Revert r301950: SpeculativeExecution: Stop using whitelist for costs
This pass doesn't correctly handle testing for when it is legal to hoist
arbitrary instructions. The whitelist happens to make it safe, so before
it is removed the pass's legality checks will need to be enhanced.
Details have been added to the code review thread for the patch.
llvm-svn: 302640
diff --git a/llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp b/llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp
index a0fc966..a7c308b 100644
--- a/llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp
+++ b/llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp
@@ -208,6 +208,47 @@
return false;
}
+static unsigned ComputeSpeculationCost(const Instruction *I,
+ const TargetTransformInfo &TTI) {
+ switch (Operator::getOpcode(I)) {
+ case Instruction::GetElementPtr:
+ case Instruction::Add:
+ case Instruction::Mul:
+ case Instruction::And:
+ case Instruction::Or:
+ case Instruction::Select:
+ case Instruction::Shl:
+ case Instruction::Sub:
+ case Instruction::LShr:
+ case Instruction::AShr:
+ case Instruction::Xor:
+ case Instruction::ZExt:
+ case Instruction::SExt:
+ case Instruction::Call:
+ case Instruction::BitCast:
+ case Instruction::PtrToInt:
+ case Instruction::IntToPtr:
+ case Instruction::AddrSpaceCast:
+ case Instruction::FPToUI:
+ case Instruction::FPToSI:
+ case Instruction::UIToFP:
+ case Instruction::SIToFP:
+ case Instruction::FPExt:
+ case Instruction::FPTrunc:
+ case Instruction::FAdd:
+ case Instruction::FSub:
+ case Instruction::FMul:
+ case Instruction::FDiv:
+ case Instruction::FRem:
+ case Instruction::ICmp:
+ case Instruction::FCmp:
+ return TTI.getUserCost(I);
+
+ default:
+ return UINT_MAX; // Disallow anything not whitelisted.
+ }
+}
+
bool SpeculativeExecutionPass::considerHoistingFromTo(
BasicBlock &FromBlock, BasicBlock &ToBlock) {
SmallSet<const Instruction *, 8> NotHoisted;
@@ -223,7 +264,7 @@
unsigned TotalSpeculationCost = 0;
for (auto& I : FromBlock) {
- const unsigned Cost = TTI->getUserCost(&I);
+ const unsigned Cost = ComputeSpeculationCost(&I, *TTI);
if (Cost != UINT_MAX && isSafeToSpeculativelyExecute(&I) &&
AllPrecedingUsesFromBlockHoisted(&I)) {
TotalSpeculationCost += Cost;