[mips] Honour -mno-odd-spreg for vector splat (again)

Previous the lowering of FILL_FW would use the MSA128W register class when
performing a vector splat. Instead it should be honouring -mno-odd-spreg and
only use the even registers when performing a splat from word to vector
register.

Logical follow-on from r230235.

This fixes PR/31369.

A previous commit was missing the test case and had another differential
in it.

Reviewers: slthakur

Differential Revision: https://reviews.llvm.org/D28373

llvm-svn: 291566

llvm/lib/Target/Mips/MipsSEISelLowering.cpp

@@ -3377,8 +3377,12 @@ MipsSETargetLowering::emitFILL_FW(MachineInstr &MI,
   DebugLoc DL = MI.getDebugLoc();
   unsigned Wd = MI.getOperand(0).getReg();
   unsigned Fs = MI.getOperand(1).getReg();
-  unsigned Wt1 = RegInfo.createVirtualRegister(&Mips::MSA128WRegClass);
-  unsigned Wt2 = RegInfo.createVirtualRegister(&Mips::MSA128WRegClass);
+  unsigned Wt1 = RegInfo.createVirtualRegister(
+      Subtarget.useOddSPReg() ? &Mips::MSA128WRegClass
+                              : &Mips::MSA128WEvensRegClass);
+  unsigned Wt2 = RegInfo.createVirtualRegister(
+      Subtarget.useOddSPReg() ? &Mips::MSA128WRegClass
+                              : &Mips::MSA128WEvensRegClass);
 
   BuildMI(*BB, MI, DL, TII->get(Mips::IMPLICIT_DEF), Wt1);
   BuildMI(*BB, MI, DL, TII->get(Mips::INSERT_SUBREG), Wt2)

llvm/test/CodeGen/Mips/msa/msa-nooddspreg.ll

@@ -0,0 +1,55 @@
+; RUN: llc -march=mips -mcpu=mips32r5 -mattr=+fp64,+msa,+nooddspreg < %s | FileCheck %s
+
+; Test that the register allocator honours +nooddspreg and does not pick an odd
+; single precision subregister of an MSA register.
+
+@f1 = external global float
+
+@f2 = external global float
+
+@v3 = external global <4 x float>
+
+@d1 = external global double
+
+define void @test() {
+; CHECK-LABEL: test:
+entry:
+; CHECK-NOT: lwc1 $f{{[13579]+}}
+; CHECK: lwc1 $f{{[02468]+}}
+  %0 = load float, float * @f1
+  %1 = insertelement <4 x float> undef,    float %0, i32 0
+  %2 = insertelement <4 x float> %1,    float %0, i32 1
+  %3 = insertelement <4 x float> %2,    float %0, i32 2
+  %4 = insertelement <4 x float> %3,    float %0, i32 3
+
+; CHECK-NOT: lwc1 $f{{[13579]+}}
+; CHECK: lwc1 $f{{[02468]+}}
+  %5 = load float, float * @f2
+  %6 = insertelement <4 x float> undef,    float %5, i32 0
+  %7 = insertelement <4 x float> %6,    float %5, i32 1
+  %8 = insertelement <4 x float> %7,    float %5, i32 2
+  %9 = insertelement <4 x float> %8,    float %5, i32 3
+
+  %10 = fadd <4 x float> %4, %9
+  store <4 x float> %10, <4 x float> * @v3
+  ret void
+}
+
+; Test that the register allocator hnours +noodspreg and does not pick an odd
+; single precision register for a load to perform a conversion to a double.
+
+define void @test2() {
+; CHECK-LABEL: test2:
+entry:
+; CHECK-NOT: lwc1 $f{{[13579]+}}
+; CHECK: lwc1 $f{{[02468]+}}
+  %0 = load float, float * @f1
+  %1 = fpext float %0 to double
+; CHECK-NOT: lwc1 $f{{[13579]+}}
+; CHECK: lwc1 $f{{[02468]+}}
+  %2 = load float, float * @f2
+  %3 = fpext float %2 to double
+  %4 = fadd double %1, %3
+  store double%4, double * @d1
+  ret void
+}