This file provides the function DemoteRegToStack(), which takes a

virtual register computed by an Instruction& X and replaces it with
a slot in the stack frame, allocated via alloca.

llvm-svn: 4963

1 files changed, 21 insertions, 0 deletions

diff --git a/llvm/include/llvm/Transforms/Utils/DemoteRegToStack.h b/llvm/include/llvm/Transforms/Utils/DemoteRegToStack.h
new file mode 100644
index 00000000000..915a19f1125
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+++ b/llvm/include/llvm/Transforms/Utils/DemoteRegToStack.h
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+//===- DemoteRegToStack.h - Move a virtual reg. to stack --------*- C++ -*-===//
+// This file provides the function:
+//     AllocaInst* DemoteRegToStack(Instruction& X):
+//
+// This function takes a virtual register computed by an
+// Instruction& X and replaces it with a slot in the stack frame,
+// allocated via alloca.  It has to:
+// (1) Identify all Phi operations that have X as an operand and
+//     transitively other Phis that use such Phis; 
+// (2) Store all values merged with X via Phi operations to the stack slot;
+// (3) Load the value from the stack slot just before any use of X or any
+//     of the Phis that were eliminated; and
+// (4) Delete X and all the Phis, which should all now be dead.
+//
+// Returns the pointer to the alloca inserted to create a stack slot for X.
+//---------------------------------------------------------------------------- 
+
+class Instruction;
+class AllocaInst;
+
+extern AllocaInst* DemoteRegToStack(Instruction& X);