[PATCH] D157440: [clang][ConstExprEmitter] handle BinaryOperators that don't have signedness or overflow concerns for integrals
Nick Desaulniers via Phabricator via cfe-commits
cfe-commits at lists.llvm.org
Tue Aug 8 14:30:13 PDT 2023
nickdesaulniers created this revision.
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Handles binary operators: & ^ | == !=
Check that each side evaluates to a ConstantInt then combine the
results.
We probably can reuse DataRecursiveIntBinOpEvaluator or
handleIntIntBinOp from ExprConstant.cpp for the rest, or even these
cases as well.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D157440
Files:
clang/lib/CodeGen/CGExprConstant.cpp
Index: clang/lib/CodeGen/CGExprConstant.cpp
===================================================================
--- clang/lib/CodeGen/CGExprConstant.cpp
+++ clang/lib/CodeGen/CGExprConstant.cpp
@@ -1401,6 +1401,64 @@
return nullptr;
}
+ llvm::Constant *VisitBinaryOperator(BinaryOperator *B, QualType T) {
+ // Can we attempt to handle this opcode?
+ switch (B->getOpcode()) {
+ default:
+ return nullptr;
+ case BO_And:
+ case BO_Xor:
+ case BO_Or:
+ case BO_EQ:
+ case BO_NE:
+ break;
+ }
+
+ // Constant evaluate LHS
+ Expr *LHS = B->getLHS();
+ llvm::Constant *LHSC = Visit(LHS, T);
+
+ // Only handle integers for now.
+ if (!LHSC || !isa<llvm::ConstantInt>(LHSC))
+ return nullptr;
+
+ // Constant evaluate RHS
+ Expr *RHS = B->getRHS();
+ llvm::Constant *RHSC = Visit(RHS, T);
+
+ // Only handle integers for now.
+ if (!RHSC || !isa<llvm::ConstantInt>(RHSC))
+ return nullptr;
+
+ const llvm::APInt R = cast<llvm::ConstantInt>(RHSC)->getValue();
+ const llvm::APInt L = cast<llvm::ConstantInt>(LHSC)->getValue();
+ llvm::APInt Ret;
+
+ // Fold
+ switch (B->getOpcode()) {
+ default:
+ // Should have return earlier.
+ llvm_unreachable("unhandled BinaryOperator kind");
+ case BO_And:
+ Ret = L & R;
+ break;
+ case BO_Xor:
+ Ret = L ^ R;
+ break;
+ case BO_Or:
+ Ret = L | R;
+ break;
+ case BO_EQ:
+ Ret = L == R;
+ break;
+ case BO_NE:
+ Ret = L != R;
+ break;
+ }
+
+ return llvm::ConstantInt::get(CGM.getLLVMContext(), Ret);
+ }
+
// Utility methods
llvm::Type *ConvertType(QualType T) {
return CGM.getTypes().ConvertType(T);
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