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[RISCV] Add short forward branch support for lui, qc.li, and qc.e.li #167481

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Merged
hchandel merged 6 commits into from
Nov 12, 2025
Merged

[RISCV] Add short forward branch support for lui, qc.li, and qc.e.li #167481

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d549639
Working changes for SFB + qc.li, qc.e.li, lui
hchandel Nov 7, 2025
6f58db7
[RISCV] Short forward branch support for lui, qc.li, qc.e.li
hchandel Nov 10, 2025
c875268
fixup! Use separate class for qc.li to use correct imm type
hchandel Nov 10, 2025
8dfcec7
fixup! clang format
hchandel Nov 11, 2025
178eea8
fixup! Fix failures and clang-format
hchandel Nov 11, 2025
044c46f
fixup! Address comments
hchandel Nov 12, 2025
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11 changes: 11 additions & 0 deletions llvm/lib/Target/RISCV/RISCVExpandPseudoInsts.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -132,6 +132,9 @@ bool RISCVExpandPseudo::expandMI(MachineBasicBlock &MBB,
case RISCV::PseudoCCMIN:
case RISCV::PseudoCCMINU:
case RISCV::PseudoCCMUL:
case RISCV::PseudoCCLUI:
case RISCV::PseudoCCQCLI:
case RISCV::PseudoCCQCELI:
case RISCV::PseudoCCADDW:
case RISCV::PseudoCCSUBW:
case RISCV::PseudoCCSLL:
Expand Down Expand Up @@ -239,6 +242,9 @@ bool RISCVExpandPseudo::expandCCOp(MachineBasicBlock &MBB,
case RISCV::PseudoCCMAXU: NewOpc = RISCV::MAXU; break;
case RISCV::PseudoCCMINU: NewOpc = RISCV::MINU; break;
case RISCV::PseudoCCMUL: NewOpc = RISCV::MUL; break;
case RISCV::PseudoCCLUI: NewOpc = RISCV::LUI; break;
case RISCV::PseudoCCQCLI: NewOpc = RISCV::QC_LI; break;
case RISCV::PseudoCCQCELI: NewOpc = RISCV::QC_E_LI; break;
case RISCV::PseudoCCADDI: NewOpc = RISCV::ADDI; break;
case RISCV::PseudoCCSLLI: NewOpc = RISCV::SLLI; break;
case RISCV::PseudoCCSRLI: NewOpc = RISCV::SRLI; break;
Expand Down Expand Up @@ -268,6 +274,11 @@ bool RISCVExpandPseudo::expandCCOp(MachineBasicBlock &MBB,
.add(MI.getOperand(5))
.add(MI.getOperand(6))
.add(MI.getOperand(7));
}

else if (NewOpc == RISCV::LUI || NewOpc == RISCV::QC_LI ||
NewOpc == RISCV::QC_E_LI) {
BuildMI(TrueBB, DL, TII->get(NewOpc), DestReg).add(MI.getOperand(5));
} else {
BuildMI(TrueBB, DL, TII->get(NewOpc), DestReg)
.add(MI.getOperand(5))
Expand Down
3 changes: 3 additions & 0 deletions llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
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Expand Up @@ -1704,6 +1704,9 @@ unsigned getPredicatedOpcode(unsigned Opcode) {
case RISCV::MIN: return RISCV::PseudoCCMIN;
case RISCV::MINU: return RISCV::PseudoCCMINU;
case RISCV::MUL: return RISCV::PseudoCCMUL;
case RISCV::LUI: return RISCV::PseudoCCLUI;
case RISCV::QC_LI: return RISCV::PseudoCCQCLI;
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@topperc topperc Nov 11, 2025

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Can we use the same underscores in the Pseudo name? So PseudoCCQC_LI

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@hchandel hchandel Nov 12, 2025

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Done. Please have a look at the latest commit.

case RISCV::QC_E_LI: return RISCV::PseudoCCQCELI;

case RISCV::ADDI: return RISCV::PseudoCCADDI;
case RISCV::SLLI: return RISCV::PseudoCCSLLI;
Expand Down
13 changes: 13 additions & 0 deletions llvm/lib/Target/RISCV/RISCVInstrInfoSFB.td
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Original file line number Diff line number Diff line change
Expand Up @@ -69,6 +69,17 @@ class SFBALU_ri
let Constraints = "$dst = $falsev";
}

class SFBLUI
: Pseudo<(outs GPR:$dst),
(ins GPR:$lhs, GPR:$rhs, cond_code:$cc, GPR:$falsev,
uimm20_lui:$imm), []> {
let hasSideEffects = 0;
let mayLoad = 0;
let mayStore = 0;
let Size = 8;
let Constraints = "$dst = $falsev";
}

class SFBShift_ri
: Pseudo<(outs GPR:$dst),
(ins GPR:$lhs, GPR:$rhs, cond_code:$cc, GPR:$falsev, GPR:$rs1,
Expand Down Expand Up @@ -117,6 +128,8 @@ def PseudoCCANDI : SFBALU_ri;
def PseudoCCORI : SFBALU_ri;
def PseudoCCXORI : SFBALU_ri;

def PseudoCCLUI : SFBLUI;

def PseudoCCSLLI : SFBShift_ri;
def PseudoCCSRLI : SFBShift_ri;
def PseudoCCSRAI : SFBShift_ri;
Expand Down
27 changes: 27 additions & 0 deletions llvm/lib/Target/RISCV/RISCVInstrInfoXqci.td
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Expand Up @@ -817,6 +817,28 @@ class QCIRVInst48EJ<bits<2> func2, string opcodestr>
let Inst{6-0} = 0b0011111;
}

class SFBQCLI
: Pseudo<(outs GPR:$dst),
(ins GPR:$lhs, GPR:$rhs, cond_code:$cc, GPR:$falsev,
simm20_li:$imm), []> {
let hasSideEffects = 0;
let mayLoad = 0;
let mayStore = 0;
let Size = 8;
let Constraints = "$dst = $falsev";
}

class SFBQCELI
: Pseudo<(outs GPR:$dst),
(ins GPR:$lhs, GPR:$rhs, cond_code:$cc, GPR:$falsev,
bare_simm32:$imm), []> {
let hasSideEffects = 0;
let mayLoad = 0;
let mayStore = 0;
let Size = 10;
let Constraints = "$dst = $falsev";
}

//===----------------------------------------------------------------------===//
// Instructions
//===----------------------------------------------------------------------===//
Expand Down Expand Up @@ -1308,6 +1330,11 @@ def PseudoQC_E_SH : PseudoStore<"qc.e.sh">;
def PseudoQC_E_SW : PseudoStore<"qc.e.sw">;
} // Predicates = [HasVendorXqcilo, IsRV32]

let Predicates = [HasShortForwardBranchOpt] in {
def PseudoCCQCLI : SFBQCLI;
def PseudoCCQCELI : SFBQCELI;
}

//===----------------------------------------------------------------------===//
// Code Gen Patterns
//===----------------------------------------------------------------------===//
Expand Down
18 changes: 12 additions & 6 deletions llvm/test/CodeGen/RISCV/select-const.ll
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@lenary lenary Nov 11, 2025

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For other reviewers: We do indeed prefer the new sequences to the previous sequences in this file.

Original file line number Diff line number Diff line change
Expand Up @@ -177,9 +177,11 @@ define float @select_const_fp(i1 zeroext %a) nounwind {
;
; RV32IXQCI-LABEL: select_const_fp:
; RV32IXQCI: # %bb.0:
; RV32IXQCI-NEXT: lui a2, 263168
; RV32IXQCI-NEXT: lui a1, 264192
; RV32IXQCI-NEXT: qc.mvnei a1, a0, 0, a2
; RV32IXQCI-NEXT: beqz a0, .LBB4_2
; RV32IXQCI-NEXT: # %bb.1:
; RV32IXQCI-NEXT: lui a1, 263168
; RV32IXQCI-NEXT: .LBB4_2:
; RV32IXQCI-NEXT: mv a0, a1
; RV32IXQCI-NEXT: ret
;
Expand Down Expand Up @@ -653,9 +655,11 @@ define i32 @select_nonnegative_lui_addi(i32 signext %x) {
;
; RV32IXQCI-LABEL: select_nonnegative_lui_addi:
; RV32IXQCI: # %bb.0:
; RV32IXQCI-NEXT: lui a2, 4
; RV32IXQCI-NEXT: li a1, 25
; RV32IXQCI-NEXT: qc.mvgei a1, a0, 0, a2
; RV32IXQCI-NEXT: bltz a0, .LBB21_2
; RV32IXQCI-NEXT: # %bb.1:
; RV32IXQCI-NEXT: lui a1, 4
; RV32IXQCI-NEXT: .LBB21_2:
; RV32IXQCI-NEXT: mv a0, a1
; RV32IXQCI-NEXT: ret
;
Expand Down Expand Up @@ -724,9 +728,11 @@ define i32 @select_nonnegative_lui_addi_swapped(i32 signext %x) {
;
; RV32IXQCI-LABEL: select_nonnegative_lui_addi_swapped:
; RV32IXQCI: # %bb.0:
; RV32IXQCI-NEXT: li a2, 25
; RV32IXQCI-NEXT: li a1, 25
; RV32IXQCI-NEXT: bgez a0, .LBB22_2
; RV32IXQCI-NEXT: # %bb.1:
; RV32IXQCI-NEXT: lui a1, 4
; RV32IXQCI-NEXT: qc.mvgei a1, a0, 0, a2
; RV32IXQCI-NEXT: .LBB22_2:
; RV32IXQCI-NEXT: mv a0, a1
; RV32IXQCI-NEXT: ret
;
Expand Down
139 changes: 139 additions & 0 deletions llvm/test/CodeGen/RISCV/short-forward-branch-load-imm.ll
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@@ -0,0 +1,139 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 6
; RUN: llc < %s -verify-machineinstrs -mtriple=riscv32 -mattr=+experimental-xqcili | FileCheck %s --check-prefixes=RV32I
; RUN: llc < %s -verify-machineinstrs -mtriple=riscv64 | FileCheck %s --check-prefixes=RV64I
; RUN: llc < %s -verify-machineinstrs -mtriple=riscv32 -mattr=+experimental-xqcili,+short-forward-branch-opt | \
; RUN: FileCheck %s --check-prefixes=RV32I-SFB
; RUN: llc < %s -verify-machineinstrs -mtriple=riscv64 -mattr=+short-forward-branch-opt | \
; RUN: FileCheck %s --check-prefixes=RV64I-SFB

define i32 @select_example_1(i32 %a, i32 %b, i1 zeroext %x, i32 %y) {
; RV32I-LABEL: select_example_1:
; RV32I: # %bb.0: # %entry
; RV32I-NEXT: lui a0, 16
; RV32I-NEXT: bnez a2, .LBB0_2
; RV32I-NEXT: # %bb.1: # %entry
; RV32I-NEXT: mv a0, a1
; RV32I-NEXT: .LBB0_2: # %entry
; RV32I-NEXT: ret
;
; RV64I-LABEL: select_example_1:
; RV64I: # %bb.0: # %entry
; RV64I-NEXT: lui a0, 16
; RV64I-NEXT: bnez a2, .LBB0_2
; RV64I-NEXT: # %bb.1: # %entry
; RV64I-NEXT: mv a0, a1
; RV64I-NEXT: .LBB0_2: # %entry
; RV64I-NEXT: ret
;
; RV32I-SFB-LABEL: select_example_1:
; RV32I-SFB: # %bb.0: # %entry
; RV32I-SFB-NEXT: mv a0, a1
; RV32I-SFB-NEXT: beqz a2, .LBB0_2
; RV32I-SFB-NEXT: # %bb.1: # %entry
; RV32I-SFB-NEXT: lui a0, 16
; RV32I-SFB-NEXT: .LBB0_2: # %entry
; RV32I-SFB-NEXT: ret
;
; RV64I-SFB-LABEL: select_example_1:
; RV64I-SFB: # %bb.0: # %entry
; RV64I-SFB-NEXT: mv a0, a1
; RV64I-SFB-NEXT: beqz a2, .LBB0_2
; RV64I-SFB-NEXT: # %bb.1: # %entry
; RV64I-SFB-NEXT: lui a0, 16
; RV64I-SFB-NEXT: .LBB0_2: # %entry
; RV64I-SFB-NEXT: ret
entry:
%sel = select i1 %x, i32 65536, i32 %b
ret i32 %sel
}

define i32 @select_example_2(i32 %a, i32 %b, i1 zeroext %x, i32 %y) {
; RV32I-LABEL: select_example_2:
; RV32I: # %bb.0: # %entry
; RV32I-NEXT: bnez a2, .LBB1_2
; RV32I-NEXT: # %bb.1: # %entry
; RV32I-NEXT: mv a0, a1
; RV32I-NEXT: ret
; RV32I-NEXT: .LBB1_2:
; RV32I-NEXT: qc.li a0, 65543
; RV32I-NEXT: ret
;
; RV64I-LABEL: select_example_2:
; RV64I: # %bb.0: # %entry
; RV64I-NEXT: bnez a2, .LBB1_2
; RV64I-NEXT: # %bb.1: # %entry
; RV64I-NEXT: mv a0, a1
; RV64I-NEXT: ret
; RV64I-NEXT: .LBB1_2:
; RV64I-NEXT: lui a0, 16
; RV64I-NEXT: addi a0, a0, 7
; RV64I-NEXT: ret
;
; RV32I-SFB-LABEL: select_example_2:
; RV32I-SFB: # %bb.0: # %entry
; RV32I-SFB-NEXT: mv a0, a1
; RV32I-SFB-NEXT: beqz a2, .LBB1_2
; RV32I-SFB-NEXT: # %bb.1: # %entry
; RV32I-SFB-NEXT: qc.li a0, 65543
; RV32I-SFB-NEXT: .LBB1_2: # %entry
; RV32I-SFB-NEXT: ret
;
; RV64I-SFB-LABEL: select_example_2:
; RV64I-SFB: # %bb.0: # %entry
; RV64I-SFB-NEXT: mv a0, a1
; RV64I-SFB-NEXT: lui a1, 16
; RV64I-SFB-NEXT: beqz a2, .LBB1_2
; RV64I-SFB-NEXT: # %bb.1: # %entry
; RV64I-SFB-NEXT: addi a0, a1, 7
; RV64I-SFB-NEXT: .LBB1_2: # %entry
; RV64I-SFB-NEXT: ret
entry:
%sel = select i1 %x, i32 65543, i32 %b
ret i32 %sel
}

define i32 @select_example_3(i32 %a, i32 %b, i1 zeroext %x, i32 %y) {
; RV32I-LABEL: select_example_3:
; RV32I: # %bb.0: # %entry
; RV32I-NEXT: bnez a2, .LBB2_2
; RV32I-NEXT: # %bb.1: # %entry
; RV32I-NEXT: mv a0, a1
; RV32I-NEXT: ret
; RV32I-NEXT: .LBB2_2:
; RV32I-NEXT: qc.e.li a0, 4198928
; RV32I-NEXT: ret
;
; RV64I-LABEL: select_example_3:
; RV64I: # %bb.0: # %entry
; RV64I-NEXT: bnez a2, .LBB2_2
; RV64I-NEXT: # %bb.1: # %entry
; RV64I-NEXT: mv a0, a1
; RV64I-NEXT: ret
; RV64I-NEXT: .LBB2_2:
; RV64I-NEXT: lui a0, 1025
; RV64I-NEXT: addi a0, a0, 528
; RV64I-NEXT: ret
;
; RV32I-SFB-LABEL: select_example_3:
; RV32I-SFB: # %bb.0: # %entry
; RV32I-SFB-NEXT: mv a0, a1
; RV32I-SFB-NEXT: beqz a2, .LBB2_2
; RV32I-SFB-NEXT: # %bb.1: # %entry
; RV32I-SFB-NEXT: qc.e.li a0, 4198928
; RV32I-SFB-NEXT: .LBB2_2: # %entry
; RV32I-SFB-NEXT: ret
;
; RV64I-SFB-LABEL: select_example_3:
; RV64I-SFB: # %bb.0: # %entry
; RV64I-SFB-NEXT: mv a0, a1
; RV64I-SFB-NEXT: lui a1, 1025
; RV64I-SFB-NEXT: beqz a2, .LBB2_2
; RV64I-SFB-NEXT: # %bb.1: # %entry
; RV64I-SFB-NEXT: addi a0, a1, 528
; RV64I-SFB-NEXT: .LBB2_2: # %entry
; RV64I-SFB-NEXT: ret
entry:
%sel = select i1 %x, i32 4198928, i32 %b
ret i32 %sel
}

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