Merging r326394:
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r326394 | rnk | 2018-02-28 16:09:35 -0800 (Wed, 28 Feb 2018) | 10 lines
[DAE] don't remove args of musttail target/caller
`musttail` requires identical signatures of caller and callee. Removing
arguments breaks `musttail` semantics.
PR36441
Patch by Fedor Indutny
Differential Revision: https://reviews.llvm.org/D43708
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_60@334464 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/IPO/DeadArgumentElimination.cpp b/lib/Transforms/IPO/DeadArgumentElimination.cpp
index 5446541..b2afa6f 100644
--- a/lib/Transforms/IPO/DeadArgumentElimination.cpp
+++ b/lib/Transforms/IPO/DeadArgumentElimination.cpp
@@ -507,14 +507,28 @@
// MaybeLive. Initialized to a list of RetCount empty lists.
RetUses MaybeLiveRetUses(RetCount);
- for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
- if (const ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator()))
+ bool HasMustTailCalls = false;
+
+ for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
+ if (const ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
if (RI->getNumOperands() != 0 && RI->getOperand(0)->getType()
!= F.getFunctionType()->getReturnType()) {
// We don't support old style multiple return values.
MarkLive(F);
return;
}
+ }
+
+ // If we have any returns of `musttail` results - the signature can't
+ // change
+ if (BB->getTerminatingMustTailCall() != nullptr)
+ HasMustTailCalls = true;
+ }
+
+ if (HasMustTailCalls) {
+ DEBUG(dbgs() << "DeadArgumentEliminationPass - " << F.getName()
+ << " has musttail calls\n");
+ }
if (!F.hasLocalLinkage() && (!ShouldHackArguments || F.isIntrinsic())) {
MarkLive(F);
@@ -526,6 +540,9 @@
// Keep track of the number of live retvals, so we can skip checks once all
// of them turn out to be live.
unsigned NumLiveRetVals = 0;
+
+ bool HasMustTailCallers = false;
+
// Loop all uses of the function.
for (const Use &U : F.uses()) {
// If the function is PASSED IN as an argument, its address has been
@@ -536,6 +553,11 @@
return;
}
+ // The number of arguments for `musttail` call must match the number of
+ // arguments of the caller
+ if (CS.isMustTailCall())
+ HasMustTailCallers = true;
+
// If this use is anything other than a call site, the function is alive.
const Instruction *TheCall = CS.getInstruction();
if (!TheCall) { // Not a direct call site?
@@ -580,6 +602,11 @@
}
}
+ if (HasMustTailCallers) {
+ DEBUG(dbgs() << "DeadArgumentEliminationPass - " << F.getName()
+ << " has musttail callers\n");
+ }
+
// Now we've inspected all callers, record the liveness of our return values.
for (unsigned i = 0; i != RetCount; ++i)
MarkValue(CreateRet(&F, i), RetValLiveness[i], MaybeLiveRetUses[i]);
@@ -593,12 +620,19 @@
for (Function::const_arg_iterator AI = F.arg_begin(),
E = F.arg_end(); AI != E; ++AI, ++i) {
Liveness Result;
- if (F.getFunctionType()->isVarArg()) {
+ if (F.getFunctionType()->isVarArg() || HasMustTailCallers ||
+ HasMustTailCalls) {
// Variadic functions will already have a va_arg function expanded inside
// them, making them potentially very sensitive to ABI changes resulting
// from removing arguments entirely, so don't. For example AArch64 handles
// register and stack HFAs very differently, and this is reflected in the
// IR which has already been generated.
+ //
+ // `musttail` calls to this function restrict argument removal attempts.
+ // The signature of the caller must match the signature of the function.
+ //
+ // `musttail` calls in this function prevents us from changing its
+ // signature
Result = Live;
} else {
// See what the effect of this use is (recording any uses that cause
diff --git a/test/Transforms/DeadArgElim/musttail-caller.ll b/test/Transforms/DeadArgElim/musttail-caller.ll
new file mode 100644
index 0000000..981326b
--- /dev/null
+++ b/test/Transforms/DeadArgElim/musttail-caller.ll
@@ -0,0 +1,16 @@
+; RUN: opt -deadargelim -S < %s | FileCheck %s
+; PR36441
+; Dead arguments should not be removed in presence of `musttail` calls.
+
+; CHECK-LABEL: define internal void @test(i32 %a, i32 %b)
+; CHECK: musttail call void @foo(i32 %a, i32 0)
+; FIXME: we should replace those with `undef`s
+define internal void @test(i32 %a, i32 %b) {
+ musttail call void @foo(i32 %a, i32 0)
+ ret void
+}
+
+; CHECK-LABEL: define internal void @foo(i32 %a, i32 %b)
+define internal void @foo(i32 %a, i32 %b) {
+ ret void
+}
