https://bugs.llvm.org/show_bug.cgi?id=50223
Bug ID: 50223
Summary: Bad time complexity in Straight Line Strength Reduce ?
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Scalar Optimizations
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Created attachment 24826
--> https://bugs.llvm.org/attachment.cgi?id=24826&action=edit
bbi-55824.ll reproducer
It looks like something in slsr has bad time complexity, where increasing the
size of a basic block with 6 instructions makes the execution time increase
with a factor 4.
Reproducer:
opt -slsr -o /dev/null bbi-55824.ll
The reproducer above seems too hang, but perhaps it finishes at some point.
However, in the input file I've made a few comments:
; 3s
; 12s
; 45s
; 3m
; 12m
If commenting out all instructions (except the ending "rets") after the "3s"
comment, execution time is roughly 3 seconds on my machine. If instead
commenting out everything after "12s" it takes 12 seconds etc.
So it looks like every 6 new instructions makes the execution time increase
with a factor 4.
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