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Prevent potential NOREX bug.

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A GR8_NOREX virtual register is created when extrating a sub_8bit_hi
sub-register:

  %vreg2<def> = COPY %vreg1:sub_8bit_hi; GR8_NOREX:%vreg2 %GR64_ABCD:%vreg1
  TEST8ri_NOREX %vreg2, 1, %EFLAGS<imp-def>; GR8_NOREX:%vreg2

If such a live range is ever split, its register class must not be
inflated to GR8.  The sub-register copy can only target GR8_NOREX.

I dont have a test case for this theoretical bug.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@141500 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2011-10-08 20:20:03 +00:00
parent ed74482704
commit b7994fedcb
1 changed files with 11 additions and 0 deletions
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11
lib/Target/X86/X86RegisterInfo.cpp
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@ -246,6 +246,17 @@ X86RegisterInfo::getMatchingSuperRegClass(const TargetRegisterClass *A,
const TargetRegisterClass*
X86RegisterInfo::getLargestLegalSuperClass(const TargetRegisterClass *RC) const{
// Don't allow super-classes of GR8_NOREX. This class is only used after
// extrating sub_8bit_hi sub-registers. The H sub-registers cannot be copied
// to the full GR8 register class in 64-bit mode, so we cannot allow the
// reigster class inflation.
//
// The GR8_NOREX class is always used in a way that won't be constrained to a
// sub-class, so sub-classes like GR8_ABCD_L are allowed to expand to the
// full GR8 class.
if (RC == X86::GR8_NOREXRegisterClass)
return RC;
const TargetRegisterClass *Super = RC;
TargetRegisterClass::sc_iterator I = RC->getSuperClasses();
do {