[TTI] Add isExpensiveToSpeculativelyExecute wrapper

CGP uses a raw `getInstructionCost(I, TargetTransformInfo::TCK_SizeAndLatency) >= TCC_Expensive` check to see if its better to move an expensive instruction used in a select behind a branch instead.

This is causing issues with upcoming improvements to TCK_SizeAndLatency costs on X86 as we need to use TCK_SizeAndLatency as an uop count (so its compatible with various target-specific buffer sizes - see D132288), but we can have instructions that have a low TCK_SizeAndLatency value but should still be treated as 'expensive' (FDIV for example) - by adding a isExpensiveToSpeculativelyExecute wrapper we can keep the current behaviour but still add an x86 override in a future patch when the cost tables are updated to compensate.

1 files changed, 1 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index 6786e90..cd6ee4e 100644
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -6604,8 +6604,7 @@ static bool sinkSelectOperand(const TargetTransformInfo *TTI, Value *V) {
   // If it's safe to speculatively execute, then it should not have side
   // effects; therefore, it's safe to sink and possibly *not* execute.
   return I && I->hasOneUse() && isSafeToSpeculativelyExecute(I) &&
-         TTI->getInstructionCost(I, TargetTransformInfo::TCK_SizeAndLatency) >=
-             TargetTransformInfo::TCC_Expensive;
+         TTI->isExpensiveToSpeculativelyExecute(I);
 }
 
 /// Returns true if a SelectInst should be turned into an explicit branch.