Additional length modifiers under Altivec/VMX¶

The following additional length modifiers are supported on platforms that have the Altivec/VMX (Power ISA 2.01 with Vector extensions). Since the VSX facility is predicated on VMX support these additional length modifiers are also supported on platforms that have the VSX facility. In this section the term, `integer conversion' stands for the d, i, o, u, x, X, and c conversions. The term, `floating point conversion' stands for the f, F, e, E, g, G, a, and A conversions.

vl, lv

(vee-ell,ell-vee) A following integer conversion corresponds to a 16 byte vector composed of four vector unsigned ints or vector signed ints.

vh, hv

A following integer conversions corresponds to a 16 byte vector composed of eight vector unsigned shorts or vector signed shorts.

v

A following integer conversion corresponds to a 16 byte vector composed of sixteen vector unsigned chars or vector signed chars. A following floating point conversion corresponds to a 16 byte vector composed of four vector float single-precision floating point values.

Additional length modifiers under VSX (Power ISA 2.06)¶

The following additional length modifiers are ONLY supported on platforms that have the VSX facility. In this section the term, `floating point conversion' stands for the f, F, e, E, g, G, a, and A conversions.

vv

(vee-vee) A following floating point conversion corresponds to a 16 byte vector composed of two vector double double-precision floating point values.

conversion specifiers¶

The following integer printf conversion specifiers are supported by libvecpf:

d, i, o, u, x, X, c

The following floating point printf conversion specifiers are supported by libvecpf:

f, F, e, E, g, G, a, A

valid simple format strings under AltiVec/VMX¶

%vld, %lvd

Output a vector of four signed ints in signed decimal notation.

%vli, %lvi

Same as %vld and %lvd.

%vlu, %lvu

Output a vector of four unsigned ints in unsigned decimal notation.

%vlo, %lvo

Output a vector of four unsigned ints in unsigned octal notation.

%vlx, %lvx

Output a vector of four unsigned ints in unsigned hexadecimal (x) notation where the letters abcdef are used.

%vlX, %lvX

Output a vector of four unsigned ints in unsigned hexadecimal (X) notation where the letters ABCDEF are used.

%vhd, %hvd

Output a vector of eight signed shorts in signed decimal notation.

%vhi, %hvi

Same as %vhd and %hvd.

%vhu,%hvu

Output a vector of eight unsigned shorts in unsigned decimal notation.

%vho, %hvo

Output a vector of eight unsigned shorts in unsigned octal notation.

%vhx, %hvx

Output a vector of eight unsigned shorts in unsigned hexadecimal 'x' notation where the letters abcdef are used.

%vhX, %hvX

Output a vector of eight unsigned shorts in unsigned hexadecimal (X) notation where the letters ABCDEF are used.

%vd

Output a vector of sixteen signed chars in signed decimal notation.

%vi

Same as %vd.

%vu

Output a vector of sixteen unsigned chars in unsigned decimal notation.

%vo

Output a vector of sixteen unsigned chars in unsigned octal notation.

%vx

Output a vector of sixteen unsigned chars in unsigned hexadecimal 'x' notation where the letters abcdef are used.

%vX

Output a vector of sixteen unsigned chars in unsigned hexadecimal (X) notation where the letters ABCDEF are used.

%vc

Output a vector of sixteen unsigned chars as characters.

%ve, %vE

Output a vector of four single-precision floats in the manner indicated in man printf(3) in The conversion specifier section, under the e and E specifiers, respectively.

%vf, %vF

Output a vector of four single-precision floats in the manner indicated in man printf(3) in The conversion specifier section, under the f and F specifiers, respectively.

%vg, %vG

Output a vector of four single-precision floats in the manner indicated in man printf(3) in The conversion specifier section, under the g and G specifiers, respectively.

%va, %vA

Output a vector of four single-precision floats in the manner indicated in man printf(3) in The conversion specifier section, under the a and A specifiers, respectively.

valid simple format strings under VSX¶

%vve, %vvE

Output a vector of two double-precision doubles in the manner indicated in man printf(3) in The conversion specifier section, under the e and E specifiers, respectively.

%vvf, %vvF

Output a vector of two double-precision doubles in the manner indicated in man printf(3) in The conversion specifier section, under the f and F specifiers, respectively.

%vvg, %vvG

Output a vector of two double-precision doubles in the manner indicated in man printf(3) in The conversion specifier section, under the g and G specifiers, respectively.

%vva, %vvA

Output a vector of two double-precision doubles in the manner indicated in man printf(3) in The conversion specifier section, under the a and A specifiers, respectively.

Warnings¶

Using the additional printf length modifiers defined by this library in a program will cause the GCC compiler to complain in the following manner when compiled with -Wall:

warning: unknown conversion type character ‘v’ in format

This warning can be suppressed with the -Wno-format compiler switch. Only suppress warnings with care.

dynamic linking¶

"gcc -maltivec -O3 m32 -g -Wall -o foo foo.c -mcpu=power7 -lvecpf -Wno-format"

static linking¶

Compiling an application and linking it against the static library libvecpf.a will expose a default feature of the link editor (ld) which purges unused symbols. The link editor sees constructors as unused in this context and purges them from the final archive. This will prevent the registration of the printf-hook callback mechanism and printf will not support Vector data types.

In order to prevent the link editor from purging the libvecpf constructor on the final link of a static linking operation explicitly tell it to not purge the constructor by passing

-Wl,-u,__libvecpf_init

gcc -static -maltivec -O3 -m32 -g -Wall -o foo foo.c -mcpu=power7 -Wl,-u,__libvecpf_init -lvecpf -Wno-format