[mips][FastISel] Instantiate the MipsFastISel class only for targets that support FastISel.

Summary:
Instead of instantiating the MipsFastISel class and checking if the
target is supported in the overriden methods, we should perform that
check before creating the class. This allows us to enable FastISel *only*
for targets that truly support it, ie. MIPS32 to MIPS32R5.

Reviewers: sdardis

Subscribers: ehostunreach, llvm-commits

Differential Revision: https://reviews.llvm.org/D24824

llvm-svn: 284475

lib/Target/Mips/MipsFastISel.cpp

@@ -102,7 +102,6 @@ class MipsFastISel final : public FastISel {
   bool fastLowerCall(CallLoweringInfo &CLI) override;
   bool fastLowerIntrinsicCall(const IntrinsicInst *II) override;
 
-  bool TargetSupported;
   bool UnsupportedFPMode; // To allow fast-isel to proceed and just not handle
   // floating point but not reject doing fast-isel in other
   // situations
@@ -212,10 +211,6 @@ public:
         TII(*Subtarget->getInstrInfo()), TLI(*Subtarget->getTargetLowering()) {
     MFI = funcInfo.MF->getInfo<MipsFunctionInfo>();
     Context = &funcInfo.Fn->getContext();
-    bool ISASupported = !Subtarget->hasMips32r6() &&
-                        !Subtarget->inMicroMipsMode() && Subtarget->hasMips32();
-    TargetSupported =
-        ISASupported && TM.isPositionIndependent() && getABI().IsO32();
     UnsupportedFPMode = Subtarget->isFP64bit() || Subtarget->useSoftFloat();
   }
 
@@ -291,9 +286,6 @@ unsigned MipsFastISel::emitLogicalOp(unsigned ISDOpc, MVT RetVT,
 }
 
 unsigned MipsFastISel::fastMaterializeAlloca(const AllocaInst *AI) {
-  if (!TargetSupported)
-    return 0;
-
   assert(TLI.getValueType(DL, AI->getType(), true) == MVT::i32 &&
          "Alloca should always return a pointer.");
 
@@ -404,9 +396,6 @@ unsigned MipsFastISel::materializeExternalCallSym(MCSymbol *Sym) {
 // Materialize a constant into a register, and return the register
 // number (or zero if we failed to handle it).
 unsigned MipsFastISel::fastMaterializeConstant(const Constant *C) {
-  if (!TargetSupported)
-    return 0;
-
   EVT CEVT = TLI.getValueType(DL, C->getType(), true);
 
   // Only handle simple types.
@@ -1444,9 +1433,6 @@ bool MipsFastISel::fastLowerArguments() {
 }
 
 bool MipsFastISel::fastLowerCall(CallLoweringInfo &CLI) {
-  if (!TargetSupported)
-    return false;
-
   CallingConv::ID CC = CLI.CallConv;
   bool IsTailCall = CLI.IsTailCall;
   bool IsVarArg = CLI.IsVarArg;
@@ -1531,9 +1517,6 @@ bool MipsFastISel::fastLowerCall(CallLoweringInfo &CLI) {
 }
 
 bool MipsFastISel::fastLowerIntrinsicCall(const IntrinsicInst *II) {
-  if (!TargetSupported)
-    return false;
-
   switch (II->getIntrinsicID()) {
   default:
     return false;
@@ -1980,8 +1963,6 @@ bool MipsFastISel::selectShift(const Instruction *I) {
 }
 
 bool MipsFastISel::fastSelectInstruction(const Instruction *I) {
-  if (!TargetSupported)
-    return false;
   switch (I->getOpcode()) {
   default:
     break;

lib/Target/Mips/MipsISelLowering.cpp

@@ -458,9 +458,19 @@ const MipsTargetLowering *MipsTargetLowering::create(const MipsTargetMachine &TM
 FastISel *
 MipsTargetLowering::createFastISel(FunctionLoweringInfo &funcInfo,
                                   const TargetLibraryInfo *libInfo) const {
-  if (!funcInfo.MF->getTarget().Options.EnableFastISel)
+  const MipsTargetMachine &TM =
-    return TargetLowering::createFastISel(funcInfo, libInfo);
+      static_cast<const MipsTargetMachine &>(funcInfo.MF->getTarget());
-  return Mips::createFastISel(funcInfo, libInfo);
+
+  // We support only the standard encoding [MIPS32,MIPS32R5] ISAs.
+  bool UseFastISel = TM.Options.EnableFastISel && Subtarget.hasMips32() &&
+                     !Subtarget.hasMips32r6() && !Subtarget.inMips16Mode() &&
+                     !Subtarget.inMicroMipsMode();
+
+  // Disable if we don't generate PIC or the ABI isn't O32.
+  if (!TM.isPositionIndependent() || !TM.getABI().IsO32())
+    UseFastISel = false;
+
+  return UseFastISel ? Mips::createFastISel(funcInfo, libInfo) : nullptr;
 }
 
 EVT MipsTargetLowering::getSetCCResultType(const DataLayout &, LLVMContext &,

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

@@ -1,3 +1,4 @@
+; Targets where we should not enable FastISel.
 ; 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 -target-abi n64 \
@@ -7,8 +8,16 @@
 
 ; RUN: llc -march=mips -mcpu=mips32r6 -O0 -relocation-model=pic \
 ; RUN:     -fast-isel-verbose <%s 2>&1 | FileCheck %s
+
+; RUN: llc -march=mips -mattr=mips16 -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=mips32r3 -mattr=+micromips -O0 -relocation-model=pic \
+; RUN:     -fast-isel-verbose <%s 2>&1 | FileCheck %s
+; RUN: llc -march=mips -mcpu=mips32r5 -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 -target-abi n64 \
 ; RUN:     -fast-isel-verbose <%s 2>&1 | FileCheck %s
@@ -21,9 +30,26 @@
 ; RUN: llc -march=mips -mcpu=mips32r6 -O0 -relocation-model=pic \
 ; RUN:     -fast-isel-verbose <%s 2>&1 | FileCheck %s
 
-; CHECK: FastISel missed terminator:   ret i32 0
+; Valid targets for FastISel.
+; RUN: llc -march=mips -mcpu=mips32r0 -O0 -relocation-model=pic \
+; RUN:     -fast-isel-verbose <%s 2>&1 | FileCheck %s -check-prefix=FISEL
+; RUN: llc -march=mips -mcpu=mips32r2 -O0 -relocation-model=pic \
+; RUN:     -fast-isel-verbose <%s 2>&1 | FileCheck %s -check-prefix=FISEL
 
-define i32 @foo() {
+; The CHECK prefix is being used by those targets that do not support FastISel.
+; By checking that we don't emit the "FastISel missed terminator..." message,
+; we ensure that we do not generate code through FastISel.
+
+; CHECK-NOT: FastISel missed terminator:   ret i64 0
+
+; The above CHECK will only be valid as long as we *do* emit the missed
+; terminator message for targets that support FastISel. If we add support
+; for i64 return values in the future, then the following FISEL check-prefix
+; will fail and we will have to come up with a new test.
+
+; FISEL: FastISel missed terminator:   ret i64 0
+
+define i64 @foo() {
 entry:
-  ret i32 0
+  ret i64 0
 }

test/CodeGen/Mips/Fast-ISel/double-arg.ll

@@ -1,5 +1,5 @@
-; RUN: not llc -march=mipsel -mcpu=mips32r2 -fast-isel -mattr=+fp64 < %s \
+; RUN: not llc -march=mipsel -mcpu=mips32r2 -mattr=+fp64 \
-; RUN:     -fast-isel-abort=3
+; RUN:         -O0 -relocation-model=pic -fast-isel-abort=3 < %s
 
 ; Check that FastISel aborts when we have 64bit FPU registers. FastISel currently
 ; supports AFGR64 only, which uses paired 32 bit registers.

test/CodeGen/Mips/tailcall/tail-call-arguments-clobber.ll

@@ -21,6 +21,7 @@
 declare i32 @func2(i32, i32, i32, i32, i32, i32)
 
 define i32 @func1(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e, i32 %f){
+; MIPS32-LABEL: func1:
 
 ; MIPS32: lw ${{[0-9]+}}, {{[0-9]+}}($sp)
 ; MIPS32-NEXT: lw ${{[0-9]+}}, {{[0-9]+}}($sp)
@@ -40,6 +41,7 @@ declare i64 @func4(i64, i64, i64, i64, i64, i64, i64, i64, i64, i64)
 define i64 @func3(i64 %a, i64 %b, i64 %c, i64 %d,
                   i64 %e, i64 %f, i64 %g, i64 %h,
                   i64 %i, i64 %j){
+; MIPS64-LABEL: func3:
 
 ; MIPS64: ld ${{[0-9]+}}, {{[0-9]+}}($sp)
 ; MIPS64-NEXT: ld ${{[0-9]+}}, {{[0-9]+}}($sp)

test/DebugInfo/Mips/dsr-non-fixed-objects.ll

@@ -1,6 +1,6 @@
-; RUN: llc -march=mips -mcpu=mips32r2 -O0 -filetype=obj <%s | \
+; RUN: llc -march=mips -mcpu=mips32r2 -O0 -filetype=obj -fast-isel=0 <%s | \
 ; RUN:    llvm-dwarfdump -debug-dump=all - | FileCheck %s -check-prefix=F2
-; RUN: llc -march=mips -mcpu=mips32r2 -O0 -filetype=obj <%s | \
+; RUN: llc -march=mips -mcpu=mips32r2 -O0 -filetype=obj -fast-isel=0 <%s | \
 ; RUN:    llvm-dwarfdump -debug-dump=all - | FileCheck %s -check-prefix=F3
 
 declare void @llvm.dbg.declare(metadata, metadata, metadata)