[WebAssembly] Implement __builtin_frame_address.

Differential Revision: http://reviews.llvm.org/D17307

llvm-svn: 261032

4 files changed, 23 insertions, 8 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp
index 27274c066b2..1c358b340bd 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp
@@ -44,11 +44,11 @@ using namespace llvm;
 /// register.
 bool WebAssemblyFrameLowering::hasFP(const MachineFunction &MF) const {
   const MachineFrameInfo *MFI = MF.getFrameInfo();
-  assert(!MFI->isFrameAddressTaken());
   const auto *RegInfo =
       MF.getSubtarget<WebAssemblySubtarget>().getRegisterInfo();
-  return MFI->hasVarSizedObjects() || MFI->hasStackMap() ||
-         MFI->hasPatchPoint() || RegInfo->needsStackRealignment(MF);
+  return MFI->isFrameAddressTaken() || MFI->hasVarSizedObjects() ||
+         MFI->hasStackMap() || MFI->hasPatchPoint() ||
+         RegInfo->needsStackRealignment(MF);
 }
 
 /// Under normal circumstances, when a frame pointer is not required, we reserve
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
index 2027e8ba678..c5ec506804c 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
@@ -542,9 +542,8 @@ SDValue WebAssemblyTargetLowering::LowerOperation(SDValue Op,
     case ISD::RETURNADDR: // Probably nothing meaningful can be returned here.
       fail(DL, DAG, "WebAssembly hasn't implemented __builtin_return_address");
       return SDValue();
-    case ISD::FRAMEADDR: // TODO: Make this return the userspace frame address
-      fail(DL, DAG, "WebAssembly hasn't implemented __builtin_frame_address");
-      return SDValue();
+    case ISD::FRAMEADDR:
+      return LowerFRAMEADDR(Op, DAG);
     case ISD::CopyToReg:
       return LowerCopyToReg(Op, DAG);
   }
@@ -579,6 +578,21 @@ SDValue WebAssemblyTargetLowering::LowerFrameIndex(SDValue Op,
   return DAG.getTargetFrameIndex(FI, Op.getValueType());
 }
 
+SDValue WebAssemblyTargetLowering::LowerFRAMEADDR(SDValue Op,
+                                                  SelectionDAG &DAG) const {
+  // Non-zero depths are not supported by WebAssembly currently. Use the
+  // legalizer's default expansion, which is to return 0 (what this function is
+  // documented to do).
+  if (cast<ConstantSDNode>(Op.getOperand(0))->getZExtValue() > 0)
+    return SDValue();
+
+  DAG.getMachineFunction().getFrameInfo()->setFrameAddressIsTaken(true);
+  EVT VT = Op.getValueType();
+  unsigned FP =
+      Subtarget->getRegisterInfo()->getFrameRegister(DAG.getMachineFunction());
+  return DAG.getCopyFromReg(DAG.getEntryNode(), SDLoc(Op), FP, VT);
+}
+
 SDValue WebAssemblyTargetLowering::LowerGlobalAddress(SDValue Op,
                                                       SelectionDAG &DAG) const {
   SDLoc DL(Op);
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.h b/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.h
index 4aed2b1ec82..5b538fda479 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.h
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.h
@@ -78,6 +78,7 @@ class WebAssemblyTargetLowering final : public TargetLowering {
   // Custom lowering hooks.
   SDValue LowerOperation(SDValue Op, SelectionDAG &DAG) const override;
   SDValue LowerFrameIndex(SDValue Op, SelectionDAG &DAG) const;
+  SDValue LowerFRAMEADDR(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerGlobalAddress(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerExternalSymbol(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerBR_JT(SDValue Op, SelectionDAG &DAG) const;
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyRegNumbering.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyRegNumbering.cpp
index f38f635d822..76ea0d72f6d 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyRegNumbering.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyRegNumbering.cpp
@@ -108,11 +108,11 @@ bool WebAssemblyRegNumbering::runOnMachineFunction(MachineFunction &MF) {
     }
   }
   // Allocate locals for used physical registers
-  if (FrameInfo.getStackSize() > 0 || FrameInfo.adjustsStack()) {
+  bool HasFP = MF.getSubtarget().getFrameLowering()->hasFP(MF);
+  if (FrameInfo.getStackSize() > 0 || FrameInfo.adjustsStack() || HasFP) {
     DEBUG(dbgs() << "PReg SP " << CurReg << "\n");
     MFI.addPReg(WebAssembly::SP32, CurReg++);
   }
-  bool HasFP = MF.getSubtarget().getFrameLowering()->hasFP(MF);
   if (HasFP) {
     DEBUG(dbgs() << "PReg FP " << CurReg << "\n");
     MFI.addPReg(WebAssembly::FP32, CurReg++);