<div dir="ltr">Yea, I think this is the right direction.<div><br></div><div>Let's clean up how the API is structured though:</div><div><br></div><div>1) pass FastMathFlags by value, and default construct the obvious value.</div><div><br></div><div>2) what about making a SimplifyFPBinOp which *requires* a flags parameter in addition to the opcode? Then SimplifyBinOp could delegate to this with a default constructed flags for the FP cases. In the caller code, I feel like this would be a touch cleaner / less prone to minor errors. Because we already have to test whether the operation is FP and could have flags, we might as well call a specialized routine.</div><div><br></div><div>As a nit-pick, it'd be nice to use clang-format on the caller, I think it will do a nice job with these long argument lists. (Unless you did, and clang-format is just choosing this... somewhat surprising layout?)</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Jan 29, 2015 at 6:02 PM, Michael Zolotukhin <span dir="ltr"><<a href="mailto:mzolotukhin@apple.com" target="_blank">mzolotukhin@apple.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word"><br><div><span class=""><blockquote type="cite"><div>On Jan 29, 2015, at 6:01 PM, Michael Zolotukhin <<a href="mailto:mzolotukhin@apple.com" target="_blank">mzolotukhin@apple.com</a>> wrote:</div><br><div><div style="word-wrap:break-word"><br><div><blockquote type="cite"><div>On Jan 29, 2015, at 4:21 PM, Chandler Carruth <<a href="mailto:chandlerc@google.com" target="_blank">chandlerc@google.com</a>> wrote:</div><br><div><div dir="ltr">Do we use the context instruction to extract fast math flags elsewhere?<div><br></div><div>I wouldn't expect that to be reliably at all. Nothing *requires* the context instruction to be the one governing the semantics.</div><div><br></div><div>I think we need to pass the fast math flags directly into SimplifyBinOp for this to work.</div></div></div></blockquote><div><br></div><div>I tried to avoid adding a new argument, but you are right: using the context instruction isn’t appropriate for this.</div><div><br></div><div>Updated patch is attached, is it better?</div></div></div></div></blockquote></span>Oops, I forgot the patch. Here it is:</div><div><br></div><div></div></div><br><div style="word-wrap:break-word"><div></div><div><br></div><div>Michael<br><blockquote type="cite"><div><div style="word-wrap:break-word"><div><div><br></div><div><br></div><div><br></div><div>Michael</div><div><br></div><blockquote type="cite"><div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Jan 29, 2015 at 4:12 PM, Michael Zolotukhin <span dir="ltr"><<a href="mailto:mzolotukhin@apple.com" target="_blank">mzolotukhin@apple.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi,<br>
<br>
Currently InlineCost pass fails to use fast-math flags when analyzing profitability of inlining. Here is a small example to demonstrate that:<br>
<br>
float foo(float *a, float b) {<br>
float r;<br>
if (a[1] * b)<br>
r = a[1]+a[2]/a[3]-a[4]*a[5]+a[6]-a[7]+a[8]*a[9]+<br>
a[11]+a[12]/a[13]-a[14]*a[15]+a[16]-a[17]+a[18]*a[19]+<br>
a[21]+a[22]/a[23]-a[24]*a[25]+a[26]-a[27]+a[28]*a[29]+<br>
a[31]+a[32]/a[33]-a[34]*a[35]+a[36]-a[37]+a[38]*a[39]+<br>
a[41]+a[42]/a[43]-a[44]*a[45]+a[46]-a[47]+a[48]*a[49]+<br>
a[51]+a[52]/a[53]-a[54]*a[55]+a[56]-a[57]+a[58]*a[59]+<br>
a[61]+a[62]/a[63]-a[64]*a[65]+a[66]-a[67]+a[68]*a[69]+<br>
a[0]*a[0]+b;<br>
else<br>
r = 1;<br>
return r;<br>
}<br>
float boo(float *a) {<br>
return foo(a, 0.0);<br>
}<br>
<br>
Here inliner can’t figure out that a[1]*b can be folded to 0 if the call is inlined, and decides not to inline.<br>
<br>
That happens because inliner drops fast-math flags in SimplifyBinOp. The attached patch fixes it by looking into the instruction math flags. Does it look good?<br>
<br>
Without patch:<br>
> clang inline.c -O3 -S -Rpass=inline -ffast-math<br>
// Empty output<br>
<br>
With patch:<br>
> clang inline.c -O3 -S -Rpass=inline -ffast-math<br>
inline.c:17:10: remark: foo inlined into boo [-Rpass=inline]<br>
return foo(a, 0.0);<br>
^<br>
<br>
<br><br>
<br>
Thanks,<br>
Michael<br>_______________________________________________<br>
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<br></blockquote></div><br></div>
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