[mips] Enable code generation for the MIPS II target.

[vkalintiris]

Summary

This patch enables code generation for the MIPS II target. Pre-Mips32
targets don't have the MUL instruction, so we add the correspondent
pattern that uses the MULT/MFLO combination in order to retrieve the
product.

This is WIP as we don't support code generation for select nodes due to
the lack of conditional-move instructions.

[dsanders]

LGTM with some test corrections and a nit. Also, please reword the title line of the commit message. At the moment it implies that MIPS-II will work after that patch and that isn't quite true yet.

I understand you're testing with a qemu that has been patched to have a MIPS-II CPU definition. Are you planning to upstream that patch to qemu.org?

lib/Target/Mips/MipsSubtarget.cpp

132–134

Nit: Line wrapping

test/CodeGen/Mips/llvm-ir/mul.ll

101

This result register isn't guaranteed to be $2. It ought to be checked with a variable.

105

This result register isn't guaranteed to be $2. It ought to be checked with a variable.

111–112

These result registers aren't guaranteed to be $2 and $4 respectively. They ought to be checked with a variable.

117

This result register isn't guaranteed to be $2. It ought to be checked with a variable.

119

This result register isn't guaranteed to be $2. It ought to be checked with a variable.

[vkalintiris]

In D6150#4, @dsanders wrote:

I understand you're testing with a qemu that has been patched to have a MIPS-II CPU definition. Are you planning to upstream that patch to qemu.org?

Hi Daniel, you are right. There wasn't any real CPU model for MIPS-II in Qemu so I added one based on the existing definition of the mips32r5-generic CPU.
I will send the patch for review to qemu sometime during this week.

[vkalintiris]

Closed by commit rL221686 (authored by @vkalintiris).

lib/Target/Mips/MipsInstrInfo.td

def : MipsPat<(subc GPR32:$lhs, GPR32:$rhs),
               (SUBu GPR32:$lhs, GPR32:$rhs)>;
 let AdditionalPredicates = [NotDSP] in {
   def : MipsPat<(addc GPR32:$lhs, GPR32:$rhs),
                 (ADDu GPR32:$lhs, GPR32:$rhs)>;
   def : MipsPat<(addc  GPR32:$src, immSExt16:$imm),
                 (ADDiu GPR32:$src, imm:$imm)>;
 }
 
+// Support multiplication for pre-Mips32 targets that don't have
+// the MUL instruction.
+def : MipsPat<(mul GPR32:$lhs, GPR32:$rhs),
+              (PseudoMFLO (PseudoMULT GPR32:$lhs, GPR32:$rhs))>,
+      ISA_MIPS1_NOT_32R6_64R6;
+
 // SYNC
 def : MipsPat<(MipsSync (i32 immz)),
               (SYNC 0)>, ISA_MIPS2;
 
 // Call
 def : MipsPat<(MipsJmpLink (i32 tglobaladdr:$dst)),
               (JAL tglobaladdr:$dst)>;
 def : MipsPat<(MipsJmpLink (i32 texternalsym:$dst)),

lib/Target/Mips/MipsSubtarget.h

 class StringRef;
 
 class MipsTargetMachine;
 
 class MipsSubtarget : public MipsGenSubtargetInfo {
   virtual void anchor();
 
   enum MipsArchEnum {
+    MipsDefault,
     Mips1, Mips2, Mips32, Mips32r2, Mips32r6, Mips3, Mips4, Mips5, Mips64,
     Mips64r2, Mips64r6
   };
 
   // Mips architecture version
   MipsArchEnum MipsArchVersion;
 
   // Selected ABI

lib/Target/Mips/MipsSubtarget.cpp

else
     Ret += "-n32-S64";
 
   return Ret;
 }
 
 MipsSubtarget::MipsSubtarget(const std::string &TT, const std::string &CPU,
                              const std::string &FS, bool little,
                              const MipsTargetMachine *_TM)
-    : MipsGenSubtargetInfo(TT, CPU, FS), MipsArchVersion(Mips32),
+    : MipsGenSubtargetInfo(TT, CPU, FS), MipsArchVersion(MipsDefault),
       ABI(MipsABIInfo::Unknown()), IsLittle(little), IsSingleFloat(false),
       IsFPXX(false), NoABICalls(false), IsFP64bit(false), UseOddSPReg(true),
       IsNaN2008bit(false), IsGP64bit(false), HasVFPU(false), HasCnMips(false),
       IsLinux(true), HasMips3_32(false), HasMips3_32r2(false),
       HasMips4_32(false), HasMips4_32r2(false), HasMips5_32r2(false),
       InMips16Mode(false), InMips16HardFloat(Mips16HardFloat),
       InMicroMipsMode(false), HasDSP(false), HasDSPR2(false),
       AllowMixed16_32(Mixed16_32 | Mips_Os16), Os16(Mips_Os16),
       HasMSA(false), TM(_TM), TargetTriple(TT),
       DL(computeDataLayout(initializeSubtargetDependencies(CPU, FS, TM))),
       TSInfo(DL), InstrInfo(MipsInstrInfo::create(*this)),
       FrameLowering(MipsFrameLowering::create(*this)),
       TLInfo(MipsTargetLowering::create(*TM, *this)) {
 
   PreviousInMips16Mode = InMips16Mode;
 
-  // Don't even attempt to generate code for MIPS-I, MIPS-II, MIPS-III, and
+  if (MipsArchVersion == MipsDefault)
+    MipsArchVersion = Mips32;
+
+  // Don't even attempt to generate code for MIPS-I, MIPS-III, and
   // MIPS-V. They have not been tested and currently exist for the integrated
   // assembler only.
   if (MipsArchVersion == Mips1)
     report_fatal_error("Code generation for MIPS-I is not implemented", false);
-  if (MipsArchVersion == Mips2)
-    report_fatal_error("Code generation for MIPS-II is not implemented", false);
   if (MipsArchVersion == Mips3)
     report_fatal_error("Code generation for MIPS-III is not implemented",
                        false);
   if (MipsArchVersion == Mips5)
     report_fatal_error("Code generation for MIPS-V is not implemented", false);
 
   // Assert exactly one ABI was chosen.
   assert(ABI.IsKnown());

test/CodeGen/Mips/llvm-ir/mul.ll

+; RUN: llc < %s -march=mips -mcpu=mips2 | \
+; RUN:    FileCheck %s -check-prefix=ALL -check-prefix=M2
+; RUN: llc < %s -march=mips -mcpu=mips32 | \
+; RUN:    FileCheck %s -check-prefix=ALL -check-prefix=32R1-R2
+; RUN: llc < %s -march=mips -mcpu=mips32r2 | \
+; RUN:    FileCheck %s -check-prefix=ALL -check-prefix=32R1-R2
+; RUN: llc < %s -march=mips -mcpu=mips32r6 | \
+; RUN:    FileCheck %s -check-prefix=ALL -check-prefix=32R6
+; RUN: llc < %s -march=mips64 -mcpu=mips4 | \
+; RUN:    FileCheck %s -check-prefix=ALL -check-prefix=M4
+; RUN: llc < %s -march=mips64 -mcpu=mips64 | \
+; RUN:    FileCheck %s -check-prefix=ALL -check-prefix=64R1-R2
+; RUN: llc < %s -march=mips64 -mcpu=mips64r2 | \
+; RUN:    FileCheck %s -check-prefix=ALL -check-prefix=64R1-R2
+; RUN: llc < %s -march=mips64 -mcpu=mips64r6 | \
+; RUN:    FileCheck %s -check-prefix=ALL -check-prefix=64R6
+
+define i1 @mul_i1(i1 %a, i1 %b) {
+entry:
+; ALL-LABEL: mul_i1:
+
+  ; M2:         mult    $4, $5
+  ; M2:         mflo    $2
+
+  ; 32R1-R2:    mul     $2, $4, $5
+  ; 32R6:       mul     $2, $4, $5
+
+  ; M4:         mult    $4, $5
+  ; M4:         mflo    $2
+
+  ; 64R1-R2:    mul     $2, $4, $5
+  ; 64R6:       mul     $2, $4, $5
+  %r = mul i1 %a, %b
+  ret i1 %r
+}
+
+define i8 @mul_i8(i8 %a, i8 %b) {
+entry:
+; ALL-LABEL: mul_i8:
+
+  ; M2:         mult    $4, $5
+  ; M2:         mflo    $2
+
+  ; 32R1-R2:    mul     $2, $4, $5
+  ; 32R6:       mul     $2, $4, $5
+
+  ; M4:         mult    $4, $5
+  ; M4:         mflo    $2
+
+  ; 64R1-R2:    mul     $2, $4, $5
+  ; 64R6:       mul     $2, $4, $5
+  %r = mul i8 %a, %b
+  ret i8 %r
+}
+
+define i16 @mul_i16(i16 %a, i16 %b) {
+entry:
+; ALL-LABEL: mul_i16:
+
+  ; M2:         mult    $4, $5
+  ; M2:         mflo    $2
+
+  ; 32R1-R2:    mul     $2, $4, $5
+  ; 32R6:       mul     $2, $4, $5
+
+  ; M4:         mult    $4, $5
+  ; M4:         mflo    $2
+
+  ; 64R1-R2:    mul     $2, $4, $5
+  ; 64R6:       mul     $2, $4, $5
+  %r = mul i16 %a, %b
+  ret i16 %r
+}
+
+define i32 @mul_i32(i32 %a, i32 %b) {
+entry:
+; ALL-LABEL: mul_i32:
+
+  ; M2:         mult    $4, $5
+  ; M2:         mflo    $2
+
+  ; 32R1-R2:    mul     $2, $4, $5
+  ; 32R6:       mul     $2, $4, $5
+
+  ; M4:         mult    $4, $5
+  ; M4:         mflo    $2
+
+  ; 64R1-R2:    mul     $2, $4, $5
+  ; 64R6:       mul     $2, $4, $5
+  %r = mul i32 %a, %b
+  ret i32 %r
+}
+
+define i64 @mul_i64(i64 %a, i64 %b) {
+entry:
+; ALL-LABEL: mul_i64:
+
+  ; M2:         mult    $4, $7
+  ; M2:         mflo    $[[T0:[0-9]+]]
+  ; M2:         mult    $5, $6
+  ; M2:         mflo    $2
+  ; M2:         multu   $5, $7
+  ; M2:         mflo    $3
+  ; M2:         mfhi    $4
+  ; M2:         addu    $2, $4, $2
+  ; M2:         addu    $2, $2, $[[T0]]
+
+  ; 32R1-R2:    multu   $5, $7
+  ; 32R1-R2:    mflo    $3
+  ; 32R1-R2:    mfhi    $[[T0:[0-9]+]]
+  ; 32R1-R2:    mul     $2, $4, $7
+  ; 32R1-R2:    mul     $4, $5, $6
+  ; 32R1-R2:    addu    $[[T0]], $[[T0]], $4
+  ; 32R1-R2:    addu    $2, $[[T0]], $2
+
+  ; 32R6:       mul     $[[T0:[0-9]+]], $5, $6
+  ; 32R6:       muhu    $2, $5, $7
+  ; 32R6:       addu    $[[T0]], $2, $[[T0]]
+  ; 32R6:       mul     $2, $4, $7
+  ; 32R6:       addu    $2, $[[T0]], $2
+  ; 32R6:       mul     $3, $5, $7
+
+  ; M4:         dmult   $4, $5
+  ; M4:         mflo    $2
+
+  ; 64R1-R2:    dmult   $4, $5
+  ; 64R1-R2:    mflo    $2
+
+  ; 64R6:       dmul    $2, $4, $5
+
+  %r = mul i64 %a, %b
+  ret i64 %r
+}