[llvm] Support replacing `add rd, Zero, Zero` with `c.li rd, 0` (PR #86937)
Mark Goncharov via llvm-commits
llvm-commits at lists.llvm.org
Thu Mar 28 04:25:27 PDT 2024
https://github.com/mga-sc created https://github.com/llvm/llvm-project/pull/86937
None
>From 635929ca60c5c83fb44c8c9e6e3945b4f031cefb Mon Sep 17 00:00:00 2001
From: Mark Goncharov <mark.goncharov at syntacore.com>
Date: Thu, 28 Mar 2024 12:49:41 +0300
Subject: [PATCH] Support replacing `add rd, Zero, Zero` with `c.li rd, 0`
---
llvm/lib/Target/RISCV/RISCVInstrInfoC.td | 2 ++
llvm/test/CodeGen/RISCV/compress.ll | 9 +++++++++
2 files changed, 11 insertions(+)
diff --git a/llvm/lib/Target/RISCV/RISCVInstrInfoC.td b/llvm/lib/Target/RISCV/RISCVInstrInfoC.td
index 18d38348f7214f..1561956950e2c4 100644
--- a/llvm/lib/Target/RISCV/RISCVInstrInfoC.td
+++ b/llvm/lib/Target/RISCV/RISCVInstrInfoC.td
@@ -996,6 +996,8 @@ let Predicates = [HasStdExtCOrZca] in {
def : CompressPat<(JALR X0, GPRNoX0:$rs1, 0),
(C_JR GPRNoX0:$rs1)>;
let isCompressOnly = true in {
+def : CompressPat<(ADD GPRNoX0:$rs1, X0, X0),
+ (C_LI GPRNoX0:$rs1, 0)>;
def : CompressPat<(ADD GPRNoX0:$rs1, X0, GPRNoX0:$rs2),
(C_MV GPRNoX0:$rs1, GPRNoX0:$rs2)>;
def : CompressPat<(ADD GPRNoX0:$rs1, GPRNoX0:$rs2, X0),
diff --git a/llvm/test/CodeGen/RISCV/compress.ll b/llvm/test/CodeGen/RISCV/compress.ll
index 8fb520fac41ee0..47744492aaab6f 100644
--- a/llvm/test/CodeGen/RISCV/compress.ll
+++ b/llvm/test/CodeGen/RISCV/compress.ll
@@ -174,3 +174,12 @@ define i32 @neg_i32_hi20_only() #0 {
; RV32IC-NEXT: c.jr ra
ret i32 -65536
}
+
+define i32 @add_zero_zero_to_li() #0 {
+; RV32IC-LABEL: <add_zero_zero_to_li>:
+; RV32IC: c.li a0, 0
+; RV32IC: c.jr ra
+entry:
+ %0 = tail call i32 asm "add $0, zero, zero", "=r"()
+ ret i32 %0
+}
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