optimization/9651: [Alpha] FPE with NAN in spite of isnan protection

[Falk Hueffner <falk.hueffner@student.uni-tuebingen.de>]

>Number:         9651
>Category:       optimization
>Synopsis:       [Alpha] FPE with NAN in spite of isnan protection
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          wrong-code
>Submitter-Id:   net
>Arrival-Date:   Tue Feb 11 00:36:00 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator:     Falk Hueffner
>Release:        3.4 20030203 (experimental)
>Organization:
>Environment:
System: Linux juist 2.5.59 #4 Sat Jan 18 12:46:41 CET 2003 alpha unknown unknown GNU/Linux
Architecture: alpha

	
host: alphaev68-unknown-linux-gnu
build: alphaev68-unknown-linux-gnu
target: alphaev68-unknown-linux-gnu
configured with: ../configure --disable-nls --enable-languags=c++ --with-gcc-version-trigger=/src/gcc-2003.02.03/gcc/version.c --no-create --no-recursion : (reconfigured) ../configure --disable-nls --enable-languages=c++
>Description:
% cat test.cc
#include <math.h>
double f(void);
int foo() {
    double d = f();

    if (isnan(d) || (d != (int) d))
        d = 0;
    return (int) d;
}
double f(void) { return NAN; }
int main() { return foo(); }
% g++ -O2 -mcpu=ev4 test.cc && ./a.out
zsh: floating point exception (core dumped)  ./a.out

It looks like a cvttq/c was dragged out of the second condition:

[...]
        .prologue 1
        jsr $26,($27),_Z1fv             !lituse_jsr!4
        ldah $29,0($26)         !gpdisp!5
        lda $29,0($29)          !gpdisp!5
        cpys $f0,$f0,$f2
        cpys $f0,$f0,$f16
        ldq $27,__isnan($29)            !literal!2
        jsr $26,($27),__isnan           !lituse_jsr!2
        ldah $29,0($26)         !gpdisp!3
        lda $29,0($29)          !gpdisp!3
->      cvttq/c $f2,$f10
        stt $f10,16($30)
        cpys $f31,$f31,$f31
        ldq $1,16($30)
        bne $0,$L3


>How-To-Repeat:
	
>Fix:
-fno-sched-interblock works around it.
>Release-Note:
>Audit-Trail:
>Unformatted: