[llvm] [RISCV] add more generic macrofusions (PR #151140)

[Pengcheng Wang via llvm-commits]

================
@@ -91,3 +91,57 @@ def TuneLDADDFusion
                    CheckIsImmOperand<2>,
                    CheckImmOperand<2, 0>
                  ]>>;
+
+// Fuse add(.uw) followed by a load (lb, lh, lw, ld, lbu, lhu, lwu):
+//   add(.uw) rd, rs1, rs2
+//   load rd, imm12(rd)
+def TuneADDLoadFusion
+  : SimpleFusion<"add-load-fusion", "HasADDLoadFusion", "Enable ADD(.UW) + load macrofusion",
+                 CheckOpcode<[ADD, ADD_UW]>,
+                 CheckOpcode<[LB, LH, LW, LD, LBU, LHU, LWU]>>;
+
+// Fuse AUIPC followed by by a load (lb, lh, lw, ld, lbu, lhu, lwu)
+//   auipc rd, imm20
+//   load rd, imm12(rd)
+def TuneAUIPCLoadFusion
+  : SimpleFusion<"auipc-load-fusion", "HasAUIPCLoadFusion",
+                 "Enable AUIPC + load macrofusion",
+                 CheckOpcode<[AUIPC]>,
+                 CheckOpcode<[LB, LH, LW, LD, LBU, LHU, LWU]>>;
+
+// Fuse LUI followed by a load (lb, lh, lw, ld, lbu, lhu, lwu)
+//   lui rd, imm[31:12]
+//   load rd, imm12(rd)
+def TuneLUILoadFusion
+  : SimpleFusion<"lui-load-fusion", "HasLUILoadFusion",
+                 "Enable LUI + load macrofusion",
+                 CheckOpcode<[LUI]>,
+                 CheckOpcode<[LB, LH, LW, LD, LBU, LHU, LWU]>>;
+
+// Bitfield extract fusion: similar to TuneShiftedZExtWFusion
+// but without the immediate restriction
+//   slli rd, rs1, imm12
+//   srli rd, rd, imm12
+def TuneBFExtFusion
+  : SimpleFusion<"bfext-fusion", "HasBFExtFusion",
+                 "Enable SLLI+SRLI (bitfield extract) macrofusion",
+                 CheckOpcode<[SLLI]>,
+                 CheckOpcode<[SRLI]>>;
+
+// Fuse ADDI followed by a load (lb, lh, lw, ld, lbu, lhu, lwu)
+//   addi rd, rs1, imm12
+//   load rd, imm12(rd)
+def TuneADDILoadFusion
+  : SimpleFusion<"addi-load-fusion", "HasADDILoadFusion",
+                 "Enable ADDI + load macrofusion",
+                 CheckOpcode<[ADDI]>,
+                 CheckOpcode<[LB, LH, LW, LD, LBU, LHU, LWU]>>;
----------------
wangpc-pp wrote:

We can use `defvar` here to remove redundancies.
```
defvar Load = [LB, LH, LW, LD, LBU, LHU, LWU];
```

https://github.com/llvm/llvm-project/pull/151140