https://bugs.llvm.org/show_bug.cgi?id=48715
Bug ID: 48715
Summary: [NPM] LoopIdiom missed opportunity
Product: new-bugs
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: enhancement
Priority: P
Component: new bugs
Assignee: unassignedbugs at nondot.org
Reporter: sjoerd.meijer at arm.com
CC: htmldeveloper at gmail.com, llvm-bugs at lists.llvm.org
Created attachment 24368
--> https://bugs.llvm.org/attachment.cgi?id=24368&action=edit
Reproducer
Compile attached reproducer loop idiom with:
clang --target=arm-arm-none-eabi -mcpu=cortex-m33 -Ofast loopidiom.c -S
-Rpass=loop-idiom -fno-experimental-new-pass-manager
shows:
loopidiom.c:156:15: remark: Transformed loop-strided store into a call to
llvm.memset.p0i8.i32() function [-Rpass=loop-idiom]
*px++ = (q31_t)(sum1 >> 31);
^
whereas with the NPM and -fexperimental-new-pass-manager this memset is not
recognised.
I appreciate this is not a very detailed bug report, and I could have reduced
and analysed this further. But I am a bit in a hurry with this as I am looking
at a lot of changes and regressions (in different benchmarks). I also don't
know yet if this is the (only) root cause, but this kernel regresses with 20%
with the NPM and it's the first obvious change I see.
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