6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-07-17 20:29:31 +00:00
Code Issues Projects Releases Wiki Activity

Relax unsafe use check. If there is one unconditional use inside the loop then it is safe to promote value even if there is another conditional use inside the loop.

Browse Source 
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@42493 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Devang Patel 2007-10-01 18:12:58 +00:00
parent fef922a4d5
commit bc2265abe1
2 changed files with 43 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

44
lib/Transforms/Scalar/LICM.cpp
View File

@ -800,24 +800,15 @@ void LICM::FindPromotableValuesInLoop(
break;
}
// Do not promote null values because it may be unsafe to do so.
if (isa<ConstantPointerNull>(V))
PointerOk = false;
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V)) {
// If GEP base is NULL then the calculated address used by Store or
// Load instruction is invalid. Do not promote this value because
// it may expose load and store instruction that are covered by
// condition which may not yet folded.
if (isa<ConstantPointerNull>(GEP->getOperand(0)))
PointerOk = false;
}
// If value V use is not dominating loop exit then promoting
// it may expose unsafe load and store instructions unconditinally.
if (PointerOk)
// If one use of value V inside the loop is safe then it is OK to promote
// this value. On the otherside if there is not any unsafe use inside the
// looop then also it is OK to promote this value. Otherwise it is
// unsafe to promote this value.
if (PointerOk) {
bool oneSafeUse = false;
bool oneUnsafeUse = false;
for(Value::use_iterator UI = V->use_begin(), UE = V->use_end();
UI != UE && PointerOk; ++UI) {
UI != UE; ++UI) {
Instruction *Use = dyn_cast<Instruction>(*UI);
if (!Use || !CurLoop->contains(Use->getParent()))
continue;
@ -825,16 +816,25 @@ void LICM::FindPromotableValuesInLoop(
ExitI = LoopExits.begin(), ExitE = LoopExits.end();
ExitI != ExitE; ++ExitI) {
Instruction *Ex = *ExitI;
if (!DT->dominates(Use, Ex)){
PointerOk = false;
if (!isa<PHINode>(Use) && DT->dominates(Use, Ex)) {
oneSafeUse = true;
break;
}
else
oneUnsafeUse = true;
}
if (!PointerOk)
if (oneSafeUse)
break;
}
if (oneSafeUse)
PointerOk = true;
else if (!oneUnsafeUse)
PointerOk = true;
else
PointerOk = false;
}
if (PointerOk) {
const Type *Ty = cast<PointerType>(V->getType())->getElementType();

21
test/Transforms/LICM/2007-10-01-PromoteSafeValue.ll Normal file
View File

@ -0,0 +1,21 @@
; RUN: llvm-as < %s | opt -licm | llvm-dis | grep promoted
; Promote value if at least one use is safe
define i32 @f2(i32* %p, i8* %q) {
entry:
br label %loop.head
loop.head: ; preds = %cond.true, %entry
store i32 20, i32* %p
%tmp3.i = icmp eq i8* null, %q ; <i1> [#uses=1]
br i1 %tmp3.i, label %exit, label %cond.true
cond.true: ; preds = %loop.head
store i32 40, i32* %p
br label %loop.head
exit: ; preds = %loop.head
ret i32 0
}