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<p class="MsoNormal">If you’re dealing with integers that wide, I’d recommend avoiding the builtin IR integers. There are dedicated libraries for wide integers; the most well-known is probably GMP.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">-Eli<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b>From:</b> llvm-dev <llvm-dev-bounces@lists.llvm.org> <b>On Behalf Of
</b>Riyaz Puthiyapurayil via llvm-dev<br>
<b>Sent:</b> Monday, August 17, 2020 11:54 AM<br>
<b>To:</b> llvm-dev <llvm-dev@lists.llvm.org><br>
<b>Subject:</b> [EXT] [llvm-dev] Code generation option for wide integers on x86_64?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:14.0pt">Is there an existing option in X86_64 target code generator to emit a loop for the following code:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas">define i4096 @add(i4096 %a, i4096 %b)
<b>alwaysinline</b> {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas"> %c = add i4096 %a, %b<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas"> ret i4096 %c<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas">}<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt">instead of:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas"> movq %rdi, %rax<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas"> addq 96(%rsp), %rsi<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas"> adcq 104(%rsp), %rdx<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas"> movq %rdx, 8(%rdi)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas"> movq %rsi, (%rdi)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas"> adcq 112(%rsp), %rcx<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas"> movq %rcx, 16(%rdi)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas"> adcq 120(%rsp), %r8<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas"> movq %r8, 24(%rdi)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas"> adcq 128(%rsp), %r9<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas"> movq %r9, 32(%rdi)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas"> movq 8(%rsp), %rcx<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas"> adcq 136(%rsp), %rcx<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas"> movq %rcx, 40(%rdi)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas"> movq 16(%rsp), %rcx<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas"> :<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas"> :<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas"> :<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt">What is the best strategy for lowering wide integer types/operations on x86_64 without causing code blow up? Should we the code run through a custom pass that replaces wide operations with a library function
call (or alternatively a loop) before code generation? Is there any existing code that can be reused?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt">Is there any documentation that describe strategies for lowering from languages that support arbitrarily wide integers?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt"><o:p> </o:p></span></p>
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