[InferAttrs] Handle roundeven like other libm functions (#170691)

It was previously missing entirely. It behaves like floor, ceil, round,
and trunc, having no side effects.

llvm/lib/Transforms/Utils/BuildLibCalls.cpp

diff --git a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
index 213869f..05c882d 100644
--- a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
@@ -1361,6 +1361,9 @@
   case LibFunc_round:
   case LibFunc_roundf:
   case LibFunc_roundl:
+  case LibFunc_roundeven:
+  case LibFunc_roundevenf:
+  case LibFunc_roundevenl:
   case LibFunc_toascii:
   case LibFunc_trunc:
   case LibFunc_truncf:

llvm/test/Transforms/InferFunctionAttrs/annotate.ll

diff --git a/llvm/test/Transforms/InferFunctionAttrs/annotate.ll b/llvm/test/Transforms/InferFunctionAttrs/annotate.ll
index 4a0a20b..f5020a9 100644
--- a/llvm/test/Transforms/InferFunctionAttrs/annotate.ll
+++ b/llvm/test/Transforms/InferFunctionAttrs/annotate.ll
@@ -918,6 +918,15 @@
 ; CHECK: declare x86_fp80 @roundl(x86_fp80) [[MEMNONE_NOFREE_NOUNWIND_WILLRETURN:#[0-9]+]]
 declare x86_fp80 @roundl(x86_fp80)
 
+; CHECK: declare double @roundeven(double) [[MEMNONE_NOFREE_NOUNWIND_WILLRETURN:#[0-9]+]]
+declare double @roundeven(double)
+
+; CHECK: declare float @roundevenf(float) [[MEMNONE_NOFREE_NOUNWIND_WILLRETURN:#[0-9]+]]
+declare float @roundevenf(float)
+
+; CHECK: declare x86_fp80 @roundevenl(x86_fp80) [[MEMNONE_NOFREE_NOUNWIND_WILLRETURN:#[0-9]+]]
+declare x86_fp80 @roundevenl(x86_fp80)
+
 ; CHECK: declare double @scalbln(double, i64) [[ERRNOMEMONLY_NOFREE_NOUNWIND_WILLRETURN:#[0-9]+]]
 declare double @scalbln(double, i64)