[GlobalISel] Accept multiple vregs for lowerCall's args

Change the interface of CallLowering::lowerCall to accept several
virtual registers for each argument, instead of just one.  This is a
follow-up to D46018.

CallLowering::lowerReturn was similarly refactored in D49660 and
lowerFormalArguments in D63549.

With this change, we no longer pack the virtual registers generated for
aggregates into one big lump before delegating to the target. Therefore,
the target can decide itself whether it wants to handle them as separate
pieces or use one big register.

ARM and AArch64 have been updated to use the passed in virtual registers
directly, which means we no longer need to generate so many
merge/extract instructions.

NFCI for AMDGPU, Mips and X86.

Differential Revision: https://reviews.llvm.org/D63551

llvm-svn: 364512

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/Target/X86/X86CallLowering.cpp b/llvm/lib/Target/X86/X86CallLowering.cpp
index 3a980f40ab8..b16b3839c85 100644
--- a/llvm/lib/Target/X86/X86CallLowering.cpp
+++ b/llvm/lib/Target/X86/X86CallLowering.cpp
@@ -409,7 +409,9 @@ bool X86CallLowering::lowerCall(MachineIRBuilder &MIRBuilder,
     if (OrigArg.Flags.isByVal())
       return false;
 
-    assert(OrigArg.Regs.size() == 1 && "Can't handle multple regs yet");
+    if (OrigArg.Regs.size() > 1)
+      return false;
+
     if (!splitToValueTypes(OrigArg, SplitArgs, DL, MRI,
                            [&](ArrayRef<Register> Regs) {
                              MIRBuilder.buildUnmerge(Regs, OrigArg.Regs[0]);