For Mips 16, add the optimization where the 16 bit form of addiu sp can be used

if the offset fits in 11 bits. This makes use of the fact that the abi
requires sp to be 8 byte aligned so the actual offset can fit in 8
bits. It will be shifted left and sign extended before being actually used.
The assembler or direct object emitter will shift right the 11 bit
signed field by 3 bits. We don't need to deal with that here.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175073 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 46 insertions, 3 deletions

diff --git a/lib/Target/Mips/Mips16InstrInfo.cpp b/lib/Target/Mips/Mips16InstrInfo.cpp
index 9f27ac3517..5a91519fd8 100644
--- a/lib/Target/Mips/Mips16InstrInfo.cpp
+++ b/lib/Target/Mips/Mips16InstrInfo.cpp
@@ -184,7 +184,7 @@ void Mips16InstrInfo::makeFrame(unsigned SP, int64_t FrameSize,
       int64_t Remainder = FrameSize - Base;
       BuildMI(MBB, I, DL, get(Mips::SaveRaF16)). addImm(Base);
       if (isInt<16>(-Remainder))
-        BuildMI(MBB, I, DL, get(Mips::AddiuSpImmX16)). addImm(-Remainder);
+        BuildAddiuSpImm(MBB, I, DL, -Remainder);
       else
         adjustStackPtrBig(SP, -Remainder, MBB, I, Mips::V0, Mips::V1);
     }
@@ -225,7 +225,7 @@ void Mips16InstrInfo::restoreFrame(unsigned SP, int64_t FrameSize,
                        // returns largest possible n bit unsigned integer
       int64_t Remainder = FrameSize - Base;
       if (isInt<16>(Remainder))
-        BuildMI(MBB, I, DL, get(Mips::AddiuSpImmX16)). addImm(Remainder);
+        BuildAddiuSpImm(MBB, I, DL, Remainder);
       else
         adjustStackPtrBig(SP, Remainder, MBB, I, Mips::A0, Mips::A1);
       BuildMI(MBB, I, DL, get(Mips::RestoreRaF16)). addImm(Base);
@@ -299,7 +299,7 @@ void Mips16InstrInfo::adjustStackPtr(unsigned SP, int64_t Amount,
                                      MachineBasicBlock::iterator I) const {
   DebugLoc DL = I != MBB.end() ? I->getDebugLoc() : DebugLoc();
   if (isInt<16>(Amount))  // need to change to addiu sp, ....and isInt<16>
-    BuildMI(MBB, I, DL, get(Mips::AddiuSpImmX16)). addImm(Amount);
+    BuildAddiuSpImm(MBB, I, DL, Amount);
   else
     adjustStackPtrBigUnrestricted(SP, Amount, MBB, I);
 }
@@ -400,6 +400,15 @@ void Mips16InstrInfo::ExpandRetRA16(MachineBasicBlock &MBB,
   BuildMI(MBB, I, I->getDebugLoc(), get(Opc));
 }
 
+void Mips16InstrInfo::BuildAddiuSpImm(
+  MachineBasicBlock &MBB,
+  MachineBasicBlock::iterator II, DebugLoc DL, int64_t Imm) const {
+  if (validSpImm8(Imm))
+    BuildMI(MBB, II, DL, get(Mips::AddiuSpImm16)).addImm(Imm);
+  else
+    BuildMI(MBB, II, DL, get(Mips::AddiuSpImmX16)).addImm(Imm);
+}
+
 const MipsInstrInfo *llvm::createMips16InstrInfo(MipsTargetMachine &TM) {
   return new Mips16InstrInfo(TM);
 }
diff --git a/lib/Target/Mips/Mips16InstrInfo.h b/lib/Target/Mips/Mips16InstrInfo.h
index 26a5a5e5fb..f8570bdc27 100644
--- a/lib/Target/Mips/Mips16InstrInfo.h
+++ b/lib/Target/Mips/Mips16InstrInfo.h
@@ -86,6 +86,18 @@ public:
                          MachineBasicBlock::iterator II, DebugLoc DL,
                          unsigned &NewImm) const;
 
+  static bool validSpImm8(int offset) {
+    return ((offset & 7) == 0) && isInt<11>(offset);
+  }
+
+  //
+  // build the proper one based on the Imm field
+  //
+  void BuildAddiuSpImm(MachineBasicBlock &MBB,
+                           MachineBasicBlock::iterator II, DebugLoc DL,
+                           int64_t Imm) const;
+
+
 private:
   virtual unsigned GetAnalyzableBrOpc(unsigned Opc) const;
 
diff --git a/lib/Target/Mips/Mips16InstrInfo.td b/lib/Target/Mips/Mips16InstrInfo.td
index c3e61bbd12..06344dbccf 100644
--- a/lib/Target/Mips/Mips16InstrInfo.td
+++ b/lib/Target/Mips/Mips16InstrInfo.td
@@ -32,6 +32,21 @@ def mem16_ea : Operand<i32> {
 }
 
 //
+//
+// I8 instruction format
+//
+
+class FI816_ins_base<bits<3> _func, string asmstr,
+                     string asmstr2, InstrItinClass itin>:
+  FI816<_func, (outs), (ins simm16:$imm), !strconcat(asmstr, asmstr2),
+        [], itin>;
+
+
+class FI816_SP_ins<bits<3> _func, string asmstr,
+                   InstrItinClass itin>:
+  FI816_ins_base<_func, asmstr, "\t$$sp, $imm # 16 bit inst", itin>;
+
+//
 // RI instruction format
 //
 
@@ -451,6 +466,13 @@ def AddiuRxPcImmX16: FEXT_RI16_PC_ins<0b00001, "addiu", IIAlu>;
 // Purpose: Add Immediate Unsigned Word (2-Operand, SP-Relative, Extended)
 // To add a constant to the stack pointer.
 //
+def AddiuSpImm16
+  : FI816_SP_ins<0b011, "addiu", IIAlu> {
+  let Defs = [SP];
+  let Uses = [SP];
+  let AddedComplexity = 5;
+}
+
 def AddiuSpImmX16
   : FEXT_I816_SP_ins<0b011, "addiu", IIAlu> {
   let Defs = [SP];