To shrink a t2LDM instruction to the 16-bit wide tLDM instruction, the base

register must be one of the destination registers for the load. Otherwise,
the tLDM instruction will write-back to the base register, which isn't what's
desired (otherwise, we'd have a t2LDM_UPD instead).

rdar://8394087

llvm-svn: 113297

1 files changed, 12 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/Thumb2SizeReduction.cpp b/llvm/lib/Target/ARM/Thumb2SizeReduction.cpp
index 1451c53112f..0c3962dd123 100644
--- a/llvm/lib/Target/ARM/Thumb2SizeReduction.cpp
+++ b/llvm/lib/Target/ARM/Thumb2SizeReduction.cpp
@@ -315,6 +315,18 @@ Thumb2SizeReduce::ReduceLoadStore(MachineBasicBlock &MBB, MachineInstr *MI,
     ARM_AM::AMSubMode Mode = ARM_AM::getAM4SubMode(MI->getOperand(1).getImm());
     if (!isARMLowRegister(BaseReg) || Mode != ARM_AM::ia)
       return false;
+    // For the non-writeback version (this one), the base register must be
+    // one of the registers being loaded.
+    bool isOK = false;
+    for (unsigned i = 4; i < MI->getNumOperands(); ++i) {
+      if (MI->getOperand(i).getReg() == BaseReg) {
+        isOK = true;
+        break;
+      }
+    }
+    if (!isOK)
+      return false;
+
     OpNum = 0;
     isLdStMul = true;
     break;