https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110564
Bug ID: 110564
Summary: Incorrect results from floating point computations on
x86 when optimized
Product: gcc
Version: 9.4.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: ada
Assignee: unassigned at gcc dot gnu.org
Reporter: drh at sqlite dot org
CC: dkm at gcc dot gnu.org
Target Milestone: ---
Created attachment 55484
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=55484&action=edit
bug.c - compile and run to demonstrate the problem
Simplified test case attached. Incorrect floating point result on Linux x86
when compiling and running as follows:
gcc bug.c -m32 -O1 && ./a.out
The problem goes away under any one or more of the following conditions:
* Omit the -m32 flag (to generate x86_64 code)
* Omit the -O flag or use -O0
* Add the -ffloat-store option
* Uncomment both of the "printf()" statements in the test case
Please advise if I am doing something wrong (undefined or unspecified behavior)
so that I might fix it.
SQLite bug report at https://sqlite.org/forum/forumpost/ee7278611394034c. A
work-around has been checked into SQLite at
https://sqlite.org/src/info/5d9e9364808793d6. Please advise if there is a
better work-around.
