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Do not generate branches to entry block. This fixes several test suite

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failures on PPC (can happen only when prologue code is null)


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36979 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dale Johannesen 2007-05-10 23:59:23 +00:00
parent 432a7faf03
commit 54f4a6780a
1 changed files with 19 additions and 4 deletions
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23
lib/CodeGen/BranchFolding.cpp
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@ -338,6 +338,14 @@ static bool ShouldSplitFirstBlock(MachineBasicBlock *MBB1,
MachineBasicBlock::iterator MBB2I, MachineBasicBlock::iterator MBB2I,
const TargetInstrInfo *TII, const TargetInstrInfo *TII,
MachineBasicBlock *PredBB) { MachineBasicBlock *PredBB) {
// If one block is the entry block, split the other one; we can't generate
// a branch to the entry block, as its label is not emitted.
MachineBasicBlock *Entry = MBB1->getParent()->begin();
if (MBB1 == Entry)
return false;
if (MBB2 == Entry)
return true;
// If one block falls through into the common successor, choose that // If one block falls through into the common successor, choose that
// one to split; it is one instruction less to do that. // one to split; it is one instruction less to do that.
if (PredBB) { if (PredBB) {
@ -456,8 +464,14 @@ bool BranchFolder::TryMergeBlocks(MachineBasicBlock *SuccBB,
MachineBasicBlock *MBB2 = (MergePotentials.end()-2)->second; MachineBasicBlock *MBB2 = (MergePotentials.end()-2)->second;
// If neither block is the entire common tail, split the tail of one block // If neither block is the entire common tail, split the tail of one block
// to make it redundant with the other tail. // to make it redundant with the other tail. Also, we cannot jump to the
if (CurMBB->begin() != BBI1 && MBB2->begin() != BBI2) { // entry block, so if one block is the entry block, split the other one.
MachineBasicBlock *Entry = CurMBB->getParent()->begin();
if (CurMBB->begin() == BBI1 && CurMBB != Entry)
; // CurMBB is common tail
else if (MBB2->begin() == BBI2 && MBB2 != Entry)
; // MBB2 is common tail
else {
if (0) { // Enable this to disable partial tail merges. if (0) { // Enable this to disable partial tail merges.
MergePotentials.pop_back(); MergePotentials.pop_back();
continue; continue;
@ -475,13 +489,14 @@ bool BranchFolder::TryMergeBlocks(MachineBasicBlock *SuccBB,
} }
} }
if (MBB2->begin() == BBI2) { if (MBB2->begin() == BBI2 && MBB2 != Entry) {
// Hack the end off CurMBB, making it jump to MBBI@ instead. // Hack the end off CurMBB, making it jump to MBBI@ instead.
ReplaceTailWithBranchTo(BBI1, MBB2); ReplaceTailWithBranchTo(BBI1, MBB2);
// This modifies CurMBB, so remove it from the worklist. // This modifies CurMBB, so remove it from the worklist.
MergePotentials.pop_back(); MergePotentials.pop_back();
} else { } else {
assert(CurMBB->begin() == BBI1 && "Didn't split block correctly?"); assert(CurMBB->begin() == BBI1 && CurMBB != Entry &&
"Didn't split block correctly?");
// Hack the end off MBB2, making it jump to CurMBB instead. // Hack the end off MBB2, making it jump to CurMBB instead.
ReplaceTailWithBranchTo(BBI2, CurMBB); ReplaceTailWithBranchTo(BBI2, CurMBB);
// This modifies MBB2, so remove it from the worklist. // This modifies MBB2, so remove it from the worklist.