Add support for floating-point minnum and maxnum

The select pattern recognition in ValueTracking (as used by InstCombine
and SelectionDAGBuilder) only knew about integer patterns. This teaches
it about minimum and maximum operations.

matchSelectPattern() has been extended to return a struct containing the
existing Flavor and a new enum defining the pattern's behavior when
given one NaN operand.

C minnum() is defined to return the non-NaN operand in this case, but
the idiomatic C "a < b ? a : b" would return the NaN operand.

ARM and AArch64 at least have different instructions for these different cases.

llvm-svn: 244580

1 files changed, 2 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index e31ba326d09..805e68ff11e 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -2298,7 +2298,8 @@ void SelectionDAGBuilder::visitSelect(const User &I) {
   // Min/max matching is only viable if all output VTs are the same.
   if (std::equal(ValueVTs.begin(), ValueVTs.end(), ValueVTs.begin())) {
     Value *LHS, *RHS;
-    SelectPatternFlavor SPF = matchSelectPattern(const_cast<User*>(&I), LHS, RHS);
+    SelectPatternFlavor SPF =
+      matchSelectPattern(const_cast<User*>(&I), LHS, RHS).Flavor;
     ISD::NodeType Opc = ISD::DELETED_NODE;
     switch (SPF) {
     case SPF_UMAX: Opc = ISD::UMAX; break;