factor some instcombine simplifications for getelementptr out to a new
SimplifyGEPInst method in InstructionSimplify.h. No functionality change.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@89980 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp
index f9953e3..7a7eb6b 100644
--- a/lib/Analysis/InstructionSimplify.cpp
+++ b/lib/Analysis/InstructionSimplify.cpp
@@ -264,6 +264,34 @@
return 0;
}
+/// SimplifyGEPInst - Given operands for an GetElementPtrInst, see if we can
+/// fold the result. If not, this returns null.
+Value *llvm::SimplifyGEPInst(Value *const *Ops, unsigned NumOps,
+ const TargetData *TD) {
+ // getelementptr P -> P.
+ if (NumOps == 1)
+ return Ops[0];
+
+ // TODO.
+ //if (isa<UndefValue>(Ops[0]))
+ // return UndefValue::get(GEP.getType());
+
+ // getelementptr P, 0 -> P.
+ if (NumOps == 2)
+ if (ConstantInt *C = dyn_cast<ConstantInt>(Ops[1]))
+ if (C->isZero())
+ return Ops[0];
+
+ // Check to see if this is constant foldable.
+ for (unsigned i = 0; i != NumOps; ++i)
+ if (!isa<Constant>(Ops[i]))
+ return 0;
+
+ return ConstantExpr::getGetElementPtr(cast<Constant>(Ops[0]),
+ (Constant *const*)Ops+1, NumOps-1);
+}
+
+
//=== Helper functions for higher up the class hierarchy.
/// SimplifyBinOp - Given operands for a BinaryOperator, see if we can
@@ -309,6 +337,10 @@
case Instruction::FCmp:
return SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(),
I->getOperand(0), I->getOperand(1), TD);
+ case Instruction::GetElementPtr: {
+ SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end());
+ return SimplifyGEPInst(&Ops[0], Ops.size(), TD);
+ }
}
}
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index c7ab9df..95563b0 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -11429,21 +11429,16 @@
}
Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
+ SmallVector<Value*, 8> Ops(GEP.op_begin(), GEP.op_end());
+
+ if (Value *V = SimplifyGEPInst(&Ops[0], Ops.size(), TD))
+ return ReplaceInstUsesWith(GEP, V);
+
Value *PtrOp = GEP.getOperand(0);
- // Eliminate 'getelementptr %P, i32 0' and 'getelementptr %P', they are noops.
- if (GEP.getNumOperands() == 1)
- return ReplaceInstUsesWith(GEP, PtrOp);
if (isa<UndefValue>(GEP.getOperand(0)))
return ReplaceInstUsesWith(GEP, UndefValue::get(GEP.getType()));
- bool HasZeroPointerIndex = false;
- if (Constant *C = dyn_cast<Constant>(GEP.getOperand(1)))
- HasZeroPointerIndex = C->isNullValue();
-
- if (GEP.getNumOperands() == 2 && HasZeroPointerIndex)
- return ReplaceInstUsesWith(GEP, PtrOp);
-
// Eliminate unneeded casts for indices.
if (TD) {
bool MadeChange = false;
@@ -11548,6 +11543,10 @@
return 0;
}
+ bool HasZeroPointerIndex = false;
+ if (ConstantInt *C = dyn_cast<ConstantInt>(GEP.getOperand(1)))
+ HasZeroPointerIndex = C->isZero();
+
// Transform: GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ...
// into : GEP [10 x i8]* X, i32 0, ...
//