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llvm-svn: 36213
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index c6bdc2e..747a15b 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -3406,8 +3406,17 @@
}
}
+
+// Lower dynamic stack allocation to _alloca call for Cygwin/Mingw targets.
+// Calls to _alloca is needed to probe the stack when allocating more than 4k
+// bytes in one go. Touching the stack at 4K increments is necessary to ensure
+// that the guard pages used by the OS virtual memory manager are allocated in
+// correct sequence.
SDOperand X86TargetLowering::LowerDYNAMIC_STACKALLOC(SDOperand Op,
SelectionDAG &DAG) {
+ assert(Subtarget->isTargetCygMing() &&
+ "This should be used only on Cygwin/Mingw targets");
+
// Get the inputs.
SDOperand Chain = Op.getOperand(0);
SDOperand Size = Op.getOperand(1);