when eliding a byval copy due to inlining a readonly function, we have
to make sure that the reused alloca has sufficient alignment.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122236 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Utils/InlineFunction.cpp b/lib/Transforms/Utils/InlineFunction.cpp
index bca9fc4..76fdd09 100644
--- a/lib/Transforms/Utils/InlineFunction.cpp
+++ b/lib/Transforms/Utils/InlineFunction.cpp
@@ -229,17 +229,56 @@
CallerNode->removeCallEdgeFor(CS);
}
+/// HandleByValArgument - When inlining a call site that has a byval argument,
+/// we have to make the implicit memcpy explicit by adding it.
static Value *HandleByValArgument(Value *Arg, Instruction *TheCall,
const Function *CalledFunc,
InlineFunctionInfo &IFI,
unsigned ByValAlignment) {
- if (CalledFunc->onlyReadsMemory())
- return Arg;
+ const Type *AggTy = cast<PointerType>(Arg->getType())->getElementType();
+
+ // If the called function is readonly, then it could not mutate the caller's
+ // copy of the byval'd memory. In this case, it is safe to elide the copy and
+ // temporary.
+ if (CalledFunc->onlyReadsMemory()) {
+ // If the byval argument has a specified alignment that is greater than the
+ // passed in pointer, then we either have to round up the input pointer or
+ // give up on this transformation.
+ if (ByValAlignment <= 1) // 0 = unspecified, 1 = no particular alignment.
+ return Arg;
+
+ // See if the argument is a (bitcasted) pointer to an alloca. If so, we can
+ // round up the alloca if needed.
+ if (AllocaInst *AI = dyn_cast<AllocaInst>(Arg->stripPointerCasts())) {
+ unsigned AIAlign = AI->getAlignment();
+
+ // If the alloca is known at least aligned as much as the byval, we can do
+ // this optimization.
+ if (AIAlign >= ByValAlignment)
+ return Arg;
+
+ // If the alloca has a specified alignment that is less than the byval,
+ // then we can safely bump it up.
+ if (AIAlign) {
+ AI->setAlignment(ByValAlignment);
+ return Arg;
+ }
+
+ // If the alignment has an unspecified alignment, then we can only modify
+ // it if we have TD information. Doing so without TD info could end up
+ // with us rounding the alignment *down* accidentally, which is badness.
+ if (IFI.TD) {
+ AIAlign = std::max(ByValAlignment, IFI.TD->getPrefTypeAlignment(AggTy));
+ AI->setAlignment(AIAlign);
+ return Arg;
+ }
+ }
+
+ // Otherwise, we have to make a memcpy to get a safe alignment, pretty lame.
+ }
LLVMContext &Context = Arg->getContext();
-
- const Type *AggTy = cast<PointerType>(Arg->getType())->getElementType();
const Type *VoidPtrTy = Type::getInt8PtrTy(Context);
// Create the alloca. If we have TargetData, use nice alignment.