[PATCH] D75790: [PowerPC] Fix compile time issue

[Teresa Johnson via Phabricator via llvm-commits]

tejohnson created this revision.
tejohnson added a reviewer: hfinkel.
Herald added subscribers: shchenz, jsji, kbarton, hiraditya, nemanjai.
Herald added a project: LLVM.

Avoid re-examining operands on recursive walk looking for CTR.
This was causing huge compile time after some earlier optimization
created a large expression.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D75790

Files:
  llvm/lib/Target/PowerPC/PPCTargetTransformInfo.cpp
  llvm/lib/Target/PowerPC/PPCTargetTransformInfo.h


Index: llvm/lib/Target/PowerPC/PPCTargetTransformInfo.h
===================================================================
--- llvm/lib/Target/PowerPC/PPCTargetTransformInfo.h
+++ llvm/lib/Target/PowerPC/PPCTargetTransformInfo.h
@@ -33,7 +33,8 @@
 
   const PPCSubtarget *getST() const { return ST; }
   const PPCTargetLowering *getTLI() const { return TLI; }
-  bool mightUseCTR(BasicBlock *BB, TargetLibraryInfo *LibInfo);
+  bool mightUseCTR(BasicBlock *BB, TargetLibraryInfo *LibInfo,
+                   std::set<const Value *> &Visited);
 
 public:
   explicit PPCTTIImpl(const PPCTargetMachine *TM, const Function &F)
Index: llvm/lib/Target/PowerPC/PPCTargetTransformInfo.cpp
===================================================================
--- llvm/lib/Target/PowerPC/PPCTargetTransformInfo.cpp
+++ llvm/lib/Target/PowerPC/PPCTargetTransformInfo.cpp
@@ -218,7 +218,8 @@
 }
 
 bool PPCTTIImpl::mightUseCTR(BasicBlock *BB,
-                             TargetLibraryInfo *LibInfo) {
+                             TargetLibraryInfo *LibInfo,
+                             std::set<const Value *> &Visited) {
   const PPCTargetMachine &TM = ST->getTargetMachine();
 
   // Loop through the inline asm constraints and look for something that
@@ -238,7 +239,10 @@
   // Determining the address of a TLS variable results in a function call in
   // certain TLS models.
   std::function<bool(const Value*)> memAddrUsesCTR =
-    [&memAddrUsesCTR, &TM](const Value *MemAddr) -> bool {
+    [&memAddrUsesCTR, &TM, &Visited](const Value *MemAddr) -> bool {
+    // No need to traverse again if we already checked this operand.
+    if (!Visited.insert(MemAddr).second)
+      return false;
     const auto *GV = dyn_cast<GlobalValue>(MemAddr);
     if (!GV) {
       // Recurse to check for constants that refer to TLS global variables.
@@ -502,9 +506,10 @@
 
   // We don't want to spill/restore the counter register, and so we don't
   // want to use the counter register if the loop contains calls.
+  std::set<const Value *> Visited;
   for (Loop::block_iterator I = L->block_begin(), IE = L->block_end();
        I != IE; ++I)
-    if (mightUseCTR(*I, LibInfo))
+    if (mightUseCTR(*I, LibInfo, Visited))
       return false;
 
   SmallVector<BasicBlock*, 4> ExitingBlocks;


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