[llvm] bd8578c - [LoongArch] Prevent R0/R1 allocation for rj operand of [G]CSRXCHG (#140862)
via llvm-commits
llvm-commits at lists.llvm.org
Thu May 22 03:49:31 PDT 2025
Author: hev
Date: 2025-05-22T18:49:27+08:00
New Revision: bd8578c3574d77bc1231f047bced4a0053a1b000
URL: https://github.com/llvm/llvm-project/commit/bd8578c3574d77bc1231f047bced4a0053a1b000
DIFF: https://github.com/llvm/llvm-project/commit/bd8578c3574d77bc1231f047bced4a0053a1b000.diff
LOG: [LoongArch] Prevent R0/R1 allocation for rj operand of [G]CSRXCHG (#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
Added:
llvm/test/CodeGen/LoongArch/csrxchg-intrinsic.ll
Modified:
llvm/lib/Target/LoongArch/AsmParser/LoongArchAsmParser.cpp
llvm/lib/Target/LoongArch/Disassembler/LoongArchDisassembler.cpp
llvm/lib/Target/LoongArch/LoongArchInstrInfo.td
llvm/lib/Target/LoongArch/LoongArchLVZInstrInfo.td
llvm/lib/Target/LoongArch/LoongArchRegisterInfo.td
Removed:
################################################################################
diff --git a/llvm/lib/Target/LoongArch/AsmParser/LoongArchAsmParser.cpp b/llvm/lib/Target/LoongArch/AsmParser/LoongArchAsmParser.cpp
index 39c5e034f2a48..81e8c3657d5c3 100644
--- a/llvm/lib/Target/LoongArch/AsmParser/LoongArchAsmParser.cpp
+++ b/llvm/lib/Target/LoongArch/AsmParser/LoongArchAsmParser.cpp
@@ -1633,6 +1633,9 @@ LoongArchAsmParser::validateTargetOperandClass(MCParsedAsmOperand &AsmOp,
return Match_Success;
}
+ if (Kind == MCK_GPRNoR0R1 && (Reg == LoongArch::R0 || Reg == LoongArch::R1))
+ return Match_RequiresOpnd2NotR0R1;
+
return Match_InvalidOperand;
}
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 371906065957d..fcdd9a130d8b6 100644
--- a/llvm/lib/Target/LoongArch/LoongArchInstrInfo.td
+++ b/llvm/lib/Target/LoongArch/LoongArchInstrInfo.td
@@ -2445,7 +2445,7 @@ 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 = $dst"
@@ -2492,8 +2492,8 @@ def IDLE : MISC_I15<0x06488000>;
def : Pat<(loongarch_csrrd uimm14:$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..2a8cdf953e00f 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
+}
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