[llvm] [AMDGPU] Add writelane and readlane pseudos for SGPR spilling (PR #69923)

[Yashwant Singh via llvm-commits]

================
@@ -875,6 +875,25 @@ defm SI_SPILL_S384 : SI_SPILL_SGPR <SReg_384>;
 defm SI_SPILL_S512 : SI_SPILL_SGPR <SReg_512>;
 defm SI_SPILL_S1024 : SI_SPILL_SGPR <SReg_1024>;
 
+let SGPRSpill = 1 in {
+def SI_SPILL_S32_TO_VGPR : PseudoInstSI <(outs VGPR_32:$vdst),
+  (ins SReg_32:$src0, i32imm:$src1, VGPR_32:$vdst_in)> {
+  let hasSideEffects = 0;
+  let mayLoad = 0;
+  let mayStore = 0;
+  let VALU = 1;
+  let Constraints = "$vdst = $vdst_in";
+}
+
+def SI_RELOAD_S32_FROM_VGPR : PseudoInstSI <(outs SReg_32:$sdst),
----------------
yashssh wrote:

**Nit:** I think SI_RESTORE_S32_FROM_VGPR can be an even better name?

https://github.com/llvm/llvm-project/pull/69923