There are some Mips instructions that are lowered by the

assembler such as shifts greater than 32. In the case 
of direct object, the code gen needs to do this lowering 
since the assembler is not involved.

With the advent of the llvm-mc assembler, it also needs 
to do the same lowering.

This patch makes that specific lowering code accessible 
to both the direct object output and the assembler.

This patch does not affect generated output.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163287 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 86 insertions, 0 deletions

diff --git a/lib/Target/Mips/MipsDirectObjLower.cpp b/lib/Target/Mips/MipsDirectObjLower.cpp
new file mode 100644
index 0000000000..0d74db808c
--- /dev/null
+++ b/lib/Target/Mips/MipsDirectObjLower.cpp
@@ -0,0 +1,86 @@
+//===-- MipsDirectObjLower.cpp - Mips LLVM direct object lowering -----===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains code to lower Mips MCInst records that are normally
+// left to the assembler to lower such as large shifts.
+//
+//===----------------------------------------------------------------------===//
+#include "MipsDirectObjLower.h"
+#include "MipsInstrInfo.h"
+#include "llvm/MC/MCInst.h"
+#include "llvm/MC/MCStreamer.h"
+
+using namespace llvm;
+
+// If the D<shift> instruction has a shift amount that is greater
+// than 31 (checked in calling routine), lower it to a D<shift>32 instruction
+void Mips::LowerLargeShift(MCInst& Inst) {
+
+  assert(Inst.getNumOperands() == 3 && "Invalid no. of operands for shift!");
+  assert(Inst.getOperand(2).isImm());
+
+  bool isLarge = false;
+  int64_t Shift;
+  Shift = Inst.getOperand(2).getImm();
+  if (Shift > 31) {
+    Shift -= 32;
+    isLarge = true;
+  }
+
+  // saminus32
+  (Inst.getOperand(2)).setImm(Shift);
+
+  if (isLarge)
+    switch (Inst.getOpcode()) {
+    default:
+      // Calling function is not synchronized
+      llvm_unreachable("Unexpected shift instruction");
+    case Mips::DSLL:
+      Inst.setOpcode(Mips::DSLL32);
+      return;
+    case Mips::DSRL:
+      Inst.setOpcode(Mips::DSRL32);
+      return;
+    case Mips::DSRA:
+      Inst.setOpcode(Mips::DSRA32);
+      return;
+    }
+}
+
+// Pick a DEXT or DINS instruction variant based on the pos and size operands
+void Mips::LowerDextDins(MCInst& InstIn) {
+  int Opcode = InstIn.getOpcode();
+
+  if (Opcode == Mips::DEXT)
+    assert(InstIn.getNumOperands() == 4 &&
+           "Invalid no. of machine operands for DEXT!");
+  else // Only DEXT and DINS are possible
+    assert(InstIn.getNumOperands() == 5 &&
+           "Invalid no. of machine operands for DINS!");
+
+  assert(InstIn.getOperand(2).isImm());
+  int64_t pos = InstIn.getOperand(2).getImm();
+  assert(InstIn.getOperand(3).isImm());
+  int64_t size = InstIn.getOperand(3).getImm();
+
+  if (size <= 32) {
+    if ((pos < 32)) { // DEXT/DINS, do nothing
+      return;
+    } else { // DEXTU/DINSU
+      InstIn.getOperand(2).setImm(pos - 32);
+      InstIn.setOpcode((Opcode == Mips::DEXT) ? Mips::DEXTU : Mips::DINSU);
+      return;
+    }
+  } else { // DEXTM/DINSM
+    assert(pos < 32 && "DEXT/DINS cannot have both size and pos > 32");
+    InstIn.getOperand(3).setImm(size - 32);
+    InstIn.setOpcode((Opcode == Mips::DEXT) ? Mips::DEXTM : Mips::DINSM);
+    return;
+  }
+}