[Clang][Driver] Add an option to control loop-interchange (#125830)

This introduces options `-floop-interchange` and `-fno-loop-interchange`
to enable/disable the loop-interchange pass. This is part of the work
that tries to get that pass enabled by default (#124911), where it was
remarked that a user facing option to control this would be convenient
to have. The option name is the same as GCC's.

1 files changed, 2 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index 97e9bbc..57106e4 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -890,6 +890,7 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
 
   PipelineTuningOptions PTO;
   PTO.LoopUnrolling = CodeGenOpts.UnrollLoops;
+  PTO.LoopInterchange = CodeGenOpts.InterchangeLoops;
   // For historical reasons, loop interleaving is set to mirror setting for loop
   // unrolling.
   PTO.LoopInterleaving = CodeGenOpts.UnrollLoops;
@@ -1314,6 +1315,7 @@ runThinLTOBackend(CompilerInstance &CI, ModuleSummaryIndex *CombinedIndex,
   initTargetOptions(CI, Diags, Conf.Options);
   Conf.SampleProfile = std::move(SampleProfile);
   Conf.PTO.LoopUnrolling = CGOpts.UnrollLoops;
+  Conf.PTO.LoopInterchange = CGOpts.InterchangeLoops;
   // For historical reasons, loop interleaving is set to mirror setting for loop
   // unrolling.
   Conf.PTO.LoopInterleaving = CGOpts.UnrollLoops;