[SimplifyCFG][PhaseOrdering] Defer lowering switch into an integer range comparison and branch until after at least the IPSCCP

llvm/include/llvm/Transforms/Utils/SimplifyCFGOptions.h

@@ -23,6 +23,7 @@ class AssumptionCache;
 struct SimplifyCFGOptions {
   int BonusInstThreshold = 1;
   bool ForwardSwitchCondToPhi = false;
+  bool ConvertSwitchRangeToICmp = false;
   bool ConvertSwitchToLookupTable = false;
   bool NeedCanonicalLoop = true;
   bool HoistCommonInsts = false;
@@ -41,6 +42,10 @@ struct SimplifyCFGOptions {
     ForwardSwitchCondToPhi = B;
     return *this;
   }
+  SimplifyCFGOptions &convertSwitchRangeToICmp(bool B) {
+    ConvertSwitchRangeToICmp = B;
+    return *this;
+  }
   SimplifyCFGOptions &convertSwitchToLookupTable(bool B) {
     ConvertSwitchToLookupTable = B;
     return *this;

llvm/lib/Passes/PassBuilder.cpp

@@ -679,6 +679,8 @@ Expected<SimplifyCFGOptions> parseSimplifyCFGOptions(StringRef Params) {
     bool Enable = !ParamName.consume_front("no-");
     if (ParamName == "forward-switch-cond") {
       Result.forwardSwitchCondToPhi(Enable);
+    } else if (ParamName == "switch-range-to-icmp") {
+      Result.convertSwitchRangeToICmp(Enable);
     } else if (ParamName == "switch-to-lookup") {
       Result.convertSwitchToLookupTable(Enable);
     } else if (ParamName == "keep-loops") {

llvm/lib/Passes/PassBuilderPipelines.cpp

@@ -259,14 +259,16 @@ PassBuilder::buildO1FunctionSimplificationPipeline(OptimizationLevel Level,
   FPM.addPass(EarlyCSEPass(true /* Enable mem-ssa. */));
 
   // Hoisting of scalars and load expressions.
-  FPM.addPass(SimplifyCFGPass());
+  FPM.addPass(
+      SimplifyCFGPass(SimplifyCFGOptions().convertSwitchRangeToICmp(true)));
   FPM.addPass(InstCombinePass());
 
   FPM.addPass(LibCallsShrinkWrapPass());
 
   invokePeepholeEPCallbacks(FPM, Level);
 
-  FPM.addPass(SimplifyCFGPass());
+  FPM.addPass(
+      SimplifyCFGPass(SimplifyCFGOptions().convertSwitchRangeToICmp(true)));
 
   // Form canonically associated expression trees, and simplify the trees using
   // basic mathematical properties. For example, this will form (nearly)
@@ -335,7 +337,8 @@ PassBuilder::buildO1FunctionSimplificationPipeline(OptimizationLevel Level,
   FPM.addPass(createFunctionToLoopPassAdaptor(std::move(LPM1),
                                               /*UseMemorySSA=*/true,
                                               /*UseBlockFrequencyInfo=*/true));
-  FPM.addPass(SimplifyCFGPass());
+  FPM.addPass(
+      SimplifyCFGPass(SimplifyCFGOptions().convertSwitchRangeToICmp(true)));
   FPM.addPass(InstCombinePass());
   // The loop passes in LPM2 (LoopFullUnrollPass) do not preserve MemorySSA.
   // *All* loop passes must preserve it, in order to be able to use it.
@@ -373,7 +376,8 @@ PassBuilder::buildO1FunctionSimplificationPipeline(OptimizationLevel Level,
   // the simplifications and basic cleanup after all the simplifications.
   // TODO: Investigate if this is too expensive.
   FPM.addPass(ADCEPass());
-  FPM.addPass(SimplifyCFGPass());
+  FPM.addPass(
+      SimplifyCFGPass(SimplifyCFGOptions().convertSwitchRangeToICmp(true)));
   FPM.addPass(InstCombinePass());
   invokePeepholeEPCallbacks(FPM, Level);
 
@@ -408,7 +412,8 @@ PassBuilder::buildFunctionSimplificationPipeline(OptimizationLevel Level,
   // Global value numbering based sinking.
   if (EnableGVNSink) {
     FPM.addPass(GVNSinkPass());
-    FPM.addPass(SimplifyCFGPass());
+    FPM.addPass(
+        SimplifyCFGPass(SimplifyCFGOptions().convertSwitchRangeToICmp(true)));
   }
 
   if (EnableConstraintElimination)
@@ -421,7 +426,8 @@ PassBuilder::buildFunctionSimplificationPipeline(OptimizationLevel Level,
   FPM.addPass(JumpThreadingPass());
   FPM.addPass(CorrelatedValuePropagationPass());
 
-  FPM.addPass(SimplifyCFGPass());
+  FPM.addPass(
+      SimplifyCFGPass(SimplifyCFGOptions().convertSwitchRangeToICmp(true)));
   FPM.addPass(InstCombinePass());
   if (Level == OptimizationLevel::O3)
     FPM.addPass(AggressiveInstCombinePass());
@@ -438,7 +444,8 @@ PassBuilder::buildFunctionSimplificationPipeline(OptimizationLevel Level,
     FPM.addPass(PGOMemOPSizeOpt());
 
   FPM.addPass(TailCallElimPass());
-  FPM.addPass(SimplifyCFGPass());
+  FPM.addPass(
+      SimplifyCFGPass(SimplifyCFGOptions().convertSwitchRangeToICmp(true)));
 
   // Form canonically associated expression trees, and simplify the trees using
   // basic mathematical properties. For example, this will form (nearly)
@@ -510,7 +517,8 @@ PassBuilder::buildFunctionSimplificationPipeline(OptimizationLevel Level,
   FPM.addPass(createFunctionToLoopPassAdaptor(std::move(LPM1),
                                               /*UseMemorySSA=*/true,
                                               /*UseBlockFrequencyInfo=*/true));
-  FPM.addPass(SimplifyCFGPass());
+  FPM.addPass(
+      SimplifyCFGPass(SimplifyCFGOptions().convertSwitchRangeToICmp(true)));
   FPM.addPass(InstCombinePass());
   // The loop passes in LPM2 (LoopIdiomRecognizePass, IndVarSimplifyPass,
   // LoopDeletionPass and LoopFullUnrollPass) do not preserve MemorySSA.
@@ -575,8 +583,10 @@ PassBuilder::buildFunctionSimplificationPipeline(OptimizationLevel Level,
   for (auto &C : ScalarOptimizerLateEPCallbacks)
     C(FPM, Level);
 
-  FPM.addPass(SimplifyCFGPass(
-      SimplifyCFGOptions().hoistCommonInsts(true).sinkCommonInsts(true)));
+  FPM.addPass(SimplifyCFGPass(SimplifyCFGOptions()
+                                  .convertSwitchRangeToICmp(true)
+                                  .hoistCommonInsts(true)
+                                  .sinkCommonInsts(true)));
   FPM.addPass(InstCombinePass());
   invokePeepholeEPCallbacks(FPM, Level);
 
@@ -614,7 +624,8 @@ void PassBuilder::addPGOInstrPasses(ModulePassManager &MPM,
     FunctionPassManager FPM;
     FPM.addPass(SROAPass());
     FPM.addPass(EarlyCSEPass());    // Catch trivial redundancies.
-    FPM.addPass(SimplifyCFGPass()); // Merge & remove basic blocks.
+    FPM.addPass(SimplifyCFGPass(SimplifyCFGOptions().convertSwitchRangeToICmp(
+        true)));                    // Merge & remove basic blocks.
     FPM.addPass(InstCombinePass()); // Combine silly sequences.
     invokePeepholeEPCallbacks(FPM, Level);
 
@@ -928,7 +939,8 @@ PassBuilder::buildModuleSimplificationPipeline(OptimizationLevel Level,
   GlobalCleanupPM.addPass(InstCombinePass());
   invokePeepholeEPCallbacks(GlobalCleanupPM, Level);
 
-  GlobalCleanupPM.addPass(SimplifyCFGPass());
+  GlobalCleanupPM.addPass(
+      SimplifyCFGPass(SimplifyCFGOptions().convertSwitchRangeToICmp(true)));
   MPM.addPass(createModuleToFunctionPassAdaptor(std::move(GlobalCleanupPM),
                                                 PTO.EagerlyInvalidateAnalyses));
 
@@ -1015,7 +1027,8 @@ void PassBuilder::addVectorPasses(OptimizationLevel Level,
     ExtraPasses.addPass(
         createFunctionToLoopPassAdaptor(std::move(LPM), /*UseMemorySSA=*/true,
                                         /*UseBlockFrequencyInfo=*/true));
-    ExtraPasses.addPass(SimplifyCFGPass());
+    ExtraPasses.addPass(
+        SimplifyCFGPass(SimplifyCFGOptions().convertSwitchRangeToICmp(true)));
     ExtraPasses.addPass(InstCombinePass());
     FPM.addPass(std::move(ExtraPasses));
   }
@@ -1031,6 +1044,7 @@ void PassBuilder::addVectorPasses(OptimizationLevel Level,
   // before SLP vectorization.
   FPM.addPass(SimplifyCFGPass(SimplifyCFGOptions()
                                   .forwardSwitchCondToPhi(true)
+                                  .convertSwitchRangeToICmp(true)
                                   .convertSwitchToLookupTable(true)
                                   .needCanonicalLoops(false)
                                   .hoistCommonInsts(true)
@@ -1202,7 +1216,8 @@ PassBuilder::buildModuleOptimizationPipeline(OptimizationLevel Level,
 
   // LoopSink (and other loop passes since the last simplifyCFG) might have
   // resulted in single-entry-single-exit or empty blocks. Clean up the CFG.
-  OptimizePM.addPass(SimplifyCFGPass());
+  OptimizePM.addPass(
+      SimplifyCFGPass(SimplifyCFGOptions().convertSwitchRangeToICmp(true)));
 
   OptimizePM.addPass(CoroCleanupPass());
 
@@ -1676,8 +1691,9 @@ PassBuilder::buildLTODefaultPipeline(OptimizationLevel Level,
 
   // Add late LTO optimization passes.
   // Delete basic blocks, which optimization passes may have killed.
-  MPM.addPass(createModuleToFunctionPassAdaptor(
-      SimplifyCFGPass(SimplifyCFGOptions().hoistCommonInsts(true))));
+  MPM.addPass(createModuleToFunctionPassAdaptor(SimplifyCFGPass(
+      SimplifyCFGOptions().convertSwitchRangeToICmp(true).hoistCommonInsts(
+          true))));
 
   // Drop bodies of available eternally objects to improve GlobalDCE.
   MPM.addPass(EliminateAvailableExternallyPass());

llvm/lib/Passes/PassRegistry.def

@@ -423,6 +423,7 @@ FUNCTION_PASS_WITH_PARAMS("simplifycfg",
                            },
                           parseSimplifyCFGOptions,
                           "no-forward-switch-cond;forward-switch-cond;"
+                          "no-switch-range-to-icmp;switch-range-to-icmp;"
                           "no-switch-to-lookup;switch-to-lookup;"
                           "no-keep-loops;keep-loops;"
                           "no-hoist-common-insts;hoist-common-insts;"

llvm/lib/Target/AArch64/AArch64TargetMachine.cpp

@@ -531,6 +531,7 @@ void AArch64PassConfig::addIRPasses() {
   if (TM->getOptLevel() != CodeGenOpt::None && EnableAtomicTidy)
     addPass(createCFGSimplificationPass(SimplifyCFGOptions()
                                             .forwardSwitchCondToPhi(true)
+                                            .convertSwitchRangeToICmp(true)
                                             .convertSwitchToLookupTable(true)
                                             .needCanonicalLoops(false)
                                             .hoistCommonInsts(true)

llvm/lib/Target/Hexagon/HexagonTargetMachine.cpp

@@ -345,6 +345,7 @@ void HexagonPassConfig::addIRPasses() {
     if (EnableInitialCFGCleanup)
       addPass(createCFGSimplificationPass(SimplifyCFGOptions()
                                               .forwardSwitchCondToPhi(true)
+                                              .convertSwitchRangeToICmp(true)
                                               .convertSwitchToLookupTable(true)
                                               .needCanonicalLoops(false)
                                               .hoistCommonInsts(true)

llvm/lib/Transforms/IPO/PassManagerBuilder.cpp

@@ -365,7 +365,9 @@ void PassManagerBuilder::addPGOInstrPasses(legacy::PassManagerBase &MPM,
     MPM.add(createFunctionInliningPass(IP));
     MPM.add(createSROAPass());
     MPM.add(createEarlyCSEPass());             // Catch trivial redundancies
-    MPM.add(createCFGSimplificationPass());    // Merge & remove BBs
+    MPM.add(createCFGSimplificationPass(
+        SimplifyCFGOptions().convertSwitchRangeToICmp(
+            true)));                           // Merge & remove BBs
     MPM.add(createInstructionCombiningPass()); // Combine silly seq's
     addExtensionsToPM(EP_Peephole, MPM);
   }
@@ -404,7 +406,8 @@ void PassManagerBuilder::addFunctionSimplificationPasses(
       MPM.add(createGVNHoistPass());
     if (EnableGVNSink) {
       MPM.add(createGVNSinkPass());
-      MPM.add(createCFGSimplificationPass());
+      MPM.add(createCFGSimplificationPass(
+          SimplifyCFGOptions().convertSwitchRangeToICmp(true)));
     }
   }
 
@@ -418,7 +421,9 @@ void PassManagerBuilder::addFunctionSimplificationPasses(
     MPM.add(createJumpThreadingPass());         // Thread jumps.
     MPM.add(createCorrelatedValuePropagationPass()); // Propagate conditionals
   }
-  MPM.add(createCFGSimplificationPass());     // Merge & remove BBs
+  MPM.add(
+      createCFGSimplificationPass(SimplifyCFGOptions().convertSwitchRangeToICmp(
+          true))); // Merge & remove BBs
   // Combine silly seq's
   if (OptLevel > 2)
     MPM.add(createAggressiveInstCombinerPass());
@@ -434,7 +439,9 @@ void PassManagerBuilder::addFunctionSimplificationPasses(
   // TODO: Investigate the cost/benefit of tail call elimination on debugging.
   if (OptLevel > 1)
     MPM.add(createTailCallEliminationPass()); // Eliminate tail calls
-  MPM.add(createCFGSimplificationPass());      // Merge & remove BBs
+  MPM.add(
+      createCFGSimplificationPass(SimplifyCFGOptions().convertSwitchRangeToICmp(
+          true)));                            // Merge & remove BBs
   MPM.add(createReassociatePass());           // Reassociate expressions
 
   // The matrix extension can introduce large vector operations early, which can
@@ -465,7 +472,8 @@ void PassManagerBuilder::addFunctionSimplificationPasses(
   // FIXME: We break the loop pass pipeline here in order to do full
   // simplifycfg. Eventually loop-simplifycfg should be enhanced to replace the
   // need for this.
-  MPM.add(createCFGSimplificationPass());
+  MPM.add(createCFGSimplificationPass(
+      SimplifyCFGOptions().convertSwitchRangeToICmp(true)));
   MPM.add(createInstructionCombiningPass());
   // We resume loop passes creating a second loop pipeline here.
   if (EnableLoopFlatten) {
@@ -582,7 +590,8 @@ void PassManagerBuilder::addVectorPasses(legacy::PassManagerBase &PM,
     PM.add(createInstructionCombiningPass());
     PM.add(createLICMPass(LicmMssaOptCap, LicmMssaNoAccForPromotionCap));
     PM.add(createLoopUnswitchPass(SizeLevel || OptLevel < 3, DivergentTarget));
-    PM.add(createCFGSimplificationPass());
+    PM.add(createCFGSimplificationPass(
+        SimplifyCFGOptions().convertSwitchRangeToICmp(true)));
     PM.add(createInstructionCombiningPass());
   }
 
@@ -597,6 +606,7 @@ void PassManagerBuilder::addVectorPasses(legacy::PassManagerBase &PM,
   // before SLP vectorization.
   PM.add(createCFGSimplificationPass(SimplifyCFGOptions()
                                          .forwardSwitchCondToPhi(true)
+                                         .convertSwitchRangeToICmp(true)
                                          .convertSwitchToLookupTable(true)
                                          .needCanonicalLoops(false)
                                          .hoistCommonInsts(true)
@@ -772,7 +782,9 @@ void PassManagerBuilder::populateModulePassManager(
 
   MPM.add(createInstructionCombiningPass()); // Clean up after IPCP & DAE
   addExtensionsToPM(EP_Peephole, MPM);
-  MPM.add(createCFGSimplificationPass()); // Clean up after IPCP & DAE
+  MPM.add(
+      createCFGSimplificationPass(SimplifyCFGOptions().convertSwitchRangeToICmp(
+          true))); // Clean up after IPCP & DAE
 
   // For SamplePGO in ThinLTO compile phase, we do not want to do indirect
   // call promotion as it will change the CFG too much to make the 2nd
@@ -972,7 +984,8 @@ void PassManagerBuilder::populateModulePassManager(
 
   // LoopSink (and other loop passes since the last simplifyCFG) might have
   // resulted in single-entry-single-exit or empty blocks. Clean up the CFG.
-  MPM.add(createCFGSimplificationPass());
+  MPM.add(createCFGSimplificationPass(
+      SimplifyCFGOptions().convertSwitchRangeToICmp(true)));
 
   addExtensionsToPM(EP_OptimizerLast, MPM);
 

llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp

@@ -59,6 +59,11 @@ static cl::opt<bool> UserKeepLoops(
     "keep-loops", cl::Hidden, cl::init(true),
     cl::desc("Preserve canonical loop structure (default = true)"));
 
+static cl::opt<bool> UserSwitchRangeToICmp(
+    "switch-range-to-icmp", cl::Hidden, cl::init(false),
+    cl::desc(
+        "Convert switches into an integer range comparison (default = false)"));
+
 static cl::opt<bool> UserSwitchToLookup(
     "switch-to-lookup", cl::Hidden, cl::init(false),
     cl::desc("Convert switches to lookup tables (default = false)"));
@@ -311,6 +316,8 @@ static void applyCommandLineOverridesToOptions(SimplifyCFGOptions &Options) {
     Options.BonusInstThreshold = UserBonusInstThreshold;
   if (UserForwardSwitchCond.getNumOccurrences())
     Options.ForwardSwitchCondToPhi = UserForwardSwitchCond;
+  if (UserSwitchRangeToICmp.getNumOccurrences())
+    Options.ConvertSwitchRangeToICmp = UserSwitchRangeToICmp;
   if (UserSwitchToLookup.getNumOccurrences())
     Options.ConvertSwitchToLookupTable = UserSwitchToLookup;
   if (UserKeepLoops.getNumOccurrences())
@@ -337,6 +344,8 @@ void SimplifyCFGPass::printPipeline(
   OS << "<";
   OS << "bonus-inst-threshold=" << Options.BonusInstThreshold << ";";
   OS << (Options.ForwardSwitchCondToPhi ? "" : "no-") << "forward-switch-cond;";
+  OS << (Options.ConvertSwitchRangeToICmp ? "" : "no-")
+     << "switch-range-to-icmp;";
   OS << (Options.ConvertSwitchToLookupTable ? "" : "no-")
      << "switch-to-lookup;";
   OS << (Options.NeedCanonicalLoop ? "" : "no-") << "keep-loops;";

llvm/lib/Transforms/Utils/SimplifyCFG.cpp

@@ -6211,7 +6211,9 @@ bool SimplifyCFGOpt::simplifySwitch(SwitchInst *SI, IRBuilder<> &Builder) {
   }
 
   // Try to transform the switch into an icmp and a branch.
-  if (TurnSwitchRangeIntoICmp(SI, Builder))
+  // The conversion from switch to comparison may lose information on
+  // impossible switch values, so disable it early in the pipeline.
+  if (Options.ConvertSwitchRangeToICmp && TurnSwitchRangeIntoICmp(SI, Builder))
     return requestResimplify();
 
   // Remove unreachable cases.

llvm/test/Other/new-pm-print-pipeline.ll

@@ -1,7 +1,7 @@
 ;; Test that the -print-pipeline-passes option correctly prints some explicitly specified pipelines.
 
 ; RUN: opt -disable-output -disable-verify -print-pipeline-passes -passes='function(adce),function(simplifycfg<bonus-inst-threshold=123;no-forward-switch-cond;switch-to-lookup;keep-loops;no-hoist-common-insts;sink-common-insts>)' < %s | FileCheck %s --match-full-lines --check-prefixes=CHECK-0
-; CHECK-0: function(adce),function(simplifycfg<bonus-inst-threshold=123;no-forward-switch-cond;switch-to-lookup;keep-loops;no-hoist-common-insts;sink-common-insts>)
+; CHECK-0: function(adce),function(simplifycfg<bonus-inst-threshold=123;no-forward-switch-cond;no-switch-range-to-icmp;switch-to-lookup;keep-loops;no-hoist-common-insts;sink-common-insts>)
 
 ; RUN: opt -disable-output -disable-verify -print-pipeline-passes -passes='module(rpo-function-attrs,require<globals-aa>,function(float2int,lower-constant-intrinsics,loop(loop-rotate)),invalidate<globals-aa>)' < %s | FileCheck %s --match-full-lines --check-prefixes=CHECK-1
 ; CHECK-1: rpo-function-attrs,require<globals-aa>,function(float2int,lower-constant-intrinsics,loop(loop-rotate)),invalidate<globals-aa>
@@ -56,7 +56,7 @@
 ; CHECK-17: function(print<stack-lifetime><may>,print<stack-lifetime><must>)
 
 ; RUN: opt -disable-output -disable-verify -print-pipeline-passes -passes='function(simplifycfg<bonus-inst-threshold=5;forward-switch-cond;switch-to-lookup;keep-loops;hoist-common-insts;sink-common-insts>,simplifycfg<bonus-inst-threshold=7;no-forward-switch-cond;no-switch-to-lookup;no-keep-loops;no-hoist-common-insts;no-sink-common-insts>)' < %s | FileCheck %s --match-full-lines --check-prefixes=CHECK-18
-; CHECK-18: function(simplifycfg<bonus-inst-threshold=5;forward-switch-cond;switch-to-lookup;keep-loops;hoist-common-insts;sink-common-insts>,simplifycfg<bonus-inst-threshold=7;no-forward-switch-cond;no-switch-to-lookup;no-keep-loops;no-hoist-common-insts;no-sink-common-insts>)
+; CHECK-18: function(simplifycfg<bonus-inst-threshold=5;forward-switch-cond;no-switch-range-to-icmp;switch-to-lookup;keep-loops;hoist-common-insts;sink-common-insts>,simplifycfg<bonus-inst-threshold=7;no-forward-switch-cond;no-switch-range-to-icmp;no-switch-to-lookup;no-keep-loops;no-hoist-common-insts;no-sink-common-insts>)
 
 ; RUN: opt -disable-output -disable-verify -print-pipeline-passes -passes='function(loop-vectorize<no-interleave-forced-only;no-vectorize-forced-only>,loop-vectorize<interleave-forced-only;vectorize-forced-only>)' < %s | FileCheck %s --match-full-lines --check-prefixes=CHECK-19
 ; CHECK-19: function(loop-vectorize<no-interleave-forced-only;no-vectorize-forced-only;>,loop-vectorize<interleave-forced-only;vectorize-forced-only;>)

llvm/test/Transforms/Coroutines/coro-catchswitch-cleanuppad.ll

@@ -1,6 +1,6 @@
 ; Tests the PHI nodes in cleanuppads for catchswitch instructions are correctly
 ; split up.
-; RUN: opt < %s -passes='cgscc(coro-split),simplifycfg,early-cse' -S | FileCheck %s
+; RUN: opt < %s -passes='cgscc(coro-split),simplifycfg<switch-range-to-icmp>,early-cse' -S | FileCheck %s
 
 declare i32 @__CxxFrameHandler3(...)
 define i8* @f2(i1 %val) "coroutine.presplit"="1" personality i32 (...)* @__CxxFrameHandler3 {

llvm/test/Transforms/LoopUnroll/ARM/upperbound.ll

@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt -loop-unroll -simplifycfg -instcombine -simplifycfg -S -mtriple arm-none-eabi -mcpu=cortex-m7 %s | FileCheck %s
+; RUN: opt -loop-unroll -simplifycfg -switch-range-to-icmp -instcombine -simplifycfg -S -mtriple arm-none-eabi -mcpu=cortex-m7 %s | FileCheck %s
 
 ; This test is meant to check that this loop is unrolled into three iterations.
 define void @test(i32* %x, i32 %n) {