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Add some constraints to use of 'returned': 

1) Disallow 'returned' on parameter that is also 'sret' (no sensible semantics, as far as I can tell).
2) Conservatively disallow tail calls through 'returned' parameters that also are 'zext' or 'sext' (for consistency with treatment of other zero-extending and sign-extending operations in tail call position detection...can be revised later to handle situations that can be determined to be safe).

This is a new attribute that is not yet used, so there is no impact.

llvm-svn: 180118
This commit is contained in:
Stephen Lin 2013-04-23 16:31:56 +00:00
parent 038ff816e1
commit 6c70dc7842
2 changed files with 8 additions and 0 deletions
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4
llvm/lib/CodeGen/Analysis.cpp
View File

@ -269,6 +269,8 @@ static bool sameNoopInput(const Value *V1, const Value *V2,
i != e; ++i) {
unsigned attrInd = i - I->op_begin() + 1;
if (cast<CallInst>(I)->paramHasAttr(attrInd, Attribute::Returned) &&
!cast<CallInst>(I)->paramHasAttr(attrInd, Attribute::ZExt) &&
!cast<CallInst>(I)->paramHasAttr(attrInd, Attribute::SExt) &&
isNoopBitcast((*i)->getType(), I->getType(), TLI)) {
NoopInput = *i;
break;
@ -282,6 +284,8 @@ static bool sameNoopInput(const Value *V1, const Value *V2,
i != e; ++i) {
unsigned attrInd = i - I->op_begin() + 1;
if (cast<InvokeInst>(I)->paramHasAttr(attrInd, Attribute::Returned) &&
!cast<InvokeInst>(I)->paramHasAttr(attrInd, Attribute::ZExt) &&
!cast<InvokeInst>(I)->paramHasAttr(attrInd, Attribute::SExt) &&
isNoopBitcast((*i)->getType(), I->getType(), TLI)) {
NoopInput = *i;
break;

4
llvm/lib/IR/Verifier.cpp
View File

@ -740,6 +740,10 @@ void Verifier::VerifyParameterAttrs(AttributeSet Attrs, unsigned Idx, Type *Ty,
Attrs.hasAttribute(Idx, Attribute::InReg))), "Attributes "
"'byval, nest, and inreg' are incompatible!", V);
Assert1(!(Attrs.hasAttribute(Idx, Attribute::StructRet) &&
Attrs.hasAttribute(Idx, Attribute::Returned)), "Attributes "
"'sret and returned' are incompatible!", V);
Assert1(!(Attrs.hasAttribute(Idx, Attribute::ZExt) &&
Attrs.hasAttribute(Idx, Attribute::SExt)), "Attributes "
"'zeroext and signext' are incompatible!", V);