[FPEnv] Intrinsics for access to FP environment

The change implements intrinsics 'get_fpenv', 'set_fpenv' and 'reset_fpenv'.
They are used to read floating-point environment, set it or reset to
some default state. They do the same actions as C library functions
'fegetenv' and 'fesetenv'. By default these intrinsics are lowered to calls
to these functions.

The new intrinsics specify FP environment as a value of integer type, it
is convenient of most targets where the FP state is a content of some
register. Some targets however use long representations. On X86 the size
of FP environment is 256 bits, and even half of this size is not a legal
ibteger type. To facilitate legalization in such cases, two sets of DAG
nodes is used. Nodes GET_FPENV and SET_FPENV are used when FP
environment may be represented by a legal integer type. Nodes
GET_FPENV_MEM and SET_FPENV_MEM consider FP environment as a region in
memory, much like `fesetenv` and `fegetenv` do. They are used when
target has long representation for floationg-point state.

Differential Revision: https://reviews.llvm.org/D71742

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/TargetLoweringBase.cpp b/llvm/lib/CodeGen/TargetLoweringBase.cpp
index 081c9e5..f5d2b70 100644
--- a/llvm/lib/CodeGen/TargetLoweringBase.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringBase.cpp
@@ -879,6 +879,11 @@ void TargetLoweringBase::initActions() {
 #define BEGIN_REGISTER_VP_SDNODE(SDOPC, ...)                                   \
     setOperationAction(ISD::SDOPC, VT, Expand);
 #include "llvm/IR/VPIntrinsics.def"
+
+    // FP environment operations default to expand.
+    setOperationAction(ISD::GET_FPENV, VT, Expand);
+    setOperationAction(ISD::SET_FPENV, VT, Expand);
+    setOperationAction(ISD::RESET_FPENV, VT, Expand);
   }
 
   // Most targets ignore the @llvm.prefetch intrinsic.
@@ -909,6 +914,9 @@ void TargetLoweringBase::initActions() {
   setOperationAction(ISD::DEBUGTRAP, MVT::Other, Expand);
 
   setOperationAction(ISD::UBSANTRAP, MVT::Other, Expand);
+
+  setOperationAction(ISD::GET_FPENV_MEM, MVT::Other, Expand);
+  setOperationAction(ISD::SET_FPENV_MEM, MVT::Other, Expand);
 }
 
 MVT TargetLoweringBase::getScalarShiftAmountTy(const DataLayout &DL,