[llvm] [SeparateConstOffsetFromGEP] Decompose constant xor operand if possible (PR #135788)
Juan Manuel Martinez CaamaƱo via llvm-commits
llvm-commits at lists.llvm.org
Wed May 21 04:10:58 PDT 2025
================
@@ -1162,6 +1199,167 @@ bool SeparateConstOffsetFromGEP::splitGEP(GetElementPtrInst *GEP) {
return true;
}
+// Helper function to check if an instruction has at least one GEP user
+bool XorToOrDisjointTransformer::hasGEPUser(const Value *V) {
+ for (const User *U : V->users()) {
+ if (isa<GetElementPtrInst>(U)) {
+ return true;
+ }
+ }
+ return false;
+}
+
+bool XorToOrDisjointTransformer::processXorGroup(Instruction *OriginalBaseInst,
+ XorOpList &XorsInGroup) {
+ bool Changed = false;
+ if (XorsInGroup.size() <= 1)
+ return false;
+
+ // Sort XorsInGroup by the constant offset value in increasing order.
+ llvm::sort(
+ XorsInGroup.begin(), XorsInGroup.end(),
+ [](const auto &A, const auto &B) { return A.second.ult(B.second); });
+
+ // Dominance check
+ // The "base" XOR for dominance purposes is the one with the smallest
+ // constant.
+ BinaryOperator *XorWithSmallConst = XorsInGroup[0].first;
+
+ for (size_t i = 1; i < XorsInGroup.size(); ++i) {
+ BinaryOperator *currentXorToProcess = XorsInGroup[i].first;
+
+ // Check if the XorWithSmallConst dominates currentXorToProcess.
+ // If not, clone and add the instruction.
+ if (!DT.dominates(XorWithSmallConst, currentXorToProcess)) {
----------------
jmmartinez wrote:
Consider having a helper function to check if "the xor-with-small-const dominates all the other xor".
It's be easier to read
```cpp
if(xor-with-small-const doesn't dominate all other xors) {
// do the clone
}
```
than
```cpp
for(xor in xors) {
if(xor-with-small-const doesn't dominate xor) {
// do the clone
break;
}
}
```
https://github.com/llvm/llvm-project/pull/135788
More information about the llvm-commits
mailing list