From b19dd2bcaf219a3b5f144815c40b3f1b11a3d35d Mon Sep 17 00:00:00 2001 From: Hal Finkel Date: Tue, 2 Jul 2013 05:21:11 +0000 Subject: [PATCH] Revert r185257 (InstCombine: Be more agressive optimizing 'udiv' instrs with 'select' denoms) I'm reverting this commit because: 1. As discussed during review, it needs to be rewritten (to avoid creating and then deleting instructions). 2. This is causing optimizer crashes. Specifically, I'm seeing things like this: While deleting: i1 % Use still stuck around after Def is destroyed: = select i1 , i32 0, i32 1 opt: /src/llvm-trunk/lib/IR/Value.cpp:79: virtual llvm::Value::~Value(): Assertion `use_empty() && "Uses remain when a value is destroyed!"' failed. I'd guess that these will go away once we're no longer creating/deleting instructions here, but just in case, I'm adding a regression test. Because the code is bring rewritten, I've just XFAIL'd the original regression test. Original commit message: InstCombine: Be more agressive optimizing 'udiv' instrs with 'select' denoms Real world code sometimes has the denominator of a 'udiv' be a 'select'. LLVM can handle such cases but only when the 'select' operands are symmetric in structure (both select operands are a constant power of two or a left shift, etc.). This falls apart if we are dealt a 'udiv' where the code is not symetric or if the select operands lead us to more select instructions. Instead, we should treat the LHS and each select operand as a distinct divide operation and try to optimize them independently. If we can to simplify each operation, then we can replace the 'udiv' with, say, a 'lshr' that has a new select with a bunch of new operands for the select. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185415 91177308-0d34-0410-b5e6-96231b3b80d8 --- .../InstCombine/InstCombineMulDivRem.cpp | 121 +++++++----------- .../Transforms/InstCombine/div-shift-crash.ll | 101 +++++++++++++++ test/Transforms/InstCombine/div-shift.ll | 1 + 3 files changed, 146 insertions(+), 77 deletions(-) create mode 100644 test/Transforms/InstCombine/div-shift-crash.ll diff --git a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp index bc5d699e538..d0d4f41d3b4 100644 --- a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp +++ b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp @@ -705,27 +705,26 @@ static Value *dyn_castZExtVal(Value *V, Type *Ty) { return 0; } -const unsigned MaxDepth = 6; +Instruction *InstCombiner::visitUDiv(BinaryOperator &I) { + Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); + + if (Value *V = SimplifyUDivInst(Op0, Op1, TD)) + return ReplaceInstUsesWith(I, V); + + // Handle the integer div common cases + if (Instruction *Common = commonIDivTransforms(I)) + return Common; -// \brief Recursively visits the possible right hand operands of a udiv -// instruction, seeing through select instructions, to determine if we can -// replace the udiv with something simpler. If we find that an operand is not -// able to simplify the udiv, we abort the entire transformation. -// -// Inserts any intermediate instructions used for the simplification into -// NewInstrs and returns a new instruction that depends upon them. -static Instruction *visitUDivOperand(Value *Op0, Value *Op1, - const BinaryOperator &I, - SmallVectorImpl &NewInstrs, - unsigned Depth = 0) { { // X udiv 2^C -> X >> C // Check to see if this is an unsigned division with an exact power of 2, // if so, convert to a right shift. const APInt *C; if (match(Op1, m_Power2(C))) { - BinaryOperator *LShr = BinaryOperator::CreateLShr( - Op0, ConstantInt::get(Op0->getType(), C->logBase2())); + BinaryOperator *LShr = + BinaryOperator::CreateLShr(Op0, + ConstantInt::get(Op0->getType(), + C->logBase2())); if (I.isExact()) LShr->setIsExact(); return LShr; } @@ -734,68 +733,51 @@ static Instruction *visitUDivOperand(Value *Op0, Value *Op1, if (ConstantInt *C = dyn_cast(Op1)) { // X udiv C, where C >= signbit if (C->getValue().isNegative()) { - ICmpInst *IC = new ICmpInst(ICmpInst::ICMP_ULT, Op0, C); - NewInstrs.push_back(IC); - + Value *IC = Builder->CreateICmpULT(Op0, C); return SelectInst::Create(IC, Constant::getNullValue(I.getType()), ConstantInt::get(I.getType(), 1)); } } + // (x lshr C1) udiv C2 --> x udiv (C2 << C1) + if (ConstantInt *C2 = dyn_cast(Op1)) { + Value *X; + ConstantInt *C1; + if (match(Op0, m_LShr(m_Value(X), m_ConstantInt(C1)))) { + APInt NC = C2->getValue().shl(C1->getLimitedValue(C1->getBitWidth()-1)); + return BinaryOperator::CreateUDiv(X, Builder->getInt(NC)); + } + } + // X udiv (C1 << N), where C1 is "1< X >> (N+C2) { const APInt *CI; Value *N; if (match(Op1, m_Shl(m_Power2(CI), m_Value(N))) || match(Op1, m_ZExt(m_Shl(m_Power2(CI), m_Value(N))))) { - if (*CI != 1) { - N = BinaryOperator::CreateAdd( - N, ConstantInt::get(N->getType(), CI->logBase2())); - NewInstrs.push_back(cast(N)); - } - if (ZExtInst *Z = dyn_cast(Op1)) { - N = new ZExtInst(N, Z->getDestTy()); - NewInstrs.push_back(cast(N)); - } - BinaryOperator *LShr = BinaryOperator::CreateLShr(Op0, N); - if (I.isExact()) LShr->setIsExact(); - return LShr; + if (*CI != 1) + N = Builder->CreateAdd(N, + ConstantInt::get(N->getType(), CI->logBase2())); + if (ZExtInst *Z = dyn_cast(Op1)) + N = Builder->CreateZExt(N, Z->getDestTy()); + if (I.isExact()) + return BinaryOperator::CreateExactLShr(Op0, N); + return BinaryOperator::CreateLShr(Op0, N); } } - // The remaining tests are all recursive, so bail out if we hit the limit. - if (Depth++ == MaxDepth) - return 0; + // udiv X, (Select Cond, C1, C2) --> Select Cond, (shr X, C1), (shr X, C2) + // where C1&C2 are powers of two. + { Value *Cond; const APInt *C1, *C2; + if (match(Op1, m_Select(m_Value(Cond), m_Power2(C1), m_Power2(C2)))) { + // Construct the "on true" case of the select + Value *TSI = Builder->CreateLShr(Op0, C1->logBase2(), Op1->getName()+".t", + I.isExact()); - if (SelectInst *SI = dyn_cast(Op1)) - if (Instruction *LHS = - visitUDivOperand(Op0, SI->getOperand(1), I, NewInstrs)) { - NewInstrs.push_back(LHS); - if (Instruction *RHS = - visitUDivOperand(Op0, SI->getOperand(2), I, NewInstrs)) { - NewInstrs.push_back(RHS); - return SelectInst::Create(SI->getCondition(), LHS, RHS); - } - } + // Construct the "on false" case of the select + Value *FSI = Builder->CreateLShr(Op0, C2->logBase2(), Op1->getName()+".f", + I.isExact()); - return 0; -} - -Instruction *InstCombiner::visitUDiv(BinaryOperator &I) { - Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); - - if (Value *V = SimplifyUDivInst(Op0, Op1, TD)) - return ReplaceInstUsesWith(I, V); - - // Handle the integer div common cases - if (Instruction *Common = commonIDivTransforms(I)) - return Common; - - // (x lshr C1) udiv C2 --> x udiv (C2 << C1) - if (ConstantInt *C2 = dyn_cast(Op1)) { - Value *X; - ConstantInt *C1; - if (match(Op0, m_LShr(m_Value(X), m_ConstantInt(C1)))) { - APInt NC = C2->getValue().shl(C1->getLimitedValue(C1->getBitWidth()-1)); - return BinaryOperator::CreateUDiv(X, Builder->getInt(NC)); + // construct the select instruction and return it. + return SelectInst::Create(Cond, TSI, FSI); } } @@ -806,21 +788,6 @@ Instruction *InstCombiner::visitUDiv(BinaryOperator &I) { I.isExact()), I.getType()); - // (LHS udiv (select (select (...)))) -> (LHS >> (select (select (...)))) - SmallVector NewInstrs; - Instruction *RetI = visitUDivOperand(Op0, Op1, I, NewInstrs); - for (unsigned i = 0, e = NewInstrs.size(); i != e; i++) - // If we managed to replace the UDiv completely, insert the new intermediate - // instructions before where the UDiv was. - // If we couldn't, we must clean up after ourselves by deleting the new - // instructions. - if (RetI) - NewInstrs[i]->insertBefore(&I); - else - delete NewInstrs[i]; - if (RetI) - return RetI; - return 0; } diff --git a/test/Transforms/InstCombine/div-shift-crash.ll b/test/Transforms/InstCombine/div-shift-crash.ll new file mode 100644 index 00000000000..a6197245640 --- /dev/null +++ b/test/Transforms/InstCombine/div-shift-crash.ll @@ -0,0 +1,101 @@ +; RUN: opt -instcombine < %s +target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-f128:128:128-v128:128:128-n32:64" +target triple = "powerpc64-unknown-linux-gnu" + +%struct.S0.0.1.2.3.4.13.22.31.44.48.53.54.55.56.58.59.60.66.68.70.74.77.106.107.108.109.110.113.117.118.128.129 = type <{ i64 }> + +; Function Attrs: nounwind +define void @main() #0 { +entry: + %l_819.i.i = alloca %struct.S0.0.1.2.3.4.13.22.31.44.48.53.54.55.56.58.59.60.66.68.70.74.77.106.107.108.109.110.113.117.118.128.129, align 8 + br i1 undef, label %land.lhs.true, label %for.cond.i + +land.lhs.true: ; preds = %entry + br label %for.cond.i + +for.cond.i: ; preds = %land.lhs.true, %entry + %0 = getelementptr inbounds %struct.S0.0.1.2.3.4.13.22.31.44.48.53.54.55.56.58.59.60.66.68.70.74.77.106.107.108.109.110.113.117.118.128.129* %l_819.i.i, i64 0, i32 0 + br label %for.cond.i6.i.i + +for.cond.i6.i.i: ; preds = %for.body.i8.i.i, %for.cond.i + br i1 undef, label %for.body.i8.i.i, label %lbl_707.i.i.i + +for.body.i8.i.i: ; preds = %for.cond.i6.i.i + br label %for.cond.i6.i.i + +lbl_707.i.i.i: ; preds = %for.cond.i6.i.i + br i1 undef, label %lor.rhs.i.i.i, label %lor.end.i.i.i + +lor.rhs.i.i.i: ; preds = %lbl_707.i.i.i + br label %lor.end.i.i.i + +lor.end.i.i.i: ; preds = %lor.rhs.i.i.i, %lbl_707.i.i.i + br label %for.cond1.i.i.i.i + +for.cond1.i.i.i.i: ; preds = %for.body4.i.i.i.i, %lor.end.i.i.i + br i1 undef, label %for.body4.i.i.i.i, label %func_39.exit.i.i + +for.body4.i.i.i.i: ; preds = %for.cond1.i.i.i.i + br label %for.cond1.i.i.i.i + +func_39.exit.i.i: ; preds = %for.cond1.i.i.i.i + %l_8191.sroa.0.0.copyload.i.i = load i64* %0, align 1 + br label %for.cond1.i.i.i + +for.cond1.i.i.i: ; preds = %safe_div_func_uint32_t_u_u.exit.i.i.i, %func_39.exit.i.i + br i1 undef, label %for.cond7.i.i.i, label %func_11.exit.i + +for.cond7.i.i.i: ; preds = %for.end30.i.i.i, %for.cond1.i.i.i + %storemerge.i.i.i = phi i32 [ %sub.i.i.i, %for.end30.i.i.i ], [ 4, %for.cond1.i.i.i ] + br i1 undef, label %for.cond22.i.i.i, label %for.end32.i.i.i + +for.cond22.i.i.i: ; preds = %for.body25.i.i.i, %for.cond7.i.i.i + br i1 undef, label %for.body25.i.i.i, label %for.end30.i.i.i + +for.body25.i.i.i: ; preds = %for.cond22.i.i.i + br label %for.cond22.i.i.i + +for.end30.i.i.i: ; preds = %for.cond22.i.i.i + %sub.i.i.i = add nsw i32 0, -1 + br label %for.cond7.i.i.i + +for.end32.i.i.i: ; preds = %for.cond7.i.i.i + %conv33.i.i.i = trunc i64 %l_8191.sroa.0.0.copyload.i.i to i32 + %xor.i.i.i.i = xor i32 %storemerge.i.i.i, -701565022 + %sub.i.i.i.i = sub nsw i32 0, %storemerge.i.i.i + %xor3.i.i.i.i = xor i32 %sub.i.i.i.i, %storemerge.i.i.i + %and4.i.i.i.i = and i32 %xor.i.i.i.i, %xor3.i.i.i.i + %cmp.i.i.i.i = icmp slt i32 %and4.i.i.i.i, 0 + %sub5.i.i.i.i = sub nsw i32 -701565022, %storemerge.i.i.i + %.sub5.i.i.i.i = select i1 %cmp.i.i.i.i, i32 -701565022, i32 %sub5.i.i.i.i + br i1 undef, label %safe_div_func_uint32_t_u_u.exit.i.i.i, label %cond.false.i.i.i.i + +cond.false.i.i.i.i: ; preds = %for.end32.i.i.i + %div.i.i.i.i = udiv i32 %conv33.i.i.i, %.sub5.i.i.i.i + br label %safe_div_func_uint32_t_u_u.exit.i.i.i + +safe_div_func_uint32_t_u_u.exit.i.i.i: ; preds = %cond.false.i.i.i.i, %for.end32.i.i.i + %cond.i.i.i.i = phi i32 [ %div.i.i.i.i, %cond.false.i.i.i.i ], [ %conv33.i.i.i, %for.end32.i.i.i ] + %cmp35.i.i.i = icmp ne i32 %cond.i.i.i.i, -7 + br label %for.cond1.i.i.i + +func_11.exit.i: ; preds = %for.cond1.i.i.i + br i1 undef, label %for.body, label %for.end + +for.body: ; preds = %func_11.exit.i + unreachable + +for.end: ; preds = %func_11.exit.i + br label %for.cond15 + +for.cond15: ; preds = %for.cond19, %for.end + br i1 undef, label %for.cond19, label %for.end45 + +for.cond19: ; preds = %for.cond15 + br label %for.cond15 + +for.end45: ; preds = %for.cond15 + unreachable +} + +attributes #0 = { nounwind "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf"="true" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "unsafe-fp-math"="false" "use-soft-float"="false" } diff --git a/test/Transforms/InstCombine/div-shift.ll b/test/Transforms/InstCombine/div-shift.ll index 46d0f9afd70..6be5cc4ca11 100644 --- a/test/Transforms/InstCombine/div-shift.ll +++ b/test/Transforms/InstCombine/div-shift.ll @@ -1,4 +1,5 @@ ; RUN: opt < %s -instcombine -S | FileCheck %s +; XFAIL: * define i32 @t1(i16 zeroext %x, i32 %y) nounwind { entry: -- 2.34.1