From 92b4ffc68856e07efdf9b42de02f88cba000fddd Mon Sep 17 00:00:00 2001 From: Ralf Jung Date: Sun, 3 Dec 2023 14:51:31 +0100 Subject: [PATCH] handle the array case consistently for simd_select_bitmask and simd_bitmask also move the two next to each other --- src/tools/miri/src/shims/intrinsics/simd.rs | 88 +++++++++++---------- 1 file changed, 45 insertions(+), 43 deletions(-) diff --git a/src/tools/miri/src/shims/intrinsics/simd.rs b/src/tools/miri/src/shims/intrinsics/simd.rs index e16d116f621..4d30eebb1af 100644 --- a/src/tools/miri/src/shims/intrinsics/simd.rs +++ b/src/tools/miri/src/shims/intrinsics/simd.rs @@ -405,6 +405,7 @@ enum Op { this.write_immediate(*val, &dest)?; } } + // Variant of `select` that takes a bitmask rather than a "vector of bool". "select_bitmask" => { let [mask, yes, no] = check_arg_count(args)?; let (yes, yes_len) = this.operand_to_simd(yes)?; @@ -412,6 +413,11 @@ enum Op { let (dest, dest_len) = this.place_to_simd(dest)?; let bitmask_len = dest_len.max(8); + // The mask must be an integer or an array. + assert!( + mask.layout.ty.is_integral() + || matches!(mask.layout.ty.kind(), ty::Array(elemty, _) if elemty == &this.tcx.types.u8) + ); assert!(bitmask_len <= 64); assert_eq!(bitmask_len, mask.layout.size.bits()); assert_eq!(dest_len, yes_len); @@ -419,23 +425,15 @@ enum Op { let dest_len = u32::try_from(dest_len).unwrap(); let bitmask_len = u32::try_from(bitmask_len).unwrap(); - // The mask can be a single integer or an array. - let mask: u64 = match mask.layout.ty.kind() { - ty::Int(..) | ty::Uint(..) => - this.read_scalar(mask)?.to_bits(mask.layout.size)?.try_into().unwrap(), - ty::Array(elem, _) if matches!(elem.kind(), ty::Uint(ty::UintTy::U8)) => { - let mask_ty = this.machine.layouts.uint(mask.layout.size).unwrap(); - let mask = mask.transmute(mask_ty, this)?; - this.read_scalar(&mask)?.to_bits(mask_ty.size)?.try_into().unwrap() - } - _ => bug!("simd_select_bitmask: invalid mask type {}", mask.layout.ty), - }; + // To read the mask, we transmute it to an integer. + // That does the right thing wrt endianess. + let mask_ty = this.machine.layouts.uint(mask.layout.size).unwrap(); + let mask = mask.transmute(mask_ty, this)?; + let mask: u64 = this.read_scalar(&mask)?.to_bits(mask_ty.size)?.try_into().unwrap(); for i in 0..dest_len { - let mask = mask - & 1u64 - .checked_shl(simd_bitmask_index(i, dest_len, this.data_layout().endian)) - .unwrap(); + let bit_i = simd_bitmask_index(i, dest_len, this.data_layout().endian); + let mask = mask & 1u64.checked_shl(bit_i).unwrap(); let yes = this.read_immediate(&this.project_index(&yes, i.into())?)?; let no = this.read_immediate(&this.project_index(&no, i.into())?)?; let dest = this.project_index(&dest, i.into())?; @@ -445,6 +443,8 @@ enum Op { } for i in dest_len..bitmask_len { // If the mask is "padded", ensure that padding is all-zero. + // This deliberately does not use `simd_bitmask_index`; these bits are outside + // the bitmask. It does not matter in which order we check them. let mask = mask & 1u64.checked_shl(i).unwrap(); if mask != 0 { throw_ub_format!( @@ -453,6 +453,36 @@ enum Op { } } } + // Converts a "vector of bool" into a bitmask. + "bitmask" => { + let [op] = check_arg_count(args)?; + let (op, op_len) = this.operand_to_simd(op)?; + let bitmask_len = op_len.max(8); + + // Returns either an unsigned integer or array of `u8`. + assert!( + dest.layout.ty.is_integral() + || matches!(dest.layout.ty.kind(), ty::Array(elemty, _) if elemty == &this.tcx.types.u8) + ); + assert!(bitmask_len <= 64); + assert_eq!(bitmask_len, dest.layout.size.bits()); + let op_len = u32::try_from(op_len).unwrap(); + + let mut res = 0u64; + for i in 0..op_len { + let op = this.read_immediate(&this.project_index(&op, i.into())?)?; + if simd_element_to_bool(op)? { + res |= 1u64 + .checked_shl(simd_bitmask_index(i, op_len, this.data_layout().endian)) + .unwrap(); + } + } + // We have to change the type of the place to be able to write `res` into it. This + // transmutes the integer to an array, which does the right thing wrt endianess. + let dest = + dest.transmute(this.machine.layouts.uint(dest.layout.size).unwrap(), this)?; + this.write_int(res, &dest)?; + } "cast" | "as" | "cast_ptr" | "expose_addr" | "from_exposed_addr" => { let [op] = check_arg_count(args)?; let (op, op_len) = this.operand_to_simd(op)?; @@ -635,34 +665,6 @@ enum Op { } } } - "bitmask" => { - let [op] = check_arg_count(args)?; - let (op, op_len) = this.operand_to_simd(op)?; - let bitmask_len = op_len.max(8); - - // Returns either an unsigned integer or array of `u8`. - assert!( - dest.layout.ty.is_integral() - || matches!(dest.layout.ty.kind(), ty::Array(elemty, _) if elemty == &this.tcx.types.u8) - ); - assert!(bitmask_len <= 64); - assert_eq!(bitmask_len, dest.layout.size.bits()); - let op_len = u32::try_from(op_len).unwrap(); - - let mut res = 0u64; - for i in 0..op_len { - let op = this.read_immediate(&this.project_index(&op, i.into())?)?; - if simd_element_to_bool(op)? { - res |= 1u64 - .checked_shl(simd_bitmask_index(i, op_len, this.data_layout().endian)) - .unwrap(); - } - } - // We have to force the place type to be an int so that we can write `res` into it. - let mut dest = this.force_allocation(dest)?; - dest.layout = this.machine.layouts.uint(dest.layout.size).unwrap(); - this.write_int(res, &dest)?; - } name => throw_unsup_format!("unimplemented intrinsic: `simd_{name}`"), }