StackColoring: smarter check for slot overlap

[arielb1]

Summary:
The old check for slot overlap treated 2 slots S and T as
overlapping if there existed a CFG node in which both of the slots could
possibly be active. That is overly conservative and caused stack blowups
in Rust programs. Instead, check whether there is a single CFG node in
which both of the slots are possibly active together.

Fixes PR32488.

Patch by Ariel Ben-Yehuda [email protected]

Reviewers: thanm, nagisa, llvm-commits, efriedma, rnk

Reviewed By: thanm

Subscribers: dotdash

Differential Revision: https://reviews.llvm.org/D31583

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@305193 91177308-0d34-0410-b5e6-96231b3b80d8

[infinity0]

Backporting 2b622a3 to Debian LLVM 4.0.1 causes this test failure:

FAIL: LLVM :: CodeGen/X86/StackColoring.ll (9465 of 19322)
******************** TEST 'LLVM :: CodeGen/X86/StackColoring.ll' FAILED ********************
Script:
--
/<<PKGBUILDDIR>>/build-llvm/./bin/llc -mcpu=corei7 -no-stack-coloring=false < /<<PKGBUILDDIR>>/test/CodeGen/X86/StackColoring.ll | /<<PKGBUILDDIR>>/build-llvm/./bin/FileCheck /<<PKGBUILDDIR>>/test/CodeGen/X86/StackColoring.ll --check-prefix=YESCOLOR --check-prefix=CHECK
/<<PKGBUILDDIR>>/build-llvm/./bin/llc -mcpu=corei7 -no-stack-coloring=false -stackcoloring-lifetime-start-on-first-use=false < /<<PKGBUILDDIR>>/test/CodeGen/X86/StackColoring.ll | /<<PKGBUILDDIR>>/build-llvm/./bin/FileCheck /<<PKGBUILDDIR>>/test/CodeGen/X86/StackColoring.ll --check-prefix=NOFIRSTUSE --check-prefix=CHECK
/<<PKGBUILDDIR>>/build-llvm/./bin/llc -mcpu=corei7 -no-stack-coloring=true  < /<<PKGBUILDDIR>>/test/CodeGen/X86/StackColoring.ll | /<<PKGBUILDDIR>>/build-llvm/./bin/FileCheck /<<PKGBUILDDIR>>/test/CodeGen/X86/StackColoring.ll --check-prefix=NOCOLOR --check-prefix=CHECK
--
Exit Code: 2

Command Output (stderr):
--
/<<PKGBUILDDIR>>/build-llvm/./bin/llc: <stdin>:598:13: error: use of undefined value '@llvm.lifetime.end.p0i8'
  call void @llvm.lifetime.end.p0i8(i64 256, i8* %bar_i8)
            ^
FileCheck error: '-' is empty.
FileCheck command line:  /<<PKGBUILDDIR>>/build-llvm/./bin/FileCheck /<<PKGBUILDDIR>>/test/CodeGen/X86/StackColoring.ll --check-prefix=YESCOLOR --check-prefix=CHECK

--

********************

Could you have a guess as to what the correct fix is?

[infinity0]

Possibly removing ".p0i8" from the test will fix it, testing it right now, will report back. The functions are defined with ".p0i8" in the upstream version of the commit (8e83a79) but not in the rust backport (2b622a3) so the latter should also have removed ".p0i8".

[dotdash]

Just remove the .p0i8 suffix on the intrinsics names. They were renamed in a later version, but the backport into our LLVM fork didn't adjust the names, which wasn't noticed because we don't run the LLVM testsuite.

[infinity0]

Confirmed that is enough to fix the tests, all passing now.