There are some cases where icmp(add) can be folded into a new icmp. Handle them.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@46687 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 404b53d..f55aff3 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -45,6 +45,7 @@
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Support/CallSite.h"
+#include "llvm/Support/ConstantRange.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/InstVisitor.h"
@@ -5704,6 +5705,37 @@
DivRHS))
return R;
break;
+
+ case Instruction::Add:
+ // Fold: icmp pred (add, X, C1), C2
+
+ if (!ICI.isEquality()) {
+ ConstantInt *LHSC = dyn_cast<ConstantInt>(LHSI->getOperand(1));
+ if (!LHSC) break;
+ const APInt &LHSV = LHSC->getValue();
+
+ ConstantRange CR = ICI.makeConstantRange(ICI.getPredicate(), RHSV)
+ .subtract(LHSV);
+
+ if (ICI.isSignedPredicate()) {
+ if (CR.getLower().isSignBit()) {
+ return new ICmpInst(ICmpInst::ICMP_SLT, LHSI->getOperand(0),
+ ConstantInt::get(CR.getUpper()));
+ } else if (CR.getUpper().isSignBit()) {
+ return new ICmpInst(ICmpInst::ICMP_SGE, LHSI->getOperand(0),
+ ConstantInt::get(CR.getLower()));
+ }
+ } else {
+ if (CR.getLower().isMinValue()) {
+ return new ICmpInst(ICmpInst::ICMP_ULT, LHSI->getOperand(0),
+ ConstantInt::get(CR.getUpper()));
+ } else if (CR.getUpper().isMinValue()) {
+ return new ICmpInst(ICmpInst::ICMP_UGE, LHSI->getOperand(0),
+ ConstantInt::get(CR.getLower()));
+ }
+ }
+ }
+ break;
}
// Simplify icmp_eq and icmp_ne instructions with integer constant RHS.