RPCS3/llvm-mirror
1
0
Fork 0
mirror of https://github.com/RPCS3/llvm-mirror.git synced 2025-02-04 19:26:30 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

Revert 109076. It is wrong and was causing regressions. Add some

Browse Source 
comments explaining why it was wrong.  8225024.

Fix the real problem in 8213383: the code that splits very large
blocks when no other place to put constants can be found was not
considering the case that the block contained a Thumb tablejump.

llvm-svn: 109282
This commit is contained in:
Dale Johannesen 2010-07-23 22:50:23 +00:00
parent f215e55d5f
commit 50d2bc2942
1 changed files with 48 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

66
lib/Target/ARM/ARMConstantIslandPass.cpp
View File

@ -323,6 +323,8 @@ bool ARMConstantIslands::runOnMachineFunction(MachineFunction &MF) {
// constant pool users.
InitialFunctionScan(MF, CPEMIs);
CPEMIs.clear();
DEBUG(dumpBBs());
/// Remove dead constant pool entries.
RemoveUnusedCPEntries();
@ -513,9 +515,10 @@ void ARMConstantIslands::InitialFunctionScan(MachineFunction &MF,
// be right, functions containing these must be 4-byte aligned.
// tBR_JTr expands to a mov pc followed by .align 2 and then the jump
// table entries. So this code checks whether offset of tBR_JTr + 2
// is aligned.
// is aligned. That is held in Offset+MBBSize, which already has
// 2 added in for the size of the mov pc instruction.
MF.EnsureAlignment(2U);
if ((Offset+MBBSize+2)%4 != 0 || HasInlineAsm)
if ((Offset+MBBSize)%4 != 0 || HasInlineAsm)
// FIXME: Add a pseudo ALIGN instruction instead.
MBBSize += 2; // padding
continue; // Does not get an entry in ImmBranches
@ -773,28 +776,54 @@ MachineBasicBlock *ARMConstantIslands::SplitBlockBeforeInstr(MachineInstr *MI) {
WaterList.insert(IP, OrigBB);
NewWaterList.insert(OrigBB);
// Figure out how large the first NewMBB is. (It cannot
// contain a constpool_entry or tablejump.)
unsigned NewBBSize = 0;
for (MachineBasicBlock::iterator I = NewBB->begin(), E = NewBB->end();
I != E; ++I)
NewBBSize += TII->GetInstSizeInBytes(I);
unsigned OrigBBI = OrigBB->getNumber();
unsigned NewBBI = NewBB->getNumber();
// Set the size of NewBB in BBSizes.
BBSizes[NewBBI] = NewBBSize;
// We removed instructions from UserMBB, subtract that off from its size.
// Add 2 or 4 to the block to count the unconditional branch we added to it.
int delta = isThumb1 ? 2 : 4;
BBSizes[OrigBBI] -= NewBBSize - delta;
// Figure out how large the OrigBB is. As the first half of the original
// block, it cannot contain a tablejump. The size includes
// the new jump we added. (It should be possible to do this without
// recounting everything, but it's very confusing, and this is rarely
// executed.)
unsigned OrigBBSize = 0;
for (MachineBasicBlock::iterator I = OrigBB->begin(), E = OrigBB->end();
I != E; ++I)
OrigBBSize += TII->GetInstSizeInBytes(I);
BBSizes[OrigBBI] = OrigBBSize;
// ...and adjust BBOffsets for NewBB accordingly.
BBOffsets[NewBBI] = BBOffsets[OrigBBI] + BBSizes[OrigBBI];
// Figure out how large the NewMBB is. As the second half of the original
// block, it may contain a tablejump.
unsigned NewBBSize = 0;
for (MachineBasicBlock::iterator I = NewBB->begin(), E = NewBB->end();
I != E; ++I)
NewBBSize += TII->GetInstSizeInBytes(I);
// Set the size of NewBB in BBSizes. It does not include any padding now.
BBSizes[NewBBI] = NewBBSize;
MachineInstr* ThumbJTMI = prior(NewBB->end());
if (ThumbJTMI->getOpcode() == ARM::tBR_JTr) {
// We've added another 2-byte instruction before this tablejump, which
// means we will always need padding if we didn't before, and vice versa.
// The original offset of the jump instruction was:
unsigned OrigOffset = BBOffsets[OrigBBI] + BBSizes[OrigBBI] - delta;
if (OrigOffset%4 == 0) {
// We had padding before and now we don't. No net change in code size.
delta = 0;
} else {
// We didn't have padding before and now we do.
BBSizes[NewBBI] += 2;
delta = 4;
}
}
// All BBOffsets following these blocks must be modified.
AdjustBBOffsetsAfter(NewBB, delta);
if (delta)
AdjustBBOffsetsAfter(NewBB, delta);
return NewBB;
}
@ -921,11 +950,12 @@ void ARMConstantIslands::AdjustBBOffsetsAfter(MachineBasicBlock *BB,
// Thumb1 jump tables require padding. They should be at the end;
// following unconditional branches are removed by AnalyzeBranch.
// tBR_JTr expands to a mov pc followed by .align 2 and then the jump
// table entries. So this code checks whether offset of tBR_JTr + 2
// is aligned.
// table entries. So this code checks whether offset of tBR_JTr
// is aligned; if it is, the offset of the jump table following the
// instruction will not be aligned, and we need padding.
MachineInstr *ThumbJTMI = prior(MBB->end());
if (ThumbJTMI->getOpcode() == ARM::tBR_JTr) {
unsigned NewMIOffset = GetOffsetOf(ThumbJTMI) + 2;
unsigned NewMIOffset = GetOffsetOf(ThumbJTMI);
unsigned OldMIOffset = NewMIOffset - delta;
if ((OldMIOffset%4) == 0 && (NewMIOffset%4) != 0) {
// remove existing padding