Fixes are available
XL C/C++ for Linux Fix Pack 8 (October 2015 Update) for 12.1
XL C/C++ for Linux Fix Pack 4 (October 2013 Update) for 12.1
XL C/C++ for Linux Fix Pack 5 (December 2013 Update) for 12.1
XL C/C++ for Linux Fix Pack 6 (February 2014 Update) for 12.1
XL C/C++ for Linux Fix Pack 7 (May 2014 Update) for 12.1
APAR status
Closed as program error.
Error description
The compiler does not generate efficient code for double to 32-bit unsigned int conversion seen in below test case. cat dblToUint32.C unsigned int toUint32(double in) { return (unsigned int)in; } xlC_r -q64 -O2 -qlist -c dblToUint32.C -qarch=pwr5 xlC_r -q64 -O2 -qlist -c dblToUint32.C -qarch=pwr7 Currently, compiler generates: | 000000 PDEF toUint32(double) | 000000 AKA toUint32__Fd 3| PROC in,vs1 0| 000000 mfspr 7C0802A6 1 LFLR gr0=lr 0| 000004 stdu F821FF91 1 ST8U gr1,#stack(gr1,-112)=gr1 0| 000008 std F8010080 1 ST8 #stack(gr1,128)=gr0 5| 00000C bl 4BFFFFF5 1 CALLN gr3=__uitrunc,1,vs1,gr1,cr[01567]",gr0",gr4"-gr12",vs0"-vs13",mq ",lr",fcr",xer",fsr",ca",ctr",nj",vs0"-vs13",vs32"-vs51" 5| 000010 ori 60000000 1 5| 000014 rlwinm 5463003E 1 RN4 gr3=gr3,0,0xFFFFFFFF 6| 000018 ld E9810080 1 L8 gr12=#stack(gr1,128) 6| 00001C addi 38210070 1 AI gr1=gr1,112 6| 000020 mtspr 7D8803A6 1 LLR lr=gr12 6| 000024 bclr 4E800020 1 BA lr 6| CL.2: | Tag Table | 000028 00000000 00092001 80000000 00000028 | Instruction count 10 | Straight-line exec time 10 For -qarch=pwr5, fctid[z] instruction is expected. For -qarch=pwr7, exploitation of xscvdpuxws is expected.
Local fix
Modify source code sequence.
Problem summary
PROBLEM DESCRIPTION: Using library call __uitrunc instead of using power 5 and power 7 provided instructions for float to unsigned word conversion which produces suboptimal performance. USERS AFFECTED: Anyone that casts a double to an unsigned int.
Problem conclusion
Replaced library calls with code generating instructions for each of the architectures.
Temporary fix
Comments
APAR Information
APAR number
LI77666
Reported component name
XL C/C++ FOR LI
Reported component ID
5725C7300
Reported release
C10
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt
Submitted date
2013-10-28
Closed date
2013-10-28
Last modified date
2013-10-28
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
Fix information
Fixed component name
XL C/C++ FOR LI
Fixed component ID
5725C7300
Applicable component levels
RC10 PSN IV43942
UP06/09/13
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Document Information
Modified date:
14 October 2021