[mips] N64 static relocation model support

This patch makes one change to GOT handling and two changes to N64's
relocation model handling. Furthermore, the jumptable encodings have
been corrected for static N64.

Big GOT handling is now done via a new SDNode MipsGotHi - this node is
unconditionally lowered to an lui instruction.

The first change to N64's relocation handling is the lifting of the
restriction that N64 always uses PIC. Now it is possible to target static
environments.

The second change adds support for 64 bit symbols and enables them by
default. Previously N64 had patterns for sym32 mode only. In this mode all
symbols are assumed to have 32 bit addresses. sym32 mode support
is selectable with attribute 'sym32'. A follow on patch for clang will
add the necessary frontend parameter.

This partially resolves PR/23485.

Thanks to Brooks Davis for reporting the issue!

Reviewers: dsanders, seanbruno, zoran.jovanovic, vkalintiris

Differential Revision: https://reviews.llvm.org/D23652

llvm-svn: 293164

1 files changed, 47 insertions, 6 deletions

diff --git a/llvm/lib/Target/Mips/MipsISelLowering.h b/llvm/lib/Target/Mips/MipsISelLowering.h
index cddf0903ca6..abc34be6377 100644
--- a/llvm/lib/Target/Mips/MipsISelLowering.h
+++ b/llvm/lib/Target/Mips/MipsISelLowering.h
@@ -37,14 +37,23 @@ namespace llvm {
       // Tail call
       TailCall,
 
-      // Get the Higher 16 bits from a 32-bit immediate
+      // Get the Highest (63-48) 16 bits from a 64-bit immediate
+      Highest,
+
+      // Get the Higher (47-32) 16 bits from a 64-bit immediate
+      Higher,
+
+      // Get the High 16 bits from a 32/64-bit immediate
       // No relation with Mips Hi register
       Hi,
 
-      // Get the Lower 16 bits from a 32-bit immediate
+      // Get the Lower 16 bits from a 32/64-bit immediate
       // No relation with Mips Lo register
       Lo,
 
+      // Get the High 16 bits from a 32 bit immediate for accessing the GOT.
+      GotHi,
+
       // Handle gp_rel (small data/bss sections) relocation.
       GPRel,
 
@@ -297,7 +306,7 @@ namespace llvm {
     }
 
     bool isJumpTableRelative() const override {
-      return getTargetMachine().isPositionIndependent() || ABI.IsN64();
+      return getTargetMachine().isPositionIndependent();
     }
 
   protected:
@@ -344,8 +353,8 @@ namespace llvm {
                                   SelectionDAG &DAG, unsigned HiFlag,
                                   unsigned LoFlag, SDValue Chain,
                                   const MachinePointerInfo &PtrInfo) const {
-      SDValue Hi =
-          DAG.getNode(MipsISD::Hi, DL, Ty, getTargetNode(N, Ty, DAG, HiFlag));
+      SDValue Hi = DAG.getNode(MipsISD::GotHi, DL, Ty,
+                               getTargetNode(N, Ty, DAG, HiFlag));
       Hi = DAG.getNode(ISD::ADD, DL, Ty, Hi, getGlobalReg(DAG, Ty));
       SDValue Wrapper = DAG.getNode(MipsISD::Wrapper, DL, Ty, Hi,
                                     getTargetNode(N, Ty, DAG, LoFlag));
@@ -356,6 +365,8 @@ namespace llvm {
     // computing a symbol's address in non-PIC mode:
     //
     // (add %hi(sym), %lo(sym))
+    //
+    // This method covers O32, N32 and N64 in sym32 mode.
     template <class NodeTy>
     SDValue getAddrNonPIC(NodeTy *N, const SDLoc &DL, EVT Ty,
                           SelectionDAG &DAG) const {
@@ -364,7 +375,37 @@ namespace llvm {
       return DAG.getNode(ISD::ADD, DL, Ty,
                          DAG.getNode(MipsISD::Hi, DL, Ty, Hi),
                          DAG.getNode(MipsISD::Lo, DL, Ty, Lo));
-    }
+   }
+
+   // This method creates the following nodes, which are necessary for
+   // computing a symbol's address in non-PIC mode for N64.
+   //
+   // (add (shl (add (shl (add %highest(sym), %higher(sim)), 16), %high(sym)),
+   //            16), %lo(%sym))
+   //
+   // FIXME: This method is not efficent for (micro)MIPS64R6.
+   template <class NodeTy>
+   SDValue getAddrNonPICSym64(NodeTy *N, const SDLoc &DL, EVT Ty,
+                          SelectionDAG &DAG) const {
+      SDValue Hi = getTargetNode(N, Ty, DAG, MipsII::MO_ABS_HI);
+      SDValue Lo = getTargetNode(N, Ty, DAG, MipsII::MO_ABS_LO);
+
+      SDValue Highest =
+          DAG.getNode(MipsISD::Highest, DL, Ty,
+                      getTargetNode(N, Ty, DAG, MipsII::MO_HIGHEST));
+      SDValue Higher = getTargetNode(N, Ty, DAG, MipsII::MO_HIGHER);
+      SDValue HigherPart =
+          DAG.getNode(ISD::ADD, DL, Ty, Highest,
+                      DAG.getNode(MipsISD::Higher, DL, Ty, Higher));
+      SDValue Cst = DAG.getConstant(16, DL, MVT::i32);
+      SDValue Shift = DAG.getNode(ISD::SHL, DL, Ty, HigherPart, Cst);
+      SDValue Add = DAG.getNode(ISD::ADD, DL, Ty, Shift,
+                                DAG.getNode(MipsISD::Hi, DL, Ty, Hi));
+      SDValue Shift2 = DAG.getNode(ISD::SHL, DL, Ty, Add, Cst);
+
+      return DAG.getNode(ISD::ADD, DL, Ty, Shift2,
+                         DAG.getNode(MipsISD::Lo, DL, Ty, Lo));
+   }
 
     // This method creates the following nodes, which are necessary for
     // computing a symbol's address using gp-relative addressing: