comparison src/fftw-3.3.5/m4/ax_gcc_aligns_stack.m4 @ 42:2cd0e3b3e1fd

Current fftw source

+dnl @synopsis AX_GCC_ALIGNS_STACK([ACTION-IF-YES], [ACTION-IF-NO])
+dnl @summary check whether gcc can align stack to 8-byte boundary
+dnl @category Misc
+dnl
+dnl Check to see if we are using a version of gcc that aligns the stack
+dnl (true in gcc-2.95+, which have the -mpreferred-stack-boundary flag).
+dnl Also, however, checks whether main() is correctly aligned by the
+dnl OS/libc/..., as well as for a bug in the stack alignment of gcc-2.95.x
+dnl (see http://gcc.gnu.org/ml/gcc-bugs/1999-11/msg00259.html).
+dnl
+dnl ACTION-IF-YES/ACTION-IF-NO are shell commands to execute if we are
+dnl using gcc and the stack is/isn't aligned, respectively.
+dnl
+dnl Requires macro: AX_CHECK_COMPILER_FLAGS, AX_GCC_VERSION
+dnl
+dnl @version 2005-05-30
+dnl @license GPLWithACException
+dnl @author Steven G. Johnson <[e-mail]>
+AC_DEFUN([AX_GCC_ALIGNS_STACK],
+[
+AC_REQUIRE([AC_PROG_CC])
+ax_gcc_aligns_stack=no
+if test "$GCC" = "yes"; then
+AX_CHECK_COMPILER_FLAGS(-mpreferred-stack-boundary=4, [
+	AC_MSG_CHECKING([whether the stack is at least 8-byte aligned by gcc])
+	save_CFLAGS="$CFLAGS"
+	CFLAGS="-O"
+	AX_CHECK_COMPILER_FLAGS(-malign-double, CFLAGS="$CFLAGS -malign-double")
+	AC_TRY_RUN([#include <stdlib.h>
+#       include <stdio.h>
+	struct yuck { int blechh; };
+	int one(void) { return 1; }
+	struct yuck ick(void) { struct yuck y; y.blechh = 3; return y; }
+#       define CHK_ALIGN(x) if ((((long) &(x)) & 0x7)) { fprintf(stderr, "bad alignment of " #x "\n"); exit(1); }
+	void blah(int foo) { double foobar; CHK_ALIGN(foobar); }
+	int main2(void) {double ok1; struct yuck y; double ok2; CHK_ALIGN(ok1);
+                         CHK_ALIGN(ok2); y = ick(); blah(one()); return 0;}
+	int main(void) { if ((((long) (__builtin_alloca(0))) & 0x7)) __builtin_alloca(4); return main2(); }
+	], [ax_gcc_aligns_stack=yes; ax_gcc_stack_align_bug=no], 
+	ax_gcc_stack_align_bug=yes, [AX_GCC_VERSION(3,0,0, ax_gcc_stack_align_bug=no, ax_gcc_stack_align_bug=yes)])
+	CFLAGS="$save_CFLAGS"
+	AC_MSG_RESULT($ax_gcc_aligns_stack)
+])
+fi
+if test "$ax_gcc_aligns_stack" = yes; then
+	m4_default([$1], :)
+else
+	m4_default([$2], :)
+fi
+])