[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.

3 files changed, 11 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;
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index c0891d4..045cae0 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -6974,6 +6974,8 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   Args.AddLastArg(CmdArgs, options::OPT_fwritable_strings);
   Args.AddLastArg(CmdArgs, options::OPT_funroll_loops,
                   options::OPT_fno_unroll_loops);
+  Args.AddLastArg(CmdArgs, options::OPT_floop_interchange,
+                  options::OPT_fno_loop_interchange);
 
   Args.AddLastArg(CmdArgs, options::OPT_fstrict_flex_arrays_EQ);
 
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 8b1bbf1..014e629 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1665,6 +1665,11 @@ void CompilerInvocationBase::GenerateCodeGenArgs(const CodeGenOptions &Opts,
   else if (!Opts.UnrollLoops && Opts.OptimizationLevel > 1)
     GenerateArg(Consumer, OPT_fno_unroll_loops);
 
+  if (Opts.InterchangeLoops)
+    GenerateArg(Consumer, OPT_floop_interchange);
+  else
+    GenerateArg(Consumer, OPT_fno_loop_interchange);
+
   if (!Opts.BinutilsVersion.empty())
     GenerateArg(Consumer, OPT_fbinutils_version_EQ, Opts.BinutilsVersion);
 
@@ -1971,6 +1976,8 @@ bool CompilerInvocation::ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args,
   Opts.UnrollLoops =
       Args.hasFlag(OPT_funroll_loops, OPT_fno_unroll_loops,
                    (Opts.OptimizationLevel > 1));
+  Opts.InterchangeLoops =
+      Args.hasFlag(OPT_floop_interchange, OPT_fno_loop_interchange, false);
   Opts.BinutilsVersion =
       std::string(Args.getLastArgValue(OPT_fbinutils_version_EQ));