The alignment of an sret parameter is known: it must be at least the
alignment of the return type. Teach the optimizers this.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165226 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index 491224a..1004ebc 100644
--- a/lib/Analysis/ValueTracking.cpp
+++ b/lib/Analysis/ValueTracking.cpp
@@ -308,11 +308,20 @@
}
if (Argument *A = dyn_cast<Argument>(V)) {
- // Get alignment information off byval arguments if specified in the IR.
- if (A->hasByValAttr())
- if (unsigned Align = A->getParamAlignment())
- KnownZero = APInt::getLowBitsSet(BitWidth,
- CountTrailingZeros_32(Align));
+ unsigned Align = 0;
+
+ if (A->hasByValAttr()) {
+ // Get alignment information off byval arguments if specified in the IR.
+ Align = A->getParamAlignment();
+ } else if (TD && A->hasStructRetAttr()) {
+ // An sret parameter has at least the ABI alignment of the return type.
+ Type *EltTy = cast<PointerType>(A->getType())->getElementType();
+ if (EltTy->isSized())
+ Align = TD->getABITypeAlignment(EltTy);
+ }
+
+ if (Align)
+ KnownZero = APInt::getLowBitsSet(BitWidth, CountTrailingZeros_32(Align));
return;
}