Don't add crtfastmath.o for -shared to avoid changing the MXCSR
register when loading a shared library. crtfastmath.o will be used
only when building executables.
Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}.
Ok for trunk?
gcc/ChangeLog:
PR target/55522
PR target/36821
* config/i386/gnu-user-common.h (GNU_USER_TARGET_MATHFILE_SPEC):
Link crtfastmath.o when -mdaz-ftz is specified, not link it
when -shared is specified.
* config/i386/i386.opt (mdaz-ftz): New option.
* doc/invoke.texi (x86 options): Document mftz-daz.
---
gcc/config/i386/gnu-user-common.h | 2 +-
gcc/config/i386/i386.opt | 4 ++++
gcc/doc/invoke.texi | 10 +++++++++-
3 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/gcc/config/i386/gnu-user-common.h
b/gcc/config/i386/gnu-user-common.h
index cab9be2bfb7..02e4a2192a4 100644
--- a/gcc/config/i386/gnu-user-common.h
+++ b/gcc/config/i386/gnu-user-common.h
@@ -47,7 +47,7 @@ along with GCC; see the file COPYING3. If not see
/* Similar to standard GNU userspace, but adding -ffast-math support. */
#define GNU_USER_TARGET_MATHFILE_SPEC \
- "%{Ofast|ffast-math|funsafe-math-optimizations:crtfastmath.o%s} \
+
"%{Ofast|ffast-math|funsafe-math-optimizations|mdaz-ftz:%{!shared:crtfastmath.o%s}}
\
%{mpc32:crtprec32.o%s} \
%{mpc64:crtprec64.o%s} \
%{mpc80:crtprec80.o%s}"
diff --git a/gcc/config/i386/i386.opt b/gcc/config/i386/i386.opt
index fb4e57ada7c..8fd222db857 100644
--- a/gcc/config/i386/i386.opt
+++ b/gcc/config/i386/i386.opt
@@ -420,6 +420,10 @@ mpc80
Target RejectNegative
Set 80387 floating-point precision to 80-bit.
+mdaz-ftz
+Target RejectNegative
+Set the FTZ and DAZ Flags.
+
mpreferred-stack-boundary=
Target RejectNegative Joined UInteger Var(ix86_preferred_stack_boundary_arg)
Attempt to keep stack aligned to this power of 2.
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index cb40b38b73a..670e3767fbd 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -1433,7 +1433,7 @@ See RS/6000 and PowerPC Options.
-m96bit-long-double -mlong-double-64 -mlong-double-80 -mlong-double-128 @gol
-mregparm=@var{num} -msseregparm @gol
-mveclibabi=@var{type} -mvect8-ret-in-mem @gol
--mpc32 -mpc64 -mpc80 -mstackrealign @gol
+-mpc32 -mpc64 -mpc80 -mdaz-ftz -mstackrealign @gol
-momit-leaf-frame-pointer -mno-red-zone -mno-tls-direct-seg-refs @gol
-mcmodel=@var{code-model} -mabi=@var{name} -maddress-mode=@var{mode} @gol
-m32 -m64 -mx32 -m16 -miamcu -mlarge-data-threshold=@var{num} @gol
@@ -32752,6 +32752,14 @@ are enabled by default; routines in such libraries
could suffer significant
loss of accuracy, typically through so-called ``catastrophic cancellation'',
when this option is used to set the precision to less than extended precision.
+@item -mdaz-ftz
+@opindex mdaz-ftz
+
+the flush-to-zero (FTZ) and denormals-are-zero (DAZ) flags in the MXCSR
register
+are used to control floating-point calculations.SSE and AVX instructions
+including scalar and vector instructions could benefit from enabling the FTZ
+and DAZ flags when @option{-mdaz-ftz} is specified.
+
@item -mstackrealign
@opindex mstackrealign
Realign the stack at entry. On the x86, the @option{-mstackrealign}
--
2.27.0
