6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-01-01 00:33:09 +00:00
Code Issues Projects Releases Wiki Activity

Recommit r233116 better: Remove a redundant instcombine involving bitcasts of geps of bitcasts

Browse Source 
This just didn't need to be here at all, but the assertion I tried to
add wasn't appropriate either - the circumstance isn't impossible, it's
just not important to deal with it here - the gep-rooted version of this
instcombine will handle this case, we don't need to duplicate it for the
case where the gep happens to be used in a bitcast.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@233404 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Blaikie 2015-03-27 20:13:55 +00:00
parent 920bbddfe0
commit 685212e39a
1 changed files with 0 additions and 36 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

36
lib/Transforms/InstCombine/InstCombineCasts.cpp
View File

@ -1450,42 +1450,6 @@ Instruction *InstCombiner::commonPointerCastTransforms(CastInst &CI) {
CI.setOperand(0, GEP->getOperand(0));
return &CI;
}
// If the GEP has a single use, and the base pointer is a bitcast, and the
// GEP computes a constant offset, see if we can convert these three
// instructions into fewer. This typically happens with unions and other
// non-type-safe code.
unsigned AS = GEP->getPointerAddressSpace();
unsigned OffsetBits = DL.getPointerSizeInBits(AS);
APInt Offset(OffsetBits, 0);
BitCastInst *BCI = dyn_cast<BitCastInst>(GEP->getOperand(0));
if (GEP->hasOneUse() && BCI && GEP->accumulateConstantOffset(DL, Offset)) {
// FIXME: This is insufficiently tested - just a no-crash test
// (test/Transforms/InstCombine/2007-05-14-Crash.ll)
//
// Get the base pointer input of the bitcast, and the type it points to.
Value *OrigBase = BCI->getOperand(0);
SmallVector<Value*, 8> NewIndices;
if (FindElementAtOffset(OrigBase->getType(), Offset.getSExtValue(),
NewIndices)) {
// FIXME: This codepath is completely untested - could be unreachable
// for all I know.
// If we were able to index down into an element, create the GEP
// and bitcast the result. This eliminates one bitcast, potentially
// two.
Value *NGEP = cast<GEPOperator>(GEP)->isInBounds()
? Builder->CreateInBoundsGEP(OrigBase, NewIndices)
: Builder->CreateGEP(
OrigBase->getType()->getPointerElementType(),
OrigBase, NewIndices);
NGEP->takeName(GEP);
if (isa<BitCastInst>(CI))
return new BitCastInst(NGEP, CI.getType());
assert(isa<PtrToIntInst>(CI));
return new PtrToIntInst(NGEP, CI.getType());
}
}
}
return commonCastTransforms(CI);