cranelift: port sshr to ISLE on x64

cranelift/codegen/src/isa/aarch64/lower/isle/generated_code.manifest

@@ -1,4 +1,4 @@
 src/clif.isle f176ef3bba99365
-src/prelude.isle babc931e5dc5b4cf
+src/prelude.isle e5e437b1aed2a1e1
 src/isa/aarch64/inst.isle 5fa80451697b084f
 src/isa/aarch64/lower.isle 2d2e1e076a0c8a23

cranelift/codegen/src/isa/x64/inst.isle

@@ -35,6 +35,7 @@
                        (dst WritableReg)
                        (imm u8)
                        (size OperandSize))
+            (XmmUninitializedValue (dst WritableReg))
             (CmpRmiR (size OperandSize)
                      (opcode CmpOpcode)
                      (src RegMemImm)
@@ -292,6 +293,15 @@
        (Mem (addr SyntheticAmode))
        (Imm (simm32 u32))))
 
+;; Put the given clif value into a `RegMemImm` operand.
+;;
+;; Asserts that the value fits into a single register, and doesn't require
+;; multiple registers for its representation (like `i128` for example).
+;;
+;; As a side effect, this marks the value as used.
+(decl put_in_reg_mem_imm (Value) RegMemImm)
+(extern constructor put_in_reg_mem_imm put_in_reg_mem_imm)
+
 (type RegMem extern
       (enum
        (Reg (reg Reg))
@@ -319,6 +329,15 @@
       (enum (Imm8 (imm u8))
             (Reg (reg Reg))))
 
+;; Put the given clif value into a `Imm8Reg` operand.
+;;
+;; Asserts that the value fits into a single register, and doesn't require
+;; multiple registers for its representation (like `i128` for example).
+;;
+;; As a side effect, this marks the value as used.
+(decl put_in_imm8_reg (Value) Imm8Reg)
+(extern constructor put_in_imm8_reg put_in_imm8_reg)
+
 (type CC extern
       (enum O
             NO
@@ -494,6 +513,37 @@
                                          wr))))
         r))
 
+;; Helper for creating an SSE register holding an `i64x2` from two `i64` values.
+(decl make_i64x2_from_lanes (RegMem RegMem) Reg)
+(rule (make_i64x2_from_lanes lo hi)
+      (let ((dst_w WritableReg (temp_writable_reg $I64X2))
+            (dst_r Reg (writable_reg_to_reg dst_w))
+            (_0 Unit (emit (MInst.XmmUninitializedValue dst_w)))
+            (_1 Unit (emit (MInst.XmmRmRImm (SseOpcode.Pinsrd)
+                                            dst_r
+                                            lo
+                                            dst_w
+                                            0
+                                            (OperandSize.Size64))))
+            (_2 Unit (emit (MInst.XmmRmRImm (SseOpcode.Pinsrd)
+                                            dst_r
+                                            hi
+                                            dst_w
+                                            1
+                                            (OperandSize.Size64)))))
+        dst_r))
+
+;; Move a `RegMemImm.Reg` operand to an XMM register, if necessary.
+(decl reg_mem_imm_to_xmm (RegMemImm) RegMemImm)
+(rule (reg_mem_imm_to_xmm rmi @ (RegMemImm.Mem _)) rmi)
+(rule (reg_mem_imm_to_xmm rmi @ (RegMemImm.Imm _)) rmi)
+(rule (reg_mem_imm_to_xmm (RegMemImm.Reg r))
+      (RegMemImm.Reg (gpr_to_xmm $I8X16
+                                 (SseOpcode.Movd)
+                                 (RegMem.Reg r)
+                                 (OperandSize.Size32))))
+
+
 ;;;; Instruction Constructors ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;
 ;; These constructors create SSA-style `MInst`s. It is their responsibility to
@@ -1058,6 +1108,21 @@
 (rule (pminud src1 src2)
       (xmm_rm_r $I8X16 (SseOpcode.Pminud) src1 src2))
 
+;; Helper for creating `punpcklbw` instructions.
+(decl punpcklbw (Reg RegMem) Reg)
+(rule (punpcklbw src1 src2)
+      (xmm_rm_r $I8X16 (SseOpcode.Punpcklbw) src1 src2))
+
+;; Helper for creating `punpckhbw` instructions.
+(decl punpckhbw (Reg RegMem) Reg)
+(rule (punpckhbw src1 src2)
+      (xmm_rm_r $I8X16 (SseOpcode.Punpckhbw) src1 src2))
+
+;; Helper for creating `packsswb` instructions.
+(decl packsswb (Reg RegMem) Reg)
+(rule (packsswb src1 src2)
+      (xmm_rm_r $I8X16 (SseOpcode.Packsswb) src1 src2))
+
 ;; Helper for creating `MInst.XmmRmRImm` instructions.
 (decl xmm_rm_r_imm (SseOpcode Reg RegMem u8 OperandSize) Reg)
 (rule (xmm_rm_r_imm op src1 src2 imm size)
@@ -1180,6 +1245,16 @@
 (rule (psrlq src1 src2)
       (xmm_rmi_reg (SseOpcode.Psrlq) src1 src2))
 
+;; Helper for creating `psraw` instructions.
+(decl psraw (Reg RegMemImm) Reg)
+(rule (psraw src1 src2)
+      (xmm_rmi_reg (SseOpcode.Psraw) src1 src2))
+
+;; Helper for creating `psrad` instructions.
+(decl psrad (Reg RegMemImm) Reg)
+(rule (psrad src1 src2)
+      (xmm_rmi_reg (SseOpcode.Psrad) src1 src2))
+
 ;; Helper for creating `MInst.MulHi` instructions.
 ;;
 ;; Returns the (lo, hi) register halves of the multiplication.
@@ -1252,6 +1327,19 @@
 (rule (insertps src1 src2 lane)
       (xmm_rm_r_imm (SseOpcode.Insertps) src1 src2 lane (OperandSize.Size32)))
 
+;; Helper for creating `pextrd` instructions.
+(decl pextrd (Type Reg u8) Reg)
+(rule (pextrd ty src lane)
+      (let ((w_dst WritableReg (temp_writable_reg ty))
+            (r_dst Reg (writable_reg_to_reg w_dst))
+            (_ Unit (emit (MInst.XmmRmRImm (SseOpcode.Pextrd)
+                                           r_dst
+                                           (RegMem.Reg src)
+                                           w_dst
+                                           lane
+                                           (operand_size_of_type_32_64 (lane_type ty))))))
+        r_dst))
+
 ;; Helper for creating `not` instructions.
 (decl not (Type Reg) Reg)
 (rule (not ty src)

cranelift/codegen/src/isa/x64/lower.isle

@@ -623,6 +623,123 @@
       (let ((amt_ Reg (lo_reg amt)))
         (shr_i128 (put_in_regs src) amt_)))
 
+;;;; Rules for `sshr` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+;; `i64` and smaller.
+
+(rule (lower (has_type (fits_in_64 ty) (sshr src amt)))
+      (let ((src_ Reg (extend_to_reg src ty (ExtendKind.Sign)))
+            ;; NB: Only the low bits of `amt` matter since we logically mask the
+            ;; shift amount to the value's bit width.
+            (amt_ Reg (lo_reg amt)))
+        (value_reg (sar ty src_ (Imm8Reg.Reg amt_)))))
+
+(rule (lower (has_type (fits_in_64 ty) (sshr src (imm8_from_value amt))))
+      (let ((src_ Reg (extend_to_reg src ty (ExtendKind.Sign))))
+        (value_reg (sar ty src_ amt))))
+
+;; `i128`.
+
+(decl sar_i128 (ValueRegs Reg) ValueRegs)
+(rule (sar_i128 src amt)
+      ;; Unpack the low/high halves of `src`.
+      (let ((src_lo Reg (value_regs_get src 0))
+            (src_hi Reg (value_regs_get src 1))
+            ;; Do a shift of each half. NB: the low half uses an unsigned shift
+            ;; because its MSB is not a sign bit.
+            (lo_shifted Reg (shr $I64 src_lo (Imm8Reg.Reg amt)))
+            (hi_shifted Reg (sar $I64 src_hi (Imm8Reg.Reg amt)))
+            ;; `src_hi << (64 - amt)` are the bits to carry over from the low
+            ;; half to the high half.
+            (carry Reg (shl $I64 src_hi (Imm8Reg.Reg (sub $I64 (imm $I64 64) (RegMemImm.Reg amt)))))
+            ;; Nullify the carry if we are shifting by a multiple of 128.
+            (carry_ Reg (with_flags_1 (test (OperandSize.Size64) (RegMemImm.Imm 127) amt)
+                                      (cmove $I64 (CC.Z) (RegMem.Reg (imm $I64 0)) carry)))
+            ;; Add the carry into the low half.
+            (lo_shifted_ Reg (or $I64 lo_shifted (RegMemImm.Reg carry_)))
+            ;; Get all sign bits.
+            (sign_bits Reg (sar $I64 src_hi (Imm8Reg.Imm8 63))))
+        ;; Combine the two shifted halves. However, if we are shifting by >= 64
+        ;; (modulo 128), then the hi bits are all sign bits and the lo bits are
+        ;; what would otherwise be our hi bits.
+        (with_flags_2 (test (OperandSize.Size64) (RegMemImm.Imm 64) amt)
+                      (cmove $I64 (CC.Z) (RegMem.Reg lo_shifted_) hi_shifted)
+                      (cmove $I64 (CC.Z) (RegMem.Reg hi_shifted) sign_bits))))
+
+(rule (lower (has_type $I128 (sshr src amt)))
+      ;; NB: Only the low bits of `amt` matter since we logically mask the shift
+      ;; amount to the value's bit width.
+      (let ((amt_ Reg (lo_reg amt)))
+        (sar_i128 (put_in_regs src) amt_)))
+
+;; SSE.
+
+;; Since the x86 instruction set does not have an 8x16 shift instruction and the
+;; approach used for `ishl` and `ushr` cannot be easily used (the masks do not
+;; preserve the sign), we use a different approach here: separate the low and
+;; high lanes, shift them separately, and merge them into the final result.
+;;
+;; Visually, this looks like the following, where `src.i8x16 = [s0, s1, ...,
+;; s15]:
+;;
+;;   lo.i16x8 = [(s0, s0), (s1, s1), ..., (s7, s7)]
+;;   shifted_lo.i16x8 = shift each lane of `low`
+;;   hi.i16x8 = [(s8, s8), (s9, s9), ..., (s15, s15)]
+;;   shifted_hi.i16x8 = shift each lane of `high`
+;;   result = [s0'', s1'', ..., s15'']
+(rule (lower (has_type $I8X16 (sshr src amt @ (value_type amt_ty))))
+      (let ((src_ Reg (put_in_reg src))
+            ;; In order for `packsswb` later to only use the high byte of each
+            ;; 16x8 lane, we shift right an extra 8 bits, relying on `psraw` to
+            ;; fill in the upper bits appropriately.
+            (amt_ RegMemImm (sshr_i8x16_bigger_shift amt_ty (put_in_reg_mem_imm amt)))
+            (lo Reg (punpcklbw src_ (RegMem.Reg src_)))
+            (shifted_lo Reg (psraw lo amt_))
+            (hi Reg (punpckhbw src_ (RegMem.Reg src_)))
+            (shifted_hi Reg (psraw hi amt_)))
+        (value_reg (packsswb shifted_lo (RegMem.Reg shifted_hi)))))
+
+(decl sshr_i8x16_bigger_shift (Type RegMemImm) RegMemImm)
+(rule (sshr_i8x16_bigger_shift _ty (RegMemImm.Imm i))
+      (RegMemImm.Imm (u32_add i 8)))
+(rule (sshr_i8x16_bigger_shift ty (RegMemImm.Reg r))
+      (reg_mem_imm_to_xmm (RegMemImm.Reg (add ty r (RegMemImm.Imm 8)))))
+(rule (sshr_i8x16_bigger_shift ty rmi @ (RegMemImm.Mem _m))
+      (reg_mem_imm_to_xmm (RegMemImm.Reg (add ty (imm ty 8) rmi))))
+
+;; `sshr.{i16x8,i32x4}` can be a simple `psra{w,d}`, we just have to make sure
+;; that if the shift amount is in a register, it is in an XMM register.
+(rule (lower (has_type $I16X8 (sshr src amt)))
+      (value_reg (psraw (put_in_reg src)
+                        (reg_mem_imm_to_xmm (put_in_reg_mem_imm amt)))))
+(rule (lower (has_type $I32X4 (sshr src amt)))
+      (value_reg (psrad (put_in_reg src)
+                        (reg_mem_imm_to_xmm (put_in_reg_mem_imm amt)))))
+
+;; The `sshr.i64x2` CLIF instruction has no single x86 instruction in the older
+;; feature sets. Newer ones like AVX512VL + AVX512F include `vpsraq`, a 128-bit
+;; instruction that would fit here, but this backend does not currently have
+;; support for EVEX encodings. To remedy this, we extract each 64-bit lane to a
+;; GPR, shift each using a scalar instruction, and insert the shifted values
+;; back in the `dst` XMM register.
+;;
+;; (TODO: when EVEX support is available, add an alternate lowering here).
+(rule (lower (has_type $I64X2 (sshr src amt)))
+      (let ((src_ Reg (put_in_reg src))
+            (lo Reg (pextrd $I64 src_ 0))
+            (hi Reg (pextrd $I64 src_ 1))
+            (amt_ Imm8Reg (sshr_i64x2_shift_amount (put_in_imm8_reg amt)))
+            (shifted_lo Reg (sar $I64 lo amt_))
+            (shifted_hi Reg (sar $I64 hi amt_)))
+        (value_reg (make_i64x2_from_lanes (RegMem.Reg shifted_lo)
+                                          (RegMem.Reg shifted_hi)))))
+
+;; Mask the shift amount according to Cranelift's semantics.
+(decl sshr_i64x2_shift_amount (Imm8Reg) Imm8Reg)
+(rule (sshr_i64x2_shift_amount reg @ (Imm8Reg.Reg _)) reg)
+(rule (sshr_i64x2_shift_amount (Imm8Reg.Imm8 imm))
+      (Imm8Reg.Imm8 (u8_and imm 63)))
+
 ;;;; Rules for `rotl` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 ;; `i16` and `i8`: we need to extend the shift amount, or mask the