6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-03-22 10:36:10 +00:00
Code Issues Projects Releases Wiki Activity

Handle allocations that, even after removing dead uses, still have more than

Browse Source 
one use (but one is a cast).  This handles the very common case of:

 X = alloc [n x byte]
 Y = cast X to somethingbetter
 seteq X, null

In order to avoid infinite looping when there are multiple casts, we only
allow this if the xform is strictly increasing the alignment of the
allocation.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@23961 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2005-10-24 06:35:18 +00:00
parent 18e78bb09e
commit 39387a5c93
1 changed files with 15 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -3788,9 +3788,6 @@ Instruction *InstCombiner::PromoteCastOfAllocation(CastInst &CI,
}
}
// Finally, if the instruction now has one use, delete it.
if (!AI.hasOneUse()) return 0;
// Get the type really allocated and the type casted to.
const Type *AllocElTy = AI.getAllocatedType();
const Type *CastElTy = PTy->getElementType();
@ -3800,6 +3797,11 @@ Instruction *InstCombiner::PromoteCastOfAllocation(CastInst &CI,
unsigned CastElTyAlign = TD->getTypeSize(CastElTy);
if (CastElTyAlign < AllocElTyAlign) return 0;
// If the allocation has multiple uses, only promote it if we are strictly
// increasing the alignment of the resultant allocation. If we keep it the
// same, we open the door to infinite loops of various kinds.
if (!AI.hasOneUse() && CastElTyAlign == AllocElTyAlign) return 0;
uint64_t AllocElTySize = TD->getTypeSize(AllocElTy);
uint64_t CastElTySize = TD->getTypeSize(CastElTy);
@ -3815,6 +3817,16 @@ Instruction *InstCombiner::PromoteCastOfAllocation(CastInst &CI,
else
New = new AllocaInst(CastElTy, Amt, Name);
InsertNewInstBefore(New, AI);
// If the allocation has multiple uses, insert a cast and change all things
// that used it to use the new cast. This will also hack on CI, but it will
// die soon.
if (!AI.hasOneUse()) {
AddUsesToWorkList(AI);
CastInst *NewCast = new CastInst(New, AI.getType(), "tmpcast");
InsertNewInstBefore(NewCast, AI);
AI.replaceAllUsesWith(NewCast);
}
return ReplaceInstUsesWith(CI, New);
}