improve comment

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@23134 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 3 insertions, 1 deletions

diff --git a/include/llvm/CodeGen/SelectionDAGNodes.h b/include/llvm/CodeGen/SelectionDAGNodes.h
index 7f66e5ad14..ba53a18b70 100644
--- a/include/llvm/CodeGen/SelectionDAGNodes.h
+++ b/include/llvm/CodeGen/SelectionDAGNodes.h
@@ -220,7 +220,9 @@ namespace ISD {
     // DYNAMIC_STACKALLOC - Allocate some number of bytes on the stack aligned
     // to a specified boundary.  The first operand is the token chain, the
     // second is the number of bytes to allocate, and the third is the alignment
-    // boundary.
+    // boundary.  The size is guaranteed to be a multiple of the stack 
+    // alignment, and the alignment is guaranteed to be bigger than the stack 
+    // alignment (if required) or 0 to get standard stack alignment.
     DYNAMIC_STACKALLOC,
 
     // Control flow instructions.  These all have token chains.