Code size optimisation: don't expand a div to a mul and and a shift sequence.

As a result, the urem instruction will not be expanded to a sequence of umull,
lsrs, muls and sub instructions, but just a call to __aeabi_uidivmod.

Differential Revision: http://reviews.llvm.org/D22131

llvm-svn: 274843

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index dc2ff6eb918..456c5498e3c 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -14516,6 +14516,11 @@ SDValue DAGCombiner::BuildSDIVPow2(SDNode *N) {
 /// number.
 /// Ref: "Hacker's Delight" or "The PowerPC Compiler Writer's Guide".
 SDValue DAGCombiner::BuildUDIV(SDNode *N) {
+  // when optimising for size, we don't want to expand a div to a mul and
+  // and a shift.
+  if (ForCodeSize)
+    return SDValue();
+
   ConstantSDNode *C = isConstOrConstSplat(N->getOperand(1));
   if (!C)
     return SDValue();