Vax C90-EL SERIES Service Manual download pdf (Page 47)

Compiler Commands [2]

(UNICOS systems) The -h fastmd option generates shorter code sequences for

int variables when doing multiply, divide, or comparison operations, or when

converting to and from floating-point operations, but allows for only 46 bits of

significance. With -h nofastmd, this action is disabled. This option is affected

by the scalar optimization level (see Section 2.13.2, page 23).

2.15.3 -h [no]fastmodulus (CC, cc)

Default option: -h nofastmodulus

(UNICOS systems) The -h fastmodulus option generates shorter code

sequences for int variables used with the modulus operator (%), but allows

only 46 significant bits. This option is affected by the scalar optimization level,

(see Section 2.13.2, page 23).

2.15.4 -h [no]ieeeconform (CC, cc)

Default option: -h noieeeconform

Floating-point: IEEE only

The -h ieeeconform option causes the resulting executable code to conform

more closely to the IEEE floating-point standard (ANSI/IEEE Std 754–1985). Use

of this option disables many arithmetic identity optimizations and may result

in significantly slower code.

When -h noieeeconform is in effect, the compiler optimizes expressions

such as x!=xto 0 and x/x to 1 (where x has floating type). With the

-h ieeeconform option in effect, these and other similar arithmetic identity

optimizations are not performed. Optimizations on integral types are not affected

by this option.

The -h ieeeconform option also turns on a scaled complex divide, which

increases the range of complex values that can be handled without producing an

underflow or an overflow.

The -h ieeeconform option overrides the -h fastfpdivide option.

2.15.5 -h [no]fastfpdivide (CC, cc)

Default option: -h fastfpdivide

Floating-point: IEEE only

The -h fastfpdivide option decomposes a floating-point divide into

a multiply-by-reciprocal in situations where a performance gain can be

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Vax C90-EL SERIES Service Manual Page 47