[AMDGPU] Fold into uses of splat REG_SEQUENCEs through COPYs.

Author: kosarev

llvm/lib/Target/AMDGPU/SIFoldOperands.cpp

@@ -1036,11 +1036,18 @@ void SIFoldOperandsImpl::foldOperand(
     // Grab the use operands first
     SmallVector<MachineOperand *, 4> UsesToProcess(
         llvm::make_pointer_range(MRI->use_nodbg_operands(RegSeqDstReg)));
-    for (auto *RSUse : UsesToProcess) {
+    for (unsigned I = 0; I != UsesToProcess.size(); ++I) {
+      MachineOperand *RSUse = UsesToProcess[I];
       MachineInstr *RSUseMI = RSUse->getParent();
       unsigned OpNo = RSUseMI->getOperandNo(RSUse);
 
       if (SplatVal) {
+        if (RSUseMI->isCopy()) {
+          Register DstReg = RSUseMI->getOperand(0).getReg();
+          append_range(UsesToProcess,
+                       make_pointer_range(MRI->use_nodbg_operands(DstReg)));
+          continue;
+        }
         if (MachineOperand *Foldable =
                 tryFoldRegSeqSplat(RSUseMI, OpNo, SplatVal, SplatRC)) {
           appendFoldCandidate(FoldList, RSUseMI, OpNo, Foldable);

llvm/test/CodeGen/AMDGPU/packed-fp32.ll

@@ -2155,11 +2155,8 @@ define amdgpu_kernel void @fadd_fadd_fsub_0(<2 x float> %arg) {
 ; GFX90A-GISEL-LABEL: fadd_fadd_fsub_0:
 ; GFX90A-GISEL:       ; %bb.0: ; %bb
 ; GFX90A-GISEL-NEXT:    s_load_dwordx2 s[0:1], s[4:5], 0x24
-; GFX90A-GISEL-NEXT:    s_mov_b32 s2, 0
-; GFX90A-GISEL-NEXT:    s_mov_b32 s3, s2
-; GFX90A-GISEL-NEXT:    v_pk_mov_b32 v[0:1], s[2:3], s[2:3] op_sel:[0,1]
 ; GFX90A-GISEL-NEXT:    s_waitcnt lgkmcnt(0)
-; GFX90A-GISEL-NEXT:    v_pk_add_f32 v[0:1], s[0:1], v[0:1]
+; GFX90A-GISEL-NEXT:    v_pk_add_f32 v[0:1], s[0:1], 0
 ; GFX90A-GISEL-NEXT:    v_mov_b32_e32 v0, v1
 ; GFX90A-GISEL-NEXT:    v_pk_add_f32 v[0:1], v[0:1], 0
 ; GFX90A-GISEL-NEXT:    v_mov_b32_e32 v2, s0
@@ -2170,11 +2167,8 @@ define amdgpu_kernel void @fadd_fadd_fsub_0(<2 x float> %arg) {
 ; GFX942-GISEL-LABEL: fadd_fadd_fsub_0:
 ; GFX942-GISEL:       ; %bb.0: ; %bb
 ; GFX942-GISEL-NEXT:    s_load_dwordx2 s[0:1], s[4:5], 0x24
-; GFX942-GISEL-NEXT:    s_mov_b32 s2, 0
-; GFX942-GISEL-NEXT:    s_mov_b32 s3, s2
-; GFX942-GISEL-NEXT:    v_mov_b64_e32 v[0:1], s[2:3]
 ; GFX942-GISEL-NEXT:    s_waitcnt lgkmcnt(0)
-; GFX942-GISEL-NEXT:    v_pk_add_f32 v[0:1], s[0:1], v[0:1]
+; GFX942-GISEL-NEXT:    v_pk_add_f32 v[0:1], s[0:1], 0
 ; GFX942-GISEL-NEXT:    s_nop 0
 ; GFX942-GISEL-NEXT:    v_mov_b32_e32 v0, v1
 ; GFX942-GISEL-NEXT:    v_pk_add_f32 v[0:1], v[0:1], 0