Codegen: LICM Remove check for exactly 1 register def.

When considering whether to split an instruction with a memory operand
into an explicit load and a register-based instruction, we currently
check that the resulting instruction has exactly 1 def. This prevents 2
important LICM optimizations: compares with memory operands, and double
indirect calls. All the tests and the test-suite pass without the check.
My guess as to original intent is to limit the additional register pressure
created by the new instruction, but given that we only split out a single
register, it is already limited.

The licm-dominance test now checks actual memory loads for hoisting instead of
undef, and it tests compares.
hoist-invariant-load.ll now checks for 2 hoists, the intended hoist, and a bonus
from calling a got-relative function in a loop.

llvm-svn: 273616

1 files changed, 0 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/MachineLICM.cpp b/llvm/lib/CodeGen/MachineLICM.cpp
index 00dec821158..a6f1c7519c6 100644
--- a/llvm/lib/CodeGen/MachineLICM.cpp
+++ b/llvm/lib/CodeGen/MachineLICM.cpp
@@ -1171,7 +1171,6 @@ MachineInstr *MachineLICM::ExtractHoistableLoad(MachineInstr *MI) {
                                     &LoadRegIndex);
   if (NewOpc == 0) return nullptr;
   const MCInstrDesc &MID = TII->get(NewOpc);
-  if (MID.getNumDefs() != 1) return nullptr;
   MachineFunction &MF = *MI->getParent()->getParent();
   const TargetRegisterClass *RC = TII->getRegClass(MID, LoadRegIndex, TRI, MF);
   // Ok, we're unfolding. Create a temporary register and do the unfold.