[llvm] [RISCV] Use LBU for anyext i8 atomic_load. (PR #161588)
Craig Topper via llvm-commits
llvm-commits at lists.llvm.org
Wed Oct 1 14:16:54 PDT 2025
https://github.com/topperc created https://github.com/llvm/llvm-project/pull/161588
This matches what we do for regular i8 extload due to the lack of c.lb in Zbc.
This only affects global isel because SelectionDAG won't create an anyext i8 atomic_load today.
>From 615ae4034d317e586f32e2116fcfa71485a19072 Mon Sep 17 00:00:00 2001
From: Craig Topper <craig.topper at sifive.com>
Date: Wed, 1 Oct 2025 14:06:42 -0700
Subject: [PATCH] [RISCV] Use LBU for anyext i8 atomic_load.
This matches what we do for regular i8 extload due to the lack of
c.lb in Zbc.
This only affects global isel because SelectionDAG won't create
an anyext i8 atomic_load today.
---
llvm/lib/Target/RISCV/RISCVGISel.td | 5 ++-
llvm/lib/Target/RISCV/RISCVInstrInfoA.td | 7 ++--
.../RISCV/GlobalISel/atomic-load-store.ll | 40 +++++++++----------
3 files changed, 27 insertions(+), 25 deletions(-)
diff --git a/llvm/lib/Target/RISCV/RISCVGISel.td b/llvm/lib/Target/RISCV/RISCVGISel.td
index 2e5f30f8fe35a..19d5aff023d53 100644
--- a/llvm/lib/Target/RISCV/RISCVGISel.td
+++ b/llvm/lib/Target/RISCV/RISCVGISel.td
@@ -109,8 +109,9 @@ def : LdPat<extloadi8, LBU, i16>; // Prefer unsigned due to no c.lb in Zcb.
def : StPat<truncstorei8, SB, GPR, i16>;
let Predicates = [HasAtomicLdSt] in {
- def : LdPat<atomic_load_aext_8, LB, i16>;
- def : LdPat<atomic_load_nonext_16, LH, i16>;
+ // Prefer unsigned due to no c.lb in Zcb.
+ def : LdPat<atomic_load_aext_8, LBU, i16>;
+ def : LdPat<atomic_load_nonext_16, LH, i16>;
def : StPat<atomic_store_8, SB, GPR, i16>;
def : StPat<atomic_store_16, SH, GPR, i16>;
diff --git a/llvm/lib/Target/RISCV/RISCVInstrInfoA.td b/llvm/lib/Target/RISCV/RISCVInstrInfoA.td
index 59f5aebf658d8..99992d196b43d 100644
--- a/llvm/lib/Target/RISCV/RISCVInstrInfoA.td
+++ b/llvm/lib/Target/RISCV/RISCVInstrInfoA.td
@@ -165,10 +165,11 @@ class seq_cst_store<PatFrag base>
// any ordering. This is necessary because AtomicExpandPass has added fences to
// atomic load/stores and changed them to unordered ones.
let Predicates = [HasAtomicLdSt] in {
- def : LdPat<relaxed_load<atomic_load_asext_8>, LB>;
+ // Use unsigned for aext due to no c.lb in Zcb.
+ def : LdPat<relaxed_load<atomic_load_sext_8>, LB>;
+ def : LdPat<relaxed_load<atomic_load_azext_8>, LBU>;
def : LdPat<relaxed_load<atomic_load_asext_16>, LH>;
- def : LdPat<relaxed_load<atomic_load_zext_8>, LBU>;
- def : LdPat<relaxed_load<atomic_load_zext_16>, LHU>;
+ def : LdPat<relaxed_load<atomic_load_zext_16>, LHU>;
def : StPat<relaxed_store<atomic_store_8>, SB, GPR, XLenVT>;
def : StPat<relaxed_store<atomic_store_16>, SH, GPR, XLenVT>;
diff --git a/llvm/test/CodeGen/RISCV/GlobalISel/atomic-load-store.ll b/llvm/test/CodeGen/RISCV/GlobalISel/atomic-load-store.ll
index 9a1ed8f115b35..1d5d918422b28 100644
--- a/llvm/test/CodeGen/RISCV/GlobalISel/atomic-load-store.ll
+++ b/llvm/test/CodeGen/RISCV/GlobalISel/atomic-load-store.ll
@@ -37,7 +37,7 @@ define i8 @atomic_load_i8_unordered(ptr %a) nounwind {
;
; RV32IA-LABEL: atomic_load_i8_unordered:
; RV32IA: # %bb.0:
-; RV32IA-NEXT: lb a0, 0(a0)
+; RV32IA-NEXT: lbu a0, 0(a0)
; RV32IA-NEXT: ret
;
; RV64I-LABEL: atomic_load_i8_unordered:
@@ -52,7 +52,7 @@ define i8 @atomic_load_i8_unordered(ptr %a) nounwind {
;
; RV64IA-LABEL: atomic_load_i8_unordered:
; RV64IA: # %bb.0:
-; RV64IA-NEXT: lb a0, 0(a0)
+; RV64IA-NEXT: lbu a0, 0(a0)
; RV64IA-NEXT: ret
%1 = load atomic i8, ptr %a unordered, align 1
ret i8 %1
@@ -71,7 +71,7 @@ define i8 @atomic_load_i8_monotonic(ptr %a) nounwind {
;
; RV32IA-LABEL: atomic_load_i8_monotonic:
; RV32IA: # %bb.0:
-; RV32IA-NEXT: lb a0, 0(a0)
+; RV32IA-NEXT: lbu a0, 0(a0)
; RV32IA-NEXT: ret
;
; RV64I-LABEL: atomic_load_i8_monotonic:
@@ -86,7 +86,7 @@ define i8 @atomic_load_i8_monotonic(ptr %a) nounwind {
;
; RV64IA-LABEL: atomic_load_i8_monotonic:
; RV64IA: # %bb.0:
-; RV64IA-NEXT: lb a0, 0(a0)
+; RV64IA-NEXT: lbu a0, 0(a0)
; RV64IA-NEXT: ret
%1 = load atomic i8, ptr %a monotonic, align 1
ret i8 %1
@@ -105,13 +105,13 @@ define i8 @atomic_load_i8_acquire(ptr %a) nounwind {
;
; RV32IA-WMO-LABEL: atomic_load_i8_acquire:
; RV32IA-WMO: # %bb.0:
-; RV32IA-WMO-NEXT: lb a0, 0(a0)
+; RV32IA-WMO-NEXT: lbu a0, 0(a0)
; RV32IA-WMO-NEXT: fence r, rw
; RV32IA-WMO-NEXT: ret
;
; RV32IA-TSO-LABEL: atomic_load_i8_acquire:
; RV32IA-TSO: # %bb.0:
-; RV32IA-TSO-NEXT: lb a0, 0(a0)
+; RV32IA-TSO-NEXT: lbu a0, 0(a0)
; RV32IA-TSO-NEXT: ret
;
; RV64I-LABEL: atomic_load_i8_acquire:
@@ -126,35 +126,35 @@ define i8 @atomic_load_i8_acquire(ptr %a) nounwind {
;
; RV64IA-WMO-LABEL: atomic_load_i8_acquire:
; RV64IA-WMO: # %bb.0:
-; RV64IA-WMO-NEXT: lb a0, 0(a0)
+; RV64IA-WMO-NEXT: lbu a0, 0(a0)
; RV64IA-WMO-NEXT: fence r, rw
; RV64IA-WMO-NEXT: ret
;
; RV64IA-TSO-LABEL: atomic_load_i8_acquire:
; RV64IA-TSO: # %bb.0:
-; RV64IA-TSO-NEXT: lb a0, 0(a0)
+; RV64IA-TSO-NEXT: lbu a0, 0(a0)
; RV64IA-TSO-NEXT: ret
;
; RV32IA-WMO-TRAILING-FENCE-LABEL: atomic_load_i8_acquire:
; RV32IA-WMO-TRAILING-FENCE: # %bb.0:
-; RV32IA-WMO-TRAILING-FENCE-NEXT: lb a0, 0(a0)
+; RV32IA-WMO-TRAILING-FENCE-NEXT: lbu a0, 0(a0)
; RV32IA-WMO-TRAILING-FENCE-NEXT: fence r, rw
; RV32IA-WMO-TRAILING-FENCE-NEXT: ret
;
; RV32IA-TSO-TRAILING-FENCE-LABEL: atomic_load_i8_acquire:
; RV32IA-TSO-TRAILING-FENCE: # %bb.0:
-; RV32IA-TSO-TRAILING-FENCE-NEXT: lb a0, 0(a0)
+; RV32IA-TSO-TRAILING-FENCE-NEXT: lbu a0, 0(a0)
; RV32IA-TSO-TRAILING-FENCE-NEXT: ret
;
; RV64IA-WMO-TRAILING-FENCE-LABEL: atomic_load_i8_acquire:
; RV64IA-WMO-TRAILING-FENCE: # %bb.0:
-; RV64IA-WMO-TRAILING-FENCE-NEXT: lb a0, 0(a0)
+; RV64IA-WMO-TRAILING-FENCE-NEXT: lbu a0, 0(a0)
; RV64IA-WMO-TRAILING-FENCE-NEXT: fence r, rw
; RV64IA-WMO-TRAILING-FENCE-NEXT: ret
;
; RV64IA-TSO-TRAILING-FENCE-LABEL: atomic_load_i8_acquire:
; RV64IA-TSO-TRAILING-FENCE: # %bb.0:
-; RV64IA-TSO-TRAILING-FENCE-NEXT: lb a0, 0(a0)
+; RV64IA-TSO-TRAILING-FENCE-NEXT: lbu a0, 0(a0)
; RV64IA-TSO-TRAILING-FENCE-NEXT: ret
%1 = load atomic i8, ptr %a acquire, align 1
ret i8 %1
@@ -174,14 +174,14 @@ define i8 @atomic_load_i8_seq_cst(ptr %a) nounwind {
; RV32IA-WMO-LABEL: atomic_load_i8_seq_cst:
; RV32IA-WMO: # %bb.0:
; RV32IA-WMO-NEXT: fence rw, rw
-; RV32IA-WMO-NEXT: lb a0, 0(a0)
+; RV32IA-WMO-NEXT: lbu a0, 0(a0)
; RV32IA-WMO-NEXT: fence r, rw
; RV32IA-WMO-NEXT: ret
;
; RV32IA-TSO-LABEL: atomic_load_i8_seq_cst:
; RV32IA-TSO: # %bb.0:
; RV32IA-TSO-NEXT: fence rw, rw
-; RV32IA-TSO-NEXT: lb a0, 0(a0)
+; RV32IA-TSO-NEXT: lbu a0, 0(a0)
; RV32IA-TSO-NEXT: ret
;
; RV64I-LABEL: atomic_load_i8_seq_cst:
@@ -197,40 +197,40 @@ define i8 @atomic_load_i8_seq_cst(ptr %a) nounwind {
; RV64IA-WMO-LABEL: atomic_load_i8_seq_cst:
; RV64IA-WMO: # %bb.0:
; RV64IA-WMO-NEXT: fence rw, rw
-; RV64IA-WMO-NEXT: lb a0, 0(a0)
+; RV64IA-WMO-NEXT: lbu a0, 0(a0)
; RV64IA-WMO-NEXT: fence r, rw
; RV64IA-WMO-NEXT: ret
;
; RV64IA-TSO-LABEL: atomic_load_i8_seq_cst:
; RV64IA-TSO: # %bb.0:
; RV64IA-TSO-NEXT: fence rw, rw
-; RV64IA-TSO-NEXT: lb a0, 0(a0)
+; RV64IA-TSO-NEXT: lbu a0, 0(a0)
; RV64IA-TSO-NEXT: ret
;
; RV32IA-WMO-TRAILING-FENCE-LABEL: atomic_load_i8_seq_cst:
; RV32IA-WMO-TRAILING-FENCE: # %bb.0:
; RV32IA-WMO-TRAILING-FENCE-NEXT: fence rw, rw
-; RV32IA-WMO-TRAILING-FENCE-NEXT: lb a0, 0(a0)
+; RV32IA-WMO-TRAILING-FENCE-NEXT: lbu a0, 0(a0)
; RV32IA-WMO-TRAILING-FENCE-NEXT: fence r, rw
; RV32IA-WMO-TRAILING-FENCE-NEXT: ret
;
; RV32IA-TSO-TRAILING-FENCE-LABEL: atomic_load_i8_seq_cst:
; RV32IA-TSO-TRAILING-FENCE: # %bb.0:
; RV32IA-TSO-TRAILING-FENCE-NEXT: fence rw, rw
-; RV32IA-TSO-TRAILING-FENCE-NEXT: lb a0, 0(a0)
+; RV32IA-TSO-TRAILING-FENCE-NEXT: lbu a0, 0(a0)
; RV32IA-TSO-TRAILING-FENCE-NEXT: ret
;
; RV64IA-WMO-TRAILING-FENCE-LABEL: atomic_load_i8_seq_cst:
; RV64IA-WMO-TRAILING-FENCE: # %bb.0:
; RV64IA-WMO-TRAILING-FENCE-NEXT: fence rw, rw
-; RV64IA-WMO-TRAILING-FENCE-NEXT: lb a0, 0(a0)
+; RV64IA-WMO-TRAILING-FENCE-NEXT: lbu a0, 0(a0)
; RV64IA-WMO-TRAILING-FENCE-NEXT: fence r, rw
; RV64IA-WMO-TRAILING-FENCE-NEXT: ret
;
; RV64IA-TSO-TRAILING-FENCE-LABEL: atomic_load_i8_seq_cst:
; RV64IA-TSO-TRAILING-FENCE: # %bb.0:
; RV64IA-TSO-TRAILING-FENCE-NEXT: fence rw, rw
-; RV64IA-TSO-TRAILING-FENCE-NEXT: lb a0, 0(a0)
+; RV64IA-TSO-TRAILING-FENCE-NEXT: lbu a0, 0(a0)
; RV64IA-TSO-TRAILING-FENCE-NEXT: ret
%1 = load atomic i8, ptr %a seq_cst, align 1
ret i8 %1
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