http://llvm.org/bugs/show_bug.cgi?id=8096
Summary: instcombine make a call to sqrt dead but fails to
remove it
Product: libraries
Version: trunk
Platform: PC
OS/Version: Linux
Status: NEW
Severity: normal
Priority: P
Component: Scalar Optimizations
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected]
Jan Voung found this interesting test case:
---------------------------------------------------
define float @my_sqrt_f(float %d) nounwind {
entry:
%0 = fpext float %d to double
%1 = call double @sqrt(double %0) nounwind
%2 = fptrunc double %1 to float
ret float %2
}
declare double @sqrt(double) nounwind
------------------------------------------------
$ opt -instcombine test.ll -o test2.ll -S
Produces
----------------------------------------
define float @my_sqrt_f(float %d) nounwind {
entry:
%0 = fpext float %d to double
%1 = call double @sqrt(double %0) nounwind
%2 = call float @sqrtf(float %d) nounwind
ret float %2
}
declare double @sqrt(double) nounwind
declare float @sqrtf(float) nounwind
-------------------------------------
Since sqrt is not side effect free, we are now stuck with both calls.
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