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Pull in r371111 from upstream llvm trunk (by Eli Friedman):

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[IfConversion] Fix diamond conversion with unanalyzable branches.

  The code was incorrectly counting the number of identical
  instructions, and therefore tried to predicate an instruction which
  should not have been predicated.  This could have various effects: a
  compiler crash, an assembler failure, a miscompile, or just
  generating an extra, unnecessary instruction.

  Instead of depending on TargetInstrInfo::removeBranch, which only
  works on analyzable branches, just remove all branch instructions.

  Fixes https://bugs.llvm.org/show_bug.cgi?id=43121 and
  https://bugs.llvm.org/show_bug.cgi?id=41121 .

  Differential Revision: https://reviews.llvm.org/D67203

This should fix "Unable to predicate BX killed renamable $r0" errors
when building the lang/spidermonkey170 and lang/spidermonkey38 ports for
armv7 and armv6.

PR:		236567
MFC after:	3 days
This commit is contained in:
dim 2019-09-06 16:06:37 +00:00
parent 29ada79727
commit b7e6cfce0a
1 changed files with 8 additions and 2 deletions
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10
contrib/llvm/lib/CodeGen/IfConversion.cpp
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@ -1759,9 +1759,15 @@ bool IfConverter::IfConvertDiamondCommon(
if (!BBI1->IsBrAnalyzable)
verifySameBranchInstructions(&MBB1, &MBB2);
#endif
BBI1->NonPredSize -= TII->removeBranch(*BBI1->BB);
// Remove duplicated instructions.
// Remove duplicated instructions from the tail of MBB1: any branch
// instructions, and the common instructions counted by NumDups2.
DI1 = MBB1.end();
while (DI1 != MBB1.begin()) {
MachineBasicBlock::iterator Prev = std::prev(DI1);
if (!Prev->isBranch() && !Prev->isDebugInstr())
break;
DI1 = Prev;
}
for (unsigned i = 0; i != NumDups2; ) {
// NumDups2 only counted non-dbg_value instructions, so this won't
// run off the head of the list.