Refactor InferAlignment out of DAGCombine.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90917 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index c38c79b..74651c1 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -27,6 +27,7 @@
#include "llvm/CodeGen/PseudoSourceValue.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetData.h"
+#include "llvm/Target/TargetFrameInfo.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Target/TargetInstrInfo.h"
@@ -5867,6 +5868,49 @@
&Scalars[0], Scalars.size());
}
+/// InferPtrAlignment - Infer alignment of a load / store address. Return 0 if
+/// it cannot be inferred.
+unsigned SelectionDAG::InferPtrAlignment(SDValue Ptr) {
+ // If this is a direct reference to a stack slot, use information about the
+ // stack slot's alignment.
+ int FrameIdx = 1 << 31;
+ int64_t FrameOffset = 0;
+ if (FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(Ptr)) {
+ FrameIdx = FI->getIndex();
+ } else if (Ptr.getOpcode() == ISD::ADD &&
+ isa<ConstantSDNode>(Ptr.getOperand(1)) &&
+ isa<FrameIndexSDNode>(Ptr.getOperand(0))) {
+ FrameIdx = cast<FrameIndexSDNode>(Ptr.getOperand(0))->getIndex();
+ FrameOffset = Ptr.getConstantOperandVal(1);
+ }
+
+ if (FrameIdx != (1 << 31)) {
+ // FIXME: Handle FI+CST.
+ const MachineFrameInfo &MFI = *getMachineFunction().getFrameInfo();
+ if (MFI.isFixedObjectIndex(FrameIdx)) {
+ int64_t ObjectOffset = MFI.getObjectOffset(FrameIdx) + FrameOffset;
+
+ // The alignment of the frame index can be determined from its offset from
+ // the incoming frame position. If the frame object is at offset 32 and
+ // the stack is guaranteed to be 16-byte aligned, then we know that the
+ // object is 16-byte aligned.
+ unsigned StackAlign = getTarget().getFrameInfo()->getStackAlignment();
+ unsigned Align = MinAlign(ObjectOffset, StackAlign);
+
+ // Finally, the frame object itself may have a known alignment. Factor
+ // the alignment + offset into a new alignment. For example, if we know
+ // the FI is 8 byte aligned, but the pointer is 4 off, we really have a
+ // 4-byte alignment of the resultant pointer. Likewise align 4 + 4-byte
+ // offset = 4-byte alignment, align 4 + 1-byte offset = align 1, etc.
+ unsigned FIInfoAlign = MinAlign(MFI.getObjectAlignment(FrameIdx),
+ FrameOffset);
+ return std::max(Align, FIInfoAlign);
+ }
+ }
+
+ return 0;
+}
+
void SelectionDAG::dump() const {
errs() << "SelectionDAG has " << AllNodes.size() << " nodes:";