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Revert r219223, it creates invalid PHI nodes. 

llvm-svn: 219587
This commit is contained in:
Joerg Sonnenberger 2014-10-12 17:16:04 +00:00
parent 97274cfb20
commit 5ca10d0edb
4 changed files with 3 additions and 249 deletions
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170
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -76,16 +76,6 @@ STATISTIC(NumSinkCommons, "Number of common instructions sunk down to the end bl
STATISTIC(NumSpeculations, "Number of speculative executed instructions");
namespace {
// The first field contains the value that the switch produces when a certain
// case group is selected, and the second field is a vector containing the cases
// composing the case group.
typedef SmallVector<std::pair<Constant *, SmallVector<ConstantInt *, 4>>, 2>
SwitchCaseResultVectorTy;
// The first field contains the phi node that generates a result of the switch
// and the second field contains the value generated for a certain case in the switch
// for that PHI.
typedef SmallVector<std::pair<PHINode *, Constant *>, 4> SwitchCaseResultsTy;
/// ValueEqualityComparisonCase - Represents a case of a switch.
struct ValueEqualityComparisonCase {
ConstantInt *Value;
@ -3463,163 +3453,6 @@ GetCaseResults(SwitchInst *SI,
return Res.size() > 0;
}
// MapCaseToResult - Helper function used to
// add CaseVal to the list of cases that generate Result.
static void MapCaseToResult(ConstantInt *CaseVal,
SwitchCaseResultVectorTy &UniqueResults,
Constant *Result) {
for (auto &I : UniqueResults) {
if (I.first == Result) {
I.second.push_back(CaseVal);
return;
}
}
UniqueResults.push_back(std::make_pair(Result,
SmallVector<ConstantInt*, 4>(1, CaseVal)));
}
// InitializeUniqueCases - Helper function that initializes a map containing
// results for the PHI node of the common destination block for a switch
// instruction. Returns false if multiple PHI nodes have been found or if
// there is not a common destination block for the switch.
static bool InitializeUniqueCases(
SwitchInst *SI, const DataLayout *DL, PHINode *&PHI,
BasicBlock *&CommonDest,
SwitchCaseResultVectorTy &UniqueResults,
Constant *&DefaultResult) {
for (auto &I : SI->cases()) {
ConstantInt *CaseVal = I.getCaseValue();
// Resulting value at phi nodes for this case value.
SwitchCaseResultsTy Results;
if (!GetCaseResults(SI, CaseVal, I.getCaseSuccessor(), &CommonDest, Results,
DL))
return false;
// Only one value per case is permitted
if (Results.size() > 1)
return false;
MapCaseToResult(CaseVal, UniqueResults, Results.begin()->second);
// Check the PHI consistency.
if (!PHI)
PHI = Results[0].first;
else if (PHI != Results[0].first)
return false;
}
// Find the default result value.
SmallVector<std::pair<PHINode *, Constant *>, 1> DefaultResults;
BasicBlock *DefaultDest = SI->getDefaultDest();
GetCaseResults(SI, nullptr, SI->getDefaultDest(), &CommonDest, DefaultResults,
DL);
// If the default value is not found abort unless the default destination
// is unreachable.
DefaultResult =
DefaultResults.size() == 1 ? DefaultResults.begin()->second : nullptr;
if ((!DefaultResult &&
!isa<UnreachableInst>(DefaultDest->getFirstNonPHIOrDbg())))
return false;
return true;
}
// ConvertTwoCaseSwitch - Helper function that checks if it is possible to
// transform a switch with only two cases (or two cases + default)
// that produces a result into a value select.
// Example:
// switch (a) {
// case 10: %0 = icmp eq i32 %a, 10
// return 10; %1 = select i1 %0, i32 10, i32 4
// case 20: ----> %2 = icmp eq i32 %a, 20
// return 2; %3 = select i1 %2, i32 2, i32 %1
// default:
// return 4;
// }
static Value *
ConvertTwoCaseSwitch(const SwitchCaseResultVectorTy &ResultVector,
Constant *DefaultResult, Value *Condition,
IRBuilder<> &Builder) {
assert(ResultVector.size() == 2 &&
"We should have exactly two unique results at this point");
// If we are selecting between only two cases transform into a simple
// select or a two-way select if default is possible.
if (ResultVector[0].second.size() == 1 &&
ResultVector[1].second.size() == 1) {
ConstantInt *const FirstCase = ResultVector[0].second[0];
ConstantInt *const SecondCase = ResultVector[1].second[0];
bool DefaultCanTrigger = DefaultResult;
Value *SelectValue = ResultVector[1].first;
if (DefaultCanTrigger) {
Value *const ValueCompare =
Builder.CreateICmpEQ(Condition, SecondCase, "switch.selectcmp");
SelectValue = Builder.CreateSelect(ValueCompare, ResultVector[1].first,
DefaultResult, "switch.select");
}
Value *const ValueCompare =
Builder.CreateICmpEQ(Condition, FirstCase, "switch.selectcmp");
return Builder.CreateSelect(ValueCompare, ResultVector[0].first, SelectValue,
"switch.select");
}
return nullptr;
}
// RemoveSwitchAfterSelectConversion - Helper function to cleanup a switch
// instruction that has been converted into a select, fixing up PHI nodes and
// basic blocks.
static void RemoveSwitchAfterSelectConversion(SwitchInst *SI, PHINode *PHI,
Value *SelectValue,
IRBuilder<> &Builder) {
BasicBlock *SelectBB = SI->getParent();
if (PHI->getBasicBlockIndex(SelectBB) >= 0)
PHI->removeIncomingValue(SelectBB);
PHI->addIncoming(SelectValue, SelectBB);
Builder.CreateBr(PHI->getParent());
// Remove the switch.
for (unsigned i = 0, e = SI->getNumSuccessors(); i < e; ++i) {
BasicBlock *Succ = SI->getSuccessor(i);
if (Succ == PHI->getParent())
continue;
Succ->removePredecessor(SelectBB);
}
SI->eraseFromParent();
}
/// SwitchToSelect - If the switch is only used to initialize one or more
/// phi nodes in a common successor block with only two different
/// constant values, replace the switch with select.
static bool SwitchToSelect(SwitchInst *SI, IRBuilder<> &Builder,
const DataLayout *DL, AssumptionTracker *AT) {
Value *const Cond = SI->getCondition();
PHINode *PHI = nullptr;
BasicBlock *CommonDest = nullptr;
Constant *DefaultResult;
SwitchCaseResultVectorTy UniqueResults;
// Collect all the cases that will deliver the same value from the switch.
if (!InitializeUniqueCases(SI, DL, PHI, CommonDest, UniqueResults,
DefaultResult))
return false;
// Selects choose between maximum two values.
if (UniqueResults.size() != 2)
return false;
assert(PHI != nullptr && "PHI for value select not found");
Builder.SetInsertPoint(SI);
Value *SelectValue = ConvertTwoCaseSwitch(
UniqueResults,
DefaultResult, Cond, Builder);
if (SelectValue) {
RemoveSwitchAfterSelectConversion(SI, PHI, SelectValue, Builder);
return true;
}
// The switch couldn't be converted into a select.
return false;
}
namespace {
/// SwitchLookupTable - This class represents a lookup table that can be used
/// to replace a switch.
@ -4118,9 +3951,6 @@ bool SimplifyCFGOpt::SimplifySwitch(SwitchInst *SI, IRBuilder<> &Builder) {
if (EliminateDeadSwitchCases(SI, DL, AT))
return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AT) | true;
if (SwitchToSelect(SI, Builder, DL, AT))
return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AT) | true;
if (ForwardSwitchConditionToPHI(SI))
return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AT) | true;

4
llvm/test/Transforms/SimplifyCFG/UnreachableEliminate.ll
View File

@ -47,7 +47,7 @@ T:
}
; PR9450
define i32 @test4(i32 %v, i32 %w) {
define i32 @test4(i32 %v) {
; CHECK: entry:
; CHECK-NEXT: switch i32 %v, label %T [
; CHECK-NEXT: i32 3, label %V
@ -67,7 +67,7 @@ SWITCH:
default:
unreachable
U:
ret i32 %w
ret i32 1
T:
ret i32 2
}

6
llvm/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll
View File

@ -915,12 +915,8 @@ return:
%x = phi i32 [ 3, %sw.default ], [ 7, %sw.bb1 ], [ 9, %entry ]
ret i32 %x
; CHECK-LABEL: @twocases(
; CHECK-NOT: switch i32
; CHECK: switch i32
; CHECK-NOT: @switch.table
; CHECK: %switch.selectcmp
; CHECK-NEXT: %switch.select
; CHECK-NEXT: %switch.selectcmp1
; CHECK-NEXT: %switch.select2
}
; Don't build tables for switches with TLS variables.

72
llvm/test/Transforms/SimplifyCFG/switch-to-select-two-case.ll
View File

@ -1,72 +0,0 @@
; RUN: opt < %s -simplifycfg -S | FileCheck %s
; int foo1_with_default(int a) {
; switch(a) {
; case 10:
; return 10;
; case 20:
; return 2;
; }
; return 4;
; }
define i32 @foo1_with_default(i32 %a) {
; CHECK-LABEL: @foo1_with_default
; CHECK: %switch.selectcmp = icmp eq i32 %a, 20
; CHECK-NEXT: %switch.select = select i1 %switch.selectcmp, i32 2, i32 4
; CHECK-NEXT: %switch.selectcmp1 = icmp eq i32 %a, 10
; CHECK-NEXT: %switch.select2 = select i1 %switch.selectcmp1, i32 10, i32 %switch.select
entry:
switch i32 %a, label %sw.epilog [
i32 10, label %sw.bb
i32 20, label %sw.bb1
]
sw.bb:
br label %return
sw.bb1:
br label %return
sw.epilog:
br label %return
return:
%retval.0 = phi i32 [ 4, %sw.epilog ], [ 2, %sw.bb1 ], [ 10, %sw.bb ]
ret i32 %retval.0
}
; int foo1_without_default(int a) {
; switch(a) {
; case 10:
; return 10;
; case 20:
; return 2;
; }
; __builtin_unreachable();
; }
define i32 @foo1_without_default(i32 %a) {
; CHECK-LABEL: @foo1_without_default
; CHECK: %switch.selectcmp = icmp eq i32 %a, 10
; CHECK-NEXT: %switch.select = select i1 %switch.selectcmp, i32 10, i32 2
; CHECK-NOT: %switch.selectcmp1
entry:
switch i32 %a, label %sw.epilog [
i32 10, label %sw.bb
i32 20, label %sw.bb1
]
sw.bb:
br label %return
sw.bb1:
br label %return
sw.epilog:
unreachable
return:
%retval.0 = phi i32 [ 2, %sw.bb1 ], [ 10, %sw.bb ]
ret i32 %retval.0
}