Fix a recent regression. ClrOpcode is not set for i8; for i8, if

we want to clear %ah to zero before a division, just use a
zero-extending mov to %al. This fixes PR3366.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@62691 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86ISelDAGToDAG.cpp b/lib/Target/X86/X86ISelDAGToDAG.cpp
index 9b42d00..c1d886c 100644 (file)
--- a/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -1381,9 +1381,10 @@ SDNode *X86DAGToDAGISel::Select(SDValue N) {
 
       SDValue Tmp0, Tmp1, Tmp2, Tmp3;
       bool foldedLoad = TryFoldLoad(N, N1, Tmp0, Tmp1, Tmp2, Tmp3);
+      bool signBitIsZero = CurDAG->SignBitIsZero(N0);
 
       SDValue InFlag;
-      if (NVT == MVT::i8 && !isSigned) {
+      if (NVT == MVT::i8 && (!isSigned || signBitIsZero)) {
         // Special case for div8, just use a move with zero extension to AX to
         // clear the upper 8 bits (AH).
         SDValue Tmp0, Tmp1, Tmp2, Tmp3, Move, Chain;
@@ -1405,7 +1406,7 @@ SDNode *X86DAGToDAGISel::Select(SDValue N) {
         InFlag =
           CurDAG->getCopyToReg(CurDAG->getEntryNode(),
                                LoReg, N0, SDValue()).getValue(1);
-        if (isSigned && !CurDAG->SignBitIsZero(N0)) {
+        if (isSigned && !signBitIsZero) {
           // Sign extend the low part into the high part.
           InFlag =
             SDValue(CurDAG->getTargetNode(SExtOpcode, MVT::Flag, InFlag), 0);

diff --git a/test/CodeGen/X86/pr3366.ll b/test/CodeGen/X86/pr3366.ll
new file mode 100644 (file)
index 0000000..a6f3e92
--- /dev/null
+++ b/test/CodeGen/X86/pr3366.ll
@@ -0,0 +1,21 @@
+; RUN: llvm-as < %s | llc -march=x86 | grep movzbl
+; PR3366
+
+define void @_ada_c34002a() nounwind {
+entry:
+  %0 = load i8* null, align 1
+  %1 = sdiv i8 90, %0
+  %2 = icmp ne i8 %1, 3
+  %3 = zext i1 %2 to i8
+  %toBool449 = icmp ne i8 %3, 0
+  %4 = or i1 false, %toBool449
+  %5 = zext i1 %4 to i8
+  %toBool450 = icmp ne i8 %5, 0
+  br i1 %toBool450, label %bb451, label %bb457
+
+bb451:
+  br label %bb457
+
+bb457:
+  unreachable
+}