Emit a single _udivmodsi4 libcall instead of two separate _udivsi3 and

_umodsi3 libcalls if they have the same arguments. This optimization
was apparently broken if one of the node was replaced in place.
rdar://11714607

llvm-svn: 158900

Author: Evan Cheng

llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

@@ -1930,9 +1930,11 @@ static bool isDivRemLibcallAvailable(SDNode *Node, bool isSigned,
   return TLI.getLibcallName(LC) != 0;
 }
 
-/// UseDivRem - Only issue divrem libcall if both quotient and remainder are
+/// useDivRem - Only issue divrem libcall if both quotient and remainder are
 /// needed.
-static bool UseDivRem(SDNode *Node, bool isSigned, bool isDIV) {
+static bool useDivRem(SDNode *Node, bool isSigned, bool isDIV) {
+  // The other use might have been replaced with a divrem already.
+  unsigned DivRemOpc = isSigned ? ISD::SDIVREM : ISD::UDIVREM;
   unsigned OtherOpcode = 0;
   if (isSigned)
     OtherOpcode = isDIV ? ISD::SREM : ISD::SDIV;
@@ -1946,7 +1948,7 @@ static bool UseDivRem(SDNode *Node, bool isSigned, bool isDIV) {
     SDNode *User = *UI;
     if (User == Node)
       continue;
-    if (User->getOpcode() == OtherOpcode &&
+    if ((User->getOpcode() == OtherOpcode || User->getOpcode() == DivRemOpc) &&
         User->getOperand(0) == Op0 &&
         User->getOperand(1) == Op1)
       return true;
@@ -3092,7 +3094,7 @@ void SelectionDAGLegalize::ExpandNode(SDNode *Node) {
     Tmp3 = Node->getOperand(1);
     if (TLI.isOperationLegalOrCustom(DivRemOpc, VT) ||
         (isDivRemLibcallAvailable(Node, isSigned, TLI) &&
-         UseDivRem(Node, isSigned, false))) {
+         useDivRem(Node, isSigned, false))) {
       Tmp1 = DAG.getNode(DivRemOpc, dl, VTs, Tmp2, Tmp3).getValue(1);
     } else if (TLI.isOperationLegalOrCustom(DivOpc, VT)) {
       // X % Y -> X-X/Y*Y
@@ -3120,7 +3122,7 @@ void SelectionDAGLegalize::ExpandNode(SDNode *Node) {
     SDVTList VTs = DAG.getVTList(VT, VT);
     if (TLI.isOperationLegalOrCustom(DivRemOpc, VT) ||
         (isDivRemLibcallAvailable(Node, isSigned, TLI) &&
-         UseDivRem(Node, isSigned, true)))
+         useDivRem(Node, isSigned, true)))
       Tmp1 = DAG.getNode(DivRemOpc, dl, VTs, Node->getOperand(0),
                          Node->getOperand(1));
     else if (isSigned)

llvm/test/CodeGen/ARM/divmod.ll

@@ -1,4 +1,4 @@
-; RUN: llc < %s -mtriple=arm-apple-ios5.0 | FileCheck %s
+; RUN: llc < %s -mtriple=arm-apple-ios5.0 -mcpu=cortex-a8 | FileCheck %s
 
 define void @foo(i32 %x, i32 %y, i32* nocapture %P) nounwind ssp {
 entry:
@@ -56,3 +56,17 @@ bb1:
 
 declare i32 @llvm.objectsize.i32(i8*, i1) nounwind readnone
 declare i8* @__memset_chk(i8*, i32, i32, i32) nounwind
+
+; rdar://11714607
+define i32 @howmany(i32 %x, i32 %y) nounwind {
+entry:
+; CHECK: howmany:
+; CHECK: bl ___udivmodsi4
+; CHECK-NOT: ___udivsi3
+  %rem = urem i32 %x, %y
+  %div = udiv i32 %x, %y
+  %not.cmp = icmp ne i32 %rem, 0
+  %add = zext i1 %not.cmp to i32
+  %cond = add i32 %add, %div
+  ret i32 %cond
+}