6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-11-01 15:11:24 +00:00
Code Issues Projects Releases Wiki Activity

teach GVN's load PRE to insert computations of the address in predecessors

Browse Source 
where it is not available.  It's unclear how to get this inserted 
computation into GVN's scalar availability sets, Owen, help? :)


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@89997 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2009-11-27 08:25:10 +00:00
parent d280d85791
commit 616613d7a4
4 changed files with 135 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
include/llvm/Analysis/MemoryDependenceAnalysis.h
View File

@ -251,6 +251,13 @@ namespace llvm {
BasicBlock *CurBB, BasicBlock *PredBB,
const TargetData *TD) const;
/// InsertPHITranslatedPointer - Insert a computation of the PHI translated
/// version of 'V' for the edge PredBB->CurBB into the end of the PredBB
/// block.
Value *InsertPHITranslatedPointer(Value *V,
BasicBlock *CurBB, BasicBlock *PredBB,
const TargetData *TD) const;
/// removeInstruction - Remove an instruction from the dependence analysis,
/// updating the dependence of instructions that previously depended on it.
void removeInstruction(Instruction *InstToRemove);

70
lib/Analysis/MemoryDependenceAnalysis.cpp
View File

@ -752,19 +752,35 @@ PHITranslatePointer(Value *InVal, BasicBlock *CurBB, BasicBlock *Pred,
// Handle getelementptr with at least one PHI operand.
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Inst)) {
SmallVector<Value*, 8> GEPOps;
Value *APHIOp = 0;
BasicBlock *CurBB = GEP->getParent();
for (unsigned i = 0, e = GEP->getNumOperands(); i != e; ++i) {
GEPOps.push_back(GEP->getOperand(i)->DoPHITranslation(CurBB, Pred));
if (!isa<Constant>(GEPOps.back()))
APHIOp = GEPOps.back();
Value *GEPOp = GEP->getOperand(i);
// No PHI translation is needed of operands whose values are live in to
// the predecessor block.
if (!isa<Instruction>(GEPOp) ||
cast<Instruction>(GEPOp)->getParent() != CurBB) {
GEPOps.push_back(GEPOp);
continue;
}
// If the operand is a phi node, do phi translation.
if (PHINode *PN = dyn_cast<PHINode>(GEPOp)) {
GEPOps.push_back(PN->getIncomingValueForBlock(Pred));
continue;
}
// Otherwise, we can't PHI translate this random value defined in this
// block.
return 0;
}
// Simplify the GEP to handle 'gep x, 0' -> x etc.
if (Value *V = SimplifyGEPInst(&GEPOps[0], GEPOps.size(), TD))
return V;
// Scan to see if we have this GEP available.
Value *APHIOp = GEPOps[0];
for (Value::use_iterator UI = APHIOp->use_begin(), E = APHIOp->use_end();
UI != E; ++UI) {
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI))
@ -787,6 +803,52 @@ PHITranslatePointer(Value *InVal, BasicBlock *CurBB, BasicBlock *Pred,
return 0;
}
/// InsertPHITranslatedPointer - Insert a computation of the PHI translated
/// version of 'V' for the edge PredBB->CurBB into the end of the PredBB
/// block.
///
/// This is only called when PHITranslatePointer returns a value that doesn't
/// dominate the block, so we don't need to handle the trivial cases here.
Value *MemoryDependenceAnalysis::
InsertPHITranslatedPointer(Value *InVal, BasicBlock *CurBB,
BasicBlock *PredBB, const TargetData *TD) const {
// If the input value isn't an instruction in CurBB, it doesn't need phi
// translation.
Instruction *Inst = cast<Instruction>(InVal);
assert(Inst->getParent() == CurBB && "Doesn't need phi trans");
// Handle bitcast of PHI.
if (BitCastInst *BC = dyn_cast<BitCastInst>(Inst)) {
PHINode *BCPN = cast<PHINode>(BC->getOperand(0));
Value *PHIIn = BCPN->getIncomingValueForBlock(PredBB);
// Otherwise insert a bitcast at the end of PredBB.
return new BitCastInst(PHIIn, InVal->getType(),
InVal->getName()+".phi.trans.insert",
PredBB->getTerminator());
}
// Handle getelementptr with at least one PHI operand.
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Inst)) {
SmallVector<Value*, 8> GEPOps;
Value *APHIOp = 0;
BasicBlock *CurBB = GEP->getParent();
for (unsigned i = 0, e = GEP->getNumOperands(); i != e; ++i) {
GEPOps.push_back(GEP->getOperand(i)->DoPHITranslation(CurBB, PredBB));
if (!isa<Constant>(GEPOps.back()))
APHIOp = GEPOps.back();
}
GetElementPtrInst *Result =
GetElementPtrInst::Create(GEPOps[0], GEPOps.begin()+1, GEPOps.end(),
InVal->getName()+".phi.trans.insert",
PredBB->getTerminator());
Result->setIsInBounds(GEP->isInBounds());
return Result;
}
return 0;
}
/// getNonLocalPointerDepFromBB - Perform a dependency query based on
/// pointer/pointeesize starting at the end of StartBB. Add any clobber/def

46
lib/Transforms/Scalar/GVN.cpp
View File

@ -1425,25 +1425,6 @@ bool GVN::processNonLocalLoad(LoadInst *LI,
assert(UnavailablePred != 0 &&
"Fully available value should be eliminated above!");
// If the loaded pointer is PHI node defined in this block, do PHI translation
// to get its value in the predecessor.
Value *LoadPtr = MD->PHITranslatePointer(LI->getOperand(0),
LoadBB, UnavailablePred, TD);
if (LoadPtr == 0) {
DEBUG(errs() << "COULDN'T PRE LOAD BECAUSE PTR CAN'T BE PHI TRANSLATED: "
<< *LI->getOperand(0) << '\n' << *LI << "\n");
return false;
}
// Make sure the value is live in the predecessor. If it was defined by a
// non-PHI instruction in this block, we don't know how to recompute it above.
if (Instruction *LPInst = dyn_cast<Instruction>(LoadPtr))
if (!DT->dominates(LPInst->getParent(), UnavailablePred)) {
DEBUG(errs() << "COULDN'T PRE LOAD BECAUSE PTR DOES NOT DOMINATE PRED: "
<< *LPInst << '\n' << *LI << "\n");
return false;
}
// We don't currently handle critical edges :(
if (UnavailablePred->getTerminator()->getNumSuccessors() != 1) {
DEBUG(errs() << "COULD NOT PRE LOAD BECAUSE OF CRITICAL EDGE '"
@ -1451,6 +1432,33 @@ bool GVN::processNonLocalLoad(LoadInst *LI,
return false;
}
// If the loaded pointer is PHI node defined in this block, do PHI translation
// to get its value in the predecessor.
Value *LoadPtr = MD->PHITranslatePointer(LI->getOperand(0),
LoadBB, UnavailablePred, TD);
// Make sure the value is live in the predecessor. MemDep found a computation
// of LPInst with the right value, but that does not dominate UnavailablePred,
// then we can't use it.
if (Instruction *LPInst = dyn_cast_or_null<Instruction>(LoadPtr))
if (!DT->dominates(LPInst->getParent(), UnavailablePred))
LoadPtr = 0;
// If we don't have a computation of this phi translated value, try to insert
// one.
if (LoadPtr == 0) {
LoadPtr = MD->InsertPHITranslatedPointer(LI->getOperand(0),
LoadBB, UnavailablePred, TD);
if (LoadPtr == 0) {
DEBUG(errs() << "COULDN'T INSERT PHI TRANSLATED VALUE OF: "
<< *LI->getOperand(0) << "\n");
return false;
}
// FIXME: This inserts a computation, but we don't tell scalar GVN
// optimization stuff about it. How do we do this?
DEBUG(errs() << "INSERTED PHI TRANSLATED VALUE: " << *LoadPtr << "\n");
}
// Make sure it is valid to move this load here. We have to watch out for:
// @1 = getelementptr (i8* p, ...
// test p and branch if == 0

34
test/Transforms/GVN/pre-load.ll
View File

@ -22,6 +22,7 @@ block4:
; CHECK-NEXT: ret i32
}
; This is a simple phi translation case.
define i32 @test2(i32* %p, i32* %q, i1 %C) {
; CHECK: @test2
block1:
@ -46,6 +47,7 @@ block4:
; CHECK: ret i32
}
; This is a PRE case that requires phi translation through a GEP.
define i32 @test3(i32* %p, i32* %q, i32** %Hack, i1 %C) {
; CHECK: @test3
block1:
@ -73,3 +75,35 @@ block4:
; CHECK-NOT: load
; CHECK: ret i32
}
;; Here the loaded address is available, but the computation is in 'block3'
;; which does not dominate 'block2'.
define i32 @test4(i32* %p, i32* %q, i32** %Hack, i1 %C) {
; CHECK: @test4
block1:
br i1 %C, label %block2, label %block3
block2:
br label %block4
; CHECK: block2:
; CHECK: load i32*
; CHECK: br label %block4
block3:
%B = getelementptr i32* %q, i32 1
store i32* %B, i32** %Hack
%A = getelementptr i32* %p, i32 1
store i32 0, i32* %A
br label %block4
block4:
%P2 = phi i32* [%p, %block3], [%q, %block2]
%P3 = getelementptr i32* %P2, i32 1
%PRE = load i32* %P3
ret i32 %PRE
; CHECK: block4:
; CHECK-NEXT: phi i32 [
; CHECK-NOT: load
; CHECK: ret i32
}