[ARM GlobalISel] Fix G_STORE with s1

G_STORE for 1-bit values uses a STRBi12, which stores the whole byte.
Zero out the undefined bits before writing.

llvm-svn: 357154

1 files changed, 18 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/ARMInstructionSelector.cpp b/llvm/lib/Target/ARM/ARMInstructionSelector.cpp
index d0b63d676da..6df74eca6ea 100644
--- a/llvm/lib/Target/ARM/ARMInstructionSelector.cpp
+++ b/llvm/lib/Target/ARM/ARMInstructionSelector.cpp
@@ -1048,6 +1048,24 @@ bool ARMInstructionSelector::select(MachineInstr &I,
     if (NewOpc == G_LOAD || NewOpc == G_STORE)
       return false;
 
+    if (ValSize == 1 && NewOpc == Opcodes.STORE8) {
+      // Before storing a 1-bit value, make sure to clear out any unneeded bits.
+      unsigned OriginalValue = I.getOperand(0).getReg();
+
+      unsigned ValueToStore = MRI.createVirtualRegister(&ARM::GPRRegClass);
+      I.getOperand(0).setReg(ValueToStore);
+
+      auto InsertBefore = I.getIterator();
+      auto AndI = BuildMI(MBB, InsertBefore, I.getDebugLoc(), TII.get(Opcodes.AND))
+        .addDef(ValueToStore)
+        .addUse(OriginalValue)
+        .addImm(1)
+        .add(predOps(ARMCC::AL))
+        .add(condCodeOp());
+      if (!constrainSelectedInstRegOperands(*AndI, TII, TRI, RBI))
+        return false;
+    }
+
     I.setDesc(TII.get(NewOpc));
 
     if (NewOpc == ARM::LDRH || NewOpc == ARM::STRH)