[Bug driver/19848] New: "options passed" from -verbose-asm do not adequately reflect optimization

[Bug driver/19848] New: "options passed" from -verbose-asm do not adequately reflect optimization

[Thomas dot Koenig at online dot de]

This caused me a lot of pain in trying to disable specific
optimizations with -O1.

$ gfortran -O1 -o dasum-1.s -S -fverbose-asm -fno-loop-optimize -fno-tree-sra
-fno-tree-ter -fno-omit-frame-pointer -fno-tree-dse -fno-tree-dominator-opts
-fno-tree-ch -fno-tree-fre -fno-merge-constants -fno-cprop-registers
-fno-if-conversion2 -fno-defer-pop -fno-tree-lrs -fno-guess-branch-probability
-fno-tree-ccp -fno-tree-copyrename -fno-tree-dce -fno-if-conversion ../dasum.f
$ gfortran -O0 -o dasum-0.s -S -fverbose-asm  ../dasum.f

$ diff -u dasum-0.s dasum-1.s | head -30
--- dasum-0.s   2005-02-09 13:38:52.000000000 +0100
+++ dasum-1.s   2005-02-09 13:38:46.000000000 +0100
@@ -3,7 +3,12 @@
 // GNU F95 version 4.0.0 20050130 (experimental) (ia64-unknown-linux-gnu)
 //     compiled by GNU C version 4.0.0 20050130 (experimental).
 // GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
-// options passed:  -ffixed-form -auxbase-strip -O0 -fverbose-asm
+// options passed:  -ffixed-form -auxbase-strip -O1 -fverbose-asm
+// -fno-loop-optimize -fno-tree-sra -fno-tree-ter -fno-omit-frame-pointer
+// -fno-tree-dse -fno-tree-dominator-opts -fno-tree-ch -fno-tree-fre
+// -fno-merge-constants -fno-cprop-registers -fno-if-conversion2
+// -fno-defer-pop -fno-tree-lrs -fno-guess-branch-probability -fno-tree-ccp
+// -fno-tree-copyrename -fno-tree-dce -fno-if-conversion
 // options enabled:  -falign-loops -fargument-noalias-global
 // -fbranch-count-reg -fcommon -feliminate-unused-debug-types
 // -ffunction-cse -fgcse-lm -fident -fivopts -fkeep-static-consts
@@ -23,531 +28,280 @@
        .prologue 14, 35
        .save ar.pfs, r36
        alloc r36 = ar.pfs, 3, 4, 2, 0  //,,,,
+       adds r16 = -8, r12      //,,
        .vframe r37
        mov r37 = r12   //,
-       adds r12 = -80, r12     //,,
+       adds r12 = -32, r12     //,,
+       mov r17 = ar.lc //,
+       ;;
+       .savepsp ar.lc, 8
+       st8 [r16] = r17, 8      //,
        mov r38 = r1    //,

As you can see from the fact that there is no differences in
the "options enabled:" list in the assembly output, the assembly
should be identical.

However, the compilation results are very different, so -O1
seems to do other, undocumented things.

$ cat ../dasum.f
      double precision function dasum(n,dx,incx)
c
c     takes the sum of the absolute values.
c     jack dongarra, linpack, 3/11/78.
c     modified 3/93 to return if incx .le. 0.
c     modified 12/3/93, array(1) declarations changed to array(*)
c
      double precision dx(*),dtemp
      integer i,incx,m,mp1,n,nincx
c
      dasum = 0.0d0
      dtemp = 0.0d0
      if( n.le.0 .or. incx.le.0 )return
      if(incx.eq.1)go to 20
c
c        code for increment not equal to 1
c
      nincx = n*incx
      do 10 i = 1,nincx,incx
        dtemp = dtemp + dabs(dx(i))
   10 continue
      dasum = dtemp
      return
c
c        code for increment equal to 1
c
c
c        clean-up loop
c
   20 m = mod(n,6)
      if( m .eq. 0 ) go to 40
      do 30 i = 1,m
        dtemp = dtemp + dabs(dx(i))
   30 continue
      if( n .lt. 6 ) go to 60
   40 mp1 = m + 1
      do 50 i = mp1,n,6
        dtemp = dtemp + dabs(dx(i)) + dabs(dx(i + 1)) + dabs(dx(i + 2))
     *  + dabs(dx(i + 3)) + dabs(dx(i + 4)) + dabs(dx(i + 5))
   50 continue
   60 dasum = dtemp
      return
      end

-- 
           Summary: "options passed" from -verbose-asm do not adequately
                    reflect optimization
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: driver
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: Thomas dot Koenig at online dot de
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19848

[Bug driver/19848] "options passed" from -verbose-asm do not adequately reflect optimization

[Thomas dot Koenig at online dot de]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
OtherBugsDependingO|                            |5900
              nThis|                            |
            Version|unknown                     |4.0.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19848

[Bug driver/19848] "options passed" from -verbose-asm do not adequately reflect optimization

[Thomas dot Koenig at online dot de]

------- Additional Comments From Thomas dot Koenig at online dot de  2005-02-09 21:19 -------
Same thing on i686-pc-linux-gnu with the gcc driver:

$ cat main.c
int main()
{
        return 0;
}
$ gcc -S -fverbose-asm -o main-o0.s main.c
$ gcc -S -fno-cprop-registers -fno-defer-pop -fno-guess-branch-probability
-fno-if-conversion -fno-if-conversion2 -fno-loop-optimize -fno-merge-constants
-fno-tree-ccp -fno-tree-ch -fno-tree-copyrename -fno-tree-dce
-fno-tree-dominator-opts -fno-tree-dse -fno-tree-fre -fno-tree-lrs -fno-tree-sra
-fno-tree-ter -fverbose-asm -O1 -o main-o1.s main.c


$ diff -u main-o0.s main-o1.s
--- main-o0.s   2005-02-09 22:17:54.000000000 +0100
+++ main-o1.s   2005-02-09 22:18:14.000000000 +0100
@@ -2,7 +2,12 @@
 # GNU C version 4.0.0 20050208 (experimental) (i686-pc-linux-gnu)
 #      compiled by GNU C version 4.0.0 20050203 (experimental).
 # GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
-# options passed:  -mtune=pentiumpro -auxbase-strip -fverbose-asm
+# options passed:  -mtune=pentiumpro -auxbase-strip -O1
+# -fno-cprop-registers -fno-defer-pop -fno-guess-branch-probability
+# -fno-if-conversion -fno-if-conversion2 -fno-loop-optimize
+# -fno-merge-constants -fno-tree-ccp -fno-tree-ch -fno-tree-copyrename
+# -fno-tree-dce -fno-tree-dominator-opts -fno-tree-dse -fno-tree-fre
+# -fno-tree-lrs -fno-tree-sra -fno-tree-ter -fverbose-asm
 # options enabled:  -falign-loops -fargument-alias -fbranch-count-reg
 # -fcommon -feliminate-unused-debug-types -ffunction-cse -fgcse-lm -fident
 # -fivopts -fkeep-static-consts -fleading-underscore -floop-optimize2
@@ -21,13 +26,8 @@
        movl    %esp, %ebp      #,
        subl    $8, %esp        #,
        andl    $-16, %esp      #,
-       movl    $0, %eax        #, tmp60
-       addl    $15, %eax       #, tmp61
-       addl    $15, %eax       #, tmp62
-       shrl    $4, %eax        #, tmp63
-       sall    $4, %eax        #, tmp64
-       subl    %eax, %esp      # tmp64,
-       movl    $0, %eax        #, D.1118
+       subl    $16, %esp       #,
+       movl    $0, %eax        #, <result>
        leave
        ret
        .size   main, .-main


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19848

[Bug driver/19848] "options passed" from -verbose-asm do not adequately reflect optimization

[falk at debian dot org]

------- Additional Comments From falk at debian dot org  2005-02-09 22:57 -------
There are a gazillion places where we just check "if (optimize)" without
any specific flag. It would be quite a lot of work to introduce flags for all
of them, and I'm not sure it's worth it...

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19848

[Bug driver/19848] "options passed" from -verbose-asm do not adequately reflect optimization

[Thomas dot Koenig at online dot de]

------- Additional Comments From Thomas dot Koenig at online dot de  2005-02-10 08:52 -------
(In reply to comment #2)
> There are a gazillion places where we just check "if (optimize)" without
> any specific flag. It would be quite a lot of work to introduce flags for all
> of them, and I'm not sure it's worth it...

$ find . -name '*.c' | xargs grep  '( *optimize[) =!><|&]' | wc -l
    151

Hmm...

It would still be better if this could be at least lumped into an
option (maybe -foptimize-misc or whatever) which would still be
visible in -fverbose-asm.



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19848

[Bug driver/19848] "options passed" from -verbose-asm do not adequately reflect optimization

[schwab at suse dot de]

------- Additional Comments From schwab at suse dot de  2005-02-10 10:33 -------
$ find . -name '*.c' | xargs grep  '[(&|!] *optimize[) =!><|&]' | wc -l 
204 
 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19848

[Bug driver/19848] "options passed" from -verbose-asm do not adequately reflect optimization

[Thomas dot Koenig at online dot de]

------- Additional Comments From Thomas dot Koenig at online dot de  2005-02-10 20:31 -------
*** Bug 19825 has been marked as a duplicate of this bug. ***

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19848

[Bug driver/19848] "options passed" from -verbose-asm do not adequately reflect optimization

[Thomas dot Koenig at online dot de]

------- Additional Comments From Thomas dot Koenig at online dot de  2005-02-10 20:35 -------
(In reply to comment #4)
> $ find . -name '*.c' | xargs grep  '[(&|!] *optimize[) =!><|&]' | wc -l 
> 204 

Any idea how I should go about further debugging PR 5900?  There is a
wrong-code for ia-64 there, which apparently depends on one of these
204 places.

        Thomas


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19848

[Bug driver/19848] "options passed" from -verbose-asm do not adequately reflect optimization

[manu at gcc dot gnu dot org]

------- Comment #8 from manu at gcc dot gnu dot org  2007-11-14 02:38 -------
I don't think this is a valid bug. There are optimizations that won't be
controlled by a flag. We already have way too many flags.

Please, reopen if I misunderstood the report.


-- 

manu at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |manu at gcc dot gnu dot org
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19848

[Bug driver/19848] "options passed" from -verbose-asm do not adequately reflect optimization

[jvdelisle at gcc dot gnu dot org]

------- Comment #7 from jvdelisle at gcc dot gnu dot org  2005-10-07 07:30 -------
Thomas, perhaps we could divide and conquer.  We could manually eliminate each
of the 204 optimzations one at a time until the breakage disappears.  Maybe we
develop a script to locate those, bubblestrap, test, remove, and go on to the
next until its discovered.

I know its a pain, but it could be done.  If not a script, then get several
volunteers and assign them out to check.  It would be nice to claim a final
victory on this.

Any thoughts anyone


-- 

jvdelisle at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jvdelisle at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19848