[Mips] Emit proper ABI for _mcount calls

[mbrkusanin]

Summary

When -pg option is present than a call to _mcount is inserted into every
function. However since the proper ABI was not followed then the generated
gmon.out did not give proper results. By inserting needed instructions before
every _mcount we can fix this.

[mbrkusanin]

Simple use case if someone is unfamiliar with gpof and -pg options:

clang++ test.cpp -pg  ... # compile with _mcount calls
./a.out                   # generates gmon.out
gprof a.out               # shows report

For simple test.cpp:

int main() {
  return 0;
}

We now get proper results:

...
index % time    self  children    called     name
                0.00    0.00       1/1           __libc_start_main [620]
[1]      0.0    0.00    0.00       1         main [1]
...

Tested with following configurations:

mips -fpic -fast-isel=false         (used for _mcount: Mips::JALRPseudo)
mips -fpic                          (used for _mcount: Mips::JALR)
mips  -fast-isel=false              (used for _mcount: Mips::JAL)
mips                                (used for _mcount: Mips::JAL)
mips64 -fpic -fast-isel=false       (used for _mcount: Mips::JALR64Pseudo)
mips64 -fpic                        (used for _mcount: Mips::JALR64Pseudo)
mips64 -fast-isel=false             (used for _mcount: Mips::JALR64Pseudo)
mips64                              (used for _mcount: Mips::JALR64Pseudo)
micromips -fpic -fast-isel=false    (used for _mcount: Mips::JALR16_MM)
micromips -fpic                     (used for _mcount: Mips::JALR16_MM)
micromips -fast-isel=false          (used for _mcount: Mips::JAL_MM)
micromips                           (used for _mcount: Mips::JAL_MM)

Current _mcount implementation for Mips can be found here:
https://sourceware.org/git/gitweb.cgi?p=glibc.git;a=blob;f=sysdeps/mips/machine-gmon.h;hb=HEAD

[atanasyan]

LGTM

[RKSimon]

@mbrkusanin This is causing failures on EXPENSIVE_CHECKS builds, please can you take a look?

http://lab.llvm.org:8011/builders/llvm-clang-x86_64-expensive-checks-win/builds/20071/steps/test-check-all/logs/stdio

[mbrkusanin]

In D68390#1701209, @RKSimon wrote:

This is causing failures on EXPENSIVE_CHECKS builds, please can you take a look?

Thanks. I will look into it as soon as possible.

[mbrkusanin]

Tests would fail when we add -verify-machineinstrs option.

I've added this option to my test and fixed the code in: r374320

llvm/lib/Target/Mips/MipsSEISelDAGToDAG.h

private:
   /// ending at the most significant bit.
   bool selectVSplatMaskL(SDValue N, SDValue &Imm) const override;
   /// Select constant vector splats whose value is a run of set bits
   /// starting at bit zero.
   bool selectVSplatMaskR(SDValue N, SDValue &Imm) const override;
 
   bool trySelect(SDNode *Node) override;
 
+  // Emits proper ABI for _mcount profiling calls.
+  void emitMCountABI(MachineInstr &MI, MachineBasicBlock &MBB,
+                     MachineFunction &MF);
+
   void processFunctionAfterISel(MachineFunction &MF) override;
 
   bool SelectInlineAsmMemoryOperand(const SDValue &Op,
                                     unsigned ConstraintID,
                                     std::vector<SDValue> &OutOps) override;
 };
 
 FunctionPass *createMipsSEISelDag(MipsTargetMachine &TM,
                                   CodeGenOpt::Level OptLevel);
 }
 
 #endif

llvm/lib/Target/Mips/MipsSEISelDAGToDAG.cpp

if (!MRI->getRegClass(MO.getReg())->contains(ZeroReg))
       continue;
 
     MO.setReg(ZeroReg);
   }
 
   return true;
 }
 
+void MipsSEDAGToDAGISel::emitMCountABI(MachineInstr &MI, MachineBasicBlock &MBB,
+                                       MachineFunction &MF) {
+  MachineInstrBuilder MIB(MF, &MI);
+  if (!Subtarget->isABI_O32()) { // N32, N64
+    // Save current return address.
+    BuildMI(MBB, &MI, MI.getDebugLoc(), TII->get(Mips::OR))
+        .addDef(Mips::AT_64)
+        .addUse(Mips::RA_64)
+        .addUse(Mips::ZERO_64);
+    // Stops instruction above from being removed later on.
+    MIB.addUse(Mips::AT_64, RegState::Implicit);
+  } else {  // O32
+    // Save current return address.
+    BuildMI(MBB, &MI, MI.getDebugLoc(), TII->get(Mips::OR))
+        .addDef(Mips::AT)
+        .addUse(Mips::RA)
+        .addUse(Mips::ZERO);
+    // _mcount pops 2 words from stack.
+    BuildMI(MBB, &MI, MI.getDebugLoc(), TII->get(Mips::ADDiu))
+        .addDef(Mips::SP)
+        .addUse(Mips::SP)
+        .addImm(-8);
+    // Stops first instruction above from being removed later on.
+    MIB.addUse(Mips::AT, RegState::Implicit);
+  }
+}
+
 void MipsSEDAGToDAGISel::processFunctionAfterISel(MachineFunction &MF) {
   MF.getInfo<MipsFunctionInfo>()->initGlobalBaseReg();
 
   MachineRegisterInfo *MRI = &MF.getRegInfo();
 
   for (auto &MBB: MF) {
     for (auto &MI: MBB) {
       switch (MI.getOpcode()) {
for (auto &MI: MBB) {
           break;
         }
         LLVM_FALLTHROUGH;
       case Mips::BuildPairF64:
       case Mips::ExtractElementF64:
         if (Subtarget->isABI_FPXX() && !Subtarget->hasMTHC1())
           MI.addOperand(MachineOperand::CreateReg(Mips::SP, false, true));
         break;
+      case Mips::JAL:
+      case Mips::JAL_MM:
+        if (MI.getOperand(0).isGlobal() &&
+            MI.getOperand(0).getGlobal()->getGlobalIdentifier() == "_mcount")
+          emitMCountABI(MI, MBB, MF);
+        break;
+      case Mips::JALRPseudo:
+      case Mips::JALR64Pseudo:
+      case Mips::JALR16_MM:
+        if (MI.getOperand(2).isMCSymbol() &&
+            MI.getOperand(2).getMCSymbol()->getName() == "_mcount")
+          emitMCountABI(MI, MBB, MF);
+        break;
+      case Mips::JALR:
+        if (MI.getOperand(3).isMCSymbol() &&
+            MI.getOperand(3).getMCSymbol()->getName() == "_mcount")
+          emitMCountABI(MI, MBB, MF);
+        break;
       default:
         replaceUsesWithZeroReg(MRI, MI);
       }
     }
   }
 }
 
 void MipsSEDAGToDAGISel::selectAddE(SDNode *Node, const SDLoc &DL) const {

llvm/test/CodeGen/Mips/mcount.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+
+; RUN: llc -march=mips < %s | FileCheck %s -check-prefix=MIPS32
+; RUN: llc -march=mips -relocation-model=pic < %s | FileCheck %s -check-prefix=MIPS32-PIC
+; RUN: llc -march=mips64 < %s | FileCheck %s -check-prefix=MIPS64
+; RUN: llc -march=mips64 -relocation-model=pic < %s | FileCheck %s -check-prefix=MIPS64-PIC
+; RUN: llc -march=mips -mattr=+micromips < %s | FileCheck %s -check-prefix=MIPS32-MM
+; RUN: llc -march=mips -relocation-model=pic -mattr=+micromips < %s | FileCheck %s -check-prefix=MIPS32-MM-PIC
+
+; Test that checks ABI for _mcount calls.
+
+; Function Attrs: noinline nounwind optnone
+define void @foo() #0 {
+; MIPS32-LABEL: foo:
+; MIPS32:       # %bb.0: # %entry
+; MIPS32-NEXT:    addiu $sp, $sp, -24
+; MIPS32-NEXT:    .cfi_def_cfa_offset 24
+; MIPS32-NEXT:    sw $ra, 20($sp) # 4-byte Folded Spill
+; MIPS32-NEXT:    .cfi_offset 31, -4
+; MIPS32-NEXT:    move $1, $ra
+; MIPS32-NEXT:    jal _mcount
+; MIPS32-NEXT:    addiu $sp, $sp, -8
+; MIPS32-NEXT:    lw $ra, 20($sp) # 4-byte Folded Reload
+; MIPS32-NEXT:    jr $ra
+; MIPS32-NEXT:    addiu $sp, $sp, 24
+;
+; MIPS32-PIC-LABEL: foo:
+; MIPS32-PIC:       # %bb.0: # %entry
+; MIPS32-PIC-NEXT:    lui $2, %hi(_gp_disp)
+; MIPS32-PIC-NEXT:    addiu $2, $2, %lo(_gp_disp)
+; MIPS32-PIC-NEXT:    addiu $sp, $sp, -24
+; MIPS32-PIC-NEXT:    .cfi_def_cfa_offset 24
+; MIPS32-PIC-NEXT:    sw $ra, 20($sp) # 4-byte Folded Spill
+; MIPS32-PIC-NEXT:    .cfi_offset 31, -4
+; MIPS32-PIC-NEXT:    addu $gp, $2, $25
+; MIPS32-PIC-NEXT:    lw $25, %call16(_mcount)($gp)
+; MIPS32-PIC-NEXT:    move $1, $ra
+; MIPS32-PIC-NEXT:    .reloc ($tmp0), R_MIPS_JALR, _mcount
+; MIPS32-PIC-NEXT:  $tmp0:
+; MIPS32-PIC-NEXT:    jalr $25
+; MIPS32-PIC-NEXT:    addiu $sp, $sp, -8
+; MIPS32-PIC-NEXT:    lw $ra, 20($sp) # 4-byte Folded Reload
+; MIPS32-PIC-NEXT:    jr $ra
+; MIPS32-PIC-NEXT:    addiu $sp, $sp, 24
+;
+; MIPS64-LABEL: foo:
+; MIPS64:       # %bb.0: # %entry
+; MIPS64-NEXT:    daddiu $sp, $sp, -16
+; MIPS64-NEXT:    .cfi_def_cfa_offset 16
+; MIPS64-NEXT:    sd $ra, 8($sp) # 8-byte Folded Spill
+; MIPS64-NEXT:    .cfi_offset 31, -8
+; MIPS64-NEXT:    or $1, $ra, $zero
+; MIPS64-NEXT:    jal _mcount
+; MIPS64-NEXT:    nop
+; MIPS64-NEXT:    ld $ra, 8($sp) # 8-byte Folded Reload
+; MIPS64-NEXT:    jr $ra
+; MIPS64-NEXT:    daddiu $sp, $sp, 16
+;
+; MIPS64-PIC-LABEL: foo:
+; MIPS64-PIC:       # %bb.0: # %entry
+; MIPS64-PIC-NEXT:    daddiu $sp, $sp, -16
+; MIPS64-PIC-NEXT:    .cfi_def_cfa_offset 16
+; MIPS64-PIC-NEXT:    sd $ra, 8($sp) # 8-byte Folded Spill
+; MIPS64-PIC-NEXT:    sd $gp, 0($sp) # 8-byte Folded Spill
+; MIPS64-PIC-NEXT:    .cfi_offset 31, -8
+; MIPS64-PIC-NEXT:    .cfi_offset 28, -16
+; MIPS64-PIC-NEXT:    lui $1, %hi(%neg(%gp_rel(foo)))
+; MIPS64-PIC-NEXT:    daddu $1, $1, $25
+; MIPS64-PIC-NEXT:    daddiu $gp, $1, %lo(%neg(%gp_rel(foo)))
+; MIPS64-PIC-NEXT:    ld $25, %call16(_mcount)($gp)
+; MIPS64-PIC-NEXT:    or $1, $ra, $zero
+; MIPS64-PIC-NEXT:    .reloc .Ltmp0, R_MIPS_JALR, _mcount
+; MIPS64-PIC-NEXT:  .Ltmp0:
+; MIPS64-PIC-NEXT:    jalr $25
+; MIPS64-PIC-NEXT:    nop
+; MIPS64-PIC-NEXT:    ld $gp, 0($sp) # 8-byte Folded Reload
+; MIPS64-PIC-NEXT:    ld $ra, 8($sp) # 8-byte Folded Reload
+; MIPS64-PIC-NEXT:    jr $ra
+; MIPS64-PIC-NEXT:    daddiu $sp, $sp, 16
+;
+; MIPS32-MM-LABEL: foo:
+; MIPS32-MM:       # %bb.0: # %entry
+; MIPS32-MM-NEXT:    addiu $sp, $sp, -24
+; MIPS32-MM-NEXT:    .cfi_def_cfa_offset 24
+; MIPS32-MM-NEXT:    sw $ra, 20($sp) # 4-byte Folded Spill
+; MIPS32-MM-NEXT:    .cfi_offset 31, -4
+; MIPS32-MM-NEXT:    move $1, $ra
+; MIPS32-MM-NEXT:    jal _mcount
+; MIPS32-MM-NEXT:    addiu $sp, $sp, -8
+; MIPS32-MM-NEXT:    lw $ra, 20($sp) # 4-byte Folded Reload
+; MIPS32-MM-NEXT:    jr $ra
+; MIPS32-MM-NEXT:    addiu $sp, $sp, 24
+;
+; MIPS32-MM-PIC-LABEL: foo:
+; MIPS32-MM-PIC:       # %bb.0: # %entry
+; MIPS32-MM-PIC-NEXT:    lui $2, %hi(_gp_disp)
+; MIPS32-MM-PIC-NEXT:    addiu $2, $2, %lo(_gp_disp)
+; MIPS32-MM-PIC-NEXT:    addiu $sp, $sp, -24
+; MIPS32-MM-PIC-NEXT:    .cfi_def_cfa_offset 24
+; MIPS32-MM-PIC-NEXT:    sw $ra, 20($sp) # 4-byte Folded Spill
+; MIPS32-MM-PIC-NEXT:    .cfi_offset 31, -4
+; MIPS32-MM-PIC-NEXT:    addu $2, $2, $25
+; MIPS32-MM-PIC-NEXT:    lw $25, %call16(_mcount)($2)
+; MIPS32-MM-PIC-NEXT:    move $gp, $2
+; MIPS32-MM-PIC-NEXT:    move $1, $ra
+; MIPS32-MM-PIC-NEXT:    .reloc ($tmp0), R_MICROMIPS_JALR, _mcount
+; MIPS32-MM-PIC-NEXT:  $tmp0:
+; MIPS32-MM-PIC-NEXT:    jalr $25
+; MIPS32-MM-PIC-NEXT:    addiu $sp, $sp, -8
+; MIPS32-MM-PIC-NEXT:    lw $ra, 20($sp) # 4-byte Folded Reload
+; MIPS32-MM-PIC-NEXT:    jr $ra
+; MIPS32-MM-PIC-NEXT:    addiu $sp, $sp, 24
+entry:
+  ret void
+}
+
+attributes #0 = { "instrument-function-entry-inlined"="_mcount" }