optimization/10087: optimizer produces wrong code when indexing malloc'ed 2D array

[p.van-hoof@qub.ac.uk]

>Number:         10087
>Category:       optimization
>Synopsis:       optimizer produces wrong code when indexing malloc'ed 2D array
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          wrong-code
>Submitter-Id:   net
>Arrival-Date:   Fri Mar 14 22:16:01 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator:     Peter van Hoof
>Release:        3.3 20030310 (prerelease)
>Organization:
Queen's University of Belfast
>Environment:
System: SunOS scooby 5.9 Generic_112233-04 sun4u sparc SUNW,Sun-Blade-100
Architecture: sun4

	
host: sparc-sun-solaris2.9
build: sparc-sun-solaris2.9
target: sparc-sun-solaris2.9
configured with: /scratch/temp/ss/gcc-20030310/configure --prefix=/opt/local/gcc330
>Description:
In the attached code a two-dimensional array of structs is malloc'ed,
then the first field of that struct is initialized to 1 for all
array members. Finally the minimum value of all these fields is
determined by looping over the array again. This should of course
return 1, but the actual result is 1.039778e-312.

This code runs OK with gcc 3.2.2
>How-To-Repeat:

scooby>	gcc -v -save-temps -O2 bug.c
Reading specs from /opt/local/gcc330/lib/gcc-lib/sparc-sun-solaris2.9/3.3/specs
Configured with: /scratch/temp/ss/gcc-20030310/configure --prefix=/opt/local/gcc330
Thread model: posix
gcc version 3.3 20030310 (prerelease)
 /opt/local/gcc330/lib/gcc-lib/sparc-sun-solaris2.9/3.3/cc1 -E -quiet -v -D__GNUC__=3 -D__GNUC_MINOR__=3 -D__GNUC_PATCHLEVEL__=0 -Dsparc -D__sparc__ -D__sparc -D__GCC_NEW_VARARGS__ -Acpu=sparc -Amachine=sparc bug.c -O2 bug.i
ignoring nonexistent directory "/opt/local/gcc330/sparc-sun-solaris2.9/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /opt/local/gcc330/include
 /opt/local/gcc330/lib/gcc-lib/sparc-sun-solaris2.9/3.3/include
 /usr/include
End of search list.
 /opt/local/gcc330/lib/gcc-lib/sparc-sun-solaris2.9/3.3/cc1 -fpreprocessed bug.i -quiet -dumpbase bug.c -auxbase bug -O2 -version -o bug.s
GNU C version 3.3 20030310 (prerelease) (sparc-sun-solaris2.9)
	compiled by GNU C version 3.3 20030310 (prerelease).
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
 /usr/ccs/bin/as -V -Qy -s -o bug.o bug.s
/usr/ccs/bin/as: Sun WorkShop 6 update 2 Compiler Common 6.2 Solaris_9_CBE 2001/04/02
 /opt/local/gcc330/lib/gcc-lib/sparc-sun-solaris2.9/3.3/collect2 -V -Y P,/usr/ccs/lib:/usr/lib -Qy /opt/local/gcc330/lib/gcc-lib/sparc-sun-solaris2.9/3.3/crt1.o /opt/local/gcc330/lib/gcc-lib/sparc-sun-solaris2.9/3.3/crti.o /usr/ccs/lib/values-Xa.o /opt/local/gcc330/lib/gcc-lib/sparc-sun-solaris2.9/3.3/crtbegin.o -L/opt/local/gcc330/lib/gcc-lib/sparc-sun-solaris2.9/3.3 -L/usr/ccs/bin -L/usr/ccs/lib -L/opt/local/gcc330/lib/gcc-lib/sparc-sun-solaris2.9/3.3/../../.. bug.o -lgcc -lgcc_eh -lc -lgcc -lgcc_eh -lc /opt/local/gcc330/lib/gcc-lib/sparc-sun-solaris2.9/3.3/crtend.o /opt/local/gcc330/lib/gcc-lib/sparc-sun-solaris2.9/3.3/crtn.o
ld: Software Generation Utilities - Solaris Link Editors: 5.9-1.373
scooby>	a.out 
result 1.039778e-312

This is the input:

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end

>Fix:
Using a lower level of optimization works around the bug.
>Release-Note:
>Audit-Trail:
>Unformatted: