Default lowering for experimental.widenable.condition

Introduces a pass that provides default lowering strategy for the
`experimental.widenable.condition` intrinsic, replacing all its uses with
`i1 true`.

Differential Revision: https://reviews.llvm.org/D56096
Reviewed By: reames

llvm-svn: 352739

3 files changed, 88 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/CMakeLists.txt b/llvm/lib/Transforms/Scalar/CMakeLists.txt
index e3548ce5cd0..9c33971ce0f 100644
--- a/llvm/lib/Transforms/Scalar/CMakeLists.txt
+++ b/llvm/lib/Transforms/Scalar/CMakeLists.txt
@@ -45,6 +45,7 @@ add_llvm_library(LLVMScalarOpts
   LowerAtomic.cpp
   LowerExpectIntrinsic.cpp
   LowerGuardIntrinsic.cpp
+  LowerWidenableCondition.cpp
   MakeGuardsExplicit.cpp
   MemCpyOptimizer.cpp
   MergeICmps.cpp
diff --git a/llvm/lib/Transforms/Scalar/LowerWidenableCondition.cpp b/llvm/lib/Transforms/Scalar/LowerWidenableCondition.cpp
new file mode 100644
index 00000000000..6a83d062b71
--- /dev/null
+++ b/llvm/lib/Transforms/Scalar/LowerWidenableCondition.cpp
@@ -0,0 +1,86 @@
+//===- LowerWidenableCondition.cpp - Lower the guard intrinsic ---------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass lowers the llvm.widenable.condition intrinsic to default value
+// which is i1 true.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Scalar/LowerWidenableCondition.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Analysis/GuardUtils.h"
+#include "llvm/IR/BasicBlock.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/InstIterator.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Intrinsics.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PatternMatch.h"
+#include "llvm/Pass.h"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Utils/GuardUtils.h"
+
+using namespace llvm;
+
+namespace {
+struct LowerWidenableConditionLegacyPass : public FunctionPass {
+  static char ID;
+  LowerWidenableConditionLegacyPass() : FunctionPass(ID) {
+    initializeLowerWidenableConditionLegacyPassPass(
+        *PassRegistry::getPassRegistry());
+  }
+
+  bool runOnFunction(Function &F) override;
+};
+}
+
+static bool lowerWidenableCondition(Function &F) {
+  // Check if we can cheaply rule out the possibility of not having any work to
+  // do.
+  auto *WCDecl = F.getParent()->getFunction(
+      Intrinsic::getName(Intrinsic::experimental_widenable_condition));
+  if (!WCDecl || WCDecl->use_empty())
+    return false;
+
+  using namespace llvm::PatternMatch;
+  SmallVector<CallInst *, 8> ToLower;
+  for (auto &I : instructions(F))
+    if (match(&I, m_Intrinsic<Intrinsic::experimental_widenable_condition>()))
+      ToLower.push_back(cast<CallInst>(&I));
+
+  if (ToLower.empty())
+    return false;
+
+  for (auto *CI : ToLower) {
+    CI->replaceAllUsesWith(ConstantInt::getTrue(CI->getContext()));
+    CI->eraseFromParent();
+  }
+  return true;
+}
+
+bool LowerWidenableConditionLegacyPass::runOnFunction(Function &F) {
+  return lowerWidenableCondition(F);
+}
+
+char LowerWidenableConditionLegacyPass::ID = 0;
+INITIALIZE_PASS(LowerWidenableConditionLegacyPass, "lower-widenable-condition",
+                "Lower the widenable condition to default true value", false,
+                false)
+
+Pass *llvm::createLowerWidenableConditionPass() {
+  return new LowerWidenableConditionLegacyPass();
+}
+
+PreservedAnalyses LowerWidenableConditionPass::run(Function &F,
+                                               FunctionAnalysisManager &AM) {
+  if (lowerWidenableCondition(F))
+    return PreservedAnalyses::none();
+
+  return PreservedAnalyses::all();
+}
diff --git a/llvm/lib/Transforms/Scalar/Scalar.cpp b/llvm/lib/Transforms/Scalar/Scalar.cpp
index f3577726f98..c91ffda6d98 100644
--- a/llvm/lib/Transforms/Scalar/Scalar.cpp
+++ b/llvm/lib/Transforms/Scalar/Scalar.cpp
@@ -80,6 +80,7 @@ void llvm::initializeScalarOpts(PassRegistry &Registry) {
   initializeLowerAtomicLegacyPassPass(Registry);
   initializeLowerExpectIntrinsicPass(Registry);
   initializeLowerGuardIntrinsicLegacyPassPass(Registry);
+  initializeLowerWidenableConditionLegacyPassPass(Registry);
   initializeMemCpyOptLegacyPassPass(Registry);
   initializeMergeICmpsPass(Registry);
   initializeMergedLoadStoreMotionLegacyPassPass(Registry);