[mips] Make sure that we don't adjust the stack pointer by zero amount.

[dsanders]

LGTM with the check for 'Amount == 0' inside adjustStackPtr(). Each caller shouldn't have to check this for itself.

test/CodeGen/Mips/adjust-callstack-sp.ll

14–16

Nit: Indentation.

lib/Target/Mips/Mips16FrameLowering.cpp

bool Mips16FrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
 
   return true;
 }
 
 // Eliminate ADJCALLSTACKDOWN, ADJCALLSTACKUP pseudo instructions
 void Mips16FrameLowering::
 eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
                               MachineBasicBlock::iterator I) const {
+  const Mips16InstrInfo &TII =
+    *static_cast<const Mips16InstrInfo *>(STI.getInstrInfo());
+
   if (!hasReservedCallFrame(MF)) {
     int64_t Amount = I->getOperand(0).getImm();
-
+    if (Amount) {
       if (I->getOpcode() == Mips::ADJCALLSTACKDOWN)
         Amount = -Amount;
 
-    const Mips16InstrInfo &TII =
-        *static_cast<const Mips16InstrInfo *>(STI.getInstrInfo());
-
       TII.adjustStackPtr(Mips::SP, Amount, MBB, I);
     }
+  }
 
   MBB.erase(I);
 }
 
 bool
 Mips16FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
   const MachineFrameInfo *MFI = MF.getFrameInfo();
   // Reserve call frame if the size of the maximum call frame fits into 15-bit

lib/Target/Mips/MipsSEFrameLowering.cpp

 void MipsSEFrameLowering::
 eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
                               MachineBasicBlock::iterator I) const {
   const MipsSEInstrInfo &TII =
       *static_cast<const MipsSEInstrInfo *>(STI.getInstrInfo());
 
   if (!hasReservedCallFrame(MF)) {
     int64_t Amount = I->getOperand(0).getImm();
-
+    if (Amount) {
       if (I->getOpcode() == Mips::ADJCALLSTACKDOWN)
         Amount = -Amount;
 
       unsigned SP = STI.isABI_N64() ? Mips::SP_64 : Mips::SP;
       TII.adjustStackPtr(SP, Amount, MBB, I);
     }
+  }
 
   MBB.erase(I);
 }
 
 void MipsSEFrameLowering::
 processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
                                      RegScavenger *RS) const {
   MachineRegisterInfo &MRI = MF.getRegInfo();

lib/Target/Mips/MipsSEInstrInfo.cpp

 void MipsSEInstrInfo::adjustStackPtr(unsigned SP, int64_t Amount,
                                      MachineBasicBlock &MBB,
                                      MachineBasicBlock::iterator I) const {
   const MipsSubtarget &STI = Subtarget;
   DebugLoc DL = I != MBB.end() ? I->getDebugLoc() : DebugLoc();
   unsigned ADDu = STI.isABI_N64() ? Mips::DADDu : Mips::ADDu;
   unsigned ADDiu = STI.isABI_N64() ? Mips::DADDiu : Mips::ADDiu;
 
+  assert(Amount && "Request to adjust stack pointer by zero amount.");
+
   if (isInt<16>(Amount))// addi sp, sp, amount
     BuildMI(MBB, I, DL, get(ADDiu), SP).addReg(SP).addImm(Amount);
   else { // Expand immediate that doesn't fit in 16-bit.
     unsigned Reg = loadImmediate(Amount, MBB, I, DL, nullptr);
     BuildMI(MBB, I, DL, get(ADDu), SP).addReg(SP).addReg(Reg, RegState::Kill);
   }
 }
 

test/CodeGen/Mips/adjust-callstack-sp.ll

+; RUN: llc < %s -march=mips -mcpu=mips16 | FileCheck %s -check-prefix=M16
+; RUN: llc < %s -march=mips -mcpu=mips2 | FileCheck %s -check-prefix=GP32
+; RUN: llc < %s -march=mips -mcpu=mips32 | FileCheck %s -check-prefix=GP32
+; RUN: llc < %s -march=mips -mcpu=mips32r6 | FileCheck %s -check-prefix=GP32
+; RUN: llc < %s -march=mips -mcpu=mips3 | FileCheck %s -check-prefix=GP64
+; RUN: llc < %s -march=mips -mcpu=mips64 | FileCheck %s -check-prefix=GP64
+; RUN: llc < %s -march=mips -mcpu=mips64r6 | FileCheck %s -check-prefix=GP64
+
+declare void @bar(i32*)
+
+define void @foo(i32 %sz) {
+  ; ALL-LABEL: foo:
+
+    ; M16-NOT:        addiu     $sp, 0 # 16 bit inst
+    ; GP32-NOT:       addiu     $sp, $sp, 0
+    ; GP64-NOT:       daddiu    $sp, $sp, 0
+  %a = alloca i32, i32 %sz
+  call void @bar(i32* %a)
+  ret void
+}