Ensure all uses of permute instructions feed vector stores

There is a problem in VSXSwapRemoval where it is incorrectly removing permute instructions.
In this case, the permute is feeding both a vector store and also a non-store instruction. In this case, the permute cannot be removed.

The fix is to simply look at all the uses of the vector register defined by the permute and ensure that all the uses are vector store instructions.

This problem was reported in PR 27735 (https://llvm.org/bugs/show_bug.cgi?id=27735).

Test case based on the original problem reported.

Phabricator Review: http://reviews.llvm.org/D21802

llvm-svn: 274645

1 files changed, 20 insertions, 0 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCVSXSwapRemoval.cpp b/llvm/lib/Target/PowerPC/PPCVSXSwapRemoval.cpp
index a1aa841eccc..d53c8e38254 100644
--- a/llvm/lib/Target/PowerPC/PPCVSXSwapRemoval.cpp
+++ b/llvm/lib/Target/PowerPC/PPCVSXSwapRemoval.cpp
@@ -692,6 +692,7 @@ void PPCVSXSwapRemoval::recordUnoptimizableWebs() {
       MachineInstr *MI = SwapVector[EntryIdx].VSEMI;
       unsigned UseReg = MI->getOperand(0).getReg();
       MachineInstr *DefMI = MRI->getVRegDef(UseReg);
+      unsigned DefReg = DefMI->getOperand(0).getReg();
       int DefIdx = SwapMap[DefMI];
 
       if (!SwapVector[DefIdx].IsSwap || SwapVector[DefIdx].IsLoad ||
@@ -707,6 +708,25 @@ void PPCVSXSwapRemoval::recordUnoptimizableWebs() {
         DEBUG(MI->dump());
         DEBUG(dbgs() << "\n");
       }
+
+      // Ensure all uses of the register defined by DefMI feed store
+      // instructions
+      for (MachineInstr &UseMI : MRI->use_nodbg_instructions(DefReg)) {
+        int UseIdx = SwapMap[&UseMI];
+
+        if (SwapVector[UseIdx].VSEMI->getOpcode() != MI->getOpcode()) {
+          SwapVector[Repr].WebRejected = 1;
+
+          DEBUG(dbgs() <<
+                format("Web %d rejected for swap not feeding only stores\n",
+                       Repr));
+          DEBUG(dbgs() << "  def " << " : ");
+          DEBUG(DefMI->dump());
+          DEBUG(dbgs() << "  use " << UseIdx << ": ");
+          DEBUG(SwapVector[UseIdx].VSEMI->dump());
+          DEBUG(dbgs() << "\n");
+        }
+      }
     }
   }