I am having a little trouble with the fcmp one instruction on doubles only.
For ordered comparisons, the LLVM manual states that true should be returned
iff neither operands is QNAN. ( http://llvm.org/docs/LangRef.html#i_fcmp)
If I do fcmp one which includes one or both operands as a NaN, the result is
expected to be 0 then.
If I run the bitcode with lli (JIT off), no problem. If I use the JIT (lli
--force-interpreted=true), then it returns 1.
(Converely, fcmp une with the JIT returns 0 instead of the expected 1 ...
without JIT it returns the expected 0).
The other operators (oeq, oge, ..., ueq, uge, ...) seem to work fine.
Is this a bug with the JIT or have I done to muck this up? I've included
source below which illustrates the problem (with doubles on fcmp one only
... ).
Thanks for your help.
~ David
declare void @exit(i32)
declare void @llvm.memcpy.i32(i8*, i8*, i32, i32)
; see if (%f1!=%f2) gives the expected result %ne_expected (doubles)
define void @testFCmpOrdered( double %f1, double %f2, i1 %ne_expected ) {
entry:
%ne_result = fcmp one double %f1, %f2
%matches = icmp eq i1 %ne_result, %ne_expected
br i1 %matches, label %return, label %no_match
no_match:
call void @exit( i32 1 )
unreachable
return:
ret void
}
; see if NaN ne comparisons work as expected
define i32 @main() {
entry:
%x = alloca i64, align 8
%nan = alloca double, align 8
; build NaN
store i64 -1, i64* %x
%nan_as_i8 = bitcast double* %nan to i8*
%x_as_i8 = bitcast i64* %x to i8*
call void @llvm.memcpy.i32( i8* %nan_as_i8, i8* %x_as_i8, i32 8, i32 8 )
; load two copies of our NaN
%nan1 = load double* %nan
%nan2 = load double* %nan
; compare NaN to 0 (NaN != 0 should return 0)
call void @testFCmpOrdered( double %nan1, double 0.000000e+00, i1 0 )
; compare NaN to itself (NaN != NaN should return 0)
call void @testFCmpOrdered( double %nan1, double %nan2, i1 0 )
ret i32 0
}
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