[llvm] 9a35951 - [RISCV] Add freeze when expanding mul by constant to two or more uses (#89290)

[via llvm-commits]

Author: Philip Reames
Date: 2024-04-22T11:40:48-07:00
New Revision: 9a3595167d3ee875e3180800cec5f5c3fd170e63

URL: https://github.com/llvm/llvm-project/commit/9a3595167d3ee875e3180800cec5f5c3fd170e63
DIFF: https://github.com/llvm/llvm-project/commit/9a3595167d3ee875e3180800cec5f5c3fd170e63.diff

LOG: [RISCV] Add freeze when expanding mul by constant to two or more uses (#89290)

topperc pointed this out in review of
https://github.com/llvm/llvm-project/pull/88791, but I believe the
problem applies
here as well. Worth noting is that the code I introduced with this bug
was mostly copied from other targets - which
also have this bug.

Added: 
    

Modified: 
    llvm/lib/Target/RISCV/RISCVISelLowering.cpp

Removed: 
    


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diff  --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
index 82339dd2072172..41483c49ae03cd 100644
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -13430,10 +13430,11 @@ static SDValue expandMul(SDNode *N, SelectionDAG &DAG,
     if (ScaleShift >= 1 && ScaleShift < 4) {
       unsigned ShiftAmt = Log2_64((MulAmt & (MulAmt - 1)));
       SDLoc DL(N);
-      SDValue Shift1 = DAG.getNode(ISD::SHL, DL, VT, N->getOperand(0),
-                                   DAG.getConstant(ShiftAmt, DL, VT));
-      SDValue Shift2 = DAG.getNode(ISD::SHL, DL, VT, N->getOperand(0),
-                                   DAG.getConstant(ScaleShift, DL, VT));
+      SDValue X = DAG.getFreeze(N->getOperand(0));
+      SDValue Shift1 =
+          DAG.getNode(ISD::SHL, DL, VT, X, DAG.getConstant(ShiftAmt, DL, VT));
+      SDValue Shift2 =
+          DAG.getNode(ISD::SHL, DL, VT, X, DAG.getConstant(ScaleShift, DL, VT));
       return DAG.getNode(ISD::ADD, DL, VT, Shift1, Shift2);
     }
   }
@@ -13464,13 +13465,13 @@ static SDValue expandMul(SDNode *N, SelectionDAG &DAG,
     if (ScaleShift >= 1 && ScaleShift < 4) {
       unsigned ShiftAmt = Log2_64(((MulAmt - 1) & (MulAmt - 2)));
       SDLoc DL(N);
-      SDValue Shift1 = DAG.getNode(ISD::SHL, DL, VT, N->getOperand(0),
-                                   DAG.getConstant(ShiftAmt, DL, VT));
-      SDValue Shift2 = DAG.getNode(ISD::SHL, DL, VT, N->getOperand(0),
-                                   DAG.getConstant(ScaleShift, DL, VT));
-      return DAG.getNode(
-          ISD::ADD, DL, VT, Shift1,
-          DAG.getNode(ISD::ADD, DL, VT, Shift2, N->getOperand(0)));
+      SDValue X = DAG.getFreeze(N->getOperand(0));
+      SDValue Shift1 =
+          DAG.getNode(ISD::SHL, DL, VT, X, DAG.getConstant(ShiftAmt, DL, VT));
+      SDValue Shift2 =
+          DAG.getNode(ISD::SHL, DL, VT, X, DAG.getConstant(ScaleShift, DL, VT));
+      return DAG.getNode(ISD::ADD, DL, VT, Shift1,
+                         DAG.getNode(ISD::ADD, DL, VT, Shift2, X));
     }
   }