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

Author: Max Kazantsev

llvm/include/llvm/InitializePasses.h

@@ -240,6 +240,7 @@ void initializeLowerAtomicLegacyPassPass(PassRegistry&);
 void initializeLowerEmuTLSPass(PassRegistry&);
 void initializeLowerExpectIntrinsicPass(PassRegistry&);
 void initializeLowerGuardIntrinsicLegacyPassPass(PassRegistry&);
+void initializeLowerWidenableConditionLegacyPassPass(PassRegistry&);
 void initializeLowerIntrinsicsPass(PassRegistry&);
 void initializeLowerInvokeLegacyPassPass(PassRegistry&);
 void initializeLowerSwitchPass(PassRegistry&);

llvm/include/llvm/Transforms/Scalar.h

@@ -357,6 +357,12 @@ Pass *createLowerAtomicPass();
 //
 Pass *createLowerGuardIntrinsicPass();
 
+//===----------------------------------------------------------------------===//
+//
+// LowerWidenableCondition - Lower widenable condition to i1 true.
+//
+Pass *createLowerWidenableConditionPass();
+
 //===----------------------------------------------------------------------===//
 //
 // MergeICmps - Merge integer comparison chains into a memcmp

llvm/include/llvm/Transforms/Scalar/LowerWidenableCondition.h

@@ -0,0 +1,27 @@
+//===--- LowerWidenableCondition.h - 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.
+//
+//===----------------------------------------------------------------------===//
+#ifndef LLVM_TRANSFORMS_SCALAR_LOWERWIDENABLECONDITION_H
+#define LLVM_TRANSFORMS_SCALAR_LOWERWIDENABLECONDITION_H
+
+#include "llvm/IR/PassManager.h"
+
+namespace llvm {
+
+struct LowerWidenableConditionPass : PassInfoMixin<LowerWidenableConditionPass> {
+  PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
+};
+
+}
+
+#endif //LLVM_TRANSFORMS_SCALAR_LOWERWIDENABLECONDITION_H

llvm/lib/Passes/PassBuilder.cpp

@@ -133,6 +133,7 @@
 #include "llvm/Transforms/Scalar/LowerAtomic.h"
 #include "llvm/Transforms/Scalar/LowerExpectIntrinsic.h"
 #include "llvm/Transforms/Scalar/LowerGuardIntrinsic.h"
+#include "llvm/Transforms/Scalar/LowerWidenableCondition.h"
 #include "llvm/Transforms/Scalar/MakeGuardsExplicit.h"
 #include "llvm/Transforms/Scalar/MemCpyOptimizer.h"
 #include "llvm/Transforms/Scalar/MergedLoadStoreMotion.h"

llvm/lib/Passes/PassRegistry.def

@@ -177,6 +177,7 @@ FUNCTION_PASS("libcalls-shrinkwrap", LibCallsShrinkWrapPass())
 FUNCTION_PASS("loweratomic", LowerAtomicPass())
 FUNCTION_PASS("lower-expect", LowerExpectIntrinsicPass())
 FUNCTION_PASS("lower-guard-intrinsic", LowerGuardIntrinsicPass())
+FUNCTION_PASS("lower-widenable-condition", LowerWidenableConditionPass())
 FUNCTION_PASS("guard-widening", GuardWideningPass())
 FUNCTION_PASS("gvn", GVN())
 FUNCTION_PASS("load-store-vectorizer", LoadStoreVectorizerPass())

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

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();
+}

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);

llvm/test/Transforms/LowerWidenableCondition/basic.ll

@@ -0,0 +1,44 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S -lower-widenable-condition < %s        | FileCheck %s
+; RUN: opt -S -passes=lower-widenable-condition < %s | FileCheck %s
+
+; Basic test case: make sure that all widenable conditions turn into i1 true.
+define void @f_0(i1 %cond_0, i1 %cond_1) {
+; CHECK-LABEL: @f_0(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[EXIPLICIT_GUARD_COND:%.*]] = and i1 [[COND_0:%.*]], true
+; CHECK-NEXT:    br i1 [[EXIPLICIT_GUARD_COND]], label [[GUARDED:%.*]], label [[DEOPT:%.*]]
+; CHECK:       deopt:
+; CHECK-NEXT:    unreachable
+; CHECK:       guarded:
+; CHECK-NEXT:    [[EXIPLICIT_GUARD_COND4:%.*]] = and i1 [[COND_1:%.*]], true
+; CHECK-NEXT:    br i1 [[EXIPLICIT_GUARD_COND4]], label [[GUARDED1:%.*]], label [[DEOPT2:%.*]]
+; CHECK:       deopt2:
+; CHECK-NEXT:    unreachable
+; CHECK:       guarded1:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %widenable_cond = call i1 @llvm.experimental.widenable.condition()
+  %exiplicit_guard_cond = and i1 %cond_0, %widenable_cond
+  br i1 %exiplicit_guard_cond, label %guarded, label %deopt
+
+deopt:                                            ; preds = %entry
+  unreachable
+
+guarded:                                          ; preds = %entry
+  %widenable_cond3 = call i1 @llvm.experimental.widenable.condition()
+  %exiplicit_guard_cond4 = and i1 %cond_1, %widenable_cond3
+  br i1 %exiplicit_guard_cond4, label %guarded1, label %deopt2
+
+deopt2:                                           ; preds = %guarded
+  unreachable
+
+guarded1:                                         ; preds = %guarded
+  ret void
+}
+
+; Function Attrs: inaccessiblememonly nounwind
+declare i1 @llvm.experimental.widenable.condition() #0
+
+attributes #0 = { inaccessiblememonly nounwind }