[llvm] r217220 - [AArch64] Add pass to enable additional comparison optimizations by CSE.
Jiangning Liu
jiangning.liu at arm.com
Thu Sep 4 19:55:26 PDT 2014
Author: jiangning
Date: Thu Sep 4 21:55:24 2014
New Revision: 217220
URL: http://llvm.org/viewvc/llvm-project?rev=217220&view=rev
Log:
[AArch64] Add pass to enable additional comparison optimizations by CSE.
Patched by Sergey Dmitrouk.
This pass tries to make consecutive compares of values use same operands to
allow CSE pass to remove duplicated instructions. For this it analyzes
branches and adjusts comparisons with immediate values by converting:
GE -> GT
GT -> GE
LT -> LE
LE -> LT
and adjusting immediate values appropriately. It basically corrects two
immediate values towards each other to make them equal.
Added:
llvm/trunk/lib/Target/AArch64/AArch64ConditionOptimizer.cpp
llvm/trunk/test/CodeGen/AArch64/combine-comparisons-by-cse.ll
Modified:
llvm/trunk/lib/Target/AArch64/AArch64.h
llvm/trunk/lib/Target/AArch64/AArch64TargetMachine.cpp
llvm/trunk/lib/Target/AArch64/CMakeLists.txt
Modified: llvm/trunk/lib/Target/AArch64/AArch64.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AArch64/AArch64.h?rev=217220&r1=217219&r2=217220&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64.h (original)
+++ llvm/trunk/lib/Target/AArch64/AArch64.h Thu Sep 4 21:55:24 2014
@@ -36,6 +36,7 @@ FunctionPass *createAArch64StorePairSupp
FunctionPass *createAArch64ExpandPseudoPass();
FunctionPass *createAArch64LoadStoreOptimizationPass();
ModulePass *createAArch64PromoteConstantPass();
+FunctionPass *createAArch64ConditionOptimizerPass();
FunctionPass *createAArch64AddressTypePromotionPass();
FunctionPass *createAArch64A57FPLoadBalancing();
/// \brief Creates an ARM-specific Target Transformation Info pass.
Added: llvm/trunk/lib/Target/AArch64/AArch64ConditionOptimizer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AArch64/AArch64ConditionOptimizer.cpp?rev=217220&view=auto
==============================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64ConditionOptimizer.cpp (added)
+++ llvm/trunk/lib/Target/AArch64/AArch64ConditionOptimizer.cpp Thu Sep 4 21:55:24 2014
@@ -0,0 +1,405 @@
+//=- AArch64ConditionOptimizer.cpp - Remove useless comparisons for AArch64 -=//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass tries to make consecutive compares of values use same operands to
+// allow CSE pass to remove duplicated instructions. For this it analyzes
+// branches and adjusts comparisons with immediate values by converting:
+// * GE -> GT
+// * GT -> GE
+// * LT -> LE
+// * LE -> LT
+// and adjusting immediate values appropriately. It basically corrects two
+// immediate values towards each other to make them equal.
+//
+// Consider the following example in C:
+//
+// if ((a < 5 && ...) || (a > 5 && ...)) {
+// ~~~~~ ~~~~~
+// ^ ^
+// x y
+//
+// Here both "x" and "y" expressions compare "a" with "5". When "x" evaluates
+// to "false", "y" can just check flags set by the first comparison. As a
+// result of the canonicalization employed by
+// SelectionDAGBuilder::visitSwitchCase, DAGCombine, and other target-specific
+// code, assembly ends up in the form that is not CSE friendly:
+//
+// ...
+// cmp w8, #4
+// b.gt .LBB0_3
+// ...
+// .LBB0_3:
+// cmp w8, #6
+// b.lt .LBB0_6
+// ...
+//
+// Same assembly after the pass:
+//
+// ...
+// cmp w8, #5
+// b.ge .LBB0_3
+// ...
+// .LBB0_3:
+// cmp w8, #5 // <-- CSE pass removes this instruction
+// b.le .LBB0_6
+// ...
+//
+// Currently only SUBS and ADDS followed by b.?? are supported.
+//
+// TODO: maybe handle TBNZ/TBZ the same way as CMP when used instead for "a < 0"
+// TODO: handle other conditional instructions (e.g. CSET)
+// TODO: allow second branching to be anything if it doesn't require adjusting
+//
+//===----------------------------------------------------------------------===//
+
+#include "AArch64.h"
+#include "llvm/ADT/DepthFirstIterator.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/CodeGen/MachineDominators.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/TargetInstrInfo.h"
+#include "llvm/Target/TargetSubtargetInfo.h"
+#include <cstdlib>
+#include <tuple>
+
+using namespace llvm;
+
+#define DEBUG_TYPE "aarch64-condopt"
+
+STATISTIC(NumConditionsAdjusted, "Number of conditions adjusted");
+
+namespace {
+class AArch64ConditionOptimizer : public MachineFunctionPass {
+ const TargetInstrInfo *TII;
+ MachineDominatorTree *DomTree;
+
+public:
+ // Stores immediate, compare instruction opcode and branch condition (in this
+ // order) of adjusted comparison.
+ typedef std::tuple<int, int, AArch64CC::CondCode> CmpInfo;
+
+ static char ID;
+ AArch64ConditionOptimizer() : MachineFunctionPass(ID) {}
+ void getAnalysisUsage(AnalysisUsage &AU) const override;
+ MachineInstr *findSuitableCompare(MachineBasicBlock *MBB);
+ CmpInfo adjustCmp(MachineInstr *CmpMI, AArch64CC::CondCode Cmp);
+ void modifyCmp(MachineInstr *CmpMI, const CmpInfo &Info);
+ bool adjustTo(MachineInstr *CmpMI, AArch64CC::CondCode Cmp, MachineInstr *To,
+ int ToImm);
+ bool runOnMachineFunction(MachineFunction &MF) override;
+ const char *getPassName() const override {
+ return "AArch64 Condition Optimizer";
+ }
+};
+} // end anonymous namespace
+
+char AArch64ConditionOptimizer::ID = 0;
+
+namespace llvm {
+void initializeAArch64ConditionOptimizerPass(PassRegistry &);
+}
+
+INITIALIZE_PASS_BEGIN(AArch64ConditionOptimizer, "aarch64-condopt",
+ "AArch64 CondOpt Pass", false, false)
+INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
+INITIALIZE_PASS_END(AArch64ConditionOptimizer, "aarch64-condopt",
+ "AArch64 CondOpt Pass", false, false)
+
+FunctionPass *llvm::createAArch64ConditionOptimizerPass() {
+ return new AArch64ConditionOptimizer();
+}
+
+void AArch64ConditionOptimizer::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<MachineDominatorTree>();
+ AU.addPreserved<MachineDominatorTree>();
+ MachineFunctionPass::getAnalysisUsage(AU);
+}
+
+// Finds compare instruction that corresponds to supported types of branching.
+// Returns the instruction or nullptr on failures or detecting unsupported
+// instructions.
+MachineInstr *AArch64ConditionOptimizer::findSuitableCompare(
+ MachineBasicBlock *MBB) {
+ MachineBasicBlock::iterator I = MBB->getFirstTerminator();
+ if (I == MBB->end()) {
+ return nullptr;
+ }
+
+ if (I->getOpcode() != AArch64::Bcc) {
+ return nullptr;
+ }
+
+ // Now find the instruction controlling the terminator.
+ for (MachineBasicBlock::iterator B = MBB->begin(); I != B;) {
+ --I;
+ assert(!I->isTerminator() && "Spurious terminator");
+ switch (I->getOpcode()) {
+ // cmp is an alias for subs with a dead destination register.
+ case AArch64::SUBSWri:
+ case AArch64::SUBSXri:
+ // cmn is an alias for adds with a dead destination register.
+ case AArch64::ADDSWri:
+ case AArch64::ADDSXri:
+ return I;
+
+ case AArch64::SUBSWrr:
+ case AArch64::SUBSXrr:
+ case AArch64::ADDSWrr:
+ case AArch64::ADDSXrr:
+ case AArch64::FCMPSrr:
+ case AArch64::FCMPDrr:
+ case AArch64::FCMPESrr:
+ case AArch64::FCMPEDrr:
+ // Skip comparison instructions without immediate operands.
+ return nullptr;
+ }
+ }
+ DEBUG(dbgs() << "Flags not defined in BB#" << MBB->getNumber() << '\n');
+ return nullptr;
+}
+
+// Changes opcode adds <-> subs considering register operand width.
+static int getComplementOpc(int Opc) {
+ switch (Opc) {
+ case AArch64::ADDSWri: return AArch64::SUBSWri;
+ case AArch64::ADDSXri: return AArch64::SUBSXri;
+ case AArch64::SUBSWri: return AArch64::ADDSWri;
+ case AArch64::SUBSXri: return AArch64::ADDSXri;
+ default:
+ llvm_unreachable("Unexpected opcode");
+ }
+}
+
+// Changes form of comparison inclusive <-> exclusive.
+static AArch64CC::CondCode getAdjustedCmp(AArch64CC::CondCode Cmp) {
+ switch (Cmp) {
+ case AArch64CC::GT: return AArch64CC::GE;
+ case AArch64CC::GE: return AArch64CC::GT;
+ case AArch64CC::LT: return AArch64CC::LE;
+ case AArch64CC::LE: return AArch64CC::LT;
+ default:
+ llvm_unreachable("Unexpected condition code");
+ }
+}
+
+// Transforms GT -> GE, GE -> GT, LT -> LE, LE -> LT by updating comparison
+// operator and condition code.
+AArch64ConditionOptimizer::CmpInfo AArch64ConditionOptimizer::adjustCmp(
+ MachineInstr *CmpMI, AArch64CC::CondCode Cmp) {
+ int Opc = CmpMI->getOpcode();
+
+ // CMN (compare with negative immediate) is an alias to ADDS (as
+ // "operand - negative" == "operand + positive")
+ bool Negative = (Opc == AArch64::ADDSWri || Opc == AArch64::ADDSXri);
+
+ int Correction = (Cmp == AArch64CC::GT) ? 1 : -1;
+ // Negate Correction value for comparison with negative immediate (CMN).
+ if (Negative) {
+ Correction = -Correction;
+ }
+
+ const int OldImm = (int)CmpMI->getOperand(2).getImm();
+ const int NewImm = std::abs(OldImm + Correction);
+
+ // Handle +0 -> -1 and -0 -> +1 (CMN with 0 immediate) transitions by
+ // adjusting compare instruction opcode.
+ if (OldImm == 0 && ((Negative && Correction == 1) ||
+ (!Negative && Correction == -1))) {
+ Opc = getComplementOpc(Opc);
+ }
+
+ return CmpInfo(NewImm, Opc, getAdjustedCmp(Cmp));
+}
+
+// Applies changes to comparison instruction suggested by adjustCmp().
+void AArch64ConditionOptimizer::modifyCmp(MachineInstr *CmpMI,
+ const CmpInfo &Info) {
+ int Imm;
+ int Opc;
+ AArch64CC::CondCode Cmp;
+ std::tie(Imm, Opc, Cmp) = Info;
+
+ MachineBasicBlock *const MBB = CmpMI->getParent();
+
+ // Change immediate in comparison instruction (ADDS or SUBS).
+ BuildMI(*MBB, CmpMI, CmpMI->getDebugLoc(), TII->get(Opc))
+ .addOperand(CmpMI->getOperand(0))
+ .addOperand(CmpMI->getOperand(1))
+ .addImm(Imm)
+ .addOperand(CmpMI->getOperand(3));
+ CmpMI->eraseFromParent();
+
+ // The fact that this comparison was picked ensures that it's related to the
+ // first terminator instruction.
+ MachineInstr *BrMI = MBB->getFirstTerminator();
+
+ // Change condition in branch instruction.
+ BuildMI(*MBB, BrMI, BrMI->getDebugLoc(), TII->get(AArch64::Bcc))
+ .addImm(Cmp)
+ .addOperand(BrMI->getOperand(1));
+ BrMI->eraseFromParent();
+
+ MBB->updateTerminator();
+
+ ++NumConditionsAdjusted;
+}
+
+// Parse a condition code returned by AnalyzeBranch, and compute the CondCode
+// corresponding to TBB.
+// Returns true if parsing was successful, otherwise false is returned.
+static bool parseCond(ArrayRef<MachineOperand> Cond, AArch64CC::CondCode &CC) {
+ // A normal br.cond simply has the condition code.
+ if (Cond[0].getImm() != -1) {
+ assert(Cond.size() == 1 && "Unknown Cond array format");
+ CC = (AArch64CC::CondCode)(int)Cond[0].getImm();
+ return true;
+ }
+ return false;
+}
+
+// Adjusts one cmp instruction to another one if result of adjustment will allow
+// CSE. Returns true if compare instruction was changed, otherwise false is
+// returned.
+bool AArch64ConditionOptimizer::adjustTo(MachineInstr *CmpMI,
+ AArch64CC::CondCode Cmp, MachineInstr *To, int ToImm)
+{
+ CmpInfo Info = adjustCmp(CmpMI, Cmp);
+ if (std::get<0>(Info) == ToImm && std::get<1>(Info) == To->getOpcode()) {
+ modifyCmp(CmpMI, Info);
+ return true;
+ }
+ return false;
+}
+
+bool AArch64ConditionOptimizer::runOnMachineFunction(MachineFunction &MF) {
+ DEBUG(dbgs() << "********** AArch64 Conditional Compares **********\n"
+ << "********** Function: " << MF.getName() << '\n');
+ TII = MF.getTarget().getSubtargetImpl()->getInstrInfo();
+ DomTree = &getAnalysis<MachineDominatorTree>();
+
+ bool Changed = false;
+
+ // Visit blocks in dominator tree pre-order. The pre-order enables multiple
+ // cmp-conversions from the same head block.
+ // Note that updateDomTree() modifies the children of the DomTree node
+ // currently being visited. The df_iterator supports that; it doesn't look at
+ // child_begin() / child_end() until after a node has been visited.
+ for (MachineDomTreeNode *I : depth_first(DomTree)) {
+ MachineBasicBlock *HBB = I->getBlock();
+
+ SmallVector<MachineOperand, 4> HeadCond;
+ MachineBasicBlock *TBB = nullptr, *FBB = nullptr;
+ if (TII->AnalyzeBranch(*HBB, TBB, FBB, HeadCond)) {
+ continue;
+ }
+
+ // Equivalence check is to skip loops.
+ if (!TBB || TBB == HBB) {
+ continue;
+ }
+
+ SmallVector<MachineOperand, 4> TrueCond;
+ MachineBasicBlock *TBB_TBB = nullptr, *TBB_FBB = nullptr;
+ if (TII->AnalyzeBranch(*TBB, TBB_TBB, TBB_FBB, TrueCond)) {
+ continue;
+ }
+
+ MachineInstr *HeadCmpMI = findSuitableCompare(HBB);
+ if (!HeadCmpMI) {
+ continue;
+ }
+
+ MachineInstr *TrueCmpMI = findSuitableCompare(TBB);
+ if (!TrueCmpMI) {
+ continue;
+ }
+
+ AArch64CC::CondCode HeadCmp;
+ if (HeadCond.empty() || !parseCond(HeadCond, HeadCmp)) {
+ continue;
+ }
+
+ AArch64CC::CondCode TrueCmp;
+ if (TrueCond.empty() || !parseCond(TrueCond, TrueCmp)) {
+ continue;
+ }
+
+ const int HeadImm = (int)HeadCmpMI->getOperand(2).getImm();
+ const int TrueImm = (int)TrueCmpMI->getOperand(2).getImm();
+
+ DEBUG(dbgs() << "Head branch:\n");
+ DEBUG(dbgs() << "\tcondition: "
+ << AArch64CC::getCondCodeName(HeadCmp) << '\n');
+ DEBUG(dbgs() << "\timmediate: " << HeadImm << '\n');
+
+ DEBUG(dbgs() << "True branch:\n");
+ DEBUG(dbgs() << "\tcondition: "
+ << AArch64CC::getCondCodeName(TrueCmp) << '\n');
+ DEBUG(dbgs() << "\timmediate: " << TrueImm << '\n');
+
+ if (((HeadCmp == AArch64CC::GT && TrueCmp == AArch64CC::LT) ||
+ (HeadCmp == AArch64CC::LT && TrueCmp == AArch64CC::GT)) &&
+ std::abs(TrueImm - HeadImm) == 2) {
+ // This branch transforms machine instructions that correspond to
+ //
+ // 1) (a > {TrueImm} && ...) || (a < {HeadImm} && ...)
+ // 2) (a < {TrueImm} && ...) || (a > {HeadImm} && ...)
+ //
+ // into
+ //
+ // 1) (a >= {NewImm} && ...) || (a <= {NewImm} && ...)
+ // 2) (a <= {NewImm} && ...) || (a >= {NewImm} && ...)
+
+ CmpInfo HeadCmpInfo = adjustCmp(HeadCmpMI, HeadCmp);
+ CmpInfo TrueCmpInfo = adjustCmp(TrueCmpMI, TrueCmp);
+ if (std::get<0>(HeadCmpInfo) == std::get<0>(TrueCmpInfo) &&
+ std::get<1>(HeadCmpInfo) == std::get<1>(TrueCmpInfo)) {
+ modifyCmp(HeadCmpMI, HeadCmpInfo);
+ modifyCmp(TrueCmpMI, TrueCmpInfo);
+ Changed = true;
+ }
+ } else if (((HeadCmp == AArch64CC::GT && TrueCmp == AArch64CC::GT) ||
+ (HeadCmp == AArch64CC::LT && TrueCmp == AArch64CC::LT)) &&
+ std::abs(TrueImm - HeadImm) == 1) {
+ // This branch transforms machine instructions that correspond to
+ //
+ // 1) (a > {TrueImm} && ...) || (a > {HeadImm} && ...)
+ // 2) (a < {TrueImm} && ...) || (a < {HeadImm} && ...)
+ //
+ // into
+ //
+ // 1) (a <= {NewImm} && ...) || (a > {NewImm} && ...)
+ // 2) (a < {NewImm} && ...) || (a >= {NewImm} && ...)
+
+ // GT -> GE transformation increases immediate value, so picking the
+ // smaller one; LT -> LE decreases immediate value so invert the choice.
+ bool adjustHeadCond = (HeadImm < TrueImm);
+ if (HeadCmp == AArch64CC::LT) {
+ adjustHeadCond = !adjustHeadCond;
+ }
+
+ if (adjustHeadCond) {
+ Changed |= adjustTo(HeadCmpMI, HeadCmp, TrueCmpMI, TrueImm);
+ } else {
+ Changed |= adjustTo(TrueCmpMI, TrueCmp, HeadCmpMI, HeadImm);
+ }
+ }
+ // Other transformation cases almost never occur due to generation of < or >
+ // comparisons instead of <= and >=.
+ }
+
+ return Changed;
+}
Modified: llvm/trunk/lib/Target/AArch64/AArch64TargetMachine.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AArch64/AArch64TargetMachine.cpp?rev=217220&r1=217219&r2=217220&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64TargetMachine.cpp (original)
+++ llvm/trunk/lib/Target/AArch64/AArch64TargetMachine.cpp Thu Sep 4 21:55:24 2014
@@ -68,6 +68,11 @@ EnableEarlyIfConversion("aarch64-enable-
cl::desc("Run early if-conversion"),
cl::init(true));
+static cl::opt<bool>
+EnableCondOpt("aarch64-condopt",
+ cl::desc("Enable the condition optimizer pass"),
+ cl::init(true), cl::Hidden);
+
extern "C" void LLVMInitializeAArch64Target() {
// Register the target.
@@ -182,6 +187,8 @@ bool AArch64PassConfig::addInstSelector(
}
bool AArch64PassConfig::addILPOpts() {
+ if (EnableCondOpt)
+ addPass(createAArch64ConditionOptimizerPass());
if (EnableCCMP)
addPass(createAArch64ConditionalCompares());
if (EnableMCR)
Modified: llvm/trunk/lib/Target/AArch64/CMakeLists.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AArch64/CMakeLists.txt?rev=217220&r1=217219&r2=217220&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AArch64/CMakeLists.txt (original)
+++ llvm/trunk/lib/Target/AArch64/CMakeLists.txt Thu Sep 4 21:55:24 2014
@@ -27,6 +27,7 @@ add_llvm_target(AArch64CodeGen
AArch64ExpandPseudoInsts.cpp
AArch64FastISel.cpp
AArch64FrameLowering.cpp
+ AArch64ConditionOptimizer.cpp
AArch64ISelDAGToDAG.cpp
AArch64ISelLowering.cpp
AArch64InstrInfo.cpp
Added: llvm/trunk/test/CodeGen/AArch64/combine-comparisons-by-cse.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AArch64/combine-comparisons-by-cse.ll?rev=217220&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/AArch64/combine-comparisons-by-cse.ll (added)
+++ llvm/trunk/test/CodeGen/AArch64/combine-comparisons-by-cse.ll Thu Sep 4 21:55:24 2014
@@ -0,0 +1,349 @@
+; RUN: llc < %s -march=aarch64 -mtriple=aarch64-linux-gnu | FileCheck %s
+
+; marked as external to prevent possible optimizations
+ at a = external global i32
+ at b = external global i32
+ at c = external global i32
+ at d = external global i32
+
+; (a > 10 && b == c) || (a >= 10 && b == d)
+define i32 @combine_gt_ge_10() #0 {
+; CHECK-LABEL: combine_gt_ge_10
+; CHECK: cmp
+; CHECK: b.le
+; CHECK: ret
+; CHECK-NOT: cmp
+; CHECK: b.lt
+entry:
+ %0 = load i32* @a, align 4
+ %cmp = icmp sgt i32 %0, 10
+ br i1 %cmp, label %land.lhs.true, label %lor.lhs.false
+
+land.lhs.true: ; preds = %entry
+ %1 = load i32* @b, align 4
+ %2 = load i32* @c, align 4
+ %cmp1 = icmp eq i32 %1, %2
+ br i1 %cmp1, label %return, label %land.lhs.true3
+
+lor.lhs.false: ; preds = %entry
+ %cmp2 = icmp sgt i32 %0, 9
+ br i1 %cmp2, label %land.lhs.true3, label %if.end
+
+land.lhs.true3: ; preds = %lor.lhs.false, %land.lhs.true
+ %3 = load i32* @b, align 4
+ %4 = load i32* @d, align 4
+ %cmp4 = icmp eq i32 %3, %4
+ br i1 %cmp4, label %return, label %if.end
+
+if.end: ; preds = %land.lhs.true3, %lor.lhs.false
+ br label %return
+
+return: ; preds = %if.end, %land.lhs.true3, %land.lhs.true
+ %retval.0 = phi i32 [ 0, %if.end ], [ 1, %land.lhs.true3 ], [ 1, %land.lhs.true ]
+ ret i32 %retval.0
+}
+
+; (a > 5 && b == c) || (a < 5 && b == d)
+define i32 @combine_gt_lt_5() #0 {
+; CHECK-LABEL: combine_gt_lt_5
+; CHECK: cmp
+; CHECK: b.le
+; CHECK: ret
+; CHECK-NOT: cmp
+; CHECK: b.ge
+entry:
+ %0 = load i32* @a, align 4
+ %cmp = icmp sgt i32 %0, 5
+ br i1 %cmp, label %land.lhs.true, label %lor.lhs.false
+
+land.lhs.true: ; preds = %entry
+ %1 = load i32* @b, align 4
+ %2 = load i32* @c, align 4
+ %cmp1 = icmp eq i32 %1, %2
+ br i1 %cmp1, label %return, label %if.end
+
+lor.lhs.false: ; preds = %entry
+ %cmp2 = icmp slt i32 %0, 5
+ br i1 %cmp2, label %land.lhs.true3, label %if.end
+
+land.lhs.true3: ; preds = %lor.lhs.false
+ %3 = load i32* @b, align 4
+ %4 = load i32* @d, align 4
+ %cmp4 = icmp eq i32 %3, %4
+ br i1 %cmp4, label %return, label %if.end
+
+if.end: ; preds = %land.lhs.true3, %lor.lhs.false, %land.lhs.true
+ br label %return
+
+return: ; preds = %if.end, %land.lhs.true3, %land.lhs.true
+ %retval.0 = phi i32 [ 0, %if.end ], [ 1, %land.lhs.true3 ], [ 1, %land.lhs.true ]
+ ret i32 %retval.0
+}
+
+; (a < 5 && b == c) || (a <= 5 && b == d)
+define i32 @combine_lt_ge_5() #0 {
+; CHECK-LABEL: combine_lt_ge_5
+; CHECK: cmp
+; CHECK: b.ge
+; CHECK: ret
+; CHECK-NOT: cmp
+; CHECK: b.gt
+entry:
+ %0 = load i32* @a, align 4
+ %cmp = icmp slt i32 %0, 5
+ br i1 %cmp, label %land.lhs.true, label %lor.lhs.false
+
+land.lhs.true: ; preds = %entry
+ %1 = load i32* @b, align 4
+ %2 = load i32* @c, align 4
+ %cmp1 = icmp eq i32 %1, %2
+ br i1 %cmp1, label %return, label %land.lhs.true3
+
+lor.lhs.false: ; preds = %entry
+ %cmp2 = icmp slt i32 %0, 6
+ br i1 %cmp2, label %land.lhs.true3, label %if.end
+
+land.lhs.true3: ; preds = %lor.lhs.false, %land.lhs.true
+ %3 = load i32* @b, align 4
+ %4 = load i32* @d, align 4
+ %cmp4 = icmp eq i32 %3, %4
+ br i1 %cmp4, label %return, label %if.end
+
+if.end: ; preds = %land.lhs.true3, %lor.lhs.false
+ br label %return
+
+return: ; preds = %if.end, %land.lhs.true3, %land.lhs.true
+ %retval.0 = phi i32 [ 0, %if.end ], [ 1, %land.lhs.true3 ], [ 1, %land.lhs.true ]
+ ret i32 %retval.0
+}
+
+; (a < 5 && b == c) || (a > 5 && b == d)
+define i32 @combine_lt_gt_5() #0 {
+; CHECK-LABEL: combine_lt_gt_5
+; CHECK: cmp
+; CHECK: b.ge
+; CHECK: ret
+; CHECK-NOT: cmp
+; CHECK: b.le
+entry:
+ %0 = load i32* @a, align 4
+ %cmp = icmp slt i32 %0, 5
+ br i1 %cmp, label %land.lhs.true, label %lor.lhs.false
+
+land.lhs.true: ; preds = %entry
+ %1 = load i32* @b, align 4
+ %2 = load i32* @c, align 4
+ %cmp1 = icmp eq i32 %1, %2
+ br i1 %cmp1, label %return, label %if.end
+
+lor.lhs.false: ; preds = %entry
+ %cmp2 = icmp sgt i32 %0, 5
+ br i1 %cmp2, label %land.lhs.true3, label %if.end
+
+land.lhs.true3: ; preds = %lor.lhs.false
+ %3 = load i32* @b, align 4
+ %4 = load i32* @d, align 4
+ %cmp4 = icmp eq i32 %3, %4
+ br i1 %cmp4, label %return, label %if.end
+
+if.end: ; preds = %land.lhs.true3, %lor.lhs.false, %land.lhs.true
+ br label %return
+
+return: ; preds = %if.end, %land.lhs.true3, %land.lhs.true
+ %retval.0 = phi i32 [ 0, %if.end ], [ 1, %land.lhs.true3 ], [ 1, %land.lhs.true ]
+ ret i32 %retval.0
+}
+
+; (a > -5 && b == c) || (a < -5 && b == d)
+define i32 @combine_gt_lt_n5() #0 {
+; CHECK-LABEL: combine_gt_lt_n5
+; CHECK: cmn
+; CHECK: b.le
+; CHECK: ret
+; CHECK-NOT: cmn
+; CHECK: b.ge
+entry:
+ %0 = load i32* @a, align 4
+ %cmp = icmp sgt i32 %0, -5
+ br i1 %cmp, label %land.lhs.true, label %lor.lhs.false
+
+land.lhs.true: ; preds = %entry
+ %1 = load i32* @b, align 4
+ %2 = load i32* @c, align 4
+ %cmp1 = icmp eq i32 %1, %2
+ br i1 %cmp1, label %return, label %if.end
+
+lor.lhs.false: ; preds = %entry
+ %cmp2 = icmp slt i32 %0, -5
+ br i1 %cmp2, label %land.lhs.true3, label %if.end
+
+land.lhs.true3: ; preds = %lor.lhs.false
+ %3 = load i32* @b, align 4
+ %4 = load i32* @d, align 4
+ %cmp4 = icmp eq i32 %3, %4
+ br i1 %cmp4, label %return, label %if.end
+
+if.end: ; preds = %land.lhs.true3, %lor.lhs.false, %land.lhs.true
+ br label %return
+
+return: ; preds = %if.end, %land.lhs.true3, %land.lhs.true
+ %retval.0 = phi i32 [ 0, %if.end ], [ 1, %land.lhs.true3 ], [ 1, %land.lhs.true ]
+ ret i32 %retval.0
+}
+
+; (a < -5 && b == c) || (a > -5 && b == d)
+define i32 @combine_lt_gt_n5() #0 {
+; CHECK-LABEL: combine_lt_gt_n5
+; CHECK: cmn
+; CHECK: b.ge
+; CHECK: ret
+; CHECK-NOT: cmn
+; CHECK: b.le
+entry:
+ %0 = load i32* @a, align 4
+ %cmp = icmp slt i32 %0, -5
+ br i1 %cmp, label %land.lhs.true, label %lor.lhs.false
+
+land.lhs.true: ; preds = %entry
+ %1 = load i32* @b, align 4
+ %2 = load i32* @c, align 4
+ %cmp1 = icmp eq i32 %1, %2
+ br i1 %cmp1, label %return, label %if.end
+
+lor.lhs.false: ; preds = %entry
+ %cmp2 = icmp sgt i32 %0, -5
+ br i1 %cmp2, label %land.lhs.true3, label %if.end
+
+land.lhs.true3: ; preds = %lor.lhs.false
+ %3 = load i32* @b, align 4
+ %4 = load i32* @d, align 4
+ %cmp4 = icmp eq i32 %3, %4
+ br i1 %cmp4, label %return, label %if.end
+
+if.end: ; preds = %land.lhs.true3, %lor.lhs.false, %land.lhs.true
+ br label %return
+
+return: ; preds = %if.end, %land.lhs.true3, %land.lhs.true
+ %retval.0 = phi i32 [ 0, %if.end ], [ 1, %land.lhs.true3 ], [ 1, %land.lhs.true ]
+ ret i32 %retval.0
+}
+
+%struct.Struct = type { i64, i64 }
+
+ at glob = internal unnamed_addr global %struct.Struct* null, align 8
+
+declare %struct.Struct* @Update(%struct.Struct*) #1
+
+; no checks for this case, it just should be processed without errors
+define void @combine_non_adjacent_cmp_br(%struct.Struct* nocapture readonly %hdCall) #0 {
+entry:
+ %size = getelementptr inbounds %struct.Struct* %hdCall, i64 0, i32 0
+ %0 = load i64* %size, align 8
+ br label %land.rhs
+
+land.rhs:
+ %rp.06 = phi i64 [ %0, %entry ], [ %sub, %while.body ]
+ %1 = load i64* inttoptr (i64 24 to i64*), align 8
+ %cmp2 = icmp sgt i64 %1, 0
+ br i1 %cmp2, label %while.body, label %while.end
+
+while.body:
+ %2 = load %struct.Struct** @glob, align 8
+ %call = tail call %struct.Struct* @Update(%struct.Struct* %2) #2
+ %sub = add nsw i64 %rp.06, -2
+ %cmp = icmp slt i64 %0, %rp.06
+ br i1 %cmp, label %land.rhs, label %while.end
+
+while.end:
+ ret void
+}
+
+; undefined external to prevent possible optimizations
+declare void @do_something() #1
+
+define i32 @do_nothing_if_resultant_opcodes_would_differ() #0 {
+; CHECK-LABEL: do_nothing_if_resultant_opcodes_would_differ
+; CHECK: cmn
+; CHECK: b.gt
+; CHECK: cmp
+; CHECK: b.gt
+entry:
+ %0 = load i32* @a, align 4
+ %cmp4 = icmp slt i32 %0, -1
+ br i1 %cmp4, label %while.body.preheader, label %while.end
+
+while.body.preheader: ; preds = %entry
+ br label %while.body
+
+while.body: ; preds = %while.body, %while.body.preheader
+ %i.05 = phi i32 [ %inc, %while.body ], [ %0, %while.body.preheader ]
+ tail call void @do_something() #2
+ %inc = add nsw i32 %i.05, 1
+ %cmp = icmp slt i32 %i.05, 0
+ br i1 %cmp, label %while.body, label %while.cond.while.end_crit_edge
+
+while.cond.while.end_crit_edge: ; preds = %while.body
+ %.pre = load i32* @a, align 4
+ br label %while.end
+
+while.end: ; preds = %while.cond.while.end_crit_edge, %entry
+ %1 = phi i32 [ %.pre, %while.cond.while.end_crit_edge ], [ %0, %entry ]
+ %cmp1 = icmp slt i32 %1, 2
+ br i1 %cmp1, label %land.lhs.true, label %if.end
+
+land.lhs.true: ; preds = %while.end
+ %2 = load i32* @b, align 4
+ %3 = load i32* @d, align 4
+ %cmp2 = icmp eq i32 %2, %3
+ br i1 %cmp2, label %return, label %if.end
+
+if.end: ; preds = %land.lhs.true, %while.end
+ br label %return
+
+return: ; preds = %if.end, %land.lhs.true
+ %retval.0 = phi i32 [ 0, %if.end ], [ 123, %land.lhs.true ]
+ ret i32 %retval.0
+}
+
+define i32 @do_nothing_if_compares_can_not_be_adjusted_to_each_other() #0 {
+; CHECK-LABEL: do_nothing_if_compares_can_not_be_adjusted_to_each_other
+; CHECK: cmp
+; CHECK: b.gt
+; CHECK: cmn
+; CHECK: b.lt
+entry:
+ %0 = load i32* @a, align 4
+ %cmp4 = icmp slt i32 %0, 1
+ br i1 %cmp4, label %while.body.preheader, label %while.end
+
+while.body.preheader: ; preds = %entry
+ br label %while.body
+
+while.body: ; preds = %while.body, %while.body.preheader
+ %i.05 = phi i32 [ %inc, %while.body ], [ %0, %while.body.preheader ]
+ tail call void @do_something() #2
+ %inc = add nsw i32 %i.05, 1
+ %cmp = icmp slt i32 %i.05, 0
+ br i1 %cmp, label %while.body, label %while.end.loopexit
+
+while.end.loopexit: ; preds = %while.body
+ br label %while.end
+
+while.end: ; preds = %while.end.loopexit, %entry
+ %1 = load i32* @c, align 4
+ %cmp1 = icmp sgt i32 %1, -3
+ br i1 %cmp1, label %land.lhs.true, label %if.end
+
+land.lhs.true: ; preds = %while.end
+ %2 = load i32* @b, align 4
+ %3 = load i32* @d, align 4
+ %cmp2 = icmp eq i32 %2, %3
+ br i1 %cmp2, label %return, label %if.end
+
+if.end: ; preds = %land.lhs.true, %while.end
+ br label %return
+
+return: ; preds = %if.end, %land.lhs.true
+ %retval.0 = phi i32 [ 0, %if.end ], [ 123, %land.lhs.true ]
+ ret i32 %retval.0
+}
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