Perform mul combine when multiplying wiht negative constants.
Patch by Weiming Zhao!
This fixes PR12212
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153049 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index 459d82c..e26dd22 100644
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -6865,33 +6865,63 @@
if (!C)
return SDValue();
- uint64_t MulAmt = C->getZExtValue();
+ int64_t MulAmt = C->getSExtValue();
unsigned ShiftAmt = CountTrailingZeros_64(MulAmt);
+
ShiftAmt = ShiftAmt & (32 - 1);
SDValue V = N->getOperand(0);
DebugLoc DL = N->getDebugLoc();
SDValue Res;
MulAmt >>= ShiftAmt;
- if (isPowerOf2_32(MulAmt - 1)) {
- // (mul x, 2^N + 1) => (add (shl x, N), x)
- Res = DAG.getNode(ISD::ADD, DL, VT,
- V, DAG.getNode(ISD::SHL, DL, VT,
- V, DAG.getConstant(Log2_32(MulAmt-1),
- MVT::i32)));
- } else if (isPowerOf2_32(MulAmt + 1)) {
- // (mul x, 2^N - 1) => (sub (shl x, N), x)
- Res = DAG.getNode(ISD::SUB, DL, VT,
- DAG.getNode(ISD::SHL, DL, VT,
- V, DAG.getConstant(Log2_32(MulAmt+1),
- MVT::i32)),
- V);
- } else
- return SDValue();
+
+ if (MulAmt >= 0) {
+ if (isPowerOf2_32(MulAmt - 1)) {
+ // (mul x, 2^N + 1) => (add (shl x, N), x)
+ Res = DAG.getNode(ISD::ADD, DL, VT,
+ V,
+ DAG.getNode(ISD::SHL, DL, VT,
+ V,
+ DAG.getConstant(Log2_32(MulAmt - 1),
+ MVT::i32)));
+ } else if (isPowerOf2_32(MulAmt + 1)) {
+ // (mul x, 2^N - 1) => (sub (shl x, N), x)
+ Res = DAG.getNode(ISD::SUB, DL, VT,
+ DAG.getNode(ISD::SHL, DL, VT,
+ V,
+ DAG.getConstant(Log2_32(MulAmt + 1),
+ MVT::i32)),
+ V);
+ } else
+ return SDValue();
+ } else {
+ uint64_t MulAmtAbs = -MulAmt;
+ if (isPowerOf2_32(MulAmtAbs + 1)) {
+ // (mul x, -(2^N - 1)) => (sub x, (shl x, N))
+ Res = DAG.getNode(ISD::SUB, DL, VT,
+ V,
+ DAG.getNode(ISD::SHL, DL, VT,
+ V,
+ DAG.getConstant(Log2_32(MulAmtAbs + 1),
+ MVT::i32)));
+ } else if (isPowerOf2_32(MulAmtAbs - 1)) {
+ // (mul x, -(2^N + 1)) => - (add (shl x, N), x)
+ Res = DAG.getNode(ISD::ADD, DL, VT,
+ V,
+ DAG.getNode(ISD::SHL, DL, VT,
+ V,
+ DAG.getConstant(Log2_32(MulAmtAbs-1),
+ MVT::i32)));
+ Res = DAG.getNode(ISD::SUB, DL, VT,
+ DAG.getConstant(0, MVT::i32),Res);
+
+ } else
+ return SDValue();
+ }
if (ShiftAmt != 0)
- Res = DAG.getNode(ISD::SHL, DL, VT, Res,
- DAG.getConstant(ShiftAmt, MVT::i32));
+ Res = DAG.getNode(ISD::SHL, DL, VT,
+ Res, DAG.getConstant(ShiftAmt, MVT::i32));
// Do not add new nodes to DAG combiner worklist.
DCI.CombineTo(N, Res, false);