[LVI] Apply transfer rule for overdefine inputs for binary operators
As pointed out by John Regehr over in http://reviews.llvm.org/D19485, LVI was being incredibly stupid about applying its transfer rules. Rather than gathering local facts from the expression itself, it was simply giving up entirely if one of the inputs was overdefined. This greatly impacts the precision of the overall analysis and makes it far more fragile as well.
This patch builds on 267609 which did the same thing for unary casts.
llvm-svn: 267620
diff --git a/llvm/lib/Analysis/LazyValueInfo.cpp b/llvm/lib/Analysis/LazyValueInfo.cpp
index 6bc639c..3b0ffb8 100644
--- a/llvm/lib/Analysis/LazyValueInfo.cpp
+++ b/llvm/lib/Analysis/LazyValueInfo.cpp
@@ -1063,22 +1063,27 @@
bool LazyValueInfoCache::solveBlockValueBinaryOp(LVILatticeVal &BBLV,
Instruction *BBI,
BasicBlock *BB) {
-
- // Figure out the range of the LHS. If that fails, bail.
- if (!hasBlockValue(BBI->getOperand(0), BB)) {
- if (pushBlockValue(std::make_pair(BB, BBI->getOperand(0))))
- return false;
- BBLV.markOverdefined();
- return true;
- }
- LVILatticeVal LHSVal = getBlockValue(BBI->getOperand(0), BB);
- intersectAssumeBlockValueConstantRange(BBI->getOperand(0), LHSVal, BBI);
- if (!LHSVal.isConstantRange()) {
- BBLV.markOverdefined();
- return true;
+ assert(BBI->getOperand(0)->getType()->isSized() &&
+ "all operands to binary operators are sized");
+
+ // Figure out the range of the LHS. If that fails, use a conservative range,
+ // but apply the transfer rule anyways. This lets us pick up facts from
+ // expressions like "and i32 (call i32 @foo()), 32"
+ if (!hasBlockValue(BBI->getOperand(0), BB))
+ if (pushBlockValue(std::make_pair(BB, BBI->getOperand(0))))
+ // More work to do before applying this transfer rule.
+ return false;
+
+ const unsigned OperandBitWidth =
+ DL.getTypeSizeInBits(BBI->getOperand(0)->getType());
+ ConstantRange LHSRange = ConstantRange(OperandBitWidth);
+ if (hasBlockValue(BBI->getOperand(0), BB)) {
+ LVILatticeVal LHSVal = getBlockValue(BBI->getOperand(0), BB);
+ intersectAssumeBlockValueConstantRange(BBI->getOperand(0), LHSVal, BBI);
+ if (LHSVal.isConstantRange())
+ LHSRange = LHSVal.getConstantRange();
}
- ConstantRange LHSRange = LHSVal.getConstantRange();
ConstantInt *RHS = cast<ConstantInt>(BBI->getOperand(1));
ConstantRange RHSRange = ConstantRange(RHS->getValue());