[mips] Set GCC-compatible MIPS asssembler options before inline asm blocks.

[tomatabacu]

Summary

When generating MIPS assembly, LLVM always overrides the default assembler options by emitting the '.set noreorder', '.set nomacro' and '.set noat' directives,
while GCC uses the default options if an assembly-level function contains inline assembly code.

This becomes a problem when the code generated by LLVM is interleaved with inline assembly which assumes GCC-like assembler options (from Linux, for example).

This patch fixes these conflicts by setting the appropriate assembler options at the beginning of an inline asm block and popping them at the end.

[dsanders]

LGTM with a couple test improvements.

test/CodeGen/Mips/inlineasm-assembler-directives.ll

12

Please check for part of the inline assembly body before checking for the pop

test/CodeGen/Mips/inlineasmmemop.ll

8

Could you add a CHECK-LABEL for the function label? Likewise for main() below.

37–52

With the possible exception of line 42, this comment doesn't explain anything that isn't also written in the code below and actually disagrees with the code below in a couple details (the number of elements in the array and the order of the inline asm statements). Could you move the useful bit to the code below and delete the remainder in a follow-up?

[tomatabacu]

Added CHECK's for the inline asm body.
Added CHECK-LABEL's for the 2 functions in inlineasmmemop.ll.

Will make further changes to inlineasmmemop.ll in a follow-up patch.

include/llvm/CodeGen/AsmPrinter.h

public:
   /// Print the specified operand of MI, an INLINEASM instruction, using the
   /// specified assembler variant as an address. Targets should override this to
   /// format as appropriate.  This method can return true if the operand is
   /// erroneous.
   virtual bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
                                      unsigned AsmVariant, const char *ExtraCode,
                                      raw_ostream &OS);
 
+  /// Let the target do anything it needs to do before emitting inlineasm.
+  /// \p StartInfo - the subtarget info before parsing inline asm
+  virtual void emitInlineAsmStart(const MCSubtargetInfo &StartInfo) const;
+
   /// Let the target do anything it needs to do after emitting inlineasm.
   /// This callback can be used restore the original mode in case the
   /// inlineasm contains directives to switch modes.
   /// \p StartInfo - the original subtarget info before inline asm
   /// \p EndInfo   - the final subtarget info after parsing the inline asm,
   ///                or NULL if the value is unknown.
   virtual void emitInlineAsmEnd(const MCSubtargetInfo &StartInfo,
                                 const MCSubtargetInfo *EndInfo) const;

lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp

void AsmPrinter::EmitInlineAsm(StringRef Str, const MDNode *LocMDNode,
   // assembler has been disabled, just emit the blob textually.
   // Otherwise parse the asm and emit it via MC support.
   // This is useful in case the asm parser doesn't handle something but the
   // system assembler does.
   const MCAsmInfo *MCAI = TM.getMCAsmInfo();
   assert(MCAI && "No MCAsmInfo");
   if (!MCAI->useIntegratedAssembler() &&
       !OutStreamer.isIntegratedAssemblerRequired()) {
+    emitInlineAsmStart(TM.getSubtarget<MCSubtargetInfo>());
     OutStreamer.EmitRawText(Str);
     emitInlineAsmEnd(TM.getSubtarget<MCSubtargetInfo>(), nullptr);
     return;
   }
 
   SourceMgr SrcMgr;
   SrcMgrDiagInfo DiagInfo;
 
report_fatal_error("Inline asm not supported by this streamer because"
                        " we don't have an asm parser for this target\n");
   Parser->setAssemblerDialect(Dialect);
   Parser->setTargetParser(*TAP.get());
   if (MF) {
     const TargetRegisterInfo *TRI = MF->getSubtarget().getRegisterInfo();
     TAP->SetFrameRegister(TRI->getFrameRegister(*MF));
   }
 
+  emitInlineAsmStart(STIOrig);
   // Don't implicitly switch to the text section before the asm.
   int Res = Parser->Run(/*NoInitialTextSection*/ true,
                         /*NoFinalize*/ true);
   emitInlineAsmEnd(STIOrig, STI.get());
   if (Res && !HasDiagHandler)
     report_fatal_error("Error parsing inline asm\n");
 }
 

 
 bool AsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
                                        unsigned AsmVariant,
                                        const char *ExtraCode, raw_ostream &O) {
   // Target doesn't support this yet!
   return true;
 }
 
+void AsmPrinter::emitInlineAsmStart(const MCSubtargetInfo &StartInfo) const {}
+
 void AsmPrinter::emitInlineAsmEnd(const MCSubtargetInfo &StartInfo,
                                   const MCSubtargetInfo *EndInfo) const {}

lib/Target/Mips/Mips16HardFloat.cpp

static void createFPFnStub(Function *F, Module *M, FPParamVariant PV,
   FStub->addFnAttr("mips16_fp_stub");
   FStub->addFnAttr(llvm::Attribute::Naked);
   FStub->addFnAttr(llvm::Attribute::NoUnwind);
   FStub->addFnAttr(llvm::Attribute::NoInline);
   FStub->addFnAttr("nomips16");
   FStub->setSection(SectionName);
   BasicBlock *BB = BasicBlock::Create(Context, "entry", FStub);
   InlineAsmHelper IAH(Context, BB);
-  IAH.Out(" .set  macro");
   if (PicMode) {
     IAH.Out(".set noreorder");
     IAH.Out(".cpload  $$25");
     IAH.Out(".set reorder");
     IAH.Out(".reloc 0,R_MIPS_NONE," + Name);
     IAH.Out("la $$25," + LocalName);
   }
   else {
-    IAH.Out(".set reorder");
     IAH.Out("la $$25," + Name);
   }
   swapFPIntParams(PV, M, IAH, LE, false);
   IAH.Out("jr $$25");
   IAH.Out(LocalName + " = " + Name);
   new UnreachableInst(FStub->getContext(), BB);
 }
 

lib/Target/Mips/MipsAsmPrinter.h

 class MCStreamer;
 class MachineInstr;
 class MachineBasicBlock;
 class MipsTargetStreamer;
 class Module;
 class raw_ostream;
 
 class LLVM_LIBRARY_VISIBILITY MipsAsmPrinter : public AsmPrinter {
-  MipsTargetStreamer &getTargetStreamer();
+  MipsTargetStreamer &getTargetStreamer() const;
 
   void EmitInstrWithMacroNoAT(const MachineInstr *MI);
 
 private:
   // tblgen'erated function.
   bool emitPseudoExpansionLowering(MCStreamer &OutStreamer,
                                    const MachineInstr *MI);
 
private:
 
   /// InConstantPool - Maintain state when emitting a sequence of constant
   /// pool entries so we can properly mark them as data regions.
   bool InConstantPool;
 
   std::map<const char *, const llvm::Mips16HardFloatInfo::FuncSignature *>
   StubsNeeded;
 
+  void emitInlineAsmStart(const MCSubtargetInfo &StartInfo) const override;
+
+  void emitInlineAsmEnd(const MCSubtargetInfo &StartInfo,
+                        const MCSubtargetInfo *EndInfo) const override;
+
   void EmitJal(MCSymbol *Symbol);
 
   void EmitInstrReg(unsigned Opcode, unsigned Reg);
 
   void EmitInstrRegReg(unsigned Opcode, unsigned Reg1, unsigned Reg2);
 
   void EmitInstrRegRegReg(unsigned Opcode, unsigned Reg1, unsigned Reg2,
                           unsigned Reg3);

lib/Target/Mips/MipsAsmPrinter.cpp

 #include "llvm/Target/TargetLoweringObjectFile.h"
 #include "llvm/Target/TargetOptions.h"
 #include <string>
 
 using namespace llvm;
 
 #define DEBUG_TYPE "mips-asm-printer"
 
-MipsTargetStreamer &MipsAsmPrinter::getTargetStreamer() {
+MipsTargetStreamer &MipsAsmPrinter::getTargetStreamer() const {
   return static_cast<MipsTargetStreamer &>(*OutStreamer.getTargetStreamer());
 }
 
 bool MipsAsmPrinter::runOnMachineFunction(MachineFunction &MF) {
   Subtarget = &TM.getSubtarget<MipsSubtarget>();
 
   // Initialize TargetLoweringObjectFile.
   const_cast<TargetLoweringObjectFile &>(getObjFileLowering())
void MipsAsmPrinter::EmitStartOfAsmFile(Module &M) {
   // accept it. We therefore emit it when it contradicts the default or an
   // option has changed the default (i.e. FPXX) and omit it otherwise.
   if (Subtarget->isABI_O32() && (!Subtarget->useOddSPReg() ||
                                  Subtarget->isABI_FPXX()))
     getTargetStreamer().emitDirectiveModuleOddSPReg(Subtarget->useOddSPReg(),
                                                     Subtarget->isABI_O32());
 }
 
+void MipsAsmPrinter::emitInlineAsmStart(
+    const MCSubtargetInfo &StartInfo) const {
+  MipsTargetStreamer &TS = getTargetStreamer();
+
+  TS.emitDirectiveSetPush();
+  TS.emitDirectiveSetAt();
+  TS.emitDirectiveSetMacro();
+  TS.emitDirectiveSetReorder();
+  OutStreamer.AddBlankLine();
+}
+
+void MipsAsmPrinter::emitInlineAsmEnd(const MCSubtargetInfo &StartInfo,
+                                      const MCSubtargetInfo *EndInfo) const {
+  OutStreamer.AddBlankLine();
+  getTargetStreamer().emitDirectiveSetPop();
+}
+
 void MipsAsmPrinter::EmitJal(MCSymbol *Symbol) {
   MCInst I;
   I.setOpcode(Mips::JAL);
   I.addOperand(
       MCOperand::CreateExpr(MCSymbolRefExpr::Create(Symbol, OutContext)));
   OutStreamer.EmitInstruction(I, getSubtargetInfo());
 }
 

test/CodeGen/Mips/fptr2.ll

-; RUN: llc -mtriple=mipsel-linux-gnu -march=mipsel -mcpu=mips16 -relocation-model=static  < %s | FileCheck %s -check-prefix=static16
-
-; Function Attrs: nounwind
-define double @my_mul(double %a, double %b) #0 {
-entry:
-  %a.addr = alloca double, align 8
-  %b.addr = alloca double, align 8
-  store double %a, double* %a.addr, align 8
-  store double %b, double* %b.addr, align 8
-  %0 = load double* %a.addr, align 8
-  %1 = load double* %b.addr, align 8
-  %mul = fmul double %0, %1
-  ret double %mul
-}
-
-; static16:           .ent  __fn_stub_my_mul
-; static16:       .set reorder
-; static16-NEXT:  #NO_APP
-; static16:           .end __fn_stub_my_mul
-attributes #0 = { nounwind "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="true" }

test/CodeGen/Mips/inlineasm-assembler-directives.ll

+; RUN: llc -march=mips < %s | FileCheck %s
+
+; Check for the emission of appropriate assembler directives before and
+; after the inline assembly code.
+define void @f() nounwind {
+entry:
+; CHECK:      #APP
+; CHECK-NEXT: .set  push
+; CHECK-NEXT: .set  at
+; CHECK-NEXT: .set  macro
+; CHECK-NEXT: .set  reorder
+; CHECK:      .set  pop
+; CHECK-NEXT: #NO_APP
+  %a = alloca i32, align 4
+  %b = alloca i32, align 4
+  store i32 20, i32* %a, align 4
+  %0 = load i32* %a, align 4
+  %1 = call i32 asm sideeffect "addi $$9, $1, 8\0A\09subi $0, $$9, 6", "=r,r,~{$1}"(i32 %0)
+  store i32 %1, i32* %b, align 4
+  ret void
+}

test/CodeGen/Mips/inlineasm-cnstrnt-reg.ll

 ; Now c with 1024: make sure register $25 is picked
 ; CHECK: #APP
 ; CHECK: addiu $25,${{[0-9]+}},1024
 ; CHECK: #NO_APP  
    tail call i32 asm sideeffect "addiu $0,$1,$2", "=c,c,I"(i32 4194304, i32 1024) nounwind
 
 ; Now l with 1024: make sure register lo is picked. We do this by checking the instruction
 ; after the inline expression for a mflo to pull the value out of lo.
-; CHECK: #APP
-; CHECK-NEXT:  mtlo ${{[0-9]+}} 
+; CHECK:       #APP
+; CHECK:       mtlo ${{[0-9]+}}
 ; CHECK-NEXT:  madd ${{[0-9]+}},${{[0-9]+}}
-; CHECK-NEXT: #NO_APP 
+; CHECK:       #NO_APP
 ; CHECK-NEXT:  mflo ${{[0-9]+}}
   %bosco = alloca i32, align 4
   call i32 asm sideeffect "\09mtlo $3 \0A\09\09madd $1,$2 ", "=l,r,r,r"(i32 7, i32 6, i32 44) nounwind
   store volatile i32 %4, i32* %bosco, align 4
  
   ret i32 0
 }

test/CodeGen/Mips/inlineasmmemop.ll

 ; RUN: llc -march=mipsel < %s | FileCheck %s
 
 ; Simple memory
 @g1 = external global i32
 
 define i32 @f1(i32 %x) nounwind {
 entry:
 ; CHECK: addiu $[[T0:[0-9]+]], $sp
 ; CHECK: #APP
 ; CHECK: sw $4, 0($[[T0]])
 ; CHECK: #NO_APP
 ; CHECK: #APP
 ; CHECK: lw $[[T3:[0-9]+]], 0($[[T0]])
 ; CHECK: #NO_APP
 ; CHECK: lw  $[[T1:[0-9]+]], %got(g1)
 ; CHECK: sw  $[[T3]], 0($[[T1]])
 
   %l1 = alloca i32, align 4
   call void asm "sw $1, $0", "=*m,r"(i32* %l1, i32 %x) nounwind
   %0 = call i32 asm "lw $0, $1", "=r,*m"(i32* %l1) nounwind
   store i32 %0, i32* @g1, align 4
   ret i32 %0
 }
 
 ; "D": Second word of double word. This works for any memory element
 ; double or single.
 ; CHECK: #APP
-; CHECK-NEXT: lw ${{[0-9]+}},4(${{[0-9]+}});
-; CHECK-NEXT: #NO_APP
+; CHECK: lw ${{[0-9]+}},4(${{[0-9]+}});
+; CHECK: #NO_APP
 
 ; No "D": First word of double word. This works for any memory element 
 ; double or single.
 ; CHECK: #APP
-; CHECK-NEXT: lw ${{[0-9]+}},0(${{[0-9]+}});
-; CHECK-NEXT: #NO_APP
+; CHECK: lw ${{[0-9]+}},0(${{[0-9]+}});
+; CHECK: #NO_APP
 
 ;int b[8] = {0,1,2,3,4,5,6,7};
 ;int main()
 ;{
 ;  int i;
 ; 
 ;  // The first word. Notice, no 'D'
 ;  { asm (
 ;    "lw    %0,%1;\n"
 ;    : "=r" (i) : "m" (*(b+4)));}
 ; 
 ;  // The second word
 ;  { asm (
 ;    "lw    %0,%D1;\n"
 ;    : "=r" (i) "m" (*(b+4)));}
 ;}
 
 @b = common global [20 x i32] zeroinitializer, align 4
 
 define void @main() {
 entry:
   tail call void asm sideeffect "    lw    $0,${1:D};", "r,*m,~{$11}"(i32 undef, i32* getelementptr inbounds ([20 x i32]* @b, i32 0, i32 3))
   tail call void asm sideeffect "    lw    $0,${1};", "r,*m,~{$11}"(i32 undef, i32* getelementptr inbounds ([20 x i32]* @b, i32 0, i32 3))
   ret void
 }
 
 attributes #0 = { nounwind }