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[CHERIoT] Fold csetboundsexact to csetboundsimm when the bounds is a constant less than 512. #149

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Merged
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May 26, 2025
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[CHERIoT] Fold csetboundsexact to csetboundsimm when the bounds is a constant less than 512. #149

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8 changes: 8 additions & 0 deletions llvm/lib/Target/RISCV/RISCVInstrInfoXCheri.td
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Original file line number Diff line number Diff line change
Expand Up @@ -1450,6 +1450,14 @@ def : PatGpcrGpcr<int_cheri_cap_type_copy, CCopyType>;
def : PatGpcrGpcr<int_cheri_cap_conditional_seal, CCSeal>;
def : PatGpcr<int_cheri_cap_seal_entry, CSealEntry, CLenVT>;

def uimm12_lt512 : Operand<XLenVT>,
ImmLeaf<XLenVT, "return isUInt<12>(Imm) && (Imm < 512);">;

let Predicates =
[HasCheriot] in def : Pat<(int_cheri_cap_bounds_set_exact GPCR:$rs1,
uimm12_lt512:$imm12),
(CSetBoundsImm GPCR:$rs1, uimm12_lt512:$imm12)>;

// TODO: Make this rematerialisable like MIPS
def : PatGpcrGpr<int_cheri_bounded_stack_cap, CSetBounds>;
def : PatGpcrUimm12<int_cheri_bounded_stack_cap, CSetBoundsImm>;
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32 changes: 32 additions & 0 deletions llvm/test/CodeGen/RISCV/cheri/cheriot-csetboundsexact.ll
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@@ -0,0 +1,32 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
; RUN: llc -mtriple=riscv32cheriot --mcpu=cheriot -target-abi=cheriot -mattr=+xcheri,+cap-mode,+xcheriot -o - %s | FileCheck %s

define i8 addrspace(200)* @test1(i8 addrspace(200)* %cap, i32 %bounds) nounwind {
; CHECK-LABEL: test1:
; CHECK: # %bb.0:
; CHECK-NEXT: ct.csetbounds ca0, ca0, 3
; CHECK-NEXT: ct.cret
%newcap = call i8 addrspace(200)* @llvm.cheri.cap.bounds.set.exact.i32(i8 addrspace(200)* %cap, i32 3)
ret i8 addrspace(200)* %newcap
}

define i8 addrspace(200)* @test2(i8 addrspace(200)* %cap, i32 %bounds) nounwind {
; CHECK-LABEL: test2:
; CHECK: # %bb.0:
; CHECK-NEXT: ct.csetbounds ca0, ca0, 511
; CHECK-NEXT: ct.cret
%newcap = call i8 addrspace(200)* @llvm.cheri.cap.bounds.set.exact.i32(i8 addrspace(200)* %cap, i32 511)
ret i8 addrspace(200)* %newcap
}

define i8 addrspace(200)* @test3(i8 addrspace(200)* %cap, i32 %bounds) nounwind {
; CHECK-LABEL: test3:
; CHECK: # %bb.0:
; CHECK-NEXT: li a1, 512
; CHECK-NEXT: ct.csetboundsexact ca0, ca0, a1
; CHECK-NEXT: ct.cret
%newcap = call i8 addrspace(200)* @llvm.cheri.cap.bounds.set.exact.i32(i8 addrspace(200)* %cap, i32 512)
ret i8 addrspace(200)* %newcap
}

declare i8 addrspace(200)* @llvm.cheri.cap.bounds.set.exact.i32(i8 addrspace(200)*, i32)