[llvm] dda8298 - DAG: Fix expansion of DYNAMIC_STACKALLOC for StackGrowsUp targets

[Matt Arsenault via llvm-commits]

Author: Matt Arsenault
Date: 2020-05-27T18:45:40-04:00
New Revision: dda82986f97747350dce4e8ebd65c27a64a37c9d

URL: https://github.com/llvm/llvm-project/commit/dda82986f97747350dce4e8ebd65c27a64a37c9d
DIFF: https://github.com/llvm/llvm-project/commit/dda82986f97747350dce4e8ebd65c27a64a37c9d.diff

LOG: 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.

Added: 
    

Modified: 
    llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

Removed: 
    


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diff  --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index 2ffcc859f805..9969786d8d43 100644
--- 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));