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s390x: Enable more runtests, and fix a few bugs (#4516)

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This enables more runtests to be executed on s390x.  Doing so
uncovered a two back-end bugs, which are fixed as well:

- The result of cls was always off by one.
- The result of popcnt.i16 has uninitialized high bits.

In addition, I found a bug in the load-op-store.clif test case:
     v3 = heap_addr.i64 heap0, v1, 4
     v4 = iconst.i64 42
     store.i32 v4, v3
This was clearly intended to perform a 32-bit store, but
actually performs a 64-bit store (it seems the type annotation
of the store opcode is ignored, and the type of the operand
is used instead).  That bug did not show any noticable symptoms
on little-endian architectures, but broke on big-endian.
This commit is contained in:
Ulrich Weigand
2022-07-25 21:37:06 +02:00
committed by GitHub
parent 7c67e620c4
commit dd40bf075a
17 changed files with 42 additions and 16 deletions
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21
cranelift/codegen/src/isa/s390x/lower.isle
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@@ -1149,17 +1149,26 @@
;;;; Rules for `cls` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; The result of cls is not supposed to count the sign bit itself, just
;; additional copies of it. Therefore, when computing cls in terms of clz,
;; we need to subtract one. Fold this into the offset computation.
(decl cls_offset (Type Reg) Reg)
(rule (cls_offset $I8 x) (add_simm16 $I8 x -57))
(rule (cls_offset $I16 x) (add_simm16 $I16 x -49))
(rule (cls_offset $I32 x) (add_simm16 $I32 x -33))
(rule (cls_offset $I64 x) (add_simm16 $I64 x -1))
;; Count leading sign-bit copies. We don't have any instruction for that,
;; so we instead count the leading zeros after inverting the input if negative,
;; i.e. computing
;; cls(x) == clz(x ^ (x >> 63))
;; cls(x) == clz(x ^ (x >> 63)) - 1
;; where x is the sign-extended input.
(rule (lower (has_type (fits_in_64 ty) (cls x)))
(let ((ext_reg Reg (put_in_reg_sext64 x))
(signbit_copies Reg (ashr_imm $I64 ext_reg 63))
(inv_reg Reg (xor_reg $I64 ext_reg signbit_copies))
(clz RegPair (clz_reg 64 inv_reg)))
(clz_offset ty (regpair_hi clz))))
(cls_offset ty (regpair_hi clz))))
;;;; Rules for `ctz` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -1214,12 +1223,14 @@
;; of each input byte separately, so we need to accumulate those partial
;; results via a series of log2(type size in bytes) - 1 additions. We
;; accumulate in the high byte, so that a final right shift will zero out
;; any unrelated bits to give a clean result.
;; any unrelated bits to give a clean result. (This does not work with
;; $I16, where we instead accumulate in the low byte and clear high bits
;; via an explicit and operation.)
(rule (lower (has_type (and (mie2_disabled) $I16) (popcnt x)))
(let ((cnt2 Reg (popcnt_byte x))
(cnt1 Reg (add_reg $I32 cnt2 (lshl_imm $I32 cnt2 8))))
(lshr_imm $I32 cnt1 8)))
(cnt1 Reg (add_reg $I32 cnt2 (lshr_imm $I32 cnt2 8))))
(and_uimm16shifted $I32 cnt1 (uimm16shifted 255 0))))
(rule (lower (has_type (and (mie2_disabled) $I32) (popcnt x)))
(let ((cnt4 Reg (popcnt_byte x))