From aefb4c3627596335a2ef2cf6f721f9e04b49ae7e Mon Sep 17 00:00:00 2001 From: Mark H Weaver Date: Sun, 27 May 2018 21:58:48 -0400 Subject: [PATCH] Fix type inference for bitwise logical operators. Fixes and related bugs. Reported by Jan Nieuwenhuizen . * 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