[Bug c/13704] New: Regression: Spurious register saves with setjmp on MIPS (and others?) (crosscompiling)

["oneill+gccbugs at cs dot hmc dot edu" <gcc-bugzilla@gcc.gnu.org>]

This bug a regression in 3.2.x and 3.3.x -- it is not in 3.0.x or 3.4 prereleases, but is in 3.2.x and 
3.3.x (including 3.3-20040112) -- it would be helpful to see it fixed in the 3.3.x series, since at 
present it means that 3.3.x cannot be used without patches for some configurations.

Consider the following code (setjmp-caller.c), which will be compiled with -mno-abicalls -fno-pic 
-ffreestanding

--- begin file: setjmp-caller.c ------------------
int setjmp(void *);

int foo()
{
    setjmp(0);
}
--- end file: setjmp-caller.c ------------------

With 3.0.4 and 3.4-20040114, we get the following CORRECT assembly output from a cross 
compiler (built with -nfp), from running:

  mips-linux-gcc-3.0.4 -mno-abicalls -fno-pic -ffreestanding -S -o setjmp-caller-3.0.4.s setjmp-
caller.c

  mips-linux-gcc-3.4-20040114 -mno-abicalls -fno-pic -ffreestanding -S -o setjmp-caller-3.4
-20040114.s setjmp-caller.c


--- begin file: setjmp-caller-3.0.4.s ------------------
	.file	1 "setjmp-caller.c"
	.text
	.align	2
	.globl	foo
	.ent	foo
		.type		 foo,@function
foo:
	.frame	$fp,24,$31		# vars= 0, regs= 2/0, args= 16, extra= 0
	.mask	0xc0000000,-4
	.fmask	0x00000000,0
	subu	$sp,$sp,24
	sw	$31,20($sp)
	sw	$fp,16($sp)
	move	$fp,$sp
	move	$4,$0
	jal	setjmp
	move	$sp,$fp
	lw	$31,20($sp)
	lw	$fp,16($sp)
	addu	$sp,$sp,24
	j	$31
	.end	foo
	.ident	"GCC: (GNU) 3.0.4"
--- end file: setjmp-caller-3.0.4.s ------------------
--- begin file: setjmp-caller-3.4-20040114.s ------------------
	.file	1 "setjmp-caller.c"
	.section .mdebug.abi32
	.previous
	.text
	.align	2
	.globl	foo
	.ent	foo
	.type	foo, @function
foo:
	.frame	$fp,24,$31		# vars= 0, regs= 2/0, args= 16, gp= 0
	.mask	0xc0000000,-4
	.fmask	0x00000000,0
	.set	noreorder
	.set	nomacro
	
	addiu	$sp,$sp,-24
	sw	$31,20($sp)
	sw	$fp,16($sp)
	move	$fp,$sp
	move	$4,$0
	jal	setjmp
	nop

	move	$sp,$fp
	lw	$31,20($sp)
	lw	$fp,16($sp)
	addiu	$sp,$sp,24
	j	$31
	nop

	.set	macro
	.set	reorder
	.end	foo
	.ident	"GCC: (GNU) 3.4.0 20040114 (experimental)"
--- end file: setjmp-caller-3.4-20040114.s ------------------

With the other versions, we get a number of spurious register saves...  For example, with 3.3.2, we 
get:

--- begin file: setjmp-caller-3.3.2.s ------------------
	.file	1 "setjmp-caller.c"
	.section .mdebug.abi32
	.previous
	.text
	.align	2
	.globl	foo
	.ent	foo
	.type	foo, @function
foo:
	.frame	$fp,104,$31		# vars= 0, regs= 10/6, args= 16, extra= 0
	.mask	0xc0ff0000,-52
	.fmask	0xfff00000,-8
	subu	$sp,$sp,104
	sw	$31,52($sp)
	sw	$fp,48($sp)
	sw	$23,44($sp)
	sw	$22,40($sp)
	sw	$21,36($sp)
	sw	$20,32($sp)
	sw	$19,28($sp)
	sw	$18,24($sp)
	sw	$17,20($sp)
	sw	$16,16($sp)
	s.d	$f30,96($sp)
	s.d	$f28,88($sp)
	s.d	$f26,80($sp)
	s.d	$f24,72($sp)
	s.d	$f22,64($sp)
	s.d	$f20,56($sp)
	move	$fp,$sp
	move	$4,$0
	jal	setjmp
	move	$sp,$fp
	lw	$31,52($sp)
	lw	$fp,48($sp)
	lw	$23,44($sp)
	lw	$22,40($sp)
	lw	$21,36($sp)
	lw	$20,32($sp)
	lw	$19,28($sp)
	lw	$18,24($sp)
	lw	$17,20($sp)
	lw	$16,16($sp)
	l.d	$f30,96($sp)
	l.d	$f28,88($sp)
	l.d	$f26,80($sp)
	l.d	$f24,72($sp)
	l.d	$f22,64($sp)
	l.d	$f20,56($sp)
	addu	$sp,$sp,104
	j	$31
	.end	foo
	.ident	"GCC: (GNU) 3.3.2"
--- end file: setjmp-caller-3.3.2.s ------------------

Since the cross compiler was configured with --nfp, this is especially bad, it's emiting floating 
point instructions for a program that doesn't use fp, on a platform that doesn't support it.

I wrote the following bandaid for 3.3.2, but I can't say that it's the right fix, it was just a "make it 
stop!" solution...

--- begin file: gcc-3.3.3-setjmp.patch ------------------
--- gcc-3.3.2+cs161/gcc/reload1.c~	2003-06-06 22:30:09.000000000 -0700
+++ gcc-3.3.2+cs161/gcc/reload1.c	2004-01-13 21:55:37.000000000 -0800
@@ -760,7 +760,7 @@
 	  && GET_MODE (insn) != VOIDmode)
 	PUT_MODE (insn, VOIDmode);
 
-      if (GET_CODE (insn) == CALL_INSN
+      if (0 && GET_CODE (insn) == CALL_INSN
 	  && find_reg_note (insn, REG_SETJMP, NULL))
 	for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
 	  if (! call_used_regs[i])
--- end file: gcc-3.3.3-setjmp.patch ------------------

Best Regards,

    M.E. O'Neill.

P.S.  For what it's worth, in case you want to look into this and you want to know how I built the 
cross compilers, it was as follows 

Download
  binutils-2.14.tar.bz2
  gcc-core-3.0.4.tar.gz
  gcc-core-3.2.3.tar.bz2
  gcc-core-3.3-20040112.tar.bz2
  gcc-core-3.3.2.tar.bz2
  gcc-core-3.4-20040114.tar.bz2

And then, in csh:

set target = mips-linux
set base = `pwd`
set prefix = $base/test-gcc
mkdir -p $prefix/bin
set path = ($path $prefix/bin)
tar xjf binutils-2.14.tar.bz2 
mkdir binutils-2.14-build
cd binutils-2.14-build
../binutils-2.14/configure --nfp --target $target --prefix $prefix
make
make install

foreach vers (3.2.3 3.3.2 3.3-20040112 3.4-20040114)
  cd $base
  if (-e gcc-core-$vers.tar.gz) tar xzf gcc-core-$vers.tar.gz
  if (-e gcc-core-$vers.tar.bz2) tar xjf gcc-core-$vers.tar.bz2
  mkdir -p gcc-$vers-build
  cd gcc-$vers-build
  ../gcc-$vers/configure --nfp --disable-shared --disable-threads --target  $target --prefix 
$prefix
  make 
  make install
  cd $base
  mv $prefix/bin/mips-linux-gcc{,-$vers}
  mv $prefix/bin/mips-linux-cpp{,-$vers}
  rehash
  mips-linux-gcc-$vers -mno-abicalls -fno-pic -ffreestanding -S -o setjmp-caller-$vers.s 
setjmp-caller.c
end

(note that the 3.4-20040114 build will die [hey, it's a snapshot], but it's easy enough to fix by 
hand)

-- 
           Summary: Regression: Spurious register saves with setjmp on MIPS
                    (and others?) (crosscompiling)
           Product: gcc
           Version: 3.3.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P1
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: oneill+gccbugs at cs dot hmc dot edu
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: mips-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13704