Sorry, I had saved this code snippet a while ago (years), and did not document
what version of the compiler it came from at that time so I don't know.
Robert
-----Original Message-----
From: IBM Mainframe Assembler List <ASSEMBLER-LIST@LISTSERV.UGA.EDU> On Behalf
Of Ian Worthington
Sent: Wednesday, August 20, 2025 14:17
To: ASSEMBLER-LIST@LISTSERV.UGA.EDU
Subject: Re: Execute-Type Instructions
Robert --
That's quite astonishing. Which was the previous compiler, and were the target
and optimisation level set the same?
Best wishes / Mejores deseos / Meilleurs vœux
Ian ...
On Wednesday, August 20, 2025 at 08:50:53 PM GMT+2, Ngan, Robert
<robert.n...@dxc.com> wrote:
Speaking of optimizations, a while back I noticed the COBOL compiler generated
the following code to edit a PIC 9(4) BINARY value into a PIX ZZZZ9 field
MVC 496(6,R13),1851(R3) # TS2=119 +185
LLH R2,8(,R2) # U010-CO-ID
VCVD VRF16,R2,0x85,0
VUPKZ VRF16,1005(,R13),0x4 #
CDZT FP0,1005(5,R13),0x8 #
ESDTR R2,FP0
VL VRF17,2224(,R3),0 #
VL VRF18,2240(,R3),0 #
VLRL VRF20,1005(,R13),0x4 #
VGBM VRF19,0x0
VLEIB VRF19,0xf0,15
VO VRF20,VRF20,VRF19
VPERM VRF16,VRF17,VRF20,VRF18
LHI R4,0x5
VSTL VRF16,R4,496(,R13) # TS2=119
VREPIB VRF20,0x40
LLC R4,2256(R2,R3) #
LTR R4,R4
JE L0642
AHI R4,0xffff
VSTL VRF20,R4,497(,R13) # TS2=119
L0642: EQU *
L R2,108(,R8) # BLL_9
MVC 8(5,R2),497(R13) # U016-CO-ID-DISPLAY TS2=119
I thought "All those vector instructions are better than an a single ED? I'd
better learn what that's doing so I can use that technique myself".
Today, I decided to recompile the module to see if it generates better code
since I noticed some of the above code could be further optimized. Our current
COBOL 6.4 compiler generated:
MVC 536(6,R13),2403(R3) # TS2=119 +2403
LLH R2,8(,R2) # U010-CO-ID
CVD R2,1050(,R13) #
ED 536(6,R13),1055(R13) # TS2=119
L R2,88(,R8) # BLL_9
MVC 8(5,R2),537(R13) # U016-CO-ID-DISPLAY TS2=119
Robert Ngan
DXC Luxoft
[snipping again!]
