This seems like a compiler bug so I am hoping it will be fixed, or is already fixed in a later release. In fact, I know some users are using the Intel compiler, and we are not hearing reports of regression failures, so I am hoping the release with this bug is not widely used.
--------------------------------------------------------------------------- Jeremy Drake wrote: > Should also warn anyone who tries this that the regression tests for > float4 and float8 fail under normal optimization flags. I managed to > track it down, and apparently some floating point optimizations (seemingly > relating to SSE) cause comparisons involving NaN to give non-standard > results. This is worked around in float[48]cmp by explicitly checking > isnan. The issue I encountered was when dividing by NaN. float[48]div do > a check that if the divisor == 0.0, then a division by zero error is > raised. With the non-standard behavior, the comparison NaN == 0 is true, > and so dividing by NaN results in a division by zero error rather than the > expected result (NaN). > > The workaround is to give the -mp1 flag to the compiler, which rectifies > the behavior. > > I do not know if this error is important enough to insert the option if > the check for the Intel compiler succeeds. > > The rest of this is an irrelevant but (imho) interesting detailed > description of why the code generated by the compiler breaks, and why the > -mp1 flag causes it to start working. > > The exact cause of the nonstandard behavior is an interesting side-effect > of the COMISD instruction, in that if the comparison is unordered, all > three of the ZF, CF, and PF are set to 1. The optimization results in > assembly which looks like (inserted constants instead of registers for > readability) > > comisd 0, NaN > je equal > ; false > equal: > ; true > > The use of the -mp1 flag results in code that checks the parity flag, > which when set indicates an unordered result, like this: > > comisd 0, NaN > jp nequal > je equal > nequal: > ; false > equal: > ; true > > > > On Fri, 21 Apr 2006, Bruce Momjian wrote: > > > > > Comment added and patch applied. Thanks. > > > > --------------------------------------------------------------------------- > > > > > > Jeremy Drake wrote: > > > This patch makes configure check for the __INTEL_COMPILER define (which is > > > the recommended way to detect the intel compiler) before adding the extra > > > CFLAGS if it thinks the compiler is GCC. I am not an autoconf hacker, so > > > I may have done it wrong or something, but it appears to work for me (ICC > > > 9.0.032 on gentoo i686 with latest packages). > > > -- > I tried the clone syscall on me, but it didn't work. > -- Mike Neuffer trying to fix a serious time problem > > ---------------------------(end of broadcast)--------------------------- > TIP 9: In versions below 8.0, the planner will ignore your desire to > choose an index scan if your joining column's datatypes do not > match > -- Bruce Momjian http://candle.pha.pa.us EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. + ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
