fix true16 usemi

Author: broxigarchen

llvm/lib/Target/AMDGPU/SIInstrInfo.cpp

@@ -7835,6 +7835,22 @@ void SIInstrInfo::moveToVALUImpl(SIInstrWorklist &Worklist,
     assert(NewDstRC);
     NewDstReg = MRI.createVirtualRegister(NewDstRC);
     MRI.replaceRegWith(DstReg, NewDstReg);
+
+    // Check useMI of NewInstr. If useMI is a true16 instruction,
+    // add a lo16 subreg access if needed
+    if (ST.useRealTrue16Insts() && 32 == RI.getRegSizeInBits(*NewDstRC)) {
+      for (MachineRegisterInfo::use_iterator I = MRI.use_begin(NewDstReg),
+                                             E = MRI.use_end();
+           I != E; ++I) {
+        MachineInstr &UseMI = *I->getParent();
+        unsigned UseMIOpcode = UseMI.getOpcode();
+        if (AMDGPU::isTrue16Inst(UseMIOpcode) &&
+            (16 ==
+             RI.getRegSizeInBits(*getOpRegClass(UseMI, I.getOperandNo())))) {
+          I->setSubReg(AMDGPU::lo16);
+        }
+      }
+    }
   }
   fixImplicitOperands(*NewInstr);
   // Legalize the operands

llvm/test/CodeGen/AMDGPU/fneg-combines.f16.ll

@@ -699,7 +699,7 @@ define amdgpu_ps half @fneg_fadd_0_f16(half inreg %tmp2, half inreg %tmp6, <4 x
 ; GFX11-SAFE-TRUE16-NEXT:    v_cmp_ngt_f16_e32 vcc_lo, s0, v0.l
 ; GFX11-SAFE-TRUE16-NEXT:    s_delay_alu instid0(VALU_DEP_2) | instskip(NEXT) | instid1(VALU_DEP_1)
 ; GFX11-SAFE-TRUE16-NEXT:    v_xor_b32_e32 v0, 0x8000, v1
-; GFX11-SAFE-TRUE16-NEXT:    v_cndmask_b16 v0.l, v0/*Invalid register, operand has 'VS_16' register class*/, s0, vcc_lo
+; GFX11-SAFE-TRUE16-NEXT:    v_cndmask_b16 v0.l, v0.l, s0, vcc_lo
 ; GFX11-SAFE-TRUE16-NEXT:    s_delay_alu instid0(VALU_DEP_1)
 ; GFX11-SAFE-TRUE16-NEXT:    v_cmp_nlt_f16_e32 vcc_lo, 0, v0.l
 ; GFX11-SAFE-TRUE16-NEXT:    v_cndmask_b16 v0.l, 0x7e00, 0, vcc_lo