[Attributor] Propagate Cold attribute inter procedurally
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Authored by kuter on Aug 3 2021, 4:24 PM.

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Summary

This patch adds AAHotCold, which propagates the cold attribute.
The Attribute marks a function as cold if all of it's callers are cold.

Other ways of propagating the hot/cold attributes are planned.

	Time	Test
	290 ms	x64 debian > LLVM.Transforms/Attributor::depgraph.ll Script: -- : 'RUN: at line 2'; /var/lib/buildkite-agent/builds/llvm-project/build/bin/opt -passes=attributor-cgscc -S < /var/lib/buildkite-agent/builds/llvm-project/llvm/test/Transforms/Attributor/depgraph.ll 2>&1 \| /var/lib/buildkite-agent/builds/llvm-project/build/bin/FileCheck --allow-unused-prefixes /var/lib/buildkite-agent/builds/llvm-project/llvm/test/Transforms/Attributor/depgraph.ll --check-prefixes=CHECK
	330 ms	x64 windows > LLVM.Transforms/Attributor::depgraph.ll Script: -- : 'RUN: at line 2'; c:\ws\w6\llvm-project\premerge-checks\build\bin\opt.exe -passes=attributor-cgscc -S < C:\ws\w6\llvm-project\premerge-checks\llvm\test\Transforms\Attributor\depgraph.ll 2>&1 \| c:\ws\w6\llvm-project\premerge-checks\build\bin\filecheck.exe --allow-unused-prefixes C:\ws\w6\llvm-project\premerge-checks\llvm\test\Transforms\Attributor\depgraph.ll --check-prefixes=CHECK

kuter requested review of this revision.Aug 3 2021, 4:24 PM

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small fix.

llvm/include/llvm/Transforms/IPO/Attributor.h
4636	We need more than a boolean state, no? Maybe we should use a 3-bit (or 4-bit) state here instead of an optional in the Impl.
llvm/lib/Transforms/IPO/AttributorAttributes.cpp
9605	let's implement this one

Fix the depgraph.ll

llvm/lib/Transforms/IPO/AttributorAttributes.cpp
9605	I implemented this in D107705

Use a BitState instead of hacky Option<bool>
I will rebase the rest of the patch set.

Lg, one nit.

llvm/test/Transforms/Attributor/ArgumentPromotion/byval.ll
162	see below.
llvm/test/Transforms/Attributor/IPConstantProp/2009-09-24-byval-ptr.ll
300	run the script on this file until the change disappears, non-determinism.