R600: Implement getRecipEstimate
This requires a new hook to prevent expanding sqrt in terms
of rsqrt and reciprocal. v_rcp_f32, v_rsq_f32, and v_sqrt_f32 are
all the same rate, so this expansion would just double the number
of instructions and cycles.
llvm-svn: 225828
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 171ee1e..e57c5a2 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -7538,7 +7538,8 @@
}
SDValue DAGCombiner::visitFSQRT(SDNode *N) {
- if (DAG.getTarget().Options.UnsafeFPMath) {
+ if (DAG.getTarget().Options.UnsafeFPMath &&
+ !TLI.isFsqrtCheap()) {
// Compute this as X * (1/sqrt(X)) = X * (X ** -0.5)
if (SDValue RV = BuildRsqrtEstimate(N->getOperand(0))) {
EVT VT = RV.getValueType();