http://llvm.org/bugs/show_bug.cgi?id=17894
Bug ID: 17894
Summary: AsmPrinter::isBlockOnlyReachableByFallthrough() only
checks register operands of a bundle instruction
Product: tools
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: llc
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
Since llvm::finalizeBundle() only collect register operands in
lib/CodeGen/MachineInstrBundle.cpp,
AsmPrinter::isBlockOnlyReachableByFallthrough() can only check its collected
register operands, and thus miss MachineOperand like MO_MachineBasicBlock,
which will lead to to errors.
For example, instruction sequence:
########## s1 start #######
...
insn1
...
jump LBB0
...
LBB0:
...
########## s1 end ########
is packetized, insn1 and "jump LBB0" is bundled, we expect:
########### s2 start #######
...
{ insn1; jump LBB0 }
...
LBB0:
...
########### s2 end ########
Instead, lcc will generate:
########### s2' start ########
...
{ insn1; jump LBB0 }
...
#LBB0:
...
########### s2' end ########
which results in linking error saying undefined reference to LBB0 if LBB0 has
no other predecessors.
This is because AsmPrinter::isBlockOnlyReachableByFallthrough() forgets to
check MachineOperand LBB0.
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