DAG: allow DAG pointer size different from memory representation.

In preparation for supporting ILP32 on AArch64, this modifies the SelectionDAG
builder code so that pointers are allowed to have a larger type when "live" in
the DAG compared to memory.

Pointers get zero-extended whenever they are loaded, and truncated prior to
stores.  In addition, a few not quite so obvious locations need updating:

  * A GEP that has not been marked inbounds needs to enforce the IR-documented
    2s-complement wrapping at the memory pointer size. Inbounds GEPs are
    undefined if they overflow the address space, so no additional operations
    are needed.
  * Signed comparisons would give incorrect results if performed on the
    zero-extended values.

This shouldn't affect CodeGen for now, but will become active when the AArch64
ILP32 support is committed.

llvm-svn: 359676

1 files changed, 12 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index e85695755d4..86e2fc2d675 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -1145,6 +1145,18 @@ SDValue SelectionDAG::getZeroExtendInReg(SDValue Op, const SDLoc &DL, EVT VT) {
                  getConstant(Imm, DL, Op.getValueType()));
 }
 
+SDValue SelectionDAG::getPtrExtOrTrunc(SDValue Op, const SDLoc &DL, EVT VT) {
+  // Only unsigned pointer semantics are supported right now. In the future this
+  // might delegate to TLI to check pointer signedness.
+  return getZExtOrTrunc(Op, DL, VT);
+}
+
+SDValue SelectionDAG::getPtrExtendInReg(SDValue Op, const SDLoc &DL, EVT VT) {
+  // Only unsigned pointer semantics are supported right now. In the future this
+  // might delegate to TLI to check pointer signedness.
+  return getZeroExtendInReg(Op, DL, VT);
+}
+
 /// getNOT - Create a bitwise NOT operation as (XOR Val, -1).
 SDValue SelectionDAG::getNOT(const SDLoc &DL, SDValue Val, EVT VT) {
   EVT EltVT = VT.getScalarType();