Add some documentation for PNaClABIInfo.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178802 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/TargetInfo.cpp b/lib/CodeGen/TargetInfo.cpp
index 931502d..7cc63b7 100644
--- a/lib/CodeGen/TargetInfo.cpp
+++ b/lib/CodeGen/TargetInfo.cpp
@@ -421,6 +421,8 @@
void PNaClABIInfo::computeInfo(CGFunctionInfo &FI) const {
FI.getReturnInfo() = classifyReturnType(FI.getReturnType());
+ // Obtain the initial number of registers available for passing integers
+ // from the function's regparm attribute.
unsigned FreeRegs = FI.getHasRegParm() ? FI.getRegParm() : 0;
for (CGFunctionInfo::arg_iterator it = FI.arg_begin(), ie = FI.arg_end();
@@ -433,15 +435,18 @@
return 0;
}
+// \brief Classify argument of given type \p Ty. \p FreeRegs is the number of
+// registers available for passing arguments - it can be updated by this
+// method.
ABIArgInfo PNaClABIInfo::classifyArgumentType(QualType Ty,
unsigned &FreeRegs) const {
if (isAggregateTypeForABI(Ty)) {
- // Records with non trivial destructors/constructors should not be passed
- // by value.
+ // In the PNaCl ABI we always pass records/structures on the stack. The
+ // byval attribute can be used if the record doesn't have non-trivial
+ // constructors/destructors.
FreeRegs = 0;
if (isRecordWithNonTrivialDestructorOrCopyConstructor(Ty))
return ABIArgInfo::getIndirect(0, /*ByVal=*/false);
-
return ABIArgInfo::getIndirect(0);
}
@@ -452,14 +457,17 @@
ABIArgInfo BaseInfo = (Ty->isPromotableIntegerType() ?
ABIArgInfo::getExtend() : ABIArgInfo::getDirect());
- // Regparm regs hold 32 bits.
- unsigned SizeInRegs = (getContext().getTypeSize(Ty) + 31) / 32;
- if (SizeInRegs == 0) return BaseInfo;
- if (SizeInRegs > FreeRegs) {
+ // Figure out how many of the free registers can be occupied by this type.
+ // regparm registers are 32-bit.
+ unsigned NumRegsRequired = (getContext().getTypeSize(Ty) + 31) / 32;
+ if (NumRegsRequired == 0) return BaseInfo;
+ if (NumRegsRequired > FreeRegs) {
+ // If this type needs more registers than we have available, no more
+ // passing in-registers can happen.
FreeRegs = 0;
return BaseInfo;
}
- FreeRegs -= SizeInRegs;
+ FreeRegs -= NumRegsRequired;
return BaseInfo.isDirect() ?
ABIArgInfo::getDirectInReg(BaseInfo.getCoerceToType()) :
ABIArgInfo::getExtendInReg(BaseInfo.getCoerceToType());
@@ -469,6 +477,7 @@
if (RetTy->isVoidType())
return ABIArgInfo::getIgnore();
+ // In the PNaCl ABI we always return records/structures on the stack.
if (isAggregateTypeForABI(RetTy))
return ABIArgInfo::getIndirect(0);