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The AND instruction leaves the V flag unmodified, so it falls victim to the same 

problem as all of the other instructions we fold with CMPs.

llvm-svn: 129602
This commit is contained in:
Cameron Zwarich 2011-04-15 20:45:00 +00:00
parent 7583dbdc88
commit 0829b3065a
2 changed files with 28 additions and 7 deletions
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13
llvm/lib/Target/ARM/ARMBaseInstrInfo.cpp
View File

@ -1638,7 +1638,11 @@ OptimizeCompareInstr(MachineInstr *CmpInstr, unsigned SrcReg, int CmpMask,
case ARM::t2SUBrr:
case ARM::t2SUBri:
case ARM::t2SBCrr:
case ARM::t2SBCri: {
case ARM::t2SBCri:
case ARM::ANDrr:
case ARM::ANDri:
case ARM::t2ANDrr:
case ARM::t2ANDri: {
// Scan forward for the use of CPSR, if it's a conditional code requires
// checking of V bit, then this is not safe to do. If we can't find the
// CPSR use (i.e. used in another block), then it's not safe to perform
@ -1677,18 +1681,13 @@ OptimizeCompareInstr(MachineInstr *CmpInstr, unsigned SrcReg, int CmpMask,
if (!isSafe)
return false;
// fallthrough
}
case ARM::ANDrr:
case ARM::ANDri:
case ARM::t2ANDrr:
case ARM::t2ANDri:
// Toggle the optional operand to CPSR.
MI->getOperand(5).setReg(ARM::CPSR);
MI->getOperand(5).setIsDef(true);
CmpInstr->eraseFromParent();
return true;
}
}
return false;
}

22
llvm/test/CodeGen/ARM/2011-04-15-AndVFlagPeepholeBug.ll Normal file
View File

@ -0,0 +1,22 @@
; RUN: llc < %s -mtriple=thumbv7-apple-darwin10 | FileCheck %s
; CHECK: _f
; CHECK-NOT: ands
; CHECK: cmp
; CHECK: blxle _g
define i32 @f(i32 %a, i32 %b) nounwind ssp {
entry:
%and = and i32 %b, %a
%cmp = icmp slt i32 %and, 1
br i1 %cmp, label %if.then, label %if.end
if.then: ; preds = %entry
tail call void (...)* @g(i32 %a, i32 %b) nounwind
br label %if.end
if.end: ; preds = %if.then, %entry
ret i32 %and
}
declare void @g(...)