[llvm] [RISCV] Add CompressPat for all cases in isCopyInstrImpl (PR #136875)

[Alex Bradbury via llvm-commits]

https://github.com/asb updated https://github.com/llvm/llvm-project/pull/136875

>From 2698e03cf7c2d8ea2a0cdbb8d853da2aa6bd58d7 Mon Sep 17 00:00:00 2001
From: Alex Bradbury <asb at igalia.com>
Date: Wed, 23 Apr 2025 15:15:38 +0100
Subject: [PATCH] [RISCV] Add CompressPat for all cases in isCopyInstrImpl

We may end up with a non-canonical move (copy) instruction after a pass like
MachineCopyPropagation that doesn't get compressed because we don't have
an explicit pattern for it. This patch addressses that by adding
additional CompressPat. This means that the generated code will be
slightly different with/without the compressed extension. This isn't
expected to be problematic as the instructions in question are all
simple arithmetic ops.
---
 llvm/lib/Target/RISCV/RISCVInstrInfoC.td | 30 ++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/llvm/lib/Target/RISCV/RISCVInstrInfoC.td b/llvm/lib/Target/RISCV/RISCVInstrInfoC.td
index 252100c814f2b..0c32acde0222c 100644
--- a/llvm/lib/Target/RISCV/RISCVInstrInfoC.td
+++ b/llvm/lib/Target/RISCV/RISCVInstrInfoC.td
@@ -1012,11 +1012,15 @@ let Predicates = [HasStdExtCOrZca] in {
 def : CompressPat<(JALR X0, GPRNoX0:$rs1, 0),
                   (C_JR GPRNoX0:$rs1)>;
 let isCompressOnly = true in {
-def : CompressPat<(ADD GPRNoX0:$rs1, X0, GPRNoX0:$rs2),
-                  (C_MV GPRNoX0:$rs1, GPRNoX0:$rs2)>;
-def : CompressPat<(ADD GPRNoX0:$rs1, GPRNoX0:$rs2, X0),
-                  (C_MV GPRNoX0:$rs1, GPRNoX0:$rs2)>;
+foreach Inst=[ADD, OR, XOR] in {
+  def : CompressPat<(Inst GPRNoX0:$rs1, X0, GPRNoX0:$rs2),
+                    (C_MV GPRNoX0:$rs1, GPRNoX0:$rs2)>;
+  def : CompressPat<(Inst GPRNoX0:$rs1, GPRNoX0:$rs2, X0),
+                    (C_MV GPRNoX0:$rs1, GPRNoX0:$rs2)>;
 }
+def : CompressPat<(SUB GPRNoX0:$rs1, GPRNoX0:$rs2, X0),
+                  (C_MV GPRNoX0:$rs1, GPRNoX0:$rs2)>;
+} // isCompressOnly = true
 def : CompressPat<(ADDI GPRNoX0:$rs1, GPRNoX0:$rs2, 0),
                   (C_MV GPRNoX0:$rs1, GPRNoX0:$rs2)>;
 def : CompressPat<(EBREAK), (C_EBREAK)>;
@@ -1053,3 +1057,21 @@ let Predicates = [HasStdExtCOrZca, IsRV64] in {
 def : CompressPat<(SD GPR:$rs2, SPMem:$rs1, uimm9_lsb000:$imm),
                   (C_SDSP GPR:$rs2, SPMem:$rs1, uimm9_lsb000:$imm)>;
 } // Predicates = [HasStdExtCOrZca, IsRV64]
+
+let isCompressOnly = true, Predicates = [HasStdExtCOrZca, HasStdExtZba] in {
+def : CompressPat<(SH1ADD GPRNoX0:$rs1, X0, GPRNoX0:$rs2),
+                  (C_MV GPRNoX0:$rs1, GPRNoX0:$rs2)>;
+def : CompressPat<(SH2ADD GPRNoX0:$rs1, X0, GPRNoX0:$rs2),
+                  (C_MV GPRNoX0:$rs1, GPRNoX0:$rs2)>;
+def : CompressPat<(SH3ADD GPRNoX0:$rs1, X0, GPRNoX0:$rs2),
+                  (C_MV GPRNoX0:$rs1, GPRNoX0:$rs2)>;
+} // isCompressOnly = true, Predicates = [HasStdExtCOrZca, HasStdExtZba]
+
+let isCompressOnly = true, Predicates = [HasStdExtCOrZca, HasStdExtZba, IsRV64] in {
+def : CompressPat<(SH1ADD_UW GPRNoX0:$rs1, X0, GPRNoX0:$rs2),
+                  (C_MV GPRNoX0:$rs1, GPRNoX0:$rs2)>;
+def : CompressPat<(SH2ADD_UW GPRNoX0:$rs1, X0, GPRNoX0:$rs2),
+                  (C_MV GPRNoX0:$rs1, GPRNoX0:$rs2)>;
+def : CompressPat<(SH3ADD_UW GPRNoX0:$rs1, X0, GPRNoX0:$rs2),
+                  (C_MV GPRNoX0:$rs1, GPRNoX0:$rs2)>;
+} // isCompressOnly = true, Predicates = [HasStdExtCOrZca, HasStdExtZba, IsRV64]