[TTI] Add SCEVExpansionBudget to loop unrolling options. (#118316)

Add an extra know to UnrollingPreferences to let backends control the
maximum budget for SCEV expansions.

This gives backends more fine-grained control on the cost of the runtime
checks for runtime unrolling.

PR: https://github.com/llvm/llvm-project/pull/118316

1 files changed, 4 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
index 0179d35..b0bc55c 100644
--- a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
@@ -582,7 +582,8 @@ bool llvm::UnrollRuntimeLoopRemainder(
     Loop *L, unsigned Count, bool AllowExpensiveTripCount,
     bool UseEpilogRemainder, bool UnrollRemainder, bool ForgetAllSCEV,
     LoopInfo *LI, ScalarEvolution *SE, DominatorTree *DT, AssumptionCache *AC,
-    const TargetTransformInfo *TTI, bool PreserveLCSSA, Loop **ResultLoop) {
+    const TargetTransformInfo *TTI, bool PreserveLCSSA,
+    unsigned SCEVExpansionBudget, Loop **ResultLoop) {
   LLVM_DEBUG(dbgs() << "Trying runtime unrolling on Loop: \n");
   LLVM_DEBUG(L->dump());
   LLVM_DEBUG(UseEpilogRemainder ? dbgs() << "Using epilog remainder.\n"
@@ -672,8 +673,8 @@ bool llvm::UnrollRuntimeLoopRemainder(
   const DataLayout &DL = Header->getDataLayout();
   SCEVExpander Expander(*SE, DL, "loop-unroll");
   if (!AllowExpensiveTripCount &&
-      Expander.isHighCostExpansion(TripCountSC, L, SCEVCheapExpansionBudget,
-                                   TTI, PreHeaderBR)) {
+      Expander.isHighCostExpansion(TripCountSC, L, SCEVExpansionBudget, TTI,
+                                   PreHeaderBR)) {
     LLVM_DEBUG(dbgs() << "High cost for expanding trip count scev!\n");
     return false;
   }