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Hey Guys, I have a newbie question about supporting the GNU atomic builtin, __sync_fetch_and_nand. It appears that LLVM 29 produces X86 assembly like the GCC versions below v4.4, i.e. NEGATE and AND notq %rax movq 48(%rsp), %rcx andq %rcx, %rax I'm looking to produce X86 assembly like GCC v4.4 and greater, i.e. NOT AND movq 48(%rsp), %rcx andq %rcx, %rax notq %rax I currently have custom code to make the switch between impleme...

..._func contains masses of code the code in main is also sometimes different (not just inlined) to the_func clang -DITER -O2 clang -DITER -O3 gives: the_func: leaq 12(%rdi), %rcx leaq 4(%rdi), %rax cmpq %rax, %rcx cmovaq %rcx, %rax movq %rdi, %rsi notq %rsi addq %rax, %rsi shrq $2, %rsi incq %rsi xorl %edx, %edx movabsq $9223372036854775800, %rax # imm = 0x7FFFFFFFFFFFFFF8 andq %rsi, %rax pxor %xmm0, %xmm0 je .LBB0_1 # BB#2: # %vector.body.p...

This set of patches converts the way frames gets created from using PUSHes/POPs to using MOVes, thus allowing (in certain cases) to avoid saving/restoring part of the register set. While the place where the (small) win from this comes from varies between CPUs, the net effect is a 1 to 2% reduction on a combined interruption entry and exit when the full state save can be avoided. 1: use MOV