http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51622
Bug #: 51622
Summary: GCC generates bad code that generate big executable
sizes when using _Decimal*
Classification: Unclassified
Product: gcc
Version: 4.6.1
Status: UNCONFIRMED
Severity: major
Priority: P3
Component: c
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: mingo...@gmail.com
Created attachment 26140
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=26140
Program and a batch file to show how strange is gcc code generation when using
_Decimal*
The main point here is to demonstrate that gcc is capable to generate good code
size when using _Decimal* but for some reason it get lost with some code
combinations and generates very big executables unnecessarily making a bad
balance between functionality/size.
Here is a program that demonstrate that gcc is generating bad code resulting in
big executables when using _Decimal*.
There is a main.c with several operations on _Decimal64, few on _Decimal128
with some combination of the code (with all operations) the final executable
file is 8KB but with a different combination (again with all operations) the
executable is 2.206KB or 2.2MB. This last one is very strange because the
diference betwen then is calling a printf to print several existing _Decimal64
variable (the biggest 2.2MB) and calling a printf to print only one existing
_Decimal64 variable ((double)discount_over_sales the smallest 8KB but if we try
to any other existing variables it goes to 2.2MB).
gcc -s -O2 -DWITH_TMP main.c -o smallest.exe -> 8KB
gcc -s -O2 -DWITH_ONE_BIG_PRINTF -DWITH_TMP main.c -o strange-big-size-jump.exe
-> 2.206KB or 2.2MB
gcc -s -O2 main.c -o good1.exe -> 8KB
gcc -s -O2 -DWITH_DEC128 -DWITH_ISNAN -DWITH_MPRINTF main.c printf.c -o
biggest.exe -> 2.444KB or 2.4MB
gcc -s -O2 -DWITH_MPRINTF main.c printf.c -o optimus.exe -> 154KB
gcc -s -O2 -DWITH_DEC128 -DWITH_MPRINTF main.c printf.c -o good2.exe -> 367KB
