[llvm] r279670 - IfConversion: Rescan diamonds.
Krzysztof Parzyszek via llvm-commits
llvm-commits at lists.llvm.org
Fri Aug 26 08:17:29 PDT 2016
Hi Kyle,
This commit seems to cause a crash on Hexagon:
--- if-crash.ll ---
target triple = "hexagon"
%struct.0 = type { i16, i16 }
@t = external local_unnamed_addr global %struct.0, align 2
define void @foo(i32 %p) local_unnamed_addr #0 {
entry:
%conv90 = trunc i32 %p to i16
%call105 = call signext i16 @bar(i16 signext 16384, i16 signext undef) #0
%call175 = call signext i16 @bar(i16 signext %conv90, i16 signext 4) #0
%call197 = call signext i16 @bar(i16 signext %conv90, i16 signext 4) #0
%cmp199 = icmp eq i16 %call197, 0
br i1 %cmp199, label %if.then200, label %if.else201
if.then200: ; preds = %entry
store i16 4, i16* getelementptr inbounds (%struct.0, %struct.0* @t,
i32 0, i32 0), align 2
store i16 0, i16* getelementptr inbounds (%struct.0, %struct.0* @t,
i32 0, i32 1), align 2
br label %if.end202
if.else201: ; preds = %entry
store i16 3, i16* getelementptr inbounds (%struct.0, %struct.0* @t,
i32 0, i32 0), align 2
br label %if.end202
if.end202: ; preds = %if.else201,
%if.then200
ret void
}
declare signext i16 @bar(i16 signext, i16 signext) local_unnamed_addr #0
attributes #0 = { optsize "target-cpu"="hexagonv55" }
-------------------
$ llc -march=hexagon < if-crash.ll
llc: lib/Target/Hexagon/HexagonInstrInfo.cpp:1374: virtual bool
llvm::HexagonInstrInfo::PredicateInstruction(llvm::MachineInstr &,
ArrayRef<llvm::MachineOperand>) const: Assertion `isPredicable(MI) &&
"Expected predicable instruction"' failed.
-Krzysztof
On 8/24/2016 4:34 PM, Kyle Butt via llvm-commits wrote:
> Author: iteratee
> Date: Wed Aug 24 16:34:24 2016
> New Revision: 279670
>
> URL: http://llvm.org/viewvc/llvm-project?rev=279670&view=rev
> Log:
> IfConversion: Rescan diamonds.
>
> The cost of predicating a diamond is only the instructions that are not shared
> between the two branches. Additionally If a predicate clobbering instruction
> occurs in the shared portion of the branches (e.g. a cond move), it may still
> be possible to if convert the sub-cfg. This change handles these two facts by
> rescanning the non-shared portion of a diamond sub-cfg to recalculate both the
> predication cost and whether both blocks are pred-clobbering.
>
> Fixed 2 bugs before recommitting. Branch instructions must be compared and found
> identical before diamond conversion. Also, predicate-clobbering instructions in
> the shared prefix disqualifies a potential diamond conversion. Includes tests
> for both.
>
> Added:
> llvm/trunk/test/CodeGen/Thumb2/ifcvt-rescan-bug-2016-08-22.ll
> Modified:
> llvm/trunk/lib/CodeGen/IfConversion.cpp
> llvm/trunk/test/CodeGen/ARM/indirectbr-3.ll
>
> Modified: llvm/trunk/lib/CodeGen/IfConversion.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/IfConversion.cpp?rev=279670&r1=279669&r2=279670&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/IfConversion.cpp (original)
> +++ llvm/trunk/lib/CodeGen/IfConversion.cpp Wed Aug 24 16:34:24 2016
> @@ -149,11 +149,15 @@ namespace {
> struct IfcvtToken {
> BBInfo &BBI;
> IfcvtKind Kind;
> - bool NeedSubsumption;
> unsigned NumDups;
> unsigned NumDups2;
> - IfcvtToken(BBInfo &b, IfcvtKind k, bool s, unsigned d, unsigned d2 = 0)
> - : BBI(b), Kind(k), NeedSubsumption(s), NumDups(d), NumDups2(d2) {}
> + bool NeedSubsumption : 1;
> + bool TClobbersPred : 1;
> + bool FClobbersPred : 1;
> + IfcvtToken(BBInfo &b, IfcvtKind k, bool s, unsigned d, unsigned d2 = 0,
> + bool tc = false, bool fc = false)
> + : BBI(b), Kind(k), NumDups(d), NumDups2(d2), NeedSubsumption(s),
> + TClobbersPred(tc), FClobbersPred(fc) {}
> };
>
> /// Results of if-conversion feasibility analysis indexed by basic block
> @@ -202,16 +206,29 @@ namespace {
> bool ValidTriangle(BBInfo &TrueBBI, BBInfo &FalseBBI,
> bool FalseBranch, unsigned &Dups,
> BranchProbability Prediction) const;
> + bool CountDuplicatedInstructions(
> + MachineBasicBlock::iterator &TIB, MachineBasicBlock::iterator &FIB,
> + MachineBasicBlock::iterator &TIE, MachineBasicBlock::iterator &FIE,
> + unsigned &Dups1, unsigned &Dups2,
> + MachineBasicBlock &TBB, MachineBasicBlock &FBB,
> + bool SkipUnconditionalBranches) const;
> bool ValidDiamond(BBInfo &TrueBBI, BBInfo &FalseBBI,
> - unsigned &Dups1, unsigned &Dups2) const;
> + unsigned &Dups1, unsigned &Dups2,
> + BBInfo &TrueBBICalc, BBInfo &FalseBBICalc) const;
> void AnalyzeBranches(BBInfo &BBI);
> void ScanInstructions(BBInfo &BBI,
> MachineBasicBlock::iterator &Begin,
> - MachineBasicBlock::iterator &End) const;
> + MachineBasicBlock::iterator &End,
> + bool BranchUnpredicable = false) const;
> + bool RescanInstructions(
> + MachineBasicBlock::iterator &TIB, MachineBasicBlock::iterator &FIB,
> + MachineBasicBlock::iterator &TIE, MachineBasicBlock::iterator &FIE,
> + BBInfo &TrueBBI, BBInfo &FalseBBI) const;
> void AnalyzeBlock(MachineBasicBlock &MBB,
> std::vector<std::unique_ptr<IfcvtToken>> &Tokens);
> bool FeasibilityAnalysis(BBInfo &BBI, SmallVectorImpl<MachineOperand> &Cond,
> - bool isTriangle = false, bool RevBranch = false);
> + bool isTriangle = false, bool RevBranch = false,
> + bool hasCommonTail = false);
> void AnalyzeBlocks(MachineFunction &MF,
> std::vector<std::unique_ptr<IfcvtToken>> &Tokens);
> void InvalidatePreds(MachineBasicBlock &MBB);
> @@ -219,7 +236,8 @@ namespace {
> bool IfConvertSimple(BBInfo &BBI, IfcvtKind Kind);
> bool IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind);
> bool IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind,
> - unsigned NumDups1, unsigned NumDups2);
> + unsigned NumDups1, unsigned NumDups2,
> + bool TClobbers, bool FClobbers);
> void PredicateBlock(BBInfo &BBI,
> MachineBasicBlock::iterator E,
> SmallVectorImpl<MachineOperand> &Cond,
> @@ -406,7 +424,9 @@ bool IfConverter::runOnMachineFunction(M
> DEBUG(dbgs() << "Ifcvt (Diamond): BB#" << BBI.BB->getNumber() << " (T:"
> << BBI.TrueBB->getNumber() << ",F:"
> << BBI.FalseBB->getNumber() << ") ");
> - RetVal = IfConvertDiamond(BBI, Kind, NumDups, NumDups2);
> + RetVal = IfConvertDiamond(BBI, Kind, NumDups, NumDups2,
> + Token->TClobbersPred,
> + Token->FClobbersPred);
> DEBUG(dbgs() << (RetVal ? "succeeded!" : "failed!") << "\n");
> if (RetVal) ++NumDiamonds;
> break;
> @@ -591,14 +611,22 @@ static inline bool skipDebugInstructions
> /// finally point to the first shared instruction in the tail.
> /// Upon return [TIB, TIE), and [FIB, FIE) mark the un-duplicated portions of
> /// two blocks.
> -static void countDuplicatedInstructions(
> +/// @param Dups1 count of duplicated instructions at the beginning of the 2
> +/// blocks.
> +/// @param Dups2 count of duplicated instructions at the end of the 2 blocks.
> +/// @param SkipUnconditionalBranches if true, Don't make sure that
> +/// unconditional branches at the end of the blocks are the same. True is
> +/// passed when the blocks are analyzable to allow for fallthrough to be
> +/// handled.
> +/// @return false if the shared portion prevents if conversion.
> +bool IfConverter::CountDuplicatedInstructions(
> MachineBasicBlock::iterator &TIB,
> MachineBasicBlock::iterator &FIB,
> MachineBasicBlock::iterator &TIE,
> MachineBasicBlock::iterator &FIE,
> unsigned &Dups1, unsigned &Dups2,
> MachineBasicBlock &TBB, MachineBasicBlock &FBB,
> - bool SkipConditionalBranches) {
> + bool SkipUnconditionalBranches) const {
>
> while (TIB != TIE && FIB != FIE) {
> // Skip dbg_value instructions. These do not count.
> @@ -608,6 +636,11 @@ static void countDuplicatedInstructions(
> break;
> if (!TIB->isIdenticalTo(*FIB))
> break;
> + // A pred-clobbering instruction in the shared portion prevents
> + // if-conversion.
> + std::vector<MachineOperand> PredDefs;
> + if (TII->DefinesPredicate(*TIB, PredDefs))
> + return false;
> ++Dups1;
> ++TIB;
> ++FIB;
> @@ -618,7 +651,7 @@ static void countDuplicatedInstructions(
> // can be left unpredicated.
> // Check for already containing all of the block.
> if (TIB == TIE || FIB == FIE)
> - return;
> + return true;
> // Now, in preparation for counting duplicate instructions at the ends of the
> // blocks, move the end iterators up past any branch instructions.
> --TIE;
> @@ -641,12 +674,7 @@ static void countDuplicatedInstructions(
> });
>
> if (!TBB.succ_empty() || !FBB.succ_empty()) {
> - if (SkipConditionalBranches) {
> - while (!TEmpty && TIE->isBranch())
> - shrinkInclusiveRange(TIB, TIE, TEmpty);
> - while (!FEmpty && FIE->isBranch())
> - shrinkInclusiveRange(FIB, FIE, FEmpty);
> - } else {
> + if (SkipUnconditionalBranches) {
> while (!TEmpty && TIE->isUnconditionalBranch())
> shrinkInclusiveRange(TIB, TIE, TEmpty);
> while (!FEmpty && FIE->isUnconditionalBranch())
> @@ -657,7 +685,7 @@ static void countDuplicatedInstructions(
> // If Dups1 includes all of a block, then don't count duplicate
> // instructions at the end of the blocks.
> if (TEmpty || FEmpty)
> - return;
> + return true;
>
> // Count duplicate instructions at the ends of the blocks.
> while (!TEmpty && !FEmpty) {
> @@ -668,19 +696,48 @@ static void countDuplicatedInstructions(
> break;
> if (!TIE->isIdenticalTo(*FIE))
> break;
> - // If we are trying to make sure the conditional branches are the same, we
> - // still don't want to count them.
> - if (SkipConditionalBranches || !TIE->isBranch())
> + // We have to verify that any branch instructions are the same, and then we
> + // don't count them toward the # of duplicate instructions.
> + if (!TIE->isBranch())
> ++Dups2;
> shrinkInclusiveRange(TIB, TIE, TEmpty);
> shrinkInclusiveRange(FIB, FIE, FEmpty);
> }
> + return true;
> +}
> +
> +/// RescanInstructions - Run ScanInstructions on a pair of blocks.
> +/// @param TIB - True Iterator Begin, points to first non-shared instruction
> +/// @param FIB - False Iterator Begin, points to first non-shared instruction
> +/// @param TIE - True Iterator End, points past last non-shared instruction
> +/// @param FIE - False Iterator End, points past last non-shared instruction
> +/// @param TrueBBI - BBInfo to update for the true block.
> +/// @param FalseBBI - BBInfo to update for the false block.
> +/// @returns - false if either block cannot be predicated or if both blocks end
> +/// with a predicate-clobbering instruction.
> +bool IfConverter::RescanInstructions(
> + MachineBasicBlock::iterator &TIB, MachineBasicBlock::iterator &FIB,
> + MachineBasicBlock::iterator &TIE, MachineBasicBlock::iterator &FIE,
> + BBInfo &TrueBBI, BBInfo &FalseBBI) const {
> + bool BranchUnpredicable = true;
> + TrueBBI.IsUnpredicable = FalseBBI.IsUnpredicable = false;
> + ScanInstructions(TrueBBI, TIB, TIE, BranchUnpredicable);
> + if (TrueBBI.IsUnpredicable)
> + return false;
> + ScanInstructions(FalseBBI, FIB, FIE, BranchUnpredicable);
> + if (FalseBBI.IsUnpredicable)
> + return false;
> + if (TrueBBI.ClobbersPred && FalseBBI.ClobbersPred)
> + return false;
> + return true;
> }
>
> /// ValidDiamond - Returns true if the 'true' and 'false' blocks (along
> /// with their common predecessor) forms a valid diamond shape for ifcvt.
> -bool IfConverter::ValidDiamond(BBInfo &TrueBBI, BBInfo &FalseBBI,
> - unsigned &Dups1, unsigned &Dups2) const {
> +bool IfConverter::ValidDiamond(
> + BBInfo &TrueBBI, BBInfo &FalseBBI,
> + unsigned &Dups1, unsigned &Dups2,
> + BBInfo &TrueBBICalc, BBInfo &FalseBBICalc) const {
> Dups1 = Dups2 = 0;
> if (TrueBBI.IsBeingAnalyzed || TrueBBI.IsDone ||
> FalseBBI.IsBeingAnalyzed || FalseBBI.IsDone)
> @@ -701,19 +758,33 @@ bool IfConverter::ValidDiamond(BBInfo &T
> return false;
>
> // FIXME: Allow true block to have an early exit?
> - if (TrueBBI.FalseBB || FalseBBI.FalseBB ||
> - (TrueBBI.ClobbersPred && FalseBBI.ClobbersPred))
> + if (TrueBBI.FalseBB || FalseBBI.FalseBB)
> return false;
>
> // Count duplicate instructions at the beginning and end of the true and
> // false blocks.
> + // Skip unconditional branches only if we are considering an analyzable
> + // diamond. Otherwise the branches must be the same.
> + bool SkipUnconditionalBranches =
> + TrueBBI.IsBrAnalyzable && FalseBBI.IsBrAnalyzable;
> MachineBasicBlock::iterator TIB = TrueBBI.BB->begin();
> MachineBasicBlock::iterator FIB = FalseBBI.BB->begin();
> MachineBasicBlock::iterator TIE = TrueBBI.BB->end();
> MachineBasicBlock::iterator FIE = FalseBBI.BB->end();
> - countDuplicatedInstructions(TIB, FIB, TIE, FIE, Dups1, Dups2,
> - *TrueBBI.BB, *FalseBBI.BB,
> - /* SkipConditionalBranches */ true);
> + if(!CountDuplicatedInstructions(TIB, FIB, TIE, FIE, Dups1, Dups2,
> + *TrueBBI.BB, *FalseBBI.BB,
> + SkipUnconditionalBranches))
> + return false;
> +
> + TrueBBICalc.BB = TrueBBI.BB;
> + FalseBBICalc.BB = FalseBBI.BB;
> + if (!RescanInstructions(TIB, FIB, TIE, FIE, TrueBBICalc, FalseBBICalc))
> + return false;
> + // The size is used to decide whether to if-convert, and the shared portions
> + // are subtracted off. Because of the subtraction, we just use the size that
> + // was calculated by the original ScanInstructions, as it is correct.
> + TrueBBICalc.NonPredSize = TrueBBI.NonPredSize;
> + FalseBBICalc.NonPredSize = FalseBBI.NonPredSize;
> return true;
> }
>
> @@ -748,7 +819,8 @@ void IfConverter::AnalyzeBranches(BBInfo
> /// If so, the block is not predicable unless it's the last instruction.
> void IfConverter::ScanInstructions(BBInfo &BBI,
> MachineBasicBlock::iterator &Begin,
> - MachineBasicBlock::iterator &End) const {
> + MachineBasicBlock::iterator &End,
> + bool BranchUnpredicable) const {
> if (BBI.IsDone || BBI.IsUnpredicable)
> return;
>
> @@ -798,6 +870,11 @@ void IfConverter::ScanInstructions(BBInf
> bool isPredicated = TII->isPredicated(MI);
> bool isCondBr = BBI.IsBrAnalyzable && MI.isConditionalBranch();
>
> + if (BranchUnpredicable && MI.isBranch()) {
> + BBI.IsUnpredicable = true;
> + return;
> + }
> +
> // A conditional branch is not predicable, but it may be eliminated.
> if (isCondBr)
> continue;
> @@ -841,11 +918,22 @@ void IfConverter::ScanInstructions(BBInf
>
> /// Determine if the block is a suitable candidate to be predicated by the
> /// specified predicate.
> +/// @param BBI BBInfo for the block to check
> +/// @param Pred Predicate array for the branch that leads to BBI
> +/// @param isTriangle true if the Analysis is for a triangle
> +/// @param RevBranch true if Reverse(Pred) leads to BBI (e.g. BBI is the false
> +/// case
> +/// @param hasCommonTail true if BBI shares a tail with a sibling block that
> +/// contains any instruction that would make the block unpredicable.
> bool IfConverter::FeasibilityAnalysis(BBInfo &BBI,
> SmallVectorImpl<MachineOperand> &Pred,
> - bool isTriangle, bool RevBranch) {
> + bool isTriangle, bool RevBranch,
> + bool hasCommonTail) {
> // If the block is dead or unpredicable, then it cannot be predicated.
> - if (BBI.IsDone || BBI.IsUnpredicable)
> + // Two blocks may share a common unpredicable tail, but this doesn't prevent
> + // them from being if-converted. The non-shared portion is assumed to have
> + // been checked
> + if (BBI.IsDone || (BBI.IsUnpredicable && !hasCommonTail))
> return false;
>
> // If it is already predicated but we couldn't analyze its terminator, the
> @@ -859,7 +947,7 @@ bool IfConverter::FeasibilityAnalysis(BB
> if (BBI.Predicate.size() && !TII->SubsumesPredicate(Pred, BBI.Predicate))
> return false;
>
> - if (BBI.BrCond.size()) {
> + if (!hasCommonTail && BBI.BrCond.size()) {
> if (!isTriangle)
> return false;
>
> @@ -966,25 +1054,37 @@ void IfConverter::AnalyzeBlock(
>
> BranchProbability Prediction = MBPI->getEdgeProbability(BB, TrueBBI.BB);
>
> - if (CanRevCond && ValidDiamond(TrueBBI, FalseBBI, Dups, Dups2) &&
> + if (CanRevCond) {
> + BBInfo TrueBBICalc, FalseBBICalc;
> + if (ValidDiamond(TrueBBI, FalseBBI, Dups, Dups2,
> + TrueBBICalc, FalseBBICalc) &&
> MeetIfcvtSizeLimit(*TrueBBI.BB, (TrueBBI.NonPredSize - (Dups + Dups2) +
> - TrueBBI.ExtraCost), TrueBBI.ExtraCost2,
> + TrueBBICalc.ExtraCost),
> + TrueBBICalc.ExtraCost2,
> *FalseBBI.BB, (FalseBBI.NonPredSize - (Dups + Dups2) +
> - FalseBBI.ExtraCost),FalseBBI.ExtraCost2,
> - Prediction) &&
> - FeasibilityAnalysis(TrueBBI, BBI.BrCond) &&
> - FeasibilityAnalysis(FalseBBI, RevCond)) {
> - // Diamond:
> - // EBB
> - // / \_
> - // | |
> - // TBB FBB
> - // \ /
> - // TailBB
> - // Note TailBB can be empty.
> - Tokens.push_back(llvm::make_unique<IfcvtToken>(
> - BBI, ICDiamond, TNeedSub | FNeedSub, Dups, Dups2));
> - Enqueued = true;
> + FalseBBICalc.ExtraCost),
> + FalseBBICalc.ExtraCost2,
> + Prediction) &&
> + FeasibilityAnalysis(TrueBBI, BBI.BrCond,
> + /* IsTriangle */ false, /* RevCond */ false,
> + /* hasCommonTail */ true) &&
> + FeasibilityAnalysis(FalseBBI, RevCond,
> + /* IsTriangle */ false, /* RevCond */ false,
> + /* hasCommonTail */ true)) {
> + // Diamond:
> + // EBB
> + // / \_
> + // | |
> + // TBB FBB
> + // \ /
> + // TailBB
> + // Note TailBB can be empty.
> + Tokens.push_back(llvm::make_unique<IfcvtToken>(
> + BBI, ICDiamond, TNeedSub | FNeedSub, Dups, Dups2,
> + (bool) TrueBBICalc.ClobbersPred,
> + (bool) FalseBBICalc.ClobbersPred));
> + Enqueued = true;
> + }
> }
>
> if (ValidTriangle(TrueBBI, FalseBBI, false, Dups, Prediction) &&
> @@ -1429,8 +1529,18 @@ bool IfConverter::IfConvertTriangle(BBIn
> }
>
> /// If convert a diamond sub-CFG.
> +/// \p BBI is the head of the diamond
> +/// \p NumDups1 - number of shared instructions at the beginning of TrueBBI and
> +/// FalseBBI
> +/// \p NumDups2 - number of shared instructions at the end of TrueBBI and
> +/// FalseBBI
> +/// \p TClobbersPred - True if the true block clobbers the predicate in the
> +/// non-shared portion.
> +/// \p TClobbersPred - True if the false block clobbers the predicate in the
> +/// non-shared portion.
> bool IfConverter::IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind,
> - unsigned NumDups1, unsigned NumDups2) {
> + unsigned NumDups1, unsigned NumDups2,
> + bool TClobbersPred, bool FClobbersPred) {
> BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
> BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
> MachineBasicBlock *TailBB = TrueBBI.TrueBB;
> @@ -1468,9 +1578,9 @@ bool IfConverter::IfConvertDiamond(BBInf
>
> // Figure out the more profitable ordering.
> bool DoSwap = false;
> - if (TrueBBI.ClobbersPred && !FalseBBI.ClobbersPred)
> + if (TClobbersPred && !FClobbersPred)
> DoSwap = true;
> - else if (TrueBBI.ClobbersPred == FalseBBI.ClobbersPred) {
> + else if (TClobbersPred == FClobbersPred) {
> if (TrueBBI.NonPredSize > FalseBBI.NonPredSize)
> DoSwap = true;
> }
>
> Modified: llvm/trunk/test/CodeGen/ARM/indirectbr-3.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/ARM/indirectbr-3.ll?rev=279670&r1=279669&r2=279670&view=diff
> ==============================================================================
> --- llvm/trunk/test/CodeGen/ARM/indirectbr-3.ll (original)
> +++ llvm/trunk/test/CodeGen/ARM/indirectbr-3.ll Wed Aug 24 16:34:24 2016
> @@ -1,4 +1,4 @@
> -; RUN: llc < %s -mtriple=thumbv7-apple-ios -arm-atomic-cfg-tidy=0 | FileCheck %s
> +; RUN: llc < %s -mtriple=thumbv7-apple-ios -arm-atomic-cfg-tidy=0 -stats 2>&1 | FileCheck %s
>
> ; If ARMBaseInstrInfo::AnalyzeBlocks returns the wrong value, which was possible
> ; for blocks with indirect branches, the IfConverter could end up deleting
> @@ -9,9 +9,17 @@
> define i32 @preserve_blocks(i32 %x) {
> ; preserve_blocks:
> ; CHECK: Block address taken
> -; CHECK: movs r0, #2
> ; CHECK: movs r0, #1
> +; CHECK: Block address taken
> +; CHECK: movs r0, #2
> ; CHECK-NOT: Address of block that was removed by CodeGen
> +
> +; Separate bug. There are no valid diamonds to if-convert in this file.
> +; There was a bug in the if-conversion code that would if-convert a false
> +; diamond where one side had a return and the other had an indirect branch.
> +; Make sure no diamond conversions occurred while compiling this file.
> +; CHECK: Statistics Collected
> +; CHECK-NOT: 1 ifcvt - Number of diamond if-conversions performed
> entry:
> %c2 = icmp slt i32 %x, 3
> %blockaddr = select i1 %c2, i8* blockaddress(@preserve_blocks, %ibt1), i8* blockaddress(@preserve_blocks, %ibt2)
>
> Added: llvm/trunk/test/CodeGen/Thumb2/ifcvt-rescan-bug-2016-08-22.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/Thumb2/ifcvt-rescan-bug-2016-08-22.ll?rev=279670&view=auto
> ==============================================================================
> --- llvm/trunk/test/CodeGen/Thumb2/ifcvt-rescan-bug-2016-08-22.ll (added)
> +++ llvm/trunk/test/CodeGen/Thumb2/ifcvt-rescan-bug-2016-08-22.ll Wed Aug 24 16:34:24 2016
> @@ -0,0 +1,36 @@
> +; RUN: llc -O2 -o - %s | FileCheck %s
> +target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
> +target triple = "thumbv7-unknown-linux-gnueabihf"
> +
> +; Function Attrs: argmemonly nounwind
> +declare void @llvm.lifetime.start(i64, i8* nocapture) #0
> +
> +; Function Attrs: nounwind
> +declare void @_ZNSaIcEC2Ev() unnamed_addr #0 align 2
> +
> +declare void @_ZNSsC1EPKcRKSaIcE() unnamed_addr #0
> +
> +; It isn't valid to If-Convert the following function, even though the calls
> +; are in common. The calls clobber the predicate info.
> +; CHECK: cbnz r{{[0-9]+}}, .LBB0_2
> +; CHECK: BB#1
> +; CHECK: .LBB0_2
> +; Function Attrs: nounwind
> +define hidden void @_ZN4llvm14DOTGraphTraitsIPNS_13ScheduleDAGMIEE17getEdgeAttributesEPKNS_5SUnitENS_13SUnitIteratorEPKNS_11ScheduleDAGE() #0 align 2 {
> + br i1 undef, label %1, label %2
> +
> +; <label>:1: ; preds = %0
> + call void @_ZNSaIcEC2Ev() #0
> + call void @_ZNSsC1EPKcRKSaIcE()
> + br label %3
> +
> +; <label>:2: ; preds = %0
> + call void @llvm.lifetime.start(i64 1, i8* undef) #0
> + call void @_ZNSaIcEC2Ev() #0
> + br label %3
> +
> +; <label>:3: ; preds = %2, %1
> + ret void
> +}
> +
> +attributes #0 = { nounwind }
>
>
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