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SimplifyCFG: Use existing constant folding logic when forming switch tables.

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Both simpler and more powerful than the hand-rolled folding logic.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194475 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer 2013-11-12 12:24:36 +00:00
parent 92e94a2ee4
commit f681437cb0
2 changed files with 26 additions and 34 deletions
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51
lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -19,6 +19,7 @@
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/ValueTracking.h"
@ -3323,28 +3324,10 @@ static Constant *LookupConstant(Value *V,
/// simple instructions such as binary operations where both operands are
/// constant or can be replaced by constants from the ConstantPool. Returns the
/// resulting constant on success, 0 otherwise.
static Constant *ConstantFold(Instruction *I,
const SmallDenseMap<Value*, Constant*>& ConstantPool) {
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) {
Constant *A = LookupConstant(BO->getOperand(0), ConstantPool);
if (!A)
return 0;
Constant *B = LookupConstant(BO->getOperand(1), ConstantPool);
if (!B)
return 0;
return ConstantExpr::get(BO->getOpcode(), A, B);
}
if (CmpInst *Cmp = dyn_cast<CmpInst>(I)) {
Constant *A = LookupConstant(I->getOperand(0), ConstantPool);
if (!A)
return 0;
Constant *B = LookupConstant(I->getOperand(1), ConstantPool);
if (!B)
return 0;
return ConstantExpr::getCompare(Cmp->getPredicate(), A, B);
}
static Constant *
ConstantFold(Instruction *I,
const SmallDenseMap<Value *, Constant *> &ConstantPool,
const DataLayout *DL) {
if (SelectInst *Select = dyn_cast<SelectInst>(I)) {
Constant *A = LookupConstant(Select->getCondition(), ConstantPool);
if (!A)
@ -3356,14 +3339,19 @@ static Constant *ConstantFold(Instruction *I,
return 0;
}
if (CastInst *Cast = dyn_cast<CastInst>(I)) {
Constant *A = LookupConstant(I->getOperand(0), ConstantPool);
if (!A)
SmallVector<Constant *, 4> COps;
for (unsigned N = 0, E = I->getNumOperands(); N != E; ++N) {
if (Constant *A = LookupConstant(I->getOperand(N), ConstantPool))
COps.push_back(A);
else
return 0;
return ConstantExpr::getCast(Cast->getOpcode(), A, Cast->getDestTy());
}
return 0;
if (CmpInst *Cmp = dyn_cast<CmpInst>(I))
return ConstantFoldCompareInstOperands(Cmp->getPredicate(), COps[0],
COps[1], DL);
return ConstantFoldInstOperands(I->getOpcode(), I->getType(), COps, DL);
}
/// GetCaseResults - Try to determine the resulting constant values in phi nodes
@ -3375,7 +3363,8 @@ GetCaseResults(SwitchInst *SI,
ConstantInt *CaseVal,
BasicBlock *CaseDest,
BasicBlock **CommonDest,
SmallVectorImpl<std::pair<PHINode*,Constant*> > &Res) {
SmallVectorImpl<std::pair<PHINode *, Constant *> > &Res,
const DataLayout *DL) {
// The block from which we enter the common destination.
BasicBlock *Pred = SI->getParent();
@ -3394,7 +3383,7 @@ GetCaseResults(SwitchInst *SI,
} else if (isa<DbgInfoIntrinsic>(I)) {
// Skip debug intrinsic.
continue;
} else if (Constant *C = ConstantFold(I, ConstantPool)) {
} else if (Constant *C = ConstantFold(I, ConstantPool, DL)) {
// Instruction is side-effect free and constant.
ConstantPool.insert(std::make_pair(I, C));
} else {
@ -3718,7 +3707,7 @@ static bool SwitchToLookupTable(SwitchInst *SI,
typedef SmallVector<std::pair<PHINode*, Constant*>, 4> ResultsTy;
ResultsTy Results;
if (!GetCaseResults(SI, CaseVal, CI.getCaseSuccessor(), &CommonDest,
Results))
Results, TD))
return false;
// Append the result from this case to the list for each phi.
@ -3732,7 +3721,7 @@ static bool SwitchToLookupTable(SwitchInst *SI,
// Get the resulting values for the default case.
SmallVector<std::pair<PHINode*, Constant*>, 4> DefaultResultsList;
if (!GetCaseResults(SI, 0, SI->getDefaultDest(), &CommonDest,
DefaultResultsList))
DefaultResultsList, TD))
return false;
for (size_t I = 0, E = DefaultResultsList.size(); I != E; ++I) {
PHINode *PHI = DefaultResultsList[I].first;

9
test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll
View File

@ -711,7 +711,7 @@ return:
ret i32 %retval.0
}
define i32 @cprop(i32 %x) {
define i32 @cprop(i32 %x, i32 %y) {
entry:
switch i32 %x, label %sw.default [
i32 1, label %return
@ -727,7 +727,8 @@ sw.bb1: br label %return
sw.bb2:
%and = and i32 %x, 1
%tobool = icmp ne i32 %and, 0
%and.ptr = inttoptr i32 %and to i8*
%tobool = icmp ne i8* %and.ptr, null
%cond = select i1 %tobool, i32 -123, i32 456
%sub = sub nsw i32 %x, %cond
br label %return
@ -735,13 +736,15 @@ sw.bb2:
sw.bb3:
%trunc = trunc i32 %x to i8
%sext = sext i8 %trunc to i32
%select.i = icmp sgt i32 %sext, 0
%select = select i1 %select.i, i32 %sext, i32 %y
br label %return
sw.default:
br label %return
return:
%retval.0 = phi i32 [ 123, %sw.default ], [ %sext, %sw.bb3 ], [ %sub, %sw.bb2 ], [ 42, %sw.bb1 ], [ 5, %entry ]
%retval.0 = phi i32 [ 123, %sw.default ], [ %select, %sw.bb3 ], [ %sub, %sw.bb2 ], [ 42, %sw.bb1 ], [ 5, %entry ]
ret i32 %retval.0
; CHECK-LABEL: @cprop(