Please consider the new patch.
This time, if the coerce-to type is larger than the real type, we
reconstruct a value of the coerce-to type in a stack allocation, then
bitcast & copy it into the destination.
This is roughly the same logic as in CreateCoercedStore, but with
multiple sources.
On Sat, Feb 4, 2012 at 6:12 PM, Evgeniy Stepanov
<[email protected]> wrote:
> On Sat, Feb 4, 2012 at 1:07 AM, Eli Friedman <[email protected]> wrote:
>> On Fri, Feb 3, 2012 at 4:05 AM, Evgeniy Stepanov
>> <[email protected]> wrote:
>>> Hi,
>>>
>>> this is a fix for PR11905.
>>>
>>> The current behaviour when generation a function prolog for arguments
>>> of coerced types is to allocate a stack temp of the real argument type
>>> and store the argument(s) there. This is wrong, because storage size
>>> of the coerce-to type can be larger than that of the real type.
>>>
>>> The new behaviour is to allocate a temp of the coerced type, copy it,
>>> and then reference through a bitcasted pointer of the real type.
>>>
>>> Please review.
>>
>> The real type is sometimes larger than the coerced type... switching
>> from one to the other only changes which cases are broken issues.
>
> Could you give an example of that?
> In that case, what would you think of allocating the largest of the two types?
>
>>
>> -Eli
Index: test/CodeGen/arm-arguments.c
===================================================================
--- test/CodeGen/arm-arguments.c (revision 149785)
+++ test/CodeGen/arm-arguments.c (working copy)
@@ -153,3 +153,15 @@
// AAPCS: define arm_aapcscc void @f30({{.*}} noalias sret
struct s30 { _Complex int f0; };
struct s30 f30() {}
+
+// PR11905
+struct s31 { char x; };
+void f31(struct s31 s) { }
+// AAPCS: @f31([1 x i32] %s.coerce)
+// AAPCS: %s = alloca %struct.s31, align 4
+// AAPCS: %tmp = alloca [1 x i32]
+// AAPCS: store [1 x i32] %s.coerce, [1 x i32]* %tmp
+// APCS-GNU: @f31([1 x i32] %s.coerce)
+// APCS-GNU: %s = alloca %struct.s31, align 4
+// APCS-GNU: %tmp = alloca [1 x i32]
+// APCS-GNU: store [1 x i32] %s.coerce, [1 x i32]* %tmp
Index: lib/CodeGen/CGCall.cpp
===================================================================
--- lib/CodeGen/CGCall.cpp (revision 149785)
+++ lib/CodeGen/CGCall.cpp (working copy)
@@ -1013,7 +1013,7 @@
break;
}
- llvm::AllocaInst *Alloca = CreateMemTemp(Ty, "coerce");
+ llvm::AllocaInst *Alloca = CreateMemTemp(Ty, Arg->getName());
// The alignment we need to use is the max of the requested alignment for
// the argument plus the alignment required by our access code below.
@@ -1037,16 +1037,37 @@
// If the coerce-to type is a first class aggregate, we flatten it and
// pass the elements. Either way is semantically identical, but fast-isel
// and the optimizer generally likes scalar values better than FCAs.
- if (llvm::StructType *STy =
- dyn_cast<llvm::StructType>(ArgI.getCoerceToType())) {
- Ptr = Builder.CreateBitCast(Ptr, llvm::PointerType::getUnqual(STy));
+ llvm::StructType *STy = dyn_cast<llvm::StructType>(ArgI.getCoerceToType());
+ if (STy && STy->getNumElements() > 1) {
+ uint64_t SrcSize = CGM.getTargetData().getTypeAllocSize(STy);
+ llvm::Type *DstTy =
+ cast<llvm::PointerType>(Ptr->getType())->getElementType();
+ uint64_t DstSize = CGM.getTargetData().getTypeAllocSize(DstTy);
- for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
- assert(AI != Fn->arg_end() && "Argument mismatch!");
- AI->setName(Arg->getName() + ".coerce" + Twine(i));
- llvm::Value *EltPtr = Builder.CreateConstGEP2_32(Ptr, 0, i);
- Builder.CreateStore(AI++, EltPtr);
- }
+ if (SrcSize <= DstSize) {
+ Ptr = Builder.CreateBitCast(Ptr, llvm::PointerType::getUnqual(STy));
+
+ for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
+ assert(AI != Fn->arg_end() && "Argument mismatch!");
+ AI->setName(Arg->getName() + ".coerce" + Twine(i));
+ llvm::Value *EltPtr = Builder.CreateConstGEP2_32(Ptr, 0, i);
+ Builder.CreateStore(AI++, EltPtr);
+ }
+ } else {
+ llvm::Value *TempAlloca = CreateTempAlloca(ArgI.getCoerceToType(), "coerce");
+
+ for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
+ assert(AI != Fn->arg_end() && "Argument mismatch!");
+ AI->setName(Arg->getName() + ".coerce" + Twine(i));
+ llvm::Value *EltPtr = Builder.CreateConstGEP2_32(TempAlloca, 0, i);
+ Builder.CreateStore(AI++, EltPtr);
+ }
+
+ llvm::Value *Casted =
+ Builder.CreateBitCast(TempAlloca, llvm::PointerType::getUnqual(ConvertTypeForMem(Ty)));
+ llvm::LoadInst *Load = Builder.CreateLoad(Casted);
+ Builder.CreateStore(Load, Ptr);
+ }
} else {
// Simple case, just do a coerced store of the argument into the alloca.
assert(AI != Fn->arg_end() && "Argument mismatch!");
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