If the CPSR is defined by a copy, then we don't want to merge it into an IT
block. E.g., if we have:
movs r1, r1
rsb r1, 0
movs r2, r2
rsb r2, 0
we don't want this to be converted to:
movs r1, r1
movs r2, r2
itt mi
rsb r1, 0
rsb r2, 0
PR11107 & <rdar://problem/10259534>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@141589 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/Thumb2ITBlockPass.cpp b/lib/Target/ARM/Thumb2ITBlockPass.cpp
index 360ec00..2bf99bf 100644
--- a/lib/Target/ARM/Thumb2ITBlockPass.cpp
+++ b/lib/Target/ARM/Thumb2ITBlockPass.cpp
@@ -124,6 +124,28 @@
if (Uses.count(DstReg) || Defs.count(SrcReg))
return false;
+ // If the CPSR is defined by this copy, then we don't want to move it. E.g.,
+ // if we have:
+ //
+ // movs r1, r1
+ // rsb r1, 0
+ // movs r2, r2
+ // rsb r2, 0
+ //
+ // we don't want this to be converted to:
+ //
+ // movs r1, r1
+ // movs r2, r2
+ // itt mi
+ // rsb r1, 0
+ // rsb r2, 0
+ //
+ //
+ for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I)
+ if (MI->getOperand(I).isReg() && MI->getOperand(I).getReg() == ARM::CPSR &&
+ MI->getOperand(I).isDef())
+ return false;
+
// Then peek at the next instruction to see if it's predicated on CC or OCC.
// If not, then there is nothing to be gained by moving the copy.
MachineBasicBlock::iterator I = MI; ++I;