http://llvm.org/bugs/show_bug.cgi?id=18846
Bug ID: 18846
Summary: needless avx spill/reload
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: Register Allocator
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
Created attachment 12063
--> http://llvm.org/bugs/attachment.cgi?id=12063&action=edit
The LLVM-IR file to reproduce this bug
When running 'llc spill-reload.ll' the generated AVX assembly contains
the following code eight times (once for each spill):
vmovups 704(%rsp), %ymm8 # 32-byte Folded Reload
vmovups %ymm8, 704(%rsp) # 32-byte Folded Spill
This is similar to PR10070, which was already fixed. Spilling the value
beforehand
and reloading it at this very position is a good decission. Even spilling the
same
value again is the right choice. However, I do not see why we need to have an
explicit copy back to the stack. We just loaded the value from the stack, so we
know that the very same value is already on the stack. I would expect LLVM to
not emmit the 'vmovups %ymm8, 704(%rsp) # 32-byte Folded Spill'
instruction.
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