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use enums for the over/underdefined markers for clarity. Switch

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to using -2/-3 instead of -1/-2 for a future xform.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92423 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2010-01-02 20:20:33 +00:00
parent 5fadf17709
commit 82602bc089
1 changed files with 23 additions and 21 deletions
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44
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -6020,9 +6020,8 @@ Instruction *InstCombiner::FoldFCmp_IntToFP_Cst(FCmpInst &I,
/// FoldCmpLoadFromIndexedGlobal - Called we see this pattern:
/// cmp pred (load (gep GV, ...)), cmpcst
/// where GV is a global variable with a constant initializer. Try to simplify
/// this into one or two simpler comparisons that do not need the load. For
/// example, we can optimize "icmp eq (load (gep "foo", 0, i)), 0" into
/// "icmp eq i, 3". We assume that eliminating a load is always goodness.
/// this into some simple computation that does not need the load. For example
/// we can optimize "icmp eq (load (gep "foo", 0, i)), 0" into "icmp eq i, 3".
Instruction *InstCombiner::
FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP, GlobalVariable *GV,
CmpInst &ICI) {
@ -6039,19 +6038,20 @@ FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP, GlobalVariable *GV,
ConstantArray *Init = dyn_cast<ConstantArray>(GV->getInitializer());
if (Init == 0 || Init->getNumOperands() > 1024) return 0;
enum { Overdefined = -3, Undefined = -2 };
// Variables for our state machines.
// FirstTrueElement/SecondTrueElement - Used to emit a comparison of the form
// "i == 47 | i == 87", where 47 is the first index the condition is true for,
// and 87 is the second (and last) index. FirstTrueElement is -1 when
// and 87 is the second (and last) index. FirstTrueElement is -2 when
// undefined, otherwise set to the first true element. SecondTrueElement is
// -1 when undefined, -2 when overdefined and >= 0 when that index is true.
int FirstTrueElement = -1, SecondTrueElement = -1;
// -2 when undefined, -3 when overdefined and >= 0 when that index is true.
int FirstTrueElement = Undefined, SecondTrueElement = Undefined;
// FirstFalseElement/SecondFalseElement - Used to emit a comparison of the
// form "i != 47 & i != 87". Same state transitions as for true elements.
int FirstFalseElement = -1, SecondFalseElement = -1;
int FirstFalseElement = Undefined, SecondFalseElement = Undefined;
// MagicBitvector - This is a magic bitvector where we set a bit if the
// comparison is true for element 'i'. If there are 64 elements or less in
@ -6080,20 +6080,20 @@ FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP, GlobalVariable *GV,
// State machine for single index comparison.
if (IsTrueForElt) {
// Update the TrueElement state machine.
if (FirstTrueElement == -1)
if (FirstTrueElement == Undefined)
FirstTrueElement = i;
else if (SecondTrueElement == -1)
else if (SecondTrueElement == Undefined)
SecondTrueElement = i;
else
SecondTrueElement = -2;
SecondTrueElement = Overdefined;
} else {
// Update the FalseElement state machine.
if (FirstFalseElement == -1)
if (FirstFalseElement == Undefined)
FirstFalseElement = i;
else if (SecondFalseElement == -1)
else if (SecondFalseElement == Undefined)
SecondFalseElement = i;
else
SecondFalseElement = -2;
SecondFalseElement = Overdefined;
}
// If this element is in range, update our magic bitvector.
@ -6101,7 +6101,8 @@ FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP, GlobalVariable *GV,
MagicBitvector |= 1ULL << i;
// If all of our states become overdefined, bail out early.
if (i >= 64 && SecondTrueElement == -2 && SecondFalseElement == -2)
if (i >= 64 && SecondTrueElement == Overdefined &&
SecondFalseElement == Overdefined)
return 0;
}
@ -6111,15 +6112,15 @@ FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP, GlobalVariable *GV,
// If the comparison is only true for one or two elements, emit direct
// comparisons.
if (SecondTrueElement != -2) {
if (SecondTrueElement != Overdefined) {
// None true -> false.
if (FirstTrueElement == -1)
if (FirstTrueElement == Undefined)
return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(*Context));
Value *FirstTrueIdx = ConstantInt::get(Idx->getType(), FirstTrueElement);
// True for one element -> 'i == 47'.
if (SecondTrueElement == -1)
if (SecondTrueElement == Undefined)
return new ICmpInst(ICmpInst::ICMP_EQ, Idx, FirstTrueIdx);
// True for two elements -> 'i == 47 | i == 72'.
@ -6131,15 +6132,15 @@ FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP, GlobalVariable *GV,
// If the comparison is only false for one or two elements, emit direct
// comparisons.
if (SecondFalseElement != -2) {
if (SecondFalseElement != Overdefined) {
// None false -> true.
if (FirstFalseElement == -1)
if (FirstFalseElement == Undefined)
return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(*Context));
Value *FirstFalseIdx = ConstantInt::get(Idx->getType(), FirstFalseElement);
// False for one element -> 'i != 47'.
if (SecondFalseElement == -1)
if (SecondFalseElement == Undefined)
return new ICmpInst(ICmpInst::ICMP_NE, Idx, FirstFalseIdx);
// False for two elements -> 'i != 47 & i != 72'.
@ -6167,6 +6168,7 @@ FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP, GlobalVariable *GV,
// TODO: Range check
// TODO: GEP 0, i, 4
// TODO: A[i]&4 == 0
//errs() << "XFORM: " << *GV << "\n";
//errs() << "\t" << *GEP << "\n";