Update documentation of AArch64 options for GCC6 to be more accurate,
fix a few minor mistakes and remove some duplication.
Tested with "make info dvi pdf html" and checked resulting PDF is as expected.
OK for trunk and backport to GCC6.1 branch?
ChangeLog:
2016-04-21 Wilco Dijkstra <wdijk...@arm.com>
gcc/
* gcc/doc/invoke.texi (AArch64 Options): Update.
--
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index
e9763d44d8d7aa6a64821a4b1811e55025aaaa4e..ddd4eeaec1502f871d0febd6045e37153c48a7e1
100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -12827,9 +12827,9 @@ These options are defined for AArch64 implementations:
@item -mabi=@var{name}
@opindex mabi
Generate code for the specified data model. Permissible values
-are @samp{ilp32} for SysV-like data model where int, long int and pointer
+are @samp{ilp32} for SysV-like data model where int, long int and pointers
are 32-bit, and @samp{lp64} for SysV-like data model where int is 32-bit,
-but long int and pointer are 64-bit.
+but long int and pointers are 64-bit.
The default depends on the specific target configuration. Note that
the LP64 and ILP32 ABIs are not link-compatible; you must compile your
@@ -12854,9 +12854,8 @@ Generate little-endian code. This is the default when
GCC is configured for an
@item -mcmodel=tiny
@opindex mcmodel=tiny
Generate code for the tiny code model. The program and its statically defined
-symbols must be within 1GB of each other. Pointers are 64 bits. Programs can
-be statically or dynamically linked. This model is not fully implemented and
-mostly treated as @samp{small}.
+symbols must be within 1MB of each other. Pointers are 64 bits. Programs can
+be statically or dynamically linked.
@item -mcmodel=small
@opindex mcmodel=small
@@ -12872,7 +12871,8 @@ statically linked only.
@item -mstrict-align
@opindex mstrict-align
-Do not assume that unaligned memory references are handled by the system.
+Avoid generating unaligned accesses when accessing objects at non-naturally
+aligned boundaries as described in the architecture.
@item -momit-leaf-frame-pointer
@itemx -mno-omit-leaf-frame-pointer
@@ -12894,7 +12894,7 @@ of TLS variables.
@item -mtls-size=@var{size}
@opindex mtls-size
Specify bit size of immediate TLS offsets. Valid values are 12, 24, 32, 48.
-This option depends on binutils higher than 2.25.
+This option requires binutils 2.26 or newer.
@item -mfix-cortex-a53-835769
@itemx -mno-fix-cortex-a53-835769
@@ -12916,10 +12916,11 @@ corresponding flag to the linker.
@item -mno-low-precision-recip-sqrt
@opindex -mlow-precision-recip-sqrt
@opindex -mno-low-precision-recip-sqrt
-When calculating the reciprocal square root approximation,
-uses one less step than otherwise, thus reducing latency and precision.
-This is only relevant if @option{-ffast-math} enables the reciprocal square
root
-approximation, which in turn depends on the target processor.
+Enable or disable reciprocal square root approximation.
+This option only has an effect if @option{-ffast-math} or
+@option{-funsafe-math-optimizations} is used as well. Enabling this reduces
+precision of reciprocal square root results to about 16 bits for
+single-precision and to 32 bits for double-precision.
@item -march=@var{name}
@opindex march
@@ -12956,17 +12957,15 @@ Specify the name of the target processor for which
GCC should tune the
performance of the code. Permissible values for this option are:
@samp{generic}, @samp{cortex-a35}, @samp{cortex-a53}, @samp{cortex-a57},
@samp{cortex-a72}, @samp{exynos-m1}, @samp{qdf24xx}, @samp{thunderx},
-@samp{xgene1}.
+@samp{xgene1}, @samp{cortex-a57.cortex-a53}, @samp{cortex-a72.cortex-a53},
+@samp{native}.
-Additionally, this option can specify that GCC should tune the performance
-of the code for a big.LITTLE system. Permissible values for this
-option are: @samp{cortex-a57.cortex-a53}, @samp{cortex-a72.cortex-a53}.
+The values @samp{cortex-a57.cortex-a53}, @samp{cortex-a72.cortex-a53}
+specify that GCC should tune for a big.LITTLE system.
Additionally on native AArch64 GNU/Linux systems the value
-@samp{native} is available. This option causes the compiler to pick
-the architecture of and tune the performance of the code for the
-processor of the host system. This option has no effect if the
-compiler is unable to recognize the architecture of the host system.
+@samp{native} tunes performance to the host system. This option has no effect
+if the compiler is unable to recognize the processor of the host system.
Where none of @option{-mtune=}, @option{-mcpu=} or @option{-march=}
are specified, the code is tuned to perform well across a range
@@ -12986,12 +12985,6 @@ documented in the sub-section on
Feature Modifiers}. Where conflicting feature modifiers are
specified, the right-most feature is used.
-Additionally on native AArch64 GNU/Linux systems the value
-@samp{native} is available. This option causes the compiler to tune
-the performance of the code for the processor of the host system.
-This option has no effect if the compiler is unable to recognize the
-architecture of the host system.
-
GCC uses @var{name} to determine what kind of instructions it can emit when
generating assembly code (as if by @option{-march}) and to determine
the target processor for which to tune for performance (as if
@@ -13010,10 +13003,10 @@ This option is only intended to be useful when
developing GCC.
@item -mpc-relative-literal-loads
@opindex mpcrelativeliteralloads
-Enable PC relative literal loads. If this option is used, literal
-pools are assumed to have a range of up to 1MiB and an appropriate
-instruction sequence is used. This option has no impact when used
-with @option{-mcmodel=tiny}.
+Enable PC relative literal loads. With this option literal pools are
+accessed using a single instruction and emitted after each function. This
+limits the maximum size of functions to 1MB. This is enabled by default for
+@option{-mcmodel=tiny}.
@end table
@@ -13044,9 +13037,9 @@ Enable Large System Extension instructions. This is on
by default for
@end table
-That is, @option{crypto} implies @option{simd} implies @option{fp}.
-Conversely, @option{nofp} (or equivalently, @option{-mgeneral-regs-only})
-implies @option{nosimd} implies @option{nocrypto}.
+Feature @option{crypto} implies @option{simd}, which implies @option{fp}.
+Conversely, @option{nofp} implies @option{nosimd}, which implies
+@option{nocrypto}.
@node Adapteva Epiphany Options
@subsection Adapteva Epiphany Options
