Fix a crash compiling 254.gap for Thumb2. The Thumb2 add/sub with 12-bit

[oota-llvm.git] / lib / Target / ARM / ARMLoadStoreOptimizer.cpp

diff --git a/lib/Target/ARM/ARMLoadStoreOptimizer.cpp b/lib/Target/ARM/ARMLoadStoreOptimizer.cpp
index 4e2d1815dc6778380ea5d5f0486b9cdedfafbe72..19f1e3ba12cfffaf0d48a4add2bd5700852369d7 100644 (file)
--- a/lib/Target/ARM/ARMLoadStoreOptimizer.cpp
+++ b/lib/Target/ARM/ARMLoadStoreOptimizer.cpp
@@ -748,11 +748,24 @@ static bool isMemoryOp(const MachineInstr *MI) {
     if (MMO->isVolatile())
       return false;
 
-    // Unaligned ldr/str is emulated by some kernels, but unaligned ldm/stm is not.
+    // Unaligned ldr/str is emulated by some kernels, but unaligned ldm/stm is
+    // not.
     if (MMO->getAlignment() < 4)
       return false;
   }
 
+  // str <undef> could probably be eliminated entirely, but for now we just want
+  // to avoid making a mess of it.
+  // FIXME: Use str <undef> as a wildcard to enable better stm folding.
+  if (MI->getNumOperands() > 0 && MI->getOperand(0).isReg() &&
+      MI->getOperand(0).isUndef())
+    return false;
+
+  // Likewise don't mess with references to undefined addresses.
+  if (MI->getNumOperands() > 1 && MI->getOperand(1).isReg() &&
+      MI->getOperand(1).isUndef())
+    return false;
+
   int Opcode = MI->getOpcode();
   switch (Opcode) {
   default: break;