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> <span style="font-family: "Segoe UI", "Segoe UI Web (West European)", "Segoe UI", -apple-system, BlinkMacSystemFont, Roboto, "Helvetica Neue", sans-serif; font-size: 15px; background-color: rgb(255, 255, 255); display: inline !important"><span> </span>It
reads as, "do an ISO C++ standard volatile load"</span></div>
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<span style="font-family: "Segoe UI", "Segoe UI Web (West European)", "Segoe UI", -apple-system, BlinkMacSystemFont, Roboto, "Helvetica Neue", sans-serif; font-size: 15px; background-color: rgb(255, 255, 255); display: inline !important"><br>
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<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<span style="font-family: "Segoe UI", "Segoe UI Web (West European)", "Segoe UI", -apple-system, BlinkMacSystemFont, Roboto, "Helvetica Neue", sans-serif; font-size: 15px; background-color: rgb(255, 255, 255); display: inline !important">That is the intended
behavior.</span></div>
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<span style="font-family: "Segoe UI", "Segoe UI Web (West European)", "Segoe UI", -apple-system, BlinkMacSystemFont, Roboto, "Helvetica Neue", sans-serif; font-size: 15px; background-color: rgb(255, 255, 255); display: inline !important"><br>
</span></div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<span style="font-family: "Segoe UI", "Segoe UI Web (West European)", "Segoe UI", -apple-system, BlinkMacSystemFont, Roboto, "Helvetica Neue", sans-serif; font-size: 15px; background-color: rgb(255, 255, 255); display: inline !important">> <span style="font-family: "Segoe UI", "Segoe UI Web (West European)", "Segoe UI", -apple-system, BlinkMacSystemFont, Roboto, "Helvetica Neue", sans-serif; background-color: rgb(255, 255, 255); display: inline !important">it
really means "do an atomic (not volatile) load"</span></span></div>
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<span style="font-family: "Segoe UI", "Segoe UI Web (West European)", "Segoe UI", -apple-system, BlinkMacSystemFont, Roboto, "Helvetica Neue", sans-serif; font-size: 15px; background-color: rgb(255, 255, 255); display: inline !important"><span style="font-family: "Segoe UI", "Segoe UI Web (West European)", "Segoe UI", -apple-system, BlinkMacSystemFont, Roboto, "Helvetica Neue", sans-serif; background-color: rgb(255, 255, 255); display: inline !important"><br>
</span></span></div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<span style="font-family: "Segoe UI", "Segoe UI Web (West European)", "Segoe UI", -apple-system, BlinkMacSystemFont, Roboto, "Helvetica Neue", sans-serif; font-size: 15px; background-color: rgb(255, 255, 255); display: inline !important"><span style="font-family: "Segoe UI", "Segoe UI Web (West European)", "Segoe UI", -apple-system, BlinkMacSystemFont, Roboto, "Helvetica Neue", sans-serif; background-color: rgb(255, 255, 255); display: inline !important">Only
if that happens to be the case on the indicated hardware. For example, MSVC++ implements seq_cst loads on ARM with an __iso_volatile_load## followed by __dmb. It only gets atomic behavior on x86 because a seq_cst load on that hardware is an ordinary load.</span></span></div>
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</span></span></div>
<div style="color: rgb(0, 0, 0);"><span style="font-size: 15px;">__iso_volatile_store is also affected, though the specific customer bug report that opened this can of worms doesn't touch that.</span></div>
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<div style="color: rgb(0, 0, 0);"><span style="font-size: 15px;">Thanks for your help!</span></div>
<div style="color: rgb(0, 0, 0);"><span style="font-size: 15px;"><br>
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<div style="color: rgb(0, 0, 0);"><span style="font-size: 15px;">Billy3</span></div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Reid Kleckner <rnk@google.com><br>
<b>Sent:</b> Thursday, March 28, 2019 02:14 PM<br>
<b>To:</b> JF Bastien<br>
<b>Cc:</b> Billy O'Neal (VC LIBS); cfe-dev<br>
<b>Subject:</b> Re: [cfe-dev] FYI, Intel folks might be looking to add the __iso_volatile_Xxx family for MSVC STL <atomic> soon</font>
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<div dir="ltr">On Thu, Mar 28, 2019 at 1:46 PM JF Bastien <<a href="mailto:jfbastien@apple.com">jfbastien@apple.com</a>> wrote:</div>
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<div>On Mar 28, 2019, at 12:02 PM, Billy O'Neal (VC LIBS) <<a href="mailto:bion@microsoft.com" target="_blank">bion@microsoft.com</a>> wrote:</div>
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Update: VS2019 Update 2 is likely to do this; who do I need to prod such that I get to use these unconditionally in our <atomic> ?<span id="x_gmail-m_7048915203350462242🙂" title=":slight_smile:">🙂</span></div>
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<div>You want the same feature in clang-cl, so I suggest talking to Reid, sending a patch to clang, and having him review it ;-)</div>
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<div>I think it's just a matter of moving code from <a href="https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fllvm%2Fllvm-project%2Fblob%2Fmaster%2Fclang%2Finclude%2Fclang%2FBasic%2FBuiltinsAArch64.def%23L82&data=02%7C01%7Cbion%40microsoft.com%7Cf794057fb30f4989fdeb08d6b3c268aa%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C1%7C636894044906044641&sdata=nrge3My1Gn0Qz1%2Bbe7C2LF5PodSwlCU%2B0D4Xd0Hg0p4%3D&reserved=0" originalsrc="https://github.com/llvm/llvm-project/blob/master/clang/include/clang/Basic/BuiltinsAArch64.def#L82" shash="Z0eRezTOohKUSbM63FkLQcCj+WkRmUyHpK0QxrDIFBCpaFRiSbCKRTMvSALJ+PQjb2pKPvt6G4GXOUVO/uqB/M9Ibq2jya9K+MGKwMrzAw7XZ450Wuv8w/w8b9WX90La9jHZxrgZZCXkhu8HpbAFM7cEAsTUEv7qF4vFYKrwmKo=">
BuiltinsAArch64.def</a> (and ARM) to Builtins.def, and maybe some followon changes.</div>
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<div>The naming for these intrinsics is confusing. It reads as, "do an ISO C++ standard volatile load", but it really means "do an atomic (not volatile) load", but I suppose the time to address that is long gone.</div>
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<div>I went ahead and started a patch to make them available.</div>
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