[llvm] [RISCV] Efficiently lower (select cond, y, rot[r/l](u, rot.amt)) using zicond extension (PR #143768)
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Wed Jun 11 12:16:03 PDT 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-backend-risc-v
Author: Ryan Buchner (bababuck)
<details>
<summary>Changes</summary>
The following lowerings now occur:
(select cond, u, rotr(u, rot.amt)) -> (rotr u, (czero_nez rot.amt, cond))
(select cond, rotr(u, rot.amt), u) -> (rotr u, (czero_eqz rot.amt, cond))
(select cond, u, rotl(u, rot.amt)) -> (rotl u, (czero_nez rot.amt, cond))
(select cond, rotl(u, rot.amt), u) -> (rotl u, (czero_eqz rot.amt, cond))
Contains the test commit from #<!-- -->143580 temporarily as that is not yet merged,
@<!-- -->mgudim
---
Full diff: https://github.com/llvm/llvm-project/pull/143768.diff
2 Files Affected:
- (modified) llvm/lib/Target/RISCV/RISCVISelLowering.cpp (+4)
- (added) llvm/test/CodeGen/RISCV/zicond-opts.ll (+275)
``````````diff
diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
index ab8b36df44d3f..eb04ff9588b92 100644
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -18104,6 +18104,8 @@ static bool combine_CC(SDValue &LHS, SDValue &RHS, SDValue &CC, const SDLoc &DL,
// (select C, (sub Y, X), Y) -> (sub Y, (select C, X, 0)).
// (select C, (or Y, X), Y) -> (or Y, (select C, X, 0)).
// (select C, (xor Y, X), Y) -> (xor Y, (select C, X, 0)).
+// (select C, (rotl Y, X), Y) -> (rotl Y, (select C, X, 0)).
+// (select C, (rotr Y, X), Y) -> (rotr Y, (select C, X, 0)).
static SDValue tryFoldSelectIntoOp(SDNode *N, SelectionDAG &DAG,
SDValue TrueVal, SDValue FalseVal,
bool Swapped) {
@@ -18116,6 +18118,8 @@ static SDValue tryFoldSelectIntoOp(SDNode *N, SelectionDAG &DAG,
case ISD::SRA:
case ISD::SRL:
case ISD::SUB:
+ case ISD::ROTL:
+ case ISD::ROTR:
Commutative = false;
break;
case ISD::ADD:
diff --git a/llvm/test/CodeGen/RISCV/zicond-opts.ll b/llvm/test/CodeGen/RISCV/zicond-opts.ll
new file mode 100644
index 0000000000000..3efb594e4b882
--- /dev/null
+++ b/llvm/test/CodeGen/RISCV/zicond-opts.ll
@@ -0,0 +1,275 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc -mtriple=riscv32 -O2 -verify-machineinstrs -mattr=+b,+zicond < %s | FileCheck %s -check-prefix=RV32ZICOND
+; RUN: llc -mtriple=riscv64 -O2 -verify-machineinstrs -mattr=+b,+zicond < %s | FileCheck %s -check-prefix=RV64ZICOND
+
+; (and (icmp x. 0, ne), (icmp y, 0, ne)) -> (czero.eqz (icmp x, 0, ne), y)
+define i32 @icmp_and(i64 %x, i64 %y) {
+; RV32ZICOND-LABEL: icmp_and:
+; RV32ZICOND: # %bb.0:
+; RV32ZICOND-NEXT: or a2, a2, a3
+; RV32ZICOND-NEXT: or a0, a0, a1
+; RV32ZICOND-NEXT: snez a1, a2
+; RV32ZICOND-NEXT: snez a0, a0
+; RV32ZICOND-NEXT: and a0, a0, a1
+; RV32ZICOND-NEXT: ret
+;
+; RV64ZICOND-LABEL: icmp_and:
+; RV64ZICOND: # %bb.0:
+; RV64ZICOND-NEXT: snez a1, a1
+; RV64ZICOND-NEXT: snez a0, a0
+; RV64ZICOND-NEXT: and a0, a0, a1
+; RV64ZICOND-NEXT: ret
+ %3 = icmp ne i64 %y, 0
+ %4 = icmp ne i64 %x, 0
+ %5 = and i1 %4, %3
+ %6 = zext i1 %5 to i32
+ ret i32 %6
+}
+
+; (and (and (icmp x, 0, ne), (icmp y, 0, ne)), (icmp z, 0, ne)) -> (czero.eqz (czero.eqz (icmp x, 0, ne), y), z)
+define i32 @icmp_and_and(i64 %x, i64 %y, i64 %z) {
+; RV32ZICOND-LABEL: icmp_and_and:
+; RV32ZICOND: # %bb.0:
+; RV32ZICOND-NEXT: or a2, a2, a3
+; RV32ZICOND-NEXT: or a0, a0, a1
+; RV32ZICOND-NEXT: or a4, a4, a5
+; RV32ZICOND-NEXT: snez a1, a2
+; RV32ZICOND-NEXT: snez a0, a0
+; RV32ZICOND-NEXT: and a0, a1, a0
+; RV32ZICOND-NEXT: snez a1, a4
+; RV32ZICOND-NEXT: and a0, a1, a0
+; RV32ZICOND-NEXT: ret
+;
+; RV64ZICOND-LABEL: icmp_and_and:
+; RV64ZICOND: # %bb.0:
+; RV64ZICOND-NEXT: snez a1, a1
+; RV64ZICOND-NEXT: snez a0, a0
+; RV64ZICOND-NEXT: and a0, a1, a0
+; RV64ZICOND-NEXT: snez a1, a2
+; RV64ZICOND-NEXT: and a0, a1, a0
+; RV64ZICOND-NEXT: ret
+ %4 = icmp ne i64 %y, 0
+ %5 = icmp ne i64 %x, 0
+ %6 = and i1 %4, %5
+ %7 = icmp ne i64 %z, 0
+ %8 = and i1 %7, %6
+ %9 = zext i1 %8 to i32
+ ret i32 %9
+}
+
+; (select cond, x, rotl(x, rot.amt)) -> (rotl x, (czero_nez rot.amt, cond))
+define i64 @rotate_l_nez(i64 %x, i64 %rot.amt, i1 %cond) {
+; RV32ZICOND-LABEL: rotate_l_nez:
+; RV32ZICOND: # %bb.0:
+; RV32ZICOND-NEXT: andi a4, a4, 1
+; RV32ZICOND-NEXT: czero.nez a2, a2, a4
+; RV32ZICOND-NEXT: bexti a3, a2, 5
+; RV32ZICOND-NEXT: czero.nez a4, a0, a3
+; RV32ZICOND-NEXT: czero.eqz a5, a1, a3
+; RV32ZICOND-NEXT: czero.nez a1, a1, a3
+; RV32ZICOND-NEXT: czero.eqz a0, a0, a3
+; RV32ZICOND-NEXT: not a3, a2
+; RV32ZICOND-NEXT: or a4, a5, a4
+; RV32ZICOND-NEXT: or a0, a0, a1
+; RV32ZICOND-NEXT: sll a1, a4, a2
+; RV32ZICOND-NEXT: srli a5, a0, 1
+; RV32ZICOND-NEXT: sll a2, a0, a2
+; RV32ZICOND-NEXT: srli a4, a4, 1
+; RV32ZICOND-NEXT: srl a0, a5, a3
+; RV32ZICOND-NEXT: srl a3, a4, a3
+; RV32ZICOND-NEXT: or a0, a1, a0
+; RV32ZICOND-NEXT: or a1, a2, a3
+; RV32ZICOND-NEXT: ret
+;
+; RV64ZICOND-LABEL: rotate_l_nez:
+; RV64ZICOND: # %bb.0:
+; RV64ZICOND-NEXT: andi a2, a2, 1
+; RV64ZICOND-NEXT: czero.nez a1, a1, a2
+; RV64ZICOND-NEXT: rol a0, a0, a1
+; RV64ZICOND-NEXT: ret
+ %6 = call i64 @llvm.fshl.i64(i64 %x, i64 %x, i64 %rot.amt)
+ %7 = select i1 %cond, i64 %x, i64 %6
+ ret i64 %7
+}
+
+; (select cond, rotl(x, rot.amt), x) -> (rotl x, (czero_eqz rot.amt, cond))
+define i64 @rotate_l_eqz(i64 %x, i64 %rot.amt, i1 %cond) {
+; RV32ZICOND-LABEL: rotate_l_eqz:
+; RV32ZICOND: # %bb.0:
+; RV32ZICOND-NEXT: andi a4, a4, 1
+; RV32ZICOND-NEXT: czero.eqz a2, a2, a4
+; RV32ZICOND-NEXT: bexti a3, a2, 5
+; RV32ZICOND-NEXT: czero.nez a4, a0, a3
+; RV32ZICOND-NEXT: czero.eqz a5, a1, a3
+; RV32ZICOND-NEXT: czero.nez a1, a1, a3
+; RV32ZICOND-NEXT: czero.eqz a0, a0, a3
+; RV32ZICOND-NEXT: not a3, a2
+; RV32ZICOND-NEXT: or a4, a5, a4
+; RV32ZICOND-NEXT: or a0, a0, a1
+; RV32ZICOND-NEXT: sll a1, a4, a2
+; RV32ZICOND-NEXT: srli a5, a0, 1
+; RV32ZICOND-NEXT: sll a2, a0, a2
+; RV32ZICOND-NEXT: srli a4, a4, 1
+; RV32ZICOND-NEXT: srl a0, a5, a3
+; RV32ZICOND-NEXT: srl a3, a4, a3
+; RV32ZICOND-NEXT: or a0, a1, a0
+; RV32ZICOND-NEXT: or a1, a2, a3
+; RV32ZICOND-NEXT: ret
+;
+; RV64ZICOND-LABEL: rotate_l_eqz:
+; RV64ZICOND: # %bb.0:
+; RV64ZICOND-NEXT: andi a2, a2, 1
+; RV64ZICOND-NEXT: czero.eqz a1, a1, a2
+; RV64ZICOND-NEXT: rol a0, a0, a1
+; RV64ZICOND-NEXT: ret
+ %6 = call i64 @llvm.fshl.i64(i64 %x, i64 %x, i64 %rot.amt)
+ %7 = select i1 %cond, i64 %6, i64 %x
+ ret i64 %7
+}
+
+; (select cond, const, t) -> (add (czero_nez t - const, cond), const)
+define i64 @select_imm_reg(i64 %t, i1 %cond) {
+; RV32ZICOND-LABEL: select_imm_reg:
+; RV32ZICOND: # %bb.0:
+; RV32ZICOND-NEXT: andi a2, a2, 1
+; RV32ZICOND-NEXT: li a3, 3
+; RV32ZICOND-NEXT: czero.nez a0, a0, a2
+; RV32ZICOND-NEXT: czero.eqz a3, a3, a2
+; RV32ZICOND-NEXT: or a0, a3, a0
+; RV32ZICOND-NEXT: czero.nez a1, a1, a2
+; RV32ZICOND-NEXT: ret
+;
+; RV64ZICOND-LABEL: select_imm_reg:
+; RV64ZICOND: # %bb.0:
+; RV64ZICOND-NEXT: andi a1, a1, 1
+; RV64ZICOND-NEXT: li a2, 3
+; RV64ZICOND-NEXT: czero.nez a0, a0, a1
+; RV64ZICOND-NEXT: czero.eqz a1, a2, a1
+; RV64ZICOND-NEXT: or a0, a1, a0
+; RV64ZICOND-NEXT: ret
+ %4 = select i1 %cond, i64 3, i64 %t
+ ret i64 %4
+}
+
+; (select cond, t, const) -> (add (czero_eqz t - const, cond), const)
+define i64 @select_reg_imm(i64 %t, i1 %cond) {
+; RV32ZICOND-LABEL: select_reg_imm:
+; RV32ZICOND: # %bb.0:
+; RV32ZICOND-NEXT: andi a2, a2, 1
+; RV32ZICOND-NEXT: li a3, 3
+; RV32ZICOND-NEXT: czero.nez a3, a3, a2
+; RV32ZICOND-NEXT: czero.eqz a0, a0, a2
+; RV32ZICOND-NEXT: or a0, a0, a3
+; RV32ZICOND-NEXT: czero.eqz a1, a1, a2
+; RV32ZICOND-NEXT: ret
+;
+; RV64ZICOND-LABEL: select_reg_imm:
+; RV64ZICOND: # %bb.0:
+; RV64ZICOND-NEXT: andi a1, a1, 1
+; RV64ZICOND-NEXT: li a2, 3
+; RV64ZICOND-NEXT: czero.nez a2, a2, a1
+; RV64ZICOND-NEXT: czero.eqz a0, a0, a1
+; RV64ZICOND-NEXT: or a0, a0, a2
+; RV64ZICOND-NEXT: ret
+ %4 = select i1 %cond, i64 %t, i64 3
+ ret i64 %4
+}
+
+; (select cond, -2048, t) -> (xor (czero_nez (xor t, -2048), cond), -2048)
+define i64 @select_imm_reg_neg_2048(i64 %t, i1 %cond) {
+; RV32ZICOND-LABEL: select_imm_reg_neg_2048:
+; RV32ZICOND: # %bb.0:
+; RV32ZICOND-NEXT: andi a2, a2, 1
+; RV32ZICOND-NEXT: li a3, -2048
+; RV32ZICOND-NEXT: czero.nez a0, a0, a2
+; RV32ZICOND-NEXT: czero.eqz a3, a3, a2
+; RV32ZICOND-NEXT: neg a2, a2
+; RV32ZICOND-NEXT: or a0, a3, a0
+; RV32ZICOND-NEXT: or a1, a2, a1
+; RV32ZICOND-NEXT: ret
+;
+; RV64ZICOND-LABEL: select_imm_reg_neg_2048:
+; RV64ZICOND: # %bb.0:
+; RV64ZICOND-NEXT: andi a1, a1, 1
+; RV64ZICOND-NEXT: li a2, -2048
+; RV64ZICOND-NEXT: czero.nez a0, a0, a1
+; RV64ZICOND-NEXT: czero.eqz a1, a2, a1
+; RV64ZICOND-NEXT: or a0, a1, a0
+; RV64ZICOND-NEXT: ret
+ %4 = select i1 %cond, i64 -2048, i64 %t
+ ret i64 %4
+}
+
+; (select cond, 2048, t) -> no transform
+define i64 @select_imm_reg_2048(i64 %t, i1 %cond) {
+; RV32ZICOND-LABEL: select_imm_reg_2048:
+; RV32ZICOND: # %bb.0:
+; RV32ZICOND-NEXT: andi a2, a2, 1
+; RV32ZICOND-NEXT: bseti a3, zero, 11
+; RV32ZICOND-NEXT: czero.nez a0, a0, a2
+; RV32ZICOND-NEXT: czero.eqz a3, a3, a2
+; RV32ZICOND-NEXT: or a0, a3, a0
+; RV32ZICOND-NEXT: czero.nez a1, a1, a2
+; RV32ZICOND-NEXT: ret
+;
+; RV64ZICOND-LABEL: select_imm_reg_2048:
+; RV64ZICOND: # %bb.0:
+; RV64ZICOND-NEXT: andi a1, a1, 1
+; RV64ZICOND-NEXT: bseti a2, zero, 11
+; RV64ZICOND-NEXT: czero.nez a0, a0, a1
+; RV64ZICOND-NEXT: czero.eqz a1, a2, a1
+; RV64ZICOND-NEXT: or a0, a1, a0
+; RV64ZICOND-NEXT: ret
+ %4 = select i1 %cond, i64 2048, i64 %t
+ ret i64 %4
+}
+
+; (select cond, (and f, ~x), f) -> (andn f, (czero_eqz x, cond))
+define i64 @test_inv_and_nez(i64 %f, i64 %x, i1 %cond) {
+; RV32ZICOND-LABEL: test_inv_and_nez:
+; RV32ZICOND: # %bb.0:
+; RV32ZICOND-NEXT: andi a4, a4, 1
+; RV32ZICOND-NEXT: addi a4, a4, -1
+; RV32ZICOND-NEXT: orn a3, a4, a3
+; RV32ZICOND-NEXT: orn a2, a4, a2
+; RV32ZICOND-NEXT: and a0, a2, a0
+; RV32ZICOND-NEXT: and a1, a3, a1
+; RV32ZICOND-NEXT: ret
+;
+; RV64ZICOND-LABEL: test_inv_and_nez:
+; RV64ZICOND: # %bb.0:
+; RV64ZICOND-NEXT: andi a2, a2, 1
+; RV64ZICOND-NEXT: andn a1, a0, a1
+; RV64ZICOND-NEXT: czero.nez a0, a0, a2
+; RV64ZICOND-NEXT: or a0, a1, a0
+; RV64ZICOND-NEXT: ret
+ %5 = xor i64 %x, -1
+ %6 = select i1 %cond, i64 %5, i64 -1
+ %7 = and i64 %6, %f
+ ret i64 %7
+}
+
+; (select cond, f, (and f, ~x)) -> (andn f, (czero_nez x, cond))
+define i64 @test_inv_and_eqz(i64 %f, i64 %x, i1 %cond) {
+; RV32ZICOND-LABEL: test_inv_and_eqz:
+; RV32ZICOND: # %bb.0:
+; RV32ZICOND-NEXT: slli a4, a4, 31
+; RV32ZICOND-NEXT: srai a4, a4, 31
+; RV32ZICOND-NEXT: orn a3, a4, a3
+; RV32ZICOND-NEXT: orn a2, a4, a2
+; RV32ZICOND-NEXT: and a0, a2, a0
+; RV32ZICOND-NEXT: and a1, a3, a1
+; RV32ZICOND-NEXT: ret
+;
+; RV64ZICOND-LABEL: test_inv_and_eqz:
+; RV64ZICOND: # %bb.0:
+; RV64ZICOND-NEXT: andi a2, a2, 1
+; RV64ZICOND-NEXT: andn a1, a0, a1
+; RV64ZICOND-NEXT: czero.eqz a0, a0, a2
+; RV64ZICOND-NEXT: or a0, a1, a0
+; RV64ZICOND-NEXT: ret
+ %5 = xor i64 %x, -1
+ %6 = select i1 %cond, i64 -1, i64 %5
+ %7 = and i64 %6, %f
+ ret i64 %7
+}
``````````
</details>
https://github.com/llvm/llvm-project/pull/143768
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