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Fix miscompile due to StackColoring incorrectly merging stack slots (PR15707)

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IR optimisation passes can result in a basic block that contains:

  llvm.lifetime.start(%buf)
  ...
  llvm.lifetime.end(%buf)
  ...
  llvm.lifetime.start(%buf)

Before this change, calculateLiveIntervals() was ignoring the second
lifetime.start() and was regarding %buf as being dead from the
lifetime.end() through to the end of the basic block.  This can cause
StackColoring to incorrectly merge %buf with another stack slot.

Fix by removing the incorrect Starts[pos].isValid() and
Finishes[pos].isValid() checks.

Just doing:
      Starts[pos] = Indexes->getMBBStartIdx(MBB);
      Finishes[pos] = Indexes->getMBBEndIdx(MBB);
unconditionally would be enough to fix the bug, but it causes some
test failures due to stack slots not being merged when they were
before.  So, in order to keep the existing tests passing, treat LiveIn
and LiveOut separately rather than approximating the live ranges by
merging LiveIn and LiveOut.

This fixes PR15707.
Patch by Mark Seaborn.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181922 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Derek Schuff 2013-05-15 21:15:09 +00:00
parent 4ef61f2ad4
commit c22cdb7203
2 changed files with 30 additions and 11 deletions
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19
lib/CodeGen/StackColoring.cpp
View File

@ -429,17 +429,14 @@ void StackColoring::calculateLiveIntervals(unsigned NumSlots) {
}
// Create the interval of the blocks that we previously found to be 'alive'.
BitVector Alive = BlockLiveness[MBB].LiveIn;
Alive |= BlockLiveness[MBB].LiveOut;
if (Alive.any()) {
for (int pos = Alive.find_first(); pos != -1;
pos = Alive.find_next(pos)) {
if (!Starts[pos].isValid())
Starts[pos] = Indexes->getMBBStartIdx(MBB);
if (!Finishes[pos].isValid())
Finishes[pos] = Indexes->getMBBEndIdx(MBB);
}
BlockLifetimeInfo &MBBLiveness = BlockLiveness[MBB];
for (int pos = MBBLiveness.LiveIn.find_first(); pos != -1;
pos = MBBLiveness.LiveIn.find_next(pos)) {
Starts[pos] = Indexes->getMBBStartIdx(MBB);
}
for (int pos = MBBLiveness.LiveOut.find_first(); pos != -1;
pos = MBBLiveness.LiveOut.find_next(pos)) {
Finishes[pos] = Indexes->getMBBEndIdx(MBB);
}
for (unsigned i = 0; i < NumSlots; ++i) {

22
test/CodeGen/X86/StackColoring.ll
View File

@ -350,6 +350,28 @@ bb3:
ret i32 0
}
; Regression test for PR15707. %buf1 and %buf2 should not be merged
; in this test case.
;YESCOLOR: myCall_pr15707
;YESCOLOR: subq $200008, %rsp
;NOCOLOR: myCall_pr15707
;NOCOLOR: subq $200008, %rsp
define void @myCall_pr15707() {
%buf1 = alloca i8, i32 100000, align 16
%buf2 = alloca i8, i32 100000, align 16
call void @llvm.lifetime.start(i64 -1, i8* %buf1)
call void @llvm.lifetime.end(i64 -1, i8* %buf1)
call void @llvm.lifetime.start(i64 -1, i8* %buf1)
call void @llvm.lifetime.start(i64 -1, i8* %buf2)
%result1 = call i32 @foo(i32 0, i8* %buf1)
%result2 = call i32 @foo(i32 0, i8* %buf2)
ret void
}
; Check that we don't assert and crash even when there are allocas
; outside the declared lifetime regions.
;YESCOLOR: bad_range