These are the ‘-m
’ options defined for the S/390 and zSeries architecture.
-mhard-float
-msoft-float
-msoft-float
is specified, functions in libgcc.a
are used to perform floating-point operations. When -mhard-float
is specified, the compiler generates IEEE floating-point instructions. This is the default. -mhard-dfp
-mno-hard-dfp
-mno-hard-dfp
is specified, functions in libgcc.a
are used to perform decimal-floating-point operations. When -mhard-dfp
is specified, the compiler generates decimal-floating-point hardware instructions. This is the default for -march=z9-ec
or higher. -mlong-double-64
-mlong-double-128
long double
type. A size of 64 bits makes the long double
type equivalent to the double
type. This is the default. -mbackchain
-mno-backchain
-mno-packed-stack
is in effect, the backchain pointer is stored at the bottom of the stack frame; when -mpacked-stack
is in effect, the backchain is placed into the topmost word of the 96/160 byte register save area. In general, code compiled with -mbackchain
is call-compatible with code compiled with -mmo-backchain
; however, use of the backchain for debugging purposes usually requires that the whole binary is built with -mbackchain
. Note that the combination of -mbackchain
, -mpacked-stack
and -mhard-float
is not supported. In order to build a linux kernel use -msoft-float
.
The default is to not maintain the backchain.
-mpacked-stack
-mno-packed-stack
-mno-packed-stack
is specified, the compiler uses the all fields of the 96/160 byte register save area only for their default purpose; unused fields still take up stack space. When -mpacked-stack
is specified, register save slots are densely packed at the top of the register save area; unused space is reused for other purposes, allowing for more efficient use of the available stack space. However, when -mbackchain
is also in effect, the topmost word of the save area is always used to store the backchain, and the return address register is always saved two words below the backchain. As long as the stack frame backchain is not used, code generated with -mpacked-stack
is call-compatible with code generated with -mno-packed-stack
. Note that some non-FSF releases of GCC 2.95 for S/390 or zSeries generated code that uses the stack frame backchain at run time, not just for debugging purposes. Such code is not call-compatible with code compiled with -mpacked-stack
. Also, note that the combination of -mbackchain
, -mpacked-stack
and -mhard-float
is not supported. In order to build a linux kernel use -msoft-float
.
The default is to not use the packed stack layout.
-msmall-exec
-mno-small-exec
bras
instruction to do subroutine calls. This only works reliably if the total executable size does not exceed 64k. The default is to use the basr
instruction instead, which does not have this limitation. -m64
-m31
-m31
is specified, generate code compliant to the GNU/Linux for S/390 ABI. When -m64
is specified, generate code compliant to the GNU/Linux for zSeries ABI. This allows GCC in particular to generate 64-bit instructions. For the ‘s390
’ targets, the default is -m31
, while the ‘s390x
’ targets default to -m64
. -mzarch
-mesa
-mzarch
is specified, generate code using the instructions available on z/Architecture. When -mesa
is specified, generate code using the instructions available on ESA/390. Note that -mesa
is not possible with -m64
. When generating code compliant to the GNU/Linux for S/390 ABI, the default is -mesa
. When generating code compliant to the GNU/Linux for zSeries ABI, the default is -mzarch
. -mmvcle
-mno-mvcle
mvcle
instruction to perform block moves. When -mno-mvcle
is specified, use a mvc
loop instead. This is the default unless optimizing for size. -mdebug
-mno-debug
-march=
cpu-type
g5
’, ‘g6
’, ‘z900
’, ‘z990
’, ‘z9-109
’, ‘z9-ec
’, ‘z10
’, ‘z196
’, and ‘zEC12
’. When generating code using the instructions available on z/Architecture, the default is -march=z900
. Otherwise, the default is -march=g5
. -mtune=
cpu-type
-march
. The default is the value used for -march
. -mtpf-trace
-mno-tpf-trace
-mfused-madd
-mno-fused-madd
-mwarn-framesize=
framesize
-mwarn-dynamicstack
alloca
or uses dynamically-sized arrays. This is generally a bad idea with a limited stack size. -mstack-guard=
stack-guard-mstack-size=
stack-size
-mhotpatch=
pre-halfwords,
post-halfwords
If both arguments are zero, hotpatching is disabled.
This option can be overridden for individual functions with the hotpatch
attribute.
© Free Software Foundation
Licensed under the GNU Free Documentation License, Version 1.3.
https://gcc.gnu.org/onlinedocs/gcc-4.9.3/gcc/S_002f390-and-zSeries-Options.html