The guaranteed alignment of ptr+offset is only the minimum of
of offset and the alignment of ptr if these are both powers of
2. While the ptr alignment is guaranteed to be a power of 2,
there is no reason to think that offset is. For example, if
offset is 12 (the size of a long double on x86-32 linux) and
the alignment of ptr is 8, then the alignment of ptr+offset
will in general be 4, not 8. Introduce a function MinAlign,
lifted from gcc, for computing the minimum guaranteed alignment.
I've tried to fix up everywhere under lib/CodeGen/SelectionDAG/.
I also changed some places that weren't wrong (because both values
were a power of 2), as a defensive change against people copying
and pasting the code.
Hopefully someone who cares about alignment will review the rest
of LLVM and fix up the remaining places. Since I'm on x86 I'm
not very motivated to do this myself...
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@43421 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 5b5a70e..d3b8b00 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -37,6 +37,7 @@
#include "llvm/Target/TargetOptions.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/Support/Alignment.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
@@ -1713,15 +1714,18 @@
// read fewer bytes from the same pointer.
unsigned PtrOff =
(MVT::getSizeInBits(LoadedVT) - MVT::getSizeInBits(EVT)) / 8;
+ unsigned Alignment = LN0->getAlignment();
SDOperand NewPtr = LN0->getBasePtr();
- if (!TLI.isLittleEndian())
+ if (!TLI.isLittleEndian()) {
NewPtr = DAG.getNode(ISD::ADD, PtrType, NewPtr,
DAG.getConstant(PtrOff, PtrType));
+ Alignment = MinAlign(Alignment, PtrOff);
+ }
AddToWorkList(NewPtr.Val);
SDOperand Load =
DAG.getExtLoad(ISD::ZEXTLOAD, VT, LN0->getChain(), NewPtr,
LN0->getSrcValue(), LN0->getSrcValueOffset(), EVT,
- LN0->isVolatile(), LN0->getAlignment());
+ LN0->isVolatile(), Alignment);
AddToWorkList(N);
CombineTo(N0.Val, Load, Load.getValue(1));
return SDOperand(N, 0); // Return N so it doesn't get rechecked!
@@ -2879,16 +2883,17 @@
if (!TLI.isLittleEndian())
ShAmt = MVT::getSizeInBits(N0.getValueType()) - ShAmt - EVTBits;
uint64_t PtrOff = ShAmt / 8;
+ unsigned NewAlign = MinAlign(LN0->getAlignment(), PtrOff);
SDOperand NewPtr = DAG.getNode(ISD::ADD, PtrType, LN0->getBasePtr(),
DAG.getConstant(PtrOff, PtrType));
AddToWorkList(NewPtr.Val);
SDOperand Load = (ExtType == ISD::NON_EXTLOAD)
? DAG.getLoad(VT, LN0->getChain(), NewPtr,
LN0->getSrcValue(), LN0->getSrcValueOffset(),
- LN0->isVolatile(), LN0->getAlignment())
+ LN0->isVolatile(), NewAlign)
: DAG.getExtLoad(ExtType, VT, LN0->getChain(), NewPtr,
LN0->getSrcValue(), LN0->getSrcValueOffset(), EVT,
- LN0->isVolatile(), LN0->getAlignment());
+ LN0->isVolatile(), NewAlign);
AddToWorkList(N);
if (CombineSRL) {
DAG.ReplaceAllUsesOfValueWith(N0.getValue(1), Load.getValue(1));
@@ -3905,8 +3910,8 @@
// Replace the chain to void dependency.
if (LD->getExtensionType() == ISD::NON_EXTLOAD) {
ReplLoad = DAG.getLoad(N->getValueType(0), BetterChain, Ptr,
- LD->getSrcValue(), LD->getSrcValueOffset(),
- LD->isVolatile(), LD->getAlignment());
+ LD->getSrcValue(), LD->getSrcValueOffset(),
+ LD->isVolatile(), LD->getAlignment());
} else {
ReplLoad = DAG.getExtLoad(LD->getExtensionType(),
LD->getValueType(0),
@@ -3980,7 +3985,7 @@
ST->getSrcValueOffset(), ST->isVolatile(),
ST->getAlignment());
} else if (TLI.isTypeLegal(MVT::i32)) {
- // Many FP stores are not make apparent until after legalize, e.g. for
+ // Many FP stores are not made apparent until after legalize, e.g. for
// argument passing. Since this is so common, custom legalize the
// 64-bit integer store into two 32-bit stores.
uint64_t Val = CFP->getValueAPF().convertToAPInt().getZExtValue();
@@ -3998,8 +4003,7 @@
Ptr = DAG.getNode(ISD::ADD, Ptr.getValueType(), Ptr,
DAG.getConstant(4, Ptr.getValueType()));
SVOffset += 4;
- if (Alignment > 4)
- Alignment = 4;
+ Alignment = MinAlign(Alignment, 4U);
SDOperand St1 = DAG.getStore(Chain, Hi, Ptr, ST->getSrcValue(),
SVOffset, isVolatile, Alignment);
return DAG.getNode(ISD::TokenFactor, MVT::Other, St0, St1);
diff --git a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index 23d132b..5ec74cd 100644
--- a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -23,9 +23,10 @@
#include "llvm/CallingConv.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
-#include "llvm/Support/MathExtras.h"
+#include "llvm/Support/Alignment.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
+#include "llvm/Support/MathExtras.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/SmallPtrSet.h"
@@ -602,6 +603,7 @@
ST->isVolatile(), Alignment);
Ptr = DAG.getNode(ISD::ADD, Ptr.getValueType(), Ptr,
DAG.getConstant(IncrementSize, TLI.getPointerTy()));
+ Alignment = MinAlign(Alignment, IncrementSize);
Store2 = DAG.getTruncStore(Chain, TLI.isLittleEndian()?Hi:Lo, Ptr,
ST->getSrcValue(), SVOffset + IncrementSize,
NewStoredVT, ST->isVolatile(), Alignment);
@@ -660,7 +662,7 @@
DAG.getConstant(IncrementSize, TLI.getPointerTy()));
Hi = DAG.getExtLoad(HiExtType, VT, Chain, Ptr, LD->getSrcValue(),
SVOffset + IncrementSize, NewLoadedVT, LD->isVolatile(),
- Alignment);
+ MinAlign(Alignment, IncrementSize));
} else {
Hi = DAG.getExtLoad(HiExtType, VT, Chain, Ptr, LD->getSrcValue(), SVOffset,
NewLoadedVT,LD->isVolatile(), Alignment);
@@ -668,7 +670,7 @@
DAG.getConstant(IncrementSize, TLI.getPointerTy()));
Lo = DAG.getExtLoad(ISD::ZEXTLOAD, VT, Chain, Ptr, LD->getSrcValue(),
SVOffset + IncrementSize, NewLoadedVT, LD->isVolatile(),
- Alignment);
+ MinAlign(Alignment, IncrementSize));
}
// aggregate the two parts
@@ -2055,7 +2057,7 @@
Tmp2 = DAG.getNode(ISD::ADD, Tmp2.getValueType(), Tmp2,
getIntPtrConstant(4));
Hi = DAG.getStore(Tmp1, Hi, Tmp2, ST->getSrcValue(), SVOffset+4,
- isVolatile, std::max(Alignment, 4U));
+ isVolatile, MinAlign(Alignment, 4U));
Result = DAG.getNode(ISD::TokenFactor, MVT::Other, Lo, Hi);
break;
@@ -2164,8 +2166,7 @@
assert(isTypeLegal(Tmp2.getValueType()) &&
"Pointers must be legal!");
SVOffset += IncrementSize;
- if (Alignment > IncrementSize)
- Alignment = IncrementSize;
+ Alignment = MinAlign(Alignment, IncrementSize);
Hi = DAG.getStore(Tmp1, Hi, Tmp2, ST->getSrcValue(),
SVOffset, isVolatile, Alignment);
Result = DAG.getNode(ISD::TokenFactor, MVT::Other, Lo, Hi);
@@ -5429,8 +5430,7 @@
Ptr = DAG.getNode(ISD::ADD, Ptr.getValueType(), Ptr,
getIntPtrConstant(IncrementSize));
SVOffset += IncrementSize;
- if (Alignment > IncrementSize)
- Alignment = IncrementSize;
+ Alignment = MinAlign(Alignment, IncrementSize);
Hi = DAG.getLoad(NVT, Ch, Ptr, LD->getSrcValue(), SVOffset,
isVolatile, Alignment);
@@ -6336,8 +6336,7 @@
Ptr = DAG.getNode(ISD::ADD, Ptr.getValueType(), Ptr,
getIntPtrConstant(IncrementSize));
SVOffset += IncrementSize;
- if (Alignment > IncrementSize)
- Alignment = IncrementSize;
+ Alignment = MinAlign(Alignment, IncrementSize);
Hi = DAG.getLoad(NewVT, Ch, Ptr, SV, SVOffset, isVolatile, Alignment);
// Build a factor node to remember that this load is independent of the
diff --git a/lib/CodeGen/SelectionDAG/LegalizeDAGTypes.cpp b/lib/CodeGen/SelectionDAG/LegalizeDAGTypes.cpp
index 8699dbc..e8bf080 100644
--- a/lib/CodeGen/SelectionDAG/LegalizeDAGTypes.cpp
+++ b/lib/CodeGen/SelectionDAG/LegalizeDAGTypes.cpp
@@ -18,6 +18,7 @@
#include "llvm/DerivedTypes.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/ADT/DenseMap.h"
+#include "llvm/Support/Alignment.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
using namespace llvm;
@@ -946,7 +947,7 @@
Ptr = DAG.getNode(ISD::ADD, Ptr.getValueType(), Ptr,
getIntPtrConstant(IncrementSize));
Hi = DAG.getLoad(NVT, Ch, Ptr, N->getSrcValue(), SVOffset+IncrementSize,
- isVolatile, std::max(Alignment, IncrementSize));
+ isVolatile, MinAlign(Alignment, IncrementSize));
// Build a factor node to remember that this load is independent of the
// other one.
@@ -994,7 +995,7 @@
getIntPtrConstant(IncrementSize));
Hi = DAG.getExtLoad(ExtType, NVT, Ch, Ptr, N->getSrcValue(),
SVOffset+IncrementSize, NEVT,
- isVolatile, std::max(Alignment, IncrementSize));
+ isVolatile, MinAlign(Alignment, IncrementSize));
// Build a factor node to remember that this load is independent of the
// other one.
@@ -1019,7 +1020,7 @@
// Load the rest of the low bits.
Lo = DAG.getExtLoad(ISD::ZEXTLOAD, NVT, Ch, Ptr, N->getSrcValue(),
SVOffset+IncrementSize, MVT::getIntegerType(ExcessBits),
- isVolatile, std::max(Alignment, IncrementSize));
+ isVolatile, MinAlign(Alignment, IncrementSize));
// Build a factor node to remember that this load is independent of the
// other one.
@@ -2002,7 +2003,7 @@
getIntPtrConstant(IncrementSize));
assert(isTypeLegal(Ptr.getValueType()) && "Pointers must be legal!");
Hi = DAG.getStore(Chain, Hi, Ptr, N->getSrcValue(), SVOffset+IncrementSize,
- isVolatile, std::max(Alignment, IncrementSize));
+ isVolatile, MinAlign(Alignment, IncrementSize));
return DAG.getNode(ISD::TokenFactor, MVT::Other, Lo, Hi);
}