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Fix PR1788 by taking the approach suggested by Richard Smith.

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Thanks to him for his detailed analysis of the problem.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44162 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2007-11-15 06:10:55 +00:00
parent ab64806af2
commit 701bc4264d
1 changed files with 16 additions and 11 deletions
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27
lib/Transforms/IPO/DeadArgumentElimination.cpp
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@ -604,23 +604,28 @@ void DAE::RemoveDeadArgumentsFromFunction(Function *F) {
}
bool DAE::runOnModule(Module &M) {
// First phase: loop through the module, determining which arguments are live.
bool Changed = false;
// First pass: Do a simple check to see if any functions can have their "..."
// removed. We can do this if they never call va_start. This loop cannot be
// fused with the next loop, because deleting a function invalidates
// information computed while surveying other functions.
DOUT << "DAE - Deleting dead varargs\n";
for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
Function &F = *I++;
if (F.getFunctionType()->isVarArg())
Changed |= DeleteDeadVarargs(F);
}
// Second phase:loop through the module, determining which arguments are live.
// We assume all arguments are dead unless proven otherwise (allowing us to
// determine that dead arguments passed into recursive functions are dead).
//
DOUT << "DAE - Determining liveness\n";
for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
Function &F = *I++;
if (F.getFunctionType()->isVarArg())
if (DeleteDeadVarargs(F))
continue;
SurveyFunction(F);
}
for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
SurveyFunction(*I);
// Loop over the instructions to inspect, propagating liveness among arguments
// and return values which are MaybeLive.
while (!InstructionsToInspect.empty()) {
Instruction *I = InstructionsToInspect.back();
InstructionsToInspect.pop_back();
@ -680,7 +685,7 @@ bool DAE::runOnModule(Module &M) {
// to do.
if (MaybeLiveArguments.empty() && DeadArguments.empty() &&
MaybeLiveRetVal.empty() && DeadRetVal.empty())
return false;
return Changed;
// Otherwise, compact into one set, and start eliminating the arguments from
// the functions.