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Except in asm-verbose mode, avoid printing labels for blocks that are

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only reachable via fall-through edges. This dramatically reduces the
number of labels printed, and thus also the number of labels the
assembler must parse and remember.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@68073 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2009-03-30 22:55:17 +00:00
parent b23c232fc8
commit 80c93e7442
2 changed files with 15 additions and 1 deletions
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9
include/llvm/CodeGen/MachineBasicBlock.h
View File

@ -253,6 +253,15 @@ public:
/// it returns end()
iterator getFirstTerminator();
/// isOnlyReachableViaFallthough - Return true if this basic block has
/// exactly one predecessor and the control transfer mechanism between
/// the predecessor and this block is a fall-through.
bool isOnlyReachableByFallthrough() const {
return !pred_empty() &&
next(pred_begin()) == pred_end() &&
(*pred_begin())->getFirstTerminator() == (*pred_begin())->end();
}
void pop_front() { Insts.pop_front(); }
void pop_back() { Insts.pop_back(); }
void push_back(MachineInstr *MI) { Insts.push_back(MI); }

7
lib/Target/X86/AsmPrinter/X86ATTAsmPrinter.cpp
View File

@ -238,7 +238,12 @@ bool X86ATTAsmPrinter::runOnMachineFunction(MachineFunction &MF) {
for (MachineFunction::const_iterator I = MF.begin(), E = MF.end();
I != E; ++I) {
// Print a label for the basic block.
if (!I->pred_empty()) {
if (!VerboseAsm && (I->pred_empty() || I->isOnlyReachableByFallthrough())) {
// This is an entry block or a block that's only reachable via a
// fallthrough edge. In non-VerboseAsm mode, don't print the label.
assert((I->pred_empty() || (*I->pred_begin())->isLayoutSuccessor(I)) &&
"Fall-through predecessor not adjacent to its successor!");
} else {
printBasicBlockLabel(I, true, true, VerboseAsm);
O << '\n';
}