From: Mark H Weaver <mhw@netris.org>
To: Jan Nieuwenhuizen <janneke@gnu.org>
Cc: 31474@debbugs.gnu.org
Subject: bug#31474: logxor+ash trigger compilation bug?
Date: Mon, 28 May 2018 08:03:01 -0400 [thread overview]
Message-ID: <87h8msxa16.fsf@netris.org> (raw)
In-Reply-To: <87wovoy1cj.fsf@netris.org> (Mark H. Weaver's message of "Sun, 27 May 2018 22:13:00 -0400")
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Here's an improved version of my patch. It's functionally equivalent
but with more comprehensible code and more comments. I think this is
ready to push to the stable-2.2 branch. Comments and suggestions
welcome.
Mark
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From aefb4c3627596335a2ef2cf6f721f9e04b49ae7e Mon Sep 17 00:00:00 2001
From: Mark H Weaver <mhw@netris.org>
Date: Sun, 27 May 2018 21:58:48 -0400
Subject: [PATCH] Fix type inference for bitwise logical operators.
Fixes <https://bugs.gnu.org/31474> and related bugs.
Reported by Jan Nieuwenhuizen <janneke@gnu.org>.
* module/language/cps/types.scm (next-power-of-two): Remove procedure.
(non-negative?, lognot*, saturate+, saturate-, logand-bounds)
(logsub-bounds, logior-bounds, logxor-bounds): New procedures. Use them
to improve and fix bugs in the range analysis of the type inferrers for
'logand', 'logsub', 'logior', 'ulogior', 'logxor', 'ulogxor', and
'lognot'.
---
module/language/cps/types.scm | 230 +++++++++++++++++++++++++---------
1 file changed, 169 insertions(+), 61 deletions(-)
diff --git a/module/language/cps/types.scm b/module/language/cps/types.scm
index c24f9b99d..4326a8d37 100644
--- a/module/language/cps/types.scm
+++ b/module/language/cps/types.scm
@@ -1,5 +1,5 @@
;;; Type analysis on CPS
-;;; Copyright (C) 2014, 2015 Free Software Foundation, Inc.
+;;; Copyright (C) 2014, 2015, 2018 Free Software Foundation, Inc.
;;;
;;; This library is free software: you can redistribute it and/or modify
;;; it under the terms of the GNU Lesser General Public License as
@@ -1273,32 +1273,79 @@ minimum, and maximum."
(define! result &u64 0 &u64-max)))
(define-type-aliases ulsh ulsh/immediate)
-(define (next-power-of-two n)
- (let lp ((out 1))
- (if (< n out)
- out
- (lp (ash out 1)))))
+(define-inlinable (non-negative? n)
+ "Return true if N is non-negative, otherwise return false."
+ (not (negative? n)))
+
+;; Like 'lognot', but handles infinities.
+(define-inlinable (lognot* n)
+ "Return the bitwise complement of N. If N is infinite, return -N."
+ (- -1 n))
+
+(define saturate+
+ (case-lambda
+ "Let N be the least upper bound of the integer lengths of the
+arguments. Return the greatest integer whose integer length is N.
+If any of the arguments are infinite, return positive infinity."
+ ((a b)
+ (if (or (inf? a) (inf? b))
+ +inf.0
+ (1- (ash 1 (max (integer-length a)
+ (integer-length b))))))
+ ((a b c)
+ (saturate+ (saturate+ a b) c))
+ ((a b c d)
+ (saturate+ (saturate+ a b) c d))))
+
+(define saturate-
+ (case-lambda
+ "Let N be the least upper bound of the integer lengths of the
+arguments. Return the least integer whose integer length is N.
+If any of the arguments are infinite, return negative infinity."
+ ((a b) (lognot* (saturate+ a b)))
+ ((a b c) (lognot* (saturate+ a b c)))
+ ((a b c d) (lognot* (saturate+ a b c d)))))
+
+(define (logand-bounds a0 a1 b0 b1)
+ "Return two values: lower and upper bounds for (logand A B)
+where (A0 <= A <= A1) and (B0 <= B <= B1)."
+ ;; For each argument, we consider three cases: (1) the argument is
+ ;; non-negative, (2) its sign is unknown, or (3) it is negative.
+ ;; To handle both arguments, we must consider a total of 9 cases:
+ ;;
+ ;; -----------------------------------------------------------------------
+ ;; LOGAND | non-negative B | unknown-sign B | negative B
+ ;; -----------------------------------------------------------------------
+ ;; non-negative A | 0 .. (min A1 B1) | 0 .. A1 | 0 .. A1
+ ;; -----------------------------------------------------------------------
+ ;; unknown-sign A | 0 .. B1 | (sat- A0 B0) | (sat- A0 B0)
+ ;; | | .. | .. A1
+ ;; | | (sat+ A1 B1) |
+ ;; -----------------------------------------------------------------------
+ ;; negative A | 0 .. B1 | (sat- A0 B0) | (sat- A0 B0)
+ ;; | | .. B1 | .. (min A1 B1)
+ ;; -----------------------------------------------------------------------
+ (values (if (or (non-negative? a0) (non-negative? b0))
+ 0
+ (saturate- a0 b0))
+ (cond ((or (and (non-negative? a0) (non-negative? b0))
+ (and (negative? a1) (negative? b1)))
+ (min a1 b1))
+ ((or (non-negative? a0) (negative? b1))
+ a1)
+ ((or (non-negative? b0) (negative? a1))
+ b1)
+ (else
+ (saturate+ a1 b1)))))
(define-simple-type-checker (logand &exact-integer &exact-integer))
(define-type-inferrer (logand a b result)
- (define (logand-min a b)
- (if (and (negative? a) (negative? b))
- (let ((min (min a b)))
- (if (inf? min)
- -inf.0
- (- 1 (next-power-of-two (- min)))))
- 0))
- (define (logand-max a b)
- (cond
- ((or (and (positive? a) (positive? b))
- (and (negative? a) (negative? b)))
- (min a b))
- (else (max a b))))
(restrict! a &exact-integer -inf.0 +inf.0)
(restrict! b &exact-integer -inf.0 +inf.0)
- (define! result &exact-integer
- (logand-min (&min a) (&min b))
- (logand-max (&max a) (&max b))))
+ (call-with-values (lambda ()
+ (logand-bounds (&min a) (&max a) (&min b) (&max b)))
+ (lambda (min max)
+ (define! result &exact-integer min max))))
(define-simple-type-checker (ulogand &u64 &u64))
(define-type-inferrer (ulogand a b result)
@@ -1306,24 +1353,17 @@ minimum, and maximum."
(restrict! b &u64 0 &u64-max)
(define! result &u64 0 (min (&max/u64 a) (&max/u64 b))))
+(define (logsub-bounds a0 a1 b0 b1)
+ "Return two values: lower and upper bounds for (logsub A B),
+i.e. (logand A (lognot B)), where (A0 <= A <= A1) and (B0 <= B <= B1)."
+ ;; Here we use 'logand-bounds' to compute the bounds, after
+ ;; computing the bounds of (lognot B) from the bounds of B.
+ ;; From (B0 <= B <= B1) it follows that (~B1 <= ~B <= ~B0),
+ ;; where ~X means (lognot X).
+ (logand-bounds a0 a1 (lognot* b1) (lognot* b0)))
+
(define-simple-type-checker (logsub &exact-integer &exact-integer))
(define-type-inferrer (logsub a b result)
- (define (logsub-bounds min-a max-a min-b max-b)
- (cond
- ((negative? max-b)
- ;; Sign bit always set on B, so result will never be negative.
- ;; If A might be negative (all leftmost bits 1), we don't know
- ;; how positive the result might be.
- (values 0 (if (negative? min-a) +inf.0 max-a)))
- ((negative? min-b)
- ;; Sign bit might be set on B.
- (values min-a (if (negative? min-a) +inf.0 max-a)))
- ((negative? min-a)
- ;; Sign bit never set on B -- result will have the sign of A.
- (values -inf.0 max-a))
- (else
- ;; Sign bit never set on A and never set on B -- the nice case.
- (values 0 max-a))))
(restrict! a &exact-integer -inf.0 +inf.0)
(restrict! b &exact-integer -inf.0 +inf.0)
(call-with-values (lambda ()
@@ -1337,26 +1377,47 @@ minimum, and maximum."
(restrict! b &u64 0 &u64-max)
(define! result &u64 0 (&max/u64 a)))
+(define (logior-bounds a0 a1 b0 b1)
+ "Return two values: lower and upper bounds for (logior A B)
+where (A0 <= A <= A1) and (B0 <= B <= B1)."
+ ;; For each argument, we consider three cases: (1) the argument is
+ ;; non-negative, (2) its sign is unknown, or (3) it is negative.
+ ;; To handle both arguments, we must consider a total of 9 cases.
+ ;;
+ ;; ---------------------------------------------------------------------
+ ;; LOGIOR | non-negative B | unknown-sign B | negative B
+ ;; ---------------------------------------------------------------------
+ ;; non-negative A | (max A0 B0) | B0 | B0 .. -1
+ ;; | .. | .. |
+ ;; | (sat+ A1 B1) | (sat+ A1 B1) |
+ ;; ---------------------------------------------------------------------
+ ;; unknown-sign A | A0 | (sat- A0 B0) | B0 .. -1
+ ;; | .. | .. |
+ ;; | (sat+ A1 B1) | (sat+ A1 B1) |
+ ;; ---------------------------------------------------------------------
+ ;; negative A | A0 .. -1 | A0 .. -1 | (max A0 B0) .. -1
+ ;; ---------------------------------------------------------------------
+ (values (cond ((or (and (non-negative? a0) (non-negative? b0))
+ (and (negative? a1) (negative? b1)))
+ (max a0 b0))
+ ((or (non-negative? a0) (negative? b1))
+ b0)
+ ((or (non-negative? b0) (negative? a1))
+ a0)
+ (else
+ (saturate- a0 b0)))
+ (if (or (negative? a1) (negative? b1))
+ -1
+ (saturate+ a1 b1))))
+
(define-simple-type-checker (logior &exact-integer &exact-integer))
(define-type-inferrer (logior a b result)
- ;; Saturate all bits of val.
- (define (saturate val)
- (1- (next-power-of-two val)))
- (define (logior-min a b)
- (cond ((and (< a 0) (<= 0 b)) a)
- ((and (< b 0) (<= 0 a)) b)
- (else (max a b))))
- (define (logior-max a b)
- ;; If either operand is negative, just assume the max is -1.
- (cond
- ((or (< a 0) (< b 0)) -1)
- ((or (inf? a) (inf? b)) +inf.0)
- (else (saturate (logior a b)))))
(restrict! a &exact-integer -inf.0 +inf.0)
(restrict! b &exact-integer -inf.0 +inf.0)
- (define! result &exact-integer
- (logior-min (&min a) (&min b))
- (logior-max (&max a) (&max b))))
+ (call-with-values (lambda ()
+ (logior-bounds (&min a) (&max a) (&min b) (&max b)))
+ (lambda (min max)
+ (define! result &exact-integer min max))))
(define-simple-type-checker (ulogior &u64 &u64))
(define-type-inferrer (ulogior a b result)
@@ -1364,23 +1425,70 @@ minimum, and maximum."
(restrict! b &u64 0 &u64-max)
(define! result &u64
(max (&min/0 a) (&min/0 b))
- (1- (next-power-of-two (logior (&max/u64 a) (&max/u64 b))))))
-
-;; For our purposes, treat logxor the same as logior.
-(define-type-aliases logior logxor)
+ (saturate+ (&max/u64 a) (&max/u64 b))))
+
+(define (logxor-bounds a0 a1 b0 b1)
+ "Return two values: lower and upper bounds for (logxor A B)
+where (A0 <= A <= A1) and (B0 <= B <= B1)."
+ ;; For each argument, we consider three cases: (1) the argument is
+ ;; non-negative, (2) its sign is unknown, or (3) it is negative.
+ ;; To handle both arguments, we must consider a total of 9 cases.
+ ;;
+ ;; --------------------------------------------------------------------
+ ;; LOGXOR | non-negative B | unknown-sign B | negative B
+ ;; --------------------------------------------------------------------
+ ;; non-negative A | 0 | (sat- A1 B0) | (sat- A1 B0)
+ ;; | .. | .. | ..
+ ;; | (sat+ A1 B1) | (sat+ A1 B1) | -1
+ ;; --------------------------------------------------------------------
+ ;; unknown-sign A | (sat- A0 B1) | (sat- A0 B1 A1 B0) | (sat- A1 B0)
+ ;; | .. | .. | ..
+ ;; | (sat+ A1 B1) | (sat+ A1 B1 A0 B0) | (sat+ A0 B0)
+ ;; --------------------------------------------------------------------
+ ;; negative A | (sat- A0 B1) | (sat- A0 B1) | 0
+ ;; | .. | .. | ..
+ ;; | -1 | (sat+ A0 B0) | (sat+ A0 B0)
+ ;; --------------------------------------------------------------------
+ (values (cond ((or (and (non-negative? a0) (non-negative? b0))
+ (and (negative? a1) (negative? b1)))
+ 0)
+ ((or (non-negative? a0) (negative? b1))
+ (saturate- a1 b0))
+ ((or (non-negative? b0) (negative? a1))
+ (saturate- a0 b1))
+ (else
+ (saturate- a0 b1 a1 b0)))
+ (cond ((or (and (non-negative? a0) (negative? b1))
+ (and (non-negative? b0) (negative? a1)))
+ -1)
+ ((or (non-negative? a0) (non-negative? b0))
+ (saturate+ a1 b1))
+ ((or (negative? a1) (negative? b1))
+ (saturate+ a0 b0))
+ (else
+ (saturate+ a1 b1 a0 b0)))))
+
+(define-simple-type-checker (logxor &exact-integer &exact-integer))
+(define-type-inferrer (logxor a b result)
+ (restrict! a &exact-integer -inf.0 +inf.0)
+ (restrict! b &exact-integer -inf.0 +inf.0)
+ (call-with-values (lambda ()
+ (logxor-bounds (&min a) (&max a) (&min b) (&max b)))
+ (lambda (min max)
+ (define! result &exact-integer min max))))
(define-simple-type-checker (ulogxor &u64 &u64))
(define-type-inferrer (ulogxor a b result)
(restrict! a &u64 0 &u64-max)
(restrict! b &u64 0 &u64-max)
- (define! result &u64 0 &u64-max))
+ (define! result &u64 0 (saturate+ (&max/u64 a) (&max/u64 b))))
(define-simple-type-checker (lognot &exact-integer))
(define-type-inferrer (lognot a result)
(restrict! a &exact-integer -inf.0 +inf.0)
(define! result &exact-integer
- (- -1 (&max a))
- (- -1 (&min a))))
+ (lognot* (&max a))
+ (lognot* (&min a))))
(define-simple-type-checker (logtest &exact-integer &exact-integer))
(define-predicate-inferrer (logtest a b true?)
--
2.17.0
next prev parent reply other threads:[~2018-05-28 12:03 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-16 18:16 bug#31474: logxor+ash trigger compilation bug? Jan Nieuwenhuizen
2018-05-28 2:13 ` Mark H Weaver
2018-05-28 12:03 ` Mark H Weaver [this message]
2018-05-28 21:17 ` Jan Nieuwenhuizen
2018-06-11 14:28 ` Mark H Weaver
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