[GlobalISel] Add a way for targets to enable GISel.

Until now, we've had to use -global-isel to enable GISel.  But using
that on other targets that don't support it will result in an abort, as we
can't build a full pipeline.
Additionally, we want to experiment with enabling GISel by default for
some targets: we can't just enable GISel by default, even among those
target that do have some support, because the level of support varies.

This first step adds an override for the target to explicitly define its
level of support.  For AArch64, do that using
a new command-line option (I know..):
  -aarch64-enable-global-isel-at-O=<N>
Where N is the opt-level below which GISel should be used.

Default that to -1, so that we still don't enable GISel anywhere.
We're not there yet!

While there, remove a couple LLVM_UNLIKELYs.  Building the pipeline is
such a cold path that in practice that shouldn't matter at all.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296710 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/CodeGen/TargetPassConfig.h b/include/llvm/CodeGen/TargetPassConfig.h
index 2287f9aca4bffe9e22049ca84699aab1d6797353..2156e87872f6d50e491edc28833d0465afc1f05e 100644 (file)
--- a/include/llvm/CodeGen/TargetPassConfig.h
+++ b/include/llvm/CodeGen/TargetPassConfig.h
@@ -286,6 +286,10 @@ public:
   /// verification is enabled.
   void addVerifyPass(const std::string &Banner);
 
+  /// Check whether or not GlobalISel should be enabled by default.
+  /// Fallback/abort behavior is controlled via other methods.
+  virtual bool isGlobalISelEnabled() const;
+
   /// Check whether or not GlobalISel should abort on error.
   /// When this is disable, GlobalISel will fall back on SDISel instead of
   /// erroring out.

diff --git a/lib/CodeGen/LLVMTargetMachine.cpp b/lib/CodeGen/LLVMTargetMachine.cpp
index 367fd66304ac5afe9c0512fe473285a88985ea39..7b1706f0f4ba9336e181639c45657ce2a9385409 100644 (file)
--- a/lib/CodeGen/LLVMTargetMachine.cpp
+++ b/lib/CodeGen/LLVMTargetMachine.cpp
@@ -42,8 +42,8 @@ static cl::opt<cl::boolOrDefault>
 EnableFastISelOption("fast-isel", cl::Hidden,
   cl::desc("Enable the \"fast\" instruction selector"));
 
-static cl::opt<bool>
-    EnableGlobalISel("global-isel", cl::Hidden, cl::init(false),
+static cl::opt<cl::boolOrDefault>
+    EnableGlobalISel("global-isel", cl::Hidden,
                      cl::desc("Enable the \"global\" instruction selector"));
 
 void LLVMTargetMachine::initAsmInfo() {
@@ -149,7 +149,9 @@ addPassesToGenerateCode(LLVMTargetMachine *TM, PassManagerBase &PM,
     TM->setFastISel(true);
 
   // Ask the target for an isel.
-  if (LLVM_UNLIKELY(EnableGlobalISel)) {
+  // Enable GlobalISel if the target wants to, but allow that to be overriden.
+  if (EnableGlobalISel == cl::BOU_TRUE || (EnableGlobalISel == cl::BOU_UNSET &&
+                                           PassConfig->isGlobalISelEnabled())) {
     if (PassConfig->addIRTranslator())
       return nullptr;
 
@@ -177,7 +179,7 @@ addPassesToGenerateCode(LLVMTargetMachine *TM, PassManagerBase &PM,
 
     // Provide a fallback path when we do not want to abort on
     // not-yet-supported input.
-    if (LLVM_UNLIKELY(!PassConfig->isGlobalISelAbortEnabled()) &&
+    if (!PassConfig->isGlobalISelAbortEnabled() &&
         PassConfig->addInstSelector())
       return nullptr;
 

diff --git a/lib/CodeGen/TargetPassConfig.cpp b/lib/CodeGen/TargetPassConfig.cpp
index 30d45b7b750f105ed38c31fb9ce432935e48547c..271f5c3c94ee01094c07663dffdc973c7ebf4925 100644 (file)
--- a/lib/CodeGen/TargetPassConfig.cpp
+++ b/lib/CodeGen/TargetPassConfig.cpp
@@ -910,6 +910,11 @@ void TargetPassConfig::addBlockPlacement() {
 //===---------------------------------------------------------------------===//
 /// GlobalISel Configuration
 //===---------------------------------------------------------------------===//
+
+bool TargetPassConfig::isGlobalISelEnabled() const {
+  return false;
+}
+
 bool TargetPassConfig::isGlobalISelAbortEnabled() const {
   return EnableGlobalISelAbort == 1;
 }

diff --git a/lib/Target/AArch64/AArch64TargetMachine.cpp b/lib/Target/AArch64/AArch64TargetMachine.cpp
index 3368c98418791fabee57c966d22cc0732ddb3478..db79eed709ea8e124d356b8da3de6138cc265f14 100644 (file)
--- a/lib/Target/AArch64/AArch64TargetMachine.cpp
+++ b/lib/Target/AArch64/AArch64TargetMachine.cpp
@@ -139,6 +139,11 @@ static cl::opt<bool>
                            cl::desc("Enable the loop data prefetch pass"),
                            cl::init(true));
 
+static cl::opt<int> EnableGlobalISelAtO(
+    "aarch64-enable-global-isel-at-O", cl::Hidden,
+    cl::desc("Enable GlobalISel at or below an opt level (-1 to disable)"),
+    cl::init(-1));
+
 extern "C" void LLVMInitializeAArch64Target() {
   // Register the target.
   RegisterTargetMachine<AArch64leTargetMachine> X(getTheAArch64leTarget());
@@ -358,6 +363,8 @@ public:
   void addPostRegAlloc() override;
   void addPreSched2() override;
   void addPreEmitPass() override;
+
+  bool isGlobalISelEnabled() const override;
 };
 
 } // end anonymous namespace
@@ -467,6 +474,10 @@ bool AArch64PassConfig::addGlobalInstructionSelect() {
 }
 #endif
 
+bool AArch64PassConfig::isGlobalISelEnabled() const {
+  return TM->getOptLevel() <= EnableGlobalISelAtO;
+}
+
 bool AArch64PassConfig::addILPOpts() {
   if (EnableCondOpt)
     addPass(createAArch64ConditionOptimizerPass());

diff --git a/test/CodeGen/AArch64/GlobalISel/gisel-commandline-option.ll b/test/CodeGen/AArch64/GlobalISel/gisel-commandline-option.ll
new file mode 100644 (file)
index 0000000..3ecdb7b
--- /dev/null
+++ b/test/CodeGen/AArch64/GlobalISel/gisel-commandline-option.ll
@@ -0,0 +1,48 @@
+; RUN: llc -mtriple=aarch64-- -debug-pass=Structure %s -o /dev/null 2>&1 \
+; RUN:   -O0 -aarch64-enable-global-isel-at-O=0 \
+; RUN:   | FileCheck %s --check-prefix ENABLED --check-prefix NOFALLBACK
+
+; RUN: llc -mtriple=aarch64-- -debug-pass=Structure %s -o /dev/null 2>&1 \
+; RUN:   -O0 -aarch64-enable-global-isel-at-O=0 -global-isel-abort=2  \
+; RUN:   | FileCheck %s --check-prefix ENABLED --check-prefix FALLBACK
+
+; RUN: llc -mtriple=aarch64-- -debug-pass=Structure %s -o /dev/null 2>&1 \
+; RUN:   -global-isel \
+; RUN:   | FileCheck %s --check-prefix ENABLED --check-prefix NOFALLBACK
+
+; RUN: llc -mtriple=aarch64-- -debug-pass=Structure %s -o /dev/null 2>&1 \
+; RUN:   -global-isel -global-isel-abort=2 \
+; RUN:   | FileCheck %s --check-prefix ENABLED --check-prefix FALLBACK
+
+; RUN: llc -mtriple=aarch64-- -debug-pass=Structure %s -o /dev/null 2>&1 \
+; RUN:   -O1 -aarch64-enable-global-isel-at-O=3 \
+; RUN:   | FileCheck %s --check-prefix ENABLED
+
+; RUN: llc -mtriple=aarch64-- -debug-pass=Structure %s -o /dev/null 2>&1 \
+; RUN:   -O1 -aarch64-enable-global-isel-at-O=0 \
+; RUN:   | FileCheck %s --check-prefix DISABLED
+
+; RUN: llc -mtriple=aarch64-- -debug-pass=Structure %s -o /dev/null 2>&1 \
+; RUN:   -aarch64-enable-global-isel-at-O=-1 \
+; RUN:   | FileCheck %s --check-prefix DISABLED
+
+; RUN: llc -mtriple=aarch64-- -debug-pass=Structure %s -o /dev/null 2>&1 \
+; RUN:   | FileCheck %s --check-prefix DISABLED
+
+; ENABLED:       IRTranslator
+; ENABLED-NEXT:  Legalizer
+; ENABLED-NEXT:  RegBankSelect
+; ENABLED-NEXT:  InstructionSelect
+; ENABLED-NEXT:  ResetMachineFunction
+
+; FALLBACK:       AArch64 Instruction Selection
+; NOFALLBACK-NOT: AArch64 Instruction Selection
+
+; DISABLED-NOT: IRTranslator
+
+; DISABLED: AArch64 Instruction Selection
+; DISABLED: Expand ISel Pseudo-instructions
+
+define void @empty() {
+  ret void
+}