It's not necessary to do rounding for alloca operations when the requested
alignment is equal to the stack alignment.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40004 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/PowerPC/PPCBranchSelector.cpp b/lib/Target/PowerPC/PPCBranchSelector.cpp
new file mode 100644
index 0000000..4286f01
--- /dev/null
+++ b/lib/Target/PowerPC/PPCBranchSelector.cpp
@@ -0,0 +1,199 @@
+//===-- PPCBranchSelector.cpp - Emit long conditional branches-----*- C++ -*-=//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file was developed by Nate Baegeman and is distributed under the
+// University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains a pass that scans a machine function to determine which
+// conditional branches need more than 16 bits of displacement to reach their
+// target basic block. It does this in two passes; a calculation of basic block
+// positions pass, and a branch psuedo op to machine branch opcode pass. This
+// pass should be run last, just before the assembly printer.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "ppc-branch-select"
+#include "PPC.h"
+#include "PPCInstrBuilder.h"
+#include "PPCInstrInfo.h"
+#include "PPCPredicates.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetAsmInfo.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/MathExtras.h"
+using namespace llvm;
+
+STATISTIC(NumExpanded, "Number of branches expanded to long format");
+
+namespace {
+ struct VISIBILITY_HIDDEN PPCBSel : public MachineFunctionPass {
+ static char ID;
+ PPCBSel() : MachineFunctionPass((intptr_t)&ID) {}
+
+ /// BlockSizes - The sizes of the basic blocks in the function.
+ std::vector<unsigned> BlockSizes;
+
+ virtual bool runOnMachineFunction(MachineFunction &Fn);
+
+ virtual const char *getPassName() const {
+ return "PowerPC Branch Selector";
+ }
+ };
+ char PPCBSel::ID = 0;
+}
+
+/// createPPCBranchSelectionPass - returns an instance of the Branch Selection
+/// Pass
+///
+FunctionPass *llvm::createPPCBranchSelectionPass() {
+ return new PPCBSel();
+}
+
+/// getNumBytesForInstruction - Return the number of bytes of code the specified
+/// instruction may be. This returns the maximum number of bytes.
+///
+static unsigned getNumBytesForInstruction(MachineInstr *MI) {
+ switch (MI->getOpcode()) {
+ case PPC::IMPLICIT_DEF_GPRC: // no asm emitted
+ case PPC::IMPLICIT_DEF_G8RC: // no asm emitted
+ case PPC::IMPLICIT_DEF_F4: // no asm emitted
+ case PPC::IMPLICIT_DEF_F8: // no asm emitted
+ case PPC::IMPLICIT_DEF_VRRC: // no asm emitted
+ return 0;
+ case PPC::INLINEASM: { // Inline Asm: Variable size.
+ MachineFunction *MF = MI->getParent()->getParent();
+ const char *AsmStr = MI->getOperand(0).getSymbolName();
+ return MF->getTarget().getTargetAsmInfo()->getInlineAsmLength(AsmStr);
+ }
+ case PPC::LABEL: {
+ return 0;
+ }
+ default:
+ return 4; // PowerPC instructions are all 4 bytes
+ }
+}
+
+
+bool PPCBSel::runOnMachineFunction(MachineFunction &Fn) {
+ const TargetInstrInfo *TII = Fn.getTarget().getInstrInfo();
+ // Give the blocks of the function a dense, in-order, numbering.
+ Fn.RenumberBlocks();
+ BlockSizes.resize(Fn.getNumBlockIDs());
+
+ // Measure each MBB and compute a size for the entire function.
+ unsigned FuncSize = 0;
+ for (MachineFunction::iterator MFI = Fn.begin(), E = Fn.end(); MFI != E;
+ ++MFI) {
+ MachineBasicBlock *MBB = MFI;
+
+ unsigned BlockSize = 0;
+ for (MachineBasicBlock::iterator MBBI = MBB->begin(), EE = MBB->end();
+ MBBI != EE; ++MBBI)
+ BlockSize += getNumBytesForInstruction(MBBI);
+
+ BlockSizes[MBB->getNumber()] = BlockSize;
+ FuncSize += BlockSize;
+ }
+
+ // If the entire function is smaller than the displacement of a branch field,
+ // we know we don't need to shrink any branches in this function. This is a
+ // common case.
+ if (FuncSize < (1 << 15)) {
+ BlockSizes.clear();
+ return false;
+ }
+
+ // For each conditional branch, if the offset to its destination is larger
+ // than the offset field allows, transform it into a long branch sequence
+ // like this:
+ // short branch:
+ // bCC MBB
+ // long branch:
+ // b!CC $PC+8
+ // b MBB
+ //
+ bool MadeChange = true;
+ bool EverMadeChange = false;
+ while (MadeChange) {
+ // Iteratively expand branches until we reach a fixed point.
+ MadeChange = false;
+
+ for (MachineFunction::iterator MFI = Fn.begin(), E = Fn.end(); MFI != E;
+ ++MFI) {
+ MachineBasicBlock &MBB = *MFI;
+ unsigned MBBStartOffset = 0;
+ for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
+ I != E; ++I) {
+ if (I->getOpcode() != PPC::BCC || I->getOperand(2).isImm()) {
+ MBBStartOffset += getNumBytesForInstruction(I);
+ continue;
+ }
+
+ // Determine the offset from the current branch to the destination
+ // block.
+ MachineBasicBlock *Dest = I->getOperand(2).getMachineBasicBlock();
+
+ int BranchSize;
+ if (Dest->getNumber() <= MBB.getNumber()) {
+ // If this is a backwards branch, the delta is the offset from the
+ // start of this block to this branch, plus the sizes of all blocks
+ // from this block to the dest.
+ BranchSize = MBBStartOffset;
+
+ for (unsigned i = Dest->getNumber(), e = MBB.getNumber(); i != e; ++i)
+ BranchSize += BlockSizes[i];
+ } else {
+ // Otherwise, add the size of the blocks between this block and the
+ // dest to the number of bytes left in this block.
+ BranchSize = -MBBStartOffset;
+
+ for (unsigned i = MBB.getNumber(), e = Dest->getNumber(); i != e; ++i)
+ BranchSize += BlockSizes[i];
+ }
+
+ // If this branch is in range, ignore it.
+ if (isInt16(BranchSize)) {
+ MBBStartOffset += 4;
+ continue;
+ }
+
+ // Otherwise, we have to expand it to a long branch.
+ // The BCC operands are:
+ // 0. PPC branch predicate
+ // 1. CR register
+ // 2. Target MBB
+ PPC::Predicate Pred = (PPC::Predicate)I->getOperand(0).getImm();
+ unsigned CRReg = I->getOperand(1).getReg();
+
+ MachineInstr *OldBranch = I;
+
+ // Jump over the uncond branch inst (i.e. $PC+8) on opposite condition.
+ BuildMI(MBB, I, TII->get(PPC::BCC))
+ .addImm(PPC::InvertPredicate(Pred)).addReg(CRReg).addImm(2);
+
+ // Uncond branch to the real destination.
+ I = BuildMI(MBB, I, TII->get(PPC::B)).addMBB(Dest);
+
+ // Remove the old branch from the function.
+ OldBranch->eraseFromParent();
+
+ // Remember that this instruction is 8-bytes, increase the size of the
+ // block by 4, remember to iterate.
+ BlockSizes[MBB.getNumber()] += 4;
+ MBBStartOffset += 8;
+ ++NumExpanded;
+ MadeChange = true;
+ }
+ }
+ EverMadeChange |= MadeChange;
+ }
+
+ BlockSizes.clear();
+ return true;
+}
+