[BasicBlockSections] Allow mixing of -basic-block-sections with MFS. (#117076)

This PR allows mixing `-basic-block-sections` with
`-enable-machine-function-splitter`. The strategy is to let
`-basic-block-sections` take precedence over functions with profiles.

1 files changed, 9 insertions, 8 deletions

diff --git a/llvm/lib/CodeGen/TargetPassConfig.cpp b/llvm/lib/CodeGen/TargetPassConfig.cpp
index a6159a38753c..d407e9f0871d 100644
--- a/llvm/lib/CodeGen/TargetPassConfig.cpp
+++ b/llvm/lib/CodeGen/TargetPassConfig.cpp
@@ -1235,13 +1235,13 @@ void TargetPassConfig::addMachinePasses() {
     addPass(createMIRAddFSDiscriminatorsPass(
         sampleprof::FSDiscriminatorPass::PassLast));
 
-  bool NeedsBBSections =
-      TM->getBBSectionsType() != llvm::BasicBlockSection::None;
-  // Machine function splitter uses the basic block sections feature. Both
-  // cannot be enabled at the same time. We do not apply machine function
-  // splitter if -basic-block-sections is requested.
-  if (!NeedsBBSections && (TM->Options.EnableMachineFunctionSplitter ||
-                           EnableMachineFunctionSplitter)) {
+  // Machine function splitter uses the basic block sections feature.
+  // When used along with `-basic-block-sections=`, the basic-block-sections
+  // feature takes precedence. This means functions eligible for
+  // basic-block-sections optimizations (`=all`, or `=list=` with function
+  // included in the list profile) will get that optimization instead.
+  if (TM->Options.EnableMachineFunctionSplitter ||
+      EnableMachineFunctionSplitter) {
     const std::string ProfileFile = getFSProfileFile(TM);
     if (!ProfileFile.empty()) {
       if (EnableFSDiscriminator) {
@@ -1260,7 +1260,8 @@ void TargetPassConfig::addMachinePasses() {
   }
   // We run the BasicBlockSections pass if either we need BB sections or BB
   // address map (or both).
-  if (NeedsBBSections || TM->Options.BBAddrMap) {
+  if (TM->getBBSectionsType() != llvm::BasicBlockSection::None ||
+      TM->Options.BBAddrMap) {
     if (TM->getBBSectionsType() == llvm::BasicBlockSection::List) {
       addPass(llvm::createBasicBlockSectionsProfileReaderWrapperPass(
           TM->getBBSectionsFuncListBuf()));