Correct result when a branch condition is live across a block
boundary. <rdar://problem/8933028>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129634 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/ARMFastISel.cpp b/lib/Target/ARM/ARMFastISel.cpp
index ce9e21f..c95b4a8 100644
--- a/lib/Target/ARM/ARMFastISel.cpp
+++ b/lib/Target/ARM/ARMFastISel.cpp
@@ -1121,10 +1121,16 @@
unsigned CmpReg = getRegForValue(BI->getCondition());
if (CmpReg == 0) return false;
- // Re-set the flags just in case.
- unsigned CmpOpc = isThumb ? ARM::t2CMPri : ARM::CMPri;
- AddOptionalDefs(BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(CmpOpc))
- .addReg(CmpReg).addImm(0));
+ // We've been divorced from our compare! Our block was split, and
+ // now our compare lives in a predecessor block. We musn't
+ // re-compare here, as the children of the compare aren't guaranteed
+ // live across the block boundary (we *could* check for this).
+ // Regardless, the compare has been done in the predecessor block,
+ // and it left a value for us in a virtual register. Ergo, we test
+ // the one-bit value left in the virtual register.
+ unsigned TstOpc = isThumb ? ARM::t2TSTri : ARM::TSTri;
+ AddOptionalDefs(BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(TstOpc))
+ .addReg(CmpReg).addImm(1));
unsigned BrOpc = isThumb ? ARM::t2Bcc : ARM::Bcc;
BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(BrOpc))