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[RISCV] Use default promotion for i32 CTLZ_ZERO_UNDEF on RV64 with XTHeadBb. #157955

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Merged
merged 1 commit into from
Sep 10, 2025
Merged

[RISCV] Use default promotion for i32 CTLZ_ZERO_UNDEF on RV64 with XTHeadBb. #157955

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8 changes: 6 additions & 2 deletions llvm/lib/Target/RISCV/RISCVISelLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -421,8 +421,12 @@ RISCVTargetLowering::RISCVTargetLowering(const TargetMachine &TM,
(Subtarget.hasVendorXCVbitmanip() && !Subtarget.is64Bit())) {
// We need the custom lowering to make sure that the resulting sequence
// for the 32bit case is efficient on 64bit targets.
if (Subtarget.is64Bit())
setOperationAction({ISD::CTLZ, ISD::CTLZ_ZERO_UNDEF}, MVT::i32, Custom);
if (Subtarget.is64Bit()) {
setOperationAction(ISD::CTLZ, MVT::i32, Custom);
// Use default promotion for XTHeadBb.
if (Subtarget.hasStdExtZbb())
setOperationAction(ISD::CTLZ_ZERO_UNDEF, MVT::i32, Custom);
}
} else {
setOperationAction(ISD::CTLZ, XLenVT, Expand);
}
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3 changes: 1 addition & 2 deletions llvm/test/CodeGen/RISCV/ctlz-cttz-ctpop.ll
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Expand Up @@ -2004,9 +2004,8 @@ define i32 @test_ctlz_i32_zero_undef(i32 %a) nounwind {
;
; RV64XTHEADBB-LABEL: test_ctlz_i32_zero_undef:
; RV64XTHEADBB: # %bb.0:
; RV64XTHEADBB-NEXT: not a0, a0
; RV64XTHEADBB-NEXT: slli a0, a0, 32
; RV64XTHEADBB-NEXT: th.ff0 a0, a0
; RV64XTHEADBB-NEXT: th.ff1 a0, a0
; RV64XTHEADBB-NEXT: ret
%tmp = call i32 @llvm.ctlz.i32(i32 %a, i1 true)
ret i32 %tmp
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5 changes: 2 additions & 3 deletions llvm/test/CodeGen/RISCV/rv64xtheadbb.ll
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Expand Up @@ -240,10 +240,9 @@ define signext i32 @findLastSet_i32(i32 signext %a) nounwind {
;
; RV64XTHEADBB-NOB-LABEL: findLastSet_i32:
; RV64XTHEADBB-NOB: # %bb.0:
; RV64XTHEADBB-NOB-NEXT: not a1, a0
; RV64XTHEADBB-NOB-NEXT: slli a1, a0, 32
; RV64XTHEADBB-NOB-NEXT: snez a0, a0
; RV64XTHEADBB-NOB-NEXT: slli a1, a1, 32
; RV64XTHEADBB-NOB-NEXT: th.ff0 a1, a1
; RV64XTHEADBB-NOB-NEXT: th.ff1 a1, a1
; RV64XTHEADBB-NOB-NEXT: xori a1, a1, 31
; RV64XTHEADBB-NOB-NEXT: addi a0, a0, -1
; RV64XTHEADBB-NOB-NEXT: or a0, a0, a1
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