DAG: Fix expansion of DYNAMIC_STACKALLOC for StackGrowsUp targets

Can't test this since I can't directly use the default expansion for
AMDGPU. It needs to scale the amount by the wave size, rather than use
the raw byte size value.

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index 2ffcc85..9969786 100644 (file)
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -1600,9 +1600,13 @@ void SelectionDAGLegalize::ExpandDYNAMIC_STACKALLOC(SDNode* Node,
   SDValue SP = DAG.getCopyFromReg(Chain, dl, SPReg, VT);
   Chain = SP.getValue(1);
   unsigned Align = cast<ConstantSDNode>(Tmp3)->getZExtValue();
-  unsigned StackAlign =
-      DAG.getSubtarget().getFrameLowering()->getStackAlignment();
-  Tmp1 = DAG.getNode(ISD::SUB, dl, VT, SP, Size);       // Value
+  const TargetFrameLowering *TFL = DAG.getSubtarget().getFrameLowering();
+  unsigned Opc =
+    TFL->getStackGrowthDirection() == TargetFrameLowering::StackGrowsUp ?
+    ISD::ADD : ISD::SUB;
+
+  unsigned StackAlign = TFL->getStackAlignment();
+  Tmp1 = DAG.getNode(Opc, dl, VT, SP, Size);       // Value
   if (Align > StackAlign)
     Tmp1 = DAG.getNode(ISD::AND, dl, VT, Tmp1,
                        DAG.getConstant(-(uint64_t)Align, dl, VT));