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LSV: Fix incorrectly increasing alignment

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If the unaligned access has a dynamic offset, it may be odd which
would make the adjusted alignment incorrect to use.

llvm-svn: 281110
This commit is contained in:
Matt Arsenault
2016-09-09 22:20:14 +00:00
parent b4d0521c92
commit 950a82047b
2 changed files with 145 additions and 18 deletions
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34
llvm/lib/Transforms/Vectorize/LoadStoreVectorizer.cpp
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@@ -31,6 +31,7 @@
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Vectorize.h"
using namespace llvm;
@@ -742,7 +743,8 @@ bool Vectorizer::vectorizeStoreChain(
// Store size should be 1B, 2B or multiple of 4B.
// TODO: Target hook for size constraint?
unsigned SzInBytes = (Sz / 8) * ChainSize;
unsigned EltSzInBytes = Sz / 8;
unsigned SzInBytes = EltSzInBytes * ChainSize;
if (SzInBytes > 2 && SzInBytes % 4 != 0) {
DEBUG(dbgs() << "LSV: Size should be 1B, 2B "
"or multiple of 4B. Splitting.\n");
@@ -790,15 +792,11 @@ bool Vectorizer::vectorizeStoreChain(
if (S0->getPointerAddressSpace() != 0)
return false;
// If we're storing to an object on the stack, we control its alignment,
// so we can cheat and change it!
Value *V = GetUnderlyingObject(S0->getPointerOperand(), DL);
if (AllocaInst *AI = dyn_cast_or_null<AllocaInst>(V)) {
AI->setAlignment(StackAdjustedAlignment);
Alignment = StackAdjustedAlignment;
} else {
unsigned NewAlign = getOrEnforceKnownAlignment(S0->getPointerOperand(),
StackAdjustedAlignment,
DL, S0, nullptr, &DT);
if (NewAlign < StackAdjustedAlignment)
return false;
}
}
BasicBlock::iterator First, Last;
@@ -899,7 +897,8 @@ bool Vectorizer::vectorizeLoadChain(
// Load size should be 1B, 2B or multiple of 4B.
// TODO: Should size constraint be a target hook?
unsigned SzInBytes = (Sz / 8) * ChainSize;
unsigned EltSzInBytes = Sz / 8;
unsigned SzInBytes = EltSzInBytes * ChainSize;
if (SzInBytes > 2 && SzInBytes % 4 != 0) {
DEBUG(dbgs() << "LSV: Size should be 1B, 2B "
"or multiple of 4B. Splitting.\n");
@@ -940,15 +939,13 @@ bool Vectorizer::vectorizeLoadChain(
if (L0->getPointerAddressSpace() != 0)
return false;
// If we're loading from an object on the stack, we control its alignment,
// so we can cheat and change it!
Value *V = GetUnderlyingObject(L0->getPointerOperand(), DL);
if (AllocaInst *AI = dyn_cast_or_null<AllocaInst>(V)) {
AI->setAlignment(StackAdjustedAlignment);
Alignment = StackAdjustedAlignment;
} else {
unsigned NewAlign = getOrEnforceKnownAlignment(L0->getPointerOperand(),
StackAdjustedAlignment,
DL, L0, nullptr, &DT);
if (NewAlign < StackAdjustedAlignment)
return false;
}
Alignment = NewAlign;
}
DEBUG({
@@ -1029,6 +1026,7 @@ bool Vectorizer::accessIsMisaligned(unsigned SzInBytes, unsigned AddressSpace,
unsigned Alignment) {
if (Alignment % SzInBytes == 0)
return false;
bool Fast = false;
bool Allows = TTI.allowsMisalignedMemoryAccesses(F.getParent()->getContext(),
SzInBytes * 8, AddressSpace,