[cheriot] CSetBoundsRoundDown instruction and intrinsic

Author: nwf

clang/include/clang/Basic/Builtins.def

@@ -1688,6 +1688,7 @@ BUILTIN(__builtin_cheri_address_set, "v*mvC*mz", "nct")
 BUILTIN(__builtin_cheri_base_get, "zvC*m", "nct")
 BUILTIN(__builtin_cheri_bounds_set, "v*mvC*mz", "nct")
 BUILTIN(__builtin_cheri_bounds_set_exact, "v*mvC*mz", "nct")
+BUILTIN(__builtin_cheri_bounds_set_round_down, "v*mvC*mz", "nct")
 BUILTIN(__builtin_cheri_equal_exact, "bvC*mvC*m", "nct")
 BUILTIN(__builtin_cheri_flags_set, "v*mvC*mz", "nct")
 BUILTIN(__builtin_cheri_flags_get, "zvC*m", "nct")

clang/lib/CodeGen/CGBuiltin.cpp

@@ -5032,6 +5032,15 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
                                 {SizeTy}, {Cap, Length}),
         Cap->getType()));
   }
+  case Builtin::BI__builtin_cheri_bounds_set_round_down: {
+    Value *Cap = EmitScalarExpr(E->getArg(0));
+    Value *Length = EmitScalarExpr(E->getArg(1));
+    return RValue::get(Builder.CreateBitCast(
+        Builder.CreateIntrinsic(
+            llvm::Intrinsic::cheri_cap_bounds_set_round_down, {SizeTy},
+            {Cap, Length}),
+        Cap->getType()));
+  }
   case Builtin::BI__builtin_cheri_flags_get:
     return RValue::get(
         Builder.CreateIntrinsic(llvm::Intrinsic::cheri_cap_flags_get, {SizeTy},

clang/test/CodeGen/cheri/cheriot-csetboundsrounddown.c

@@ -0,0 +1,12 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --version 2
+// RUN: %clang_cc1 %s -o - "-triple" "riscv32cheriot-unknown-cheriotrtos" "-emit-llvm" "-mframe-pointer=none" "-mcmodel=small" "-target-abi" "cheriot" "-Oz" "-Werror" -std=c2x | FileCheck %s
+
+// CHECK-LABEL: define dso_local ptr addrspace(200) @foo
+// CHECK-SAME: (ptr addrspace(200) noundef readnone [[CAP:%.*]], i32 noundef [[B:%.*]]) local_unnamed_addr addrspace(200) #[[ATTR0:[0-9]+]] {
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    [[TMP0:%.*]] = tail call ptr addrspace(200) @llvm.cheri.cap.bounds.set.round.down.i32(ptr addrspace(200) [[CAP]], i32 [[B]])
+// CHECK-NEXT:    ret ptr addrspace(200) [[TMP0]]
+//
+void *foo(void* cap, int b) {
+    return __builtin_cheri_bounds_set_round_down(cap, b);
+}

llvm/include/llvm/IR/IntrinsicsCHERICap.td

@@ -57,6 +57,10 @@ def int_cheri_cap_bounds_set_exact :
   Intrinsic<[llvm_cap_ty],
             [llvm_cap_ty, llvm_anyint_ty],
             [IntrNoMem, IntrWillReturn]>;
+def int_cheri_cap_bounds_set_round_down :
+  Intrinsic<[llvm_cap_ty],
+            [llvm_cap_ty, llvm_anyint_ty],
+            [IntrNoMem, IntrWillReturn]>;
 def int_cheri_cap_type_get :
   Intrinsic<[llvm_anyint_ty],
             [llvm_cap_ty],

llvm/lib/Target/RISCV/RISCVInstrInfo.cpp

@@ -1494,6 +1494,7 @@ bool RISCVInstrInfo::isSetBoundsInstr(const MachineInstr &I,
   case RISCV::CSetBounds:
   case RISCV::CSetBoundsExact:
   case RISCV::CSetBoundsImm:
+  case RISCV::CSetBoundsRoundDown:
     Base = &I.getOperand(1);
     Size = &I.getOperand(2);
     return true;

llvm/lib/Target/RISCV/RISCVInstrInfoXCheri.td

@@ -414,6 +414,7 @@ let mayTrap = 1 in {
 def CSetBounds      : Cheri_rr<0x8, "csetbounds">;
 def CSetBoundsExact : Cheri_rr<0x9, "csetboundsexact">;
 def CSetBoundsImm   : Cheri_ri<0x2, "csetbounds", 0>;
+def CSetBoundsRoundDown : Cheri_rr<0xA, "csetboundsrounddown">;
 } // mayTrap = 1
 } // let Constraints = "@traps_if_sealed $rs1"
 def CClearTag       : Cheri_r<0xb, "ccleartag", GPCR>;
@@ -1306,6 +1307,7 @@ def : PatGpcrGpr<cptradd, CIncOffset>;
 def : PatGpcrSimm12<cptradd, CIncOffsetImm>;
 def : PatGpcrGpr<int_cheri_cap_bounds_set, CSetBounds>;
 def : PatGpcrGpr<int_cheri_cap_bounds_set_exact, CSetBoundsExact>;
+def : PatGpcrGpr<int_cheri_cap_bounds_set_round_down, CSetBoundsRoundDown>;
 def : PatGpcrGpr<riscv_cap_bounds_set, CSetBounds>;
 def : PatGpcrUimm12<riscv_cap_bounds_set, CSetBoundsImm>;
 def : PatGpcrUimm12<int_cheri_cap_bounds_set, CSetBoundsImm>;

llvm/test/CodeGen/RISCV/cheri/cheriot-csetboundsrounddown.ll

@@ -0,0 +1,16 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 2
+; RUN: llc --filetype=asm --mcpu=cheriot --mtriple=riscv32cheriot-unknown-cheriotrtos -target-abi cheriot  %s -mattr=+xcheri,+cap-mode -o - | FileCheck %s
+target datalayout = "e-m:e-pf200:64:64:64:32-p:32:32-i64:64-n32-S128-A200-P200-G200"
+target triple = "riscv32cheriot-unknown-cheriotrtos"
+
+define ptr addrspace(200) @foo(ptr addrspace(200) %cap, i32 noundef %b) addrspace(200) {
+; CHECK-LABEL: foo:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    csetboundsrounddown ca0, ca0, a1
+; CHECK-NEXT:    cret
+entry:
+  %0 = tail call ptr addrspace(200) @llvm.cheri.cap.bounds.set.round.down.i32(ptr addrspace(200) %cap, i32 %b)
+  ret ptr addrspace(200) %0
+}
+
+declare ptr addrspace(200) @llvm.cheri.cap.bounds.set.round.down.i32(ptr addrspace(200), i32) addrspace(200)

llvm/test/MC/RISCV/cheri/cheriot.s

@@ -0,0 +1,19 @@
+# RUN: llvm-mc %s -triple=riscv32cheriot -mcpu=cheriot -mattr=+xcheri -riscv-no-aliases -show-encoding \
+# RUN:     | FileCheck %s
+
+csetboundsrounddown cra, cra, zero
+# CHECK: encoding: [0xdb,0x80,0x00,0x14]
+csetboundsrounddown cra, ca5, zero
+# CHECK: encoding: [0xdb,0x80,0x07,0x14]
+csetboundsrounddown cra, cra, a5
+# CHECK: encoding: [0xdb,0x80,0xf0,0x14]
+csetboundsrounddown cra, ca5, a5
+# CHECK: encoding: [0xdb,0x80,0xf7,0x14]
+csetboundsrounddown ca5, cra, zero
+# CHECK: [0xdb,0x87,0x00,0x14]
+csetboundsrounddown ca5, ca5, zero
+# CHECK: [0xdb,0x87,0x07,0x14]
+csetboundsrounddown ca5, cra, a5
+# CHECK: [0xdb,0x87,0xf0,0x14]
+csetboundsrounddown ca5, ca5, a5
+# CHECK: [0xdb,0x87,0xf7,0x14]