[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 ↗

(On Diff #22733)

Nit: Indentation.

llvm/trunk/lib/Target/Mips/Mips16InstrInfo.cpp

void Mips16InstrInfo::adjustStackPtrBigUnrestricted(
     MachineBasicBlock::iterator I) const {
    llvm_unreachable("adjust stack pointer amount exceeded");
 }
 
 /// Adjust SP by Amount bytes.
 void Mips16InstrInfo::adjustStackPtr(unsigned SP, int64_t Amount,
                                      MachineBasicBlock &MBB,
                                      MachineBasicBlock::iterator I) const {
+  if (Amount == 0)
+    return;
+
   if (isInt<16>(Amount))  // need to change to addiu sp, ....and isInt<16>
     BuildAddiuSpImm(MBB, I, Amount);
   else
     adjustStackPtrBigUnrestricted(SP, Amount, MBB, I);
 }
 
 /// This function generates the sequence of instructions needed to get the
 /// result of adding register REG and immediate IMM.

llvm/trunk/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;
 
+  if (Amount == 0)
+    return;
+
   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);
   }
 }
 

llvm/trunk/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
+}