
-                                            Ops.slice(1));
+                                            Ops.slice(1), InBounds);
   return ConstantFoldConstant(CE, Q.DL);
 }
 
-Value *llvm::SimplifyGEPInst(Type *SrcTy, ArrayRef<Value *> Ops,
+Value *llvm::SimplifyGEPInst(Type *SrcTy, ArrayRef<Value *> Ops, bool InBounds,
                              const SimplifyQuery &Q) {
-  return ::SimplifyGEPInst(SrcTy, Ops, Q, RecursionLimit);
+  return ::SimplifyGEPInst(SrcTy, Ops, InBounds, Q, RecursionLimit);
 }
 
 /// Given operands for an InsertValueInst, see if we can fold the result.
@@ -6220,8 +6221,9 @@ static Value *simplifyInstructionWithOperands(Instruction *I,
     Result = SimplifySelectInst(NewOps[0], NewOps[1], NewOps[2], Q);
     break;
   case Instruction::GetElementPtr: {
-    Result = SimplifyGEPInst(cast<GetElementPtrInst>(I)->getSourceElementType(),
-                             NewOps, Q);
+    auto *GEPI = cast<GetElementPtrInst>(I);
+    Result = SimplifyGEPInst(GEPI->getSourceElementType(), NewOps,
+                             GEPI->isInBounds(), Q);
     break;
   }
   case Instruction::InsertValue: {

diff --git a/llvm/lib/Analysis/PHITransAddr.cpp b/llvm/lib/Analysis/PHITransAddr.cpp
@@ -226,8 +226,8 @@ Value *PHITransAddr::PHITranslateSubExpr(Value *V, BasicBlock *CurBB,
       return GEP;
 
     // Simplify the GEP to handle 'gep x, 0' -> x etc.
-    if (Value *V = SimplifyGEPInst(GEP->getSourceElementType(),
-                                   GEPOps, {DL, TLI, DT, AC})) {
+    if (Value *V = SimplifyGEPInst(GEP->getSourceElementType(), GEPOps,
+                                   GEP->isInBounds(), {DL, TLI, DT, AC})) {
       for (unsigned i = 0, e = GEPOps.size(); i != e; ++i)
         RemoveInstInputs(GEPOps[i], InstInputs);
 

diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -1855,7 +1855,8 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
   Type *GEPType = GEP.getType();
   Type *GEPEltType = GEP.getSourceElementType();
   bool IsGEPSrcEleScalable = isa<ScalableVectorType>(GEPEltType);
-  if (Value *V = SimplifyGEPInst(GEPEltType, Ops, SQ.getWithInstruction(&GEP)))
+  if (Value *V = SimplifyGEPInst(GEPEltType, Ops, GEP.isInBounds(),
+                                 SQ.getWithInstruction(&GEP)))
     return replaceInstUsesWith(GEP, V);
 
   // For vector geps, use the generic demanded vector support.

diff --git a/llvm/lib/Transforms/Scalar/NewGVN.cpp b/llvm/lib/Transforms/Scalar/NewGVN.cpp
@@ -1194,9 +1194,10 @@ NewGVN::ExprResult NewGVN::createExpression(Instruction *I) const {
         SimplifyCastInst(CI->getOpcode(), E->getOperand(0), CI->getType(), SQ);
     if (auto Simplified = checkExprResults(E, I, V))
       return Simplified;
-  } else if (isa<GetElementPtrInst>(I)) {
-    Value *V = SimplifyGEPInst(
-        E->getType(), ArrayRef<Value *>(E->op_begin(), E->op_end()), SQ);
+  } else if (auto *GEPI = dyn_cast<GetElementPtrInst>(I)) {
+    Value *V = SimplifyGEPInst(GEPI->getSourceElementType(),
+                               ArrayRef<Value *>(E->op_begin(), E->op_end()),
+                               GEPI->isInBounds(), SQ);
     if (auto Simplified = checkExprResults(E, I, V))
       return Simplified;
   } else if (AllConstant) {

diff --git a/llvm/test/Transforms/InstSimplify/simplify-nested-bitcast.ll b/llvm/test/Transforms/InstSimplify/simplify-nested-bitcast.ll
@@ -28,7 +28,7 @@ entry:
 }
 
 ; CHECK-LABEL: define void @f1
-; CHECK: %1 = load i32 (i8 addrspace(4)*, i32 addrspace(1)*)*, i32 (i8 addrspace(4)*, i32 addrspace(1)*)* addrspace(4)* bitcast (i8* addrspace(4)* getelementptr (%__aaa_struct, %__aaa_struct addrspace(4)* addrspacecast (%__aaa_struct addrspace(1)* @__aaa_struct_ptr to %__aaa_struct addrspace(4)*), i64 0, i32 0, i32 3) to i32 (i8 addrspace(4)*, i32 addrspace(1)*)* addrspace(4)*), align 8
+; CHECK: %1 = load i32 (i8 addrspace(4)*, i32 addrspace(1)*)*, i32 (i8 addrspace(4)*, i32 addrspace(1)*)* addrspace(4)* bitcast (i8* addrspace(4)* getelementptr inbounds (%__aaa_struct, %__aaa_struct addrspace(4)* addrspacecast (%__aaa_struct addrspace(1)* @__aaa_struct_ptr to %__aaa_struct addrspace(4)*), i64 0, i32 0, i32 3) to i32 (i8 addrspace(4)*, i32 addrspace(1)*)* addrspace(4)*), align 8
 
 ; Function Attrs: alwaysinline nounwind
 define void @f1(i32 addrspace(1)*) #1 {