2005-10-05 Billy Biggs <billy.biggs@gmail.com>

	    Paolo Bonzini  <bonzini@gnu.org>

	PR target/23809

	* doc/extend.texi (x86 Built-ins): Document that -msse and friends
	enable the instructions and not just the built-ins.
	* doc/invoke.texi (x86 Options): Likewise.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@104979 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 3ac24ec..24f14e9 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,12 @@
+2005-10-05  Billy Biggs  <billy.biggs@gmail.com>
+           Paolo Bonzini  <bonzini@gnu.org>
+
+       PR target/23809
+
+       * doc/extend.texi (x86 Built-ins): Document that -msse and friends
+       enable the instructions and not just the built-ins.
+       * doc/invoke.texi (x86 Options): Likewise.
+
 2005-10-04  Geoffrey Keating  <geoffk@apple.com>
 
        * config/i386/t-darwin (SHLIB_VERPFX): Fix typo.

diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index 0d2f653..71518e4 100644 (file)
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -6466,6 +6466,14 @@ into the data cache.  The instruction will be issued in slot I1@.
 These built-in functions are available for the i386 and x86-64 family
 of computers, depending on the command-line switches used.
 
+Note that, if you specify command-line switches such as @option{-msse},
+the compiler could use the extended instruction sets even if the built-ins
+are not used explicitly in the program.  For this reason, applications
+which perform runtime CPU detection must compile separate files for each
+supported architecture, using the appropriate flags.  In particular,
+the file containing the CPU detection code should be compiled without
+these options.
+
 The following machine modes are available for use with MMX built-in functions
 (@pxref{Vector Extensions}): @code{V2SI} for a vector of two 32-bit integers,
 @code{V4HI} for a vector of four 16-bit integers, and @code{V8QI} for a

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 3e4af30..b859a7f 100644 (file)
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -9261,15 +9261,20 @@ preferred alignment to @option{-mpreferred-stack-boundary=2}.
 @opindex mno-sse
 @opindex m3dnow
 @opindex mno-3dnow
-These switches enable or disable the use of built-in functions that allow
-direct access to the MMX, SSE, SSE2, SSE3 and 3Dnow extensions of the
-instruction set.
-
-@xref{X86 Built-in Functions}, for details of the functions enabled
-and disabled by these switches.
+These switches enable or disable the use of instructions in the MMX,
+SSE, SSE2 or 3DNow! extended instruction sets.  These extensions are
+also available as built-in functions: see @ref{X86 Built-in Functions},
+for details of the functions enabled and disabled by these switches.
 
 To have SSE/SSE2 instructions generated automatically from floating-point
-code, see @option{-mfpmath=sse}.
+code (as opposed to 387 instructions), see @option{-mfpmath=sse}.
+
+These options will enable GCC to use these extended instructions in
+generated code, even without @option{-mfpmath=sse}.  Applications which
+perform runtime CPU detection must compile separate files for each
+supported architecture, using the appropriate flags.  In particular,
+the file containing the CPU detection code should be compiled without
+these options.
 
 @item -mpush-args
 @itemx -mno-push-args