Add intrinsics for constrained floating point operations
This commit introduces a set of experimental intrinsics intended to prevent
optimizations that make assumptions about the rounding mode and floating point
exception behavior. These intrinsics will later be extended to specify
flush-to-zero behavior. More work is also required to model instruction
dependencies in machine code and to generate these instructions from clang
(when required by pragmas and/or command line options that are not currently
supported).
Differential Revision: https://reviews.llvm.org/D27028
llvm-svn: 293226
diff --git a/llvm/lib/IR/IntrinsicInst.cpp b/llvm/lib/IR/IntrinsicInst.cpp
index 2402506..c9814a9 100644
--- a/llvm/lib/IR/IntrinsicInst.cpp
+++ b/llvm/lib/IR/IntrinsicInst.cpp
@@ -21,6 +21,7 @@
//
//===----------------------------------------------------------------------===//
+#include "llvm/ADT/StringSwitch.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/GlobalVariable.h"
@@ -93,3 +94,34 @@
LLVMContext &Context = M->getContext();
return ConstantInt::get(Type::getInt64Ty(Context), 1);
}
+
+ConstrainedFPIntrinsic::RoundingMode
+ConstrainedFPIntrinsic::getRoundingMode() const {
+ Metadata *MD = dyn_cast<MetadataAsValue>(getOperand(2))->getMetadata();
+ if (!MD || !isa<MDString>(MD))
+ return rmInvalid;
+ StringRef RoundingArg = cast<MDString>(MD)->getString();
+
+ // For dynamic rounding mode, we use round to nearest but we will set the
+ // 'exact' SDNodeFlag so that the value will not be rounded.
+ return StringSwitch<RoundingMode>(RoundingArg)
+ .Case("round.dynamic", rmDynamic)
+ .Case("round.tonearest", rmToNearest)
+ .Case("round.downward", rmDownward)
+ .Case("round.upward", rmUpward)
+ .Case("round.towardzero", rmTowardZero)
+ .Default(rmInvalid);
+}
+
+ConstrainedFPIntrinsic::ExceptionBehavior
+ConstrainedFPIntrinsic::getExceptionBehavior() const {
+ Metadata *MD = dyn_cast<MetadataAsValue>(getOperand(3))->getMetadata();
+ if (!MD || !isa<MDString>(MD))
+ return ebInvalid;
+ StringRef ExceptionArg = cast<MDString>(MD)->getString();
+ return StringSwitch<ExceptionBehavior>(ExceptionArg)
+ .Case("fpexcept.ignore", ebIgnore)
+ .Case("fpexcept.maytrap", ebMayTrap)
+ .Case("fpexcept.strict", ebStrict)
+ .Default(ebInvalid);
+}