Don't lower srem/urem X%C to X-X/C*C unless the division is actually
optimized. This avoids creating illegal divisions when the combiner is
running after legalize; this fixes PR1815. Also, it produces better
code in the included testcase by avoiding the subtract and multiply
when the division isn't optimized.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44341 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 8f6800a..3be1fdd 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -1306,15 +1306,17 @@
DAG.MaskedValueIsZero(N0, SignBit))
return DAG.getNode(ISD::UREM, VT, N0, N1);
- // Unconditionally lower X%C -> X-X/C*C. This allows the X/C logic to hack on
- // the remainder operation.
+ // If X/C can be simplified by the division-by-constant logic, lower
+ // X%C to the equivalent of X-X/C*C.
if (N1C && !N1C->isNullValue()) {
SDOperand Div = DAG.getNode(ISD::SDIV, VT, N0, N1);
- SDOperand Mul = DAG.getNode(ISD::MUL, VT, Div, N1);
- SDOperand Sub = DAG.getNode(ISD::SUB, VT, N0, Mul);
- AddToWorkList(Div.Val);
- AddToWorkList(Mul.Val);
- return Sub;
+ SDOperand OptimizedDiv = combine(Div.Val);
+ if (OptimizedDiv.Val && OptimizedDiv.Val != Div.Val) {
+ SDOperand Mul = DAG.getNode(ISD::MUL, VT, OptimizedDiv, N1);
+ SDOperand Sub = DAG.getNode(ISD::SUB, VT, N0, Mul);
+ AddToWorkList(Mul.Val);
+ return Sub;
+ }
}
// undef % X -> 0
@@ -1351,15 +1353,17 @@
}
}
- // Unconditionally lower X%C -> X-X/C*C. This allows the X/C logic to hack on
- // the remainder operation.
+ // If X/C can be simplified by the division-by-constant logic, lower
+ // X%C to the equivalent of X-X/C*C.
if (N1C && !N1C->isNullValue()) {
SDOperand Div = DAG.getNode(ISD::UDIV, VT, N0, N1);
- SDOperand Mul = DAG.getNode(ISD::MUL, VT, Div, N1);
- SDOperand Sub = DAG.getNode(ISD::SUB, VT, N0, Mul);
- AddToWorkList(Div.Val);
- AddToWorkList(Mul.Val);
- return Sub;
+ SDOperand OptimizedDiv = combine(Div.Val);
+ if (OptimizedDiv.Val && OptimizedDiv.Val != Div.Val) {
+ SDOperand Mul = DAG.getNode(ISD::MUL, VT, OptimizedDiv, N1);
+ SDOperand Sub = DAG.getNode(ISD::SUB, VT, N0, Mul);
+ AddToWorkList(Mul.Val);
+ return Sub;
+ }
}
// undef % X -> 0