[X86] Better support for the MCU psABI (LLVM part)
This adds support for the MCU psABI in a way different from r251223 and r251224,
basically reverting most of these two patches. The problem with the approach
taken in r251223/4 is that it only handled libcalls that originated from the backend.
However, the mid-end also inserts quite a few libcalls and assumes these use the
platform's default calling convention.
The previous patch tried to insert inregs when necessary both in the FE and,
somewhat hackily, in the CG. Instead, we now define a new default calling convention
for the MCU, which doesn't use inreg marking at all, similarly to what x86-64 does.
Differential Revision: http://reviews.llvm.org/D15054
llvm-svn: 256494
diff --git a/llvm/lib/Target/X86/X86FastISel.cpp b/llvm/lib/Target/X86/X86FastISel.cpp
index 914fd04..de94a13 100644
--- a/llvm/lib/Target/X86/X86FastISel.cpp
+++ b/llvm/lib/Target/X86/X86FastISel.cpp
@@ -1098,12 +1098,11 @@
RetRegs.push_back(VA.getLocReg());
}
- // The x86-64 ABI for returning structs by value requires that we copy
- // the sret argument into %rax for the return. We saved the argument into
- // a virtual register in the entry block, so now we copy the value out
- // and into %rax. We also do the same with %eax for Win32.
- if (F.hasStructRetAttr() &&
- (Subtarget->is64Bit() || Subtarget->isTargetKnownWindowsMSVC())) {
+ // All x86 ABIs require that for returning structs by value we copy
+ // the sret argument into %rax/%eax (depending on ABI) for the return.
+ // We saved the argument into a virtual register in the entry block,
+ // so now we copy the value out and into %rax/%eax.
+ if (F.hasStructRetAttr()) {
unsigned Reg = X86MFInfo->getSRetReturnReg();
assert(Reg &&
"SRetReturnReg should have been set in LowerFormalArguments()!");
@@ -2820,7 +2819,7 @@
if (CS)
if (CS->arg_empty() || !CS->paramHasAttr(1, Attribute::StructRet) ||
- CS->paramHasAttr(1, Attribute::InReg))
+ CS->paramHasAttr(1, Attribute::InReg) || Subtarget->isTargetMCU())
return 0;
return 4;