[llvm/CodeGen] Add ExpandLargeDivRem pass

Adds a pass ExpandLargeDivRem to expand div/rem instructions
with more than 128 bits into a loop computing that value.

As discussed on https://reviews.llvm.org/D120327, this approach has the advantage
that it is independent of the runtime library. This also helps the clang driver,
which otherwise would need to understand enough about the runtime library
to know whether to allow _BitInts with more than 128 bits.

Targets are still free to disable this pass and instead provide a faster
implementation in a runtime library.

Fixes https://github.com/llvm/llvm-project/issues/44994

Differential Revision: https://reviews.llvm.org/D126644

1 files changed, 1 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/CodeGen.cpp b/llvm/lib/CodeGen/CodeGen.cpp
index 5050395..219032e 100644
--- a/llvm/lib/CodeGen/CodeGen.cpp
+++ b/llvm/lib/CodeGen/CodeGen.cpp
@@ -36,6 +36,7 @@ void llvm::initializeCodeGen(PassRegistry &Registry) {
   initializeEarlyIfPredicatorPass(Registry);
   initializeEarlyMachineLICMPass(Registry);
   initializeEarlyTailDuplicatePass(Registry);
+  initializeExpandLargeDivRemLegacyPassPass(Registry);
   initializeExpandMemCmpPassPass(Registry);
   initializeExpandPostRAPass(Registry);
   initializeFEntryInserterPass(Registry);