Reland "[SelectionDAG] Enable target specific vector scalarization of calls and returns"

By target hookifying getRegisterType, getNumRegisters, getVectorBreakdown,
backends can request that LLVM to scalarize vector types for calls
and returns.

The MIPS vector ABI requires that vector arguments and returns are passed in
integer registers. With SelectionDAG's new hooks, the MIPS backend can now
handle LLVM-IR with vector types in calls and returns. E.g.
'call @foo(<4 x i32> %4)'.

Previously these cases would be scalarized for the MIPS O32/N32/N64 ABI for
calls and returns if vector types were not legal. If vector types were legal,
a single 128bit vector argument would be assigned to a single 32 bit / 64 bit
integer register.

By teaching the MIPS backend to inspect the original types, it can now
implement the MIPS vector ABI which requires a particular method of
scalarizing vectors.

Previously, the MIPS backend relied on clang to scalarize types such as "call
@foo(<4 x float> %a) into "call @foo(i32 inreg %1, i32 inreg %2, i32 inreg %3,
i32 inreg %4)".

This patch enables the MIPS backend to take either form for vector types.

The previous version of this patch had a "conditional move or jump depends on
uninitialized value".

Reviewers: zoran.jovanovic, jaydeep, vkalintiris, slthakur

Differential Revision: https://reviews.llvm.org/D27845

llvm-svn: 305083

1 files changed, 12 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
index 77e131fa551..431d52b4b9b 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
@@ -975,18 +975,28 @@ struct RegsForValue {
   /// expanded value requires multiple registers.
   SmallVector<unsigned, 4> Regs;
 
+  /// This list holds the number of registers for each value.
+  SmallVector<unsigned, 4> RegCount;
+
+  /// Records if this value needs to be treated in an ABI dependant manner,
+  /// different to normal type legalization.
+  bool IsABIMangled;
+
   RegsForValue();
 
-  RegsForValue(const SmallVector<unsigned, 4> &regs, MVT regvt, EVT valuevt);
+  RegsForValue(const SmallVector<unsigned, 4> &regs, MVT regvt, EVT valuevt,
+               bool IsABIMangledValue = false);
 
   RegsForValue(LLVMContext &Context, const TargetLowering &TLI,
-               const DataLayout &DL, unsigned Reg, Type *Ty);
+               const DataLayout &DL, unsigned Reg, Type *Ty,
+               bool IsABIMangledValue = false);
 
   /// Add the specified values to this one.
   void append(const RegsForValue &RHS) {
     ValueVTs.append(RHS.ValueVTs.begin(), RHS.ValueVTs.end());
     RegVTs.append(RHS.RegVTs.begin(), RHS.RegVTs.end());
     Regs.append(RHS.Regs.begin(), RHS.Regs.end());
+    RegCount.push_back(RHS.Regs.size());
   }
 
   /// Emit a series of CopyFromReg nodes that copies from this value and returns