[llvm] [LoongArch] Prevent R0/R1 allocation for rj operand of {G}CSRXCHG (PR #140862)
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Wed May 21 00:36:44 PDT 2025
https://github.com/heiher created https://github.com/llvm/llvm-project/pull/140862
The {G}CSRXCHG instruction must not use R0 or R1 as the rj operand, as encoding rj as 0 or 1 will be interpreted as {G}CSRRD OR {G}CSRWR, respectively, rather than {G}CSRXCHG.
This patch introduces a new register class `GPRNoR0R1` and updates the {G}CSRXCHG instruction definition to use it for the rj operand, ensuring the register allocator avoids assigning R0 or R1.
Fixes #140842
>From 02bc62ce35e0cbb3605804964f904b6aa6f2bb55 Mon Sep 17 00:00:00 2001
From: WANG Rui <wangrui at loongson.cn>
Date: Wed, 21 May 2025 14:05:54 +0800
Subject: [PATCH] [LoongArch] Prevent R0/R1 allocation for rj operand of
{G}CSRXCHG
The {G}CSRXCHG instruction must not use R0 or R1 as the rj operand, as
encoding rj as 0 or 1 will be interpreted as {G}CSRRD OR {G}CSRWR,
respectively, rather than {G}CSRXCHG.
This patch introduces a new register class `GPRNoR0R1` and updates the
{G}CSRXCHG instruction definition to use it for the rj operand, ensuring
the register allocator avoids assigning R0 or R1.
Fixes #140842
---
.../Disassembler/LoongArchDisassembler.cpp | 8 +++++++
.../Target/LoongArch/LoongArchInstrInfo.td | 6 ++---
.../Target/LoongArch/LoongArchLVZInstrInfo.td | 2 +-
.../Target/LoongArch/LoongArchRegisterInfo.td | 5 ++++
.../CodeGen/LoongArch/csrxchg-intrinsic.ll | 24 +++++++++++++++++++
.../MC/LoongArch/Basic/Privilege/invalid.s | 4 ++--
llvm/test/MC/LoongArch/lvz/lvz-err.s | 4 ++--
7 files changed, 45 insertions(+), 8 deletions(-)
create mode 100644 llvm/test/CodeGen/LoongArch/csrxchg-intrinsic.ll
diff --git a/llvm/lib/Target/LoongArch/Disassembler/LoongArchDisassembler.cpp b/llvm/lib/Target/LoongArch/Disassembler/LoongArchDisassembler.cpp
index 5963208691f72..761682423fffe 100644
--- a/llvm/lib/Target/LoongArch/Disassembler/LoongArchDisassembler.cpp
+++ b/llvm/lib/Target/LoongArch/Disassembler/LoongArchDisassembler.cpp
@@ -62,6 +62,14 @@ static DecodeStatus DecodeGPRRegisterClass(MCInst &Inst, uint64_t RegNo,
return MCDisassembler::Success;
}
+static DecodeStatus
+DecodeGPRNoR0R1RegisterClass(MCInst &Inst, uint64_t RegNo, uint64_t Address,
+ const MCDisassembler *Decoder) {
+ if (RegNo <= 1)
+ return MCDisassembler::Fail;
+ return DecodeGPRRegisterClass(Inst, RegNo, Address, Decoder);
+}
+
static DecodeStatus DecodeFPR32RegisterClass(MCInst &Inst, uint64_t RegNo,
uint64_t Address,
const MCDisassembler *Decoder) {
diff --git a/llvm/lib/Target/LoongArch/LoongArchInstrInfo.td b/llvm/lib/Target/LoongArch/LoongArchInstrInfo.td
index e0fb49698383c..c6e361dffee9a 100644
--- a/llvm/lib/Target/LoongArch/LoongArchInstrInfo.td
+++ b/llvm/lib/Target/LoongArch/LoongArchInstrInfo.td
@@ -2431,7 +2431,7 @@ let hasSideEffects = 1, Constraints = "$rd = $dst" in {
def CSRWR : FmtCSR<0x04000020, (outs GPR:$dst),
(ins GPR:$rd, uimm14:$csr_num), "$rd, $csr_num">;
def CSRXCHG : FmtCSRXCHG<0x04000000, (outs GPR:$dst),
- (ins GPR:$rd, GPR:$rj, uimm14:$csr_num),
+ (ins GPR:$rd, GPRNoR0R1:$rj, uimm14:$csr_num),
"$rd, $rj, $csr_num">;
} // hasSideEffects = 1, Constraints = "$rd = $dst"
@@ -2478,8 +2478,8 @@ def IDLE : MISC_I15<0x06488000>;
def : Pat<(loongarch_csrrd uimm14:$imm14), (CSRRD uimm14:$imm14)>;
def : Pat<(loongarch_csrwr GPR:$rd, uimm14:$imm14),
(CSRWR GPR:$rd, uimm14:$imm14)>;
-def : Pat<(loongarch_csrxchg GPR:$rd, GPR:$rj, uimm14:$imm14),
- (CSRXCHG GPR:$rd, GPR:$rj, uimm14:$imm14)>;
+def : Pat<(loongarch_csrxchg GPR:$rd, GPRNoR0R1:$rj, uimm14:$imm14),
+ (CSRXCHG GPR:$rd, GPRNoR0R1:$rj, uimm14:$imm14)>;
def : Pat<(loongarch_iocsrrd_b GPR:$rj), (IOCSRRD_B GPR:$rj)>;
def : Pat<(loongarch_iocsrrd_h GPR:$rj), (IOCSRRD_H GPR:$rj)>;
diff --git a/llvm/lib/Target/LoongArch/LoongArchLVZInstrInfo.td b/llvm/lib/Target/LoongArch/LoongArchLVZInstrInfo.td
index 50a16e2dd56b9..07b77ee971f27 100644
--- a/llvm/lib/Target/LoongArch/LoongArchLVZInstrInfo.td
+++ b/llvm/lib/Target/LoongArch/LoongArchLVZInstrInfo.td
@@ -23,7 +23,7 @@ let Constraints = "$rd = $dst" in {
def GCSRWR : FmtCSR<0x05000020, (outs GPR:$dst),
(ins GPR:$rd, uimm14:$csr_num), "$rd, $csr_num">;
def GCSRXCHG : FmtCSRXCHG<0x05000000, (outs GPR:$dst),
- (ins GPR:$rd, GPR:$rj, uimm14:$csr_num),
+ (ins GPR:$rd, GPRNoR0R1:$rj, uimm14:$csr_num),
"$rd, $rj, $csr_num">;
} // Constraints = "$rd = $dst"
diff --git a/llvm/lib/Target/LoongArch/LoongArchRegisterInfo.td b/llvm/lib/Target/LoongArch/LoongArchRegisterInfo.td
index a8419980868ee..dfba2ecd02154 100644
--- a/llvm/lib/Target/LoongArch/LoongArchRegisterInfo.td
+++ b/llvm/lib/Target/LoongArch/LoongArchRegisterInfo.td
@@ -127,6 +127,11 @@ def GPRT : GPRRegisterClass<(add // a0...a7, t0...t8
// prediction.
def GPRJR : GPRRegisterClass<(sub GPR, R1)>;
+// Don't use R0 or R1 for the rj operand of {G}CSRXCHG, because when rj is
+// encoded as 0 or 1, the instruction is interpreted as {G}CSRRD or {G}CSRWR,
+// respectively, rather than {G}CSRXCHG.
+def GPRNoR0R1 : GPRRegisterClass<(sub GPR, R0, R1)>;
+
// Floating point registers
let RegAltNameIndices = [RegAliasName] in {
diff --git a/llvm/test/CodeGen/LoongArch/csrxchg-intrinsic.ll b/llvm/test/CodeGen/LoongArch/csrxchg-intrinsic.ll
new file mode 100644
index 0000000000000..2f38b3a8c7ad1
--- /dev/null
+++ b/llvm/test/CodeGen/LoongArch/csrxchg-intrinsic.ll
@@ -0,0 +1,24 @@
+; RUN: llc --mtriple=loongarch32 --mattr=+f --verify-machineinstrs < %s | FileCheck %s
+; RUN: llc --mtriple=loongarch64 --mattr=+f --verify-machineinstrs < %s | FileCheck %s
+
+declare i32 @llvm.loongarch.csrxchg.w(i32, i32, i32 immarg)
+
+;; Check that the rj operand of csrxchg is not R0.
+define void @csrxchg_w_rj_not_r0(i32 signext %a) {
+; CHECK-NOT: csrxchg ${{[a-z]*}}, $r0, 0
+; CHECK-NOT: csrxchg ${{[a-z]*}}, $zero, 0
+entry:
+ %0 = tail call i32 @llvm.loongarch.csrxchg.w(i32 %a, i32 0, i32 0)
+ ret void
+}
+
+;; Check that the rj operand of csrxchg is not R1.
+define i32 @csrxchg_w_rj_not_r1() {
+; CHECK-NOT: csrxchg ${{[a-z]*}}, $r1, 0
+; CHECK-NOT: csrxchg ${{[a-z]*}}, $ra, 0
+entry:
+ %0 = tail call i32 asm "", "=r,r,i,{r4},{r5},{r6},{r7},{r8},{r9},{r10},{r11},{r12},{r13},{r14},{r15},{r16},{r17},{r18},{r19},{r20},{r23},{r24},{r25},{r26},{r27},{r28},{r29},{r30},{r31},0"(i32 4, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0)
+ %1 = tail call i32 @llvm.loongarch.csrxchg.w(i32 %0, i32 4, i32 0)
+ %2 = tail call i32 asm "", "=r,r,i,{r4},{r5},{r6},{r7},{r8},{r9},{r10},{r11},{r12},{r13},{r14},{r15},{r16},{r17},{r18},{r19},{r20},{r23},{r24},{r25},{r26},{r27},{r28},{r29},{r30},{r31},0"(i32 4, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 %1)
+ ret i32 %2
+}
diff --git a/llvm/test/MC/LoongArch/Basic/Privilege/invalid.s b/llvm/test/MC/LoongArch/Basic/Privilege/invalid.s
index 80d7c304956c9..2ac3fcf6e1819 100644
--- a/llvm/test/MC/LoongArch/Basic/Privilege/invalid.s
+++ b/llvm/test/MC/LoongArch/Basic/Privilege/invalid.s
@@ -3,9 +3,9 @@
## csrxchg: rj != 0,1
csrxchg $a0, $zero, 0
-# ERR: :[[#@LINE-1]]:15: error: must not be $r0 or $r1
+# ERR: :[[#@LINE-1]]:15: error: invalid operand for instruction
csrxchg $a0, $ra, 0
-# ERR: :[[#@LINE-1]]:15: error: must not be $r0 or $r1
+# ERR: :[[#@LINE-1]]:15: error: invalid operand for instruction
## LoongArch64 mnemonics
iocsrrd.d $a0, $a1
diff --git a/llvm/test/MC/LoongArch/lvz/lvz-err.s b/llvm/test/MC/LoongArch/lvz/lvz-err.s
index 64b47a1fca6d5..b4ecb9d605edb 100644
--- a/llvm/test/MC/LoongArch/lvz/lvz-err.s
+++ b/llvm/test/MC/LoongArch/lvz/lvz-err.s
@@ -19,10 +19,10 @@ gcsrxchg $a0, $a1, -1
# CHECK: :[[#@LINE-1]]:20: error: immediate must be an integer in the range [0, 16383]
gcsrxchg $a0, $ra, 1
-# CHECK: :[[#@LINE-1]]:16: error: must not be $r0 or $r1
+# CHECK: :[[#@LINE-1]]:16: error: invalid operand for instruction
gcsrxchg $a0, $zero, 1
-# CHECK: :[[#@LINE-1]]:16: error: must not be $r0 or $r1
+# CHECK: :[[#@LINE-1]]:16: error: invalid operand for instruction
hvcl 32768
# CHECK: :[[#@LINE-1]]:6: error: immediate must be an integer in the range [0, 32767]
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