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Be smarter about reusing constant pool entries.

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llvm-svn: 84173
This commit is contained in:
Bob Wilson 2009-10-15 05:52:29 +00:00
parent bfaed16c37
commit 53689872bd
1 changed files with 17 additions and 4 deletions
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21
lib/Target/ARM/ARMConstantIslandPass.cpp
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@ -74,16 +74,28 @@ namespace {
/// CPUser - One user of a constant pool, keeping the machine instruction
/// pointer, the constant pool being referenced, and the max displacement
/// allowed from the instruction to the CP.
/// allowed from the instruction to the CP. The HighWaterMark records the
/// highest basic block where a new CPEntry can be placed. To ensure this
/// pass terminates, the CP entries are initially placed at the end of the
/// function and then move monotonically to lower addresses. The
/// exception to this rule is when the current CP entry for a particular
/// CPUser is out of range, but there is another CP entry for the same
/// constant value in range. We want to use the existing in-range CP
/// entry, but if it later moves out of range, the search for new water
/// should resume where it left off. The HighWaterMark is used to record
/// that point.
struct CPUser {
MachineInstr *MI;
MachineInstr *CPEMI;
MachineBasicBlock *HighWaterMark;
unsigned MaxDisp;
bool NegOk;
bool IsSoImm;
CPUser(MachineInstr *mi, MachineInstr *cpemi, unsigned maxdisp,
bool neg, bool soimm)
: MI(mi), CPEMI(cpemi), MaxDisp(maxdisp), NegOk(neg), IsSoImm(soimm) {}
: MI(mi), CPEMI(cpemi), MaxDisp(maxdisp), NegOk(neg), IsSoImm(soimm) {
HighWaterMark = CPEMI->getParent();
}
};
/// CPUsers - Keep track of all of the machine instructions that use various
@ -962,8 +974,8 @@ bool ARMConstantIslands::LookForWater(CPUser &U, unsigned UserOffset,
B = WaterList.begin();; --IP) {
MachineBasicBlock* WaterBB = *IP;
// Check if water is in range and at a lower address than the current one.
if (WaterIsInRange(UserOffset, WaterBB, U) &&
WaterBB->getNumber() < U.CPEMI->getParent()->getNumber()) {
if (WaterBB->getNumber() < U.HighWaterMark->getNumber() &&
WaterIsInRange(UserOffset, WaterBB, U)) {
unsigned WBBId = WaterBB->getNumber();
if (isThumb &&
(BBOffsets[WBBId] + BBSizes[WBBId])%4 != 0) {
@ -1129,6 +1141,7 @@ bool ARMConstantIslands::HandleConstantPoolUser(MachineFunction &MF,
// Now that we have an island to add the CPE to, clone the original CPE and
// add it to the island.
U.HighWaterMark = NewIsland;
U.CPEMI = BuildMI(NewIsland, DebugLoc::getUnknownLoc(),
TII->get(ARM::CONSTPOOL_ENTRY))
.addImm(ID).addConstantPoolIndex(CPI).addImm(Size);