Convert llvm.returnaddress arguments to cpu_[ld|st]*() to undef, causing
the LLVM optmizer to discard the intrinsics. Needed as
llvm.returnadress is not representable in TCG, and usually results from
usage of GETPC() in helper functions.
Signed-off-by: Anton Johansson <a...@rev.ng>
---
.../PrepareForOptPass/PrepareForOptPass.cpp | 48 +++++++++++++++++++
1 file changed, 48 insertions(+)
diff --git
a/subprojects/helper-to-tcg/passes/PrepareForOptPass/PrepareForOptPass.cpp
b/subprojects/helper-to-tcg/passes/PrepareForOptPass/PrepareForOptPass.cpp
index 22509008c8..b357debb5d 100644
--- a/subprojects/helper-to-tcg/passes/PrepareForOptPass/PrepareForOptPass.cpp
+++ b/subprojects/helper-to-tcg/passes/PrepareForOptPass/PrepareForOptPass.cpp
@@ -23,6 +23,7 @@
#include <llvm/IR/Function.h>
#include <llvm/IR/Instruction.h>
#include <llvm/IR/Instructions.h>
+#include <llvm/IR/Intrinsics.h>
#include <llvm/IR/Module.h>
#include <queue>
@@ -197,9 +198,56 @@ static void cullUnusedFunctions(Module &M, AnnotationMapTy
&Annotations,
}
}
+struct RetAddrReplaceInfo {
+ User *Parent;
+ unsigned OpIndex;
+ Type *Ty;
+};
+
+static void replaceRetaddrWithUndef(Module &M)
+{
+ // Replace uses of llvm.returnaddress arguments to cpu_ld* w. undef,
+ // and let optimizations remove it. Needed as llvm.returnaddress is
+ // not reprensentable in TCG.
+ SmallVector<RetAddrReplaceInfo, 24> UsesToReplace;
+ Function *Retaddr = Intrinsic::getDeclaration(&M,
Intrinsic::returnaddress);
+ // Loop over all calls to llvm.returnaddress
+ for (auto *CallUser : Retaddr->users()) {
+ auto *Call = dyn_cast<CallInst>(CallUser);
+ if (!Call) {
+ continue;
+ }
+ for (auto *PtrToIntUser : Call->users()) {
+ auto *Cast = dyn_cast<PtrToIntInst>(PtrToIntUser);
+ if (!Cast) {
+ continue;
+ }
+ for (Use &U : Cast->uses()) {
+ auto *Call = dyn_cast<CallInst>(U.getUser());
+ Function *F = Call->getCalledFunction();
+ StringRef Name = F->getName();
+ if (Name.startswith("cpu_ld") or Name.startswith("cpu_st")) {
+ UsesToReplace.push_back({
+ .Parent = U.getUser(),
+ .OpIndex = U.getOperandNo(),
+ .Ty = U->getType(),
+ });
+ }
+ }
+ }
+ }
+
+ // Defer replacement to not invalidate iterators
+ for (RetAddrReplaceInfo &RI : UsesToReplace) {
+ auto *Undef = UndefValue::get(RI.Ty);
+ RI.Parent->setOperand(RI.OpIndex, Undef);
+ }
+}
+
PreservedAnalyses PrepareForOptPass::run(Module &M, ModuleAnalysisManager &MAM)
{
collectAnnotations(M, ResultAnnotations);
cullUnusedFunctions(M, ResultAnnotations, TranslateAllHelpers);
+ replaceRetaddrWithUndef(M);
return PreservedAnalyses::none();
}
--
2.45.2
