http://llvm.org/bugs/show_bug.cgi?id=2903
Summary: Optimization opportunity - group similarly initialized
stack slots and bulk initialize
Product: libraries
Version: 2.3
Platform: PC
OS/Version: Windows XP
Status: NEW
Severity: normal
Priority: P2
Component: Backend: X86
AssignedTo: [EMAIL PROTECTED]
ReportedBy: [EMAIL PROTECTED]
CC: [email protected]
I've run into a case (x86) where I have a bunch of zero-initialized stack slots
(rooted GC pointers) and the initialization code for them, of the form "mov
mem, 0" is 47kb.
Moving the immediate value to a register and using this register as the source
would save ~20% (8bytes/opcode instead of 10), ie:
xor eax, eax
mov mem, eax
But I was wondering if it'd be possible to group all similarly initialized
stack slots together so that "rep stos" could be used to initialize them all in
one go.
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