[mips][microMIPS] Disable FastISel for microMIPS

[milena.vujosevic.janicic]

Summary

FastIsel is not supported for microMIPS, thus it needs to be disabled.
Test micromips-zero-mat-uses.ll is deleted since the tested sequence of instructions is not generated for microMIPS without FastISel.

[dsanders]

LGTM

lib/Target/Mips/MipsFastISel.cpp

public:
   // Backend specific FastISel code.
   explicit MipsFastISel(FunctionLoweringInfo &funcInfo,
                         const TargetLibraryInfo *libInfo)
       : FastISel(funcInfo, libInfo), TM(funcInfo.MF->getTarget()),
         Subtarget(&funcInfo.MF->getSubtarget<MipsSubtarget>()),
         TII(*Subtarget->getInstrInfo()), TLI(*Subtarget->getTargetLowering()) {
     MFI = funcInfo.MF->getInfo<MipsFunctionInfo>();
     Context = &funcInfo.Fn->getContext();
-    bool ISASupported = !Subtarget->hasMips32r6() && Subtarget->hasMips32();
+    bool ISASupported = !Subtarget->hasMips32r6() &&
+                        !Subtarget->inMicroMipsMode() && Subtarget->hasMips32();
     TargetSupported =
         ISASupported && (TM.getRelocationModel() == Reloc::PIC_) &&
         (static_cast<const MipsTargetMachine &>(TM).getABI().IsO32());
     UnsupportedFPMode = Subtarget->isFP64bit();
   }
 
   unsigned fastMaterializeAlloca(const AllocaInst *AI) override;
   unsigned fastMaterializeConstant(const Constant *C) override;

test/CodeGen/Mips/Fast-ISel/check-disabled-mcpus.ll

 ; RUN: llc -march=mips -mcpu=mips2 -O0 -relocation-model=pic \
 ; RUN:     -fast-isel-verbose <%s 2>&1 | FileCheck %s
 ; RUN: llc -march=mips -mcpu=mips3 -O0 -relocation-model=pic \
 ; RUN:     -fast-isel-verbose <%s 2>&1 | FileCheck %s
 ; RUN: llc -march=mips -mcpu=mips4 -O0 -relocation-model=pic \
 ; RUN:     -fast-isel-verbose <%s 2>&1 | FileCheck %s
 
 ; RUN: llc -march=mips -mcpu=mips32r6 -O0 -relocation-model=pic \
 ; RUN:     -fast-isel-verbose <%s 2>&1 | FileCheck %s
+; RUN: llc -march=mips -mcpu=mips32r2 -mattr=+micromips -O0 -relocation-model=pic \
+; RUN:     -fast-isel-verbose <%s 2>&1 | FileCheck %s
 
 ; RUN: llc -march=mips -mcpu=mips64 -O0 -relocation-model=pic \
 ; RUN:     -fast-isel-verbose <%s 2>&1 | FileCheck %s
 ; RUN: llc -march=mips -mcpu=mips64r2 -O0 -relocation-model=pic \
 ; RUN:     -fast-isel-verbose <%s 2>&1 | FileCheck %s
 ; RUN: llc -march=mips -mcpu=mips64r3 -O0 -relocation-model=pic \
 ; RUN:     -fast-isel-verbose <%s 2>&1 | FileCheck %s
 ; RUN: llc -march=mips -mcpu=mips64r5 -O0 -relocation-model=pic \

test/CodeGen/Mips/micromips-zero-mat-uses.ll

-; RUN: llc -march=mips -mcpu=mips32r2 -mattr=+micromips,+nooddspreg -O0 < %s | FileCheck %s
-
-; CHECK: addiu    $[[R0:[0-9]+]], $zero, 0
-; CHECK: subu16   $2, $[[R0]], ${{[0-9]+}}
-define i32 @foo() {
-  %1 = sub i32 0, undef
-  ret i32 %1
-}