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Hi Dean, I have a question for 32-bit platforms. I see in the code that you used the following in compiler-rt/trunk/lib/xray/xray_interface_internal.h : struct XRaySledEntry { uint64_t Address; uint64_t Function; unsigned char Kind; unsigned char AlwaysInstrument; unsigned char Padding[14]; // Need 32 bytes }; And the peer code in llvm/trunk/lib/Target/X86/X86MCInstLower.cpp : void

> On 4 Aug 2016, at 06:27, Serge Rogatch <serge.rogatch at gmail.com> wrote: > > Hi Dean, > > I have a question about the following piece of code in compiler-rt/trunk/lib/xray/xray_trampoline_x86.S : > movq _ZN6__xray19XRayPatchedFunctionE(%rip), %rax > testq %rax, %rax > je .Ltmp0 > > // assume that %r10d has the function id. > movl %r10d,

I think that 32-bit systems (especially ARM) may be short on memory so doubling the size of the table containing (potentially) all the functions may give a tangible overhead. I would even align the entries to 4 bytes (so 12 bytes per entry) on 32-bit platforms and to 8 bytes (so 24-bytes per entry) on 64-bit platforms, to improve CPU cache hits. What do you think? Cheers, Serge On 8 August 2016