Don't force SP-relative addressing for statepoints

Summary:
...  when the offset is not statically known.

Prioritize addresses relative to the stack pointer in the stackmap, but
fallback gracefully to other modes of addressing if the offset to the
stack pointer is not a known constant.

Patch by Oscar Blumberg!

Reviewers: sanjoy

Subscribers: llvm-commits, majnemer, rnk, sanjoy, thanm

Differential Revision: http://reviews.llvm.org/D21259

llvm-svn: 272756

1 files changed, 10 insertions, 3 deletions

diff --git a/llvm/lib/CodeGen/PrologEpilogInserter.cpp b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
index bd7f34b485e..33935c421a3 100644
--- a/llvm/lib/CodeGen/PrologEpilogInserter.cpp
+++ b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
@@ -1094,9 +1094,16 @@ void PEI::replaceFrameIndices(MachineBasicBlock *BB, MachineFunction &Fn,
                "DBG_VALUE machine instruction");
         unsigned Reg;
         MachineOperand &Offset = MI->getOperand(i + 1);
-        const unsigned refOffset =
-          TFI->getFrameIndexReferenceFromSP(Fn, MI->getOperand(i).getIndex(),
-                                            Reg);
+        int refOffset;
+        // First try to get an offset relative to SP. If that's not
+        // possible use whatever the target usually uses.
+        auto SPOffset = TFI->getFrameIndexReferenceFromSP(
+            Fn, MI->getOperand(i).getIndex(), Reg, /*AllowSPAdjustment*/ false);
+        if (SPOffset)
+          refOffset = *SPOffset;
+        else
+          refOffset = TFI->getFrameIndexReference(
+              Fn, MI->getOperand(i).getIndex(), Reg);
 
         Offset.setImm(Offset.getImm() + refOffset);
         MI->getOperand(i).ChangeToRegister(Reg, false /*isDef*/);