[WebAssembly] Fix trapping behavior in fptosi/fptoui.

This adds code to protect WebAssembly's `trunc_s` family of opcodes
from values outside their domain. Even though such conversions have
full undefined behavior in C/C++, LLVM IR's `fptosi` and `fptoui` do
not, and only return undef.

This also implements the proposed non-trapping float-to-int conversion
feature and uses that instead when available.

llvm-svn: 319128

1 files changed, 2 insertions, 1 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblySubtarget.cpp b/llvm/lib/Target/WebAssembly/WebAssemblySubtarget.cpp
index 6fae72c..9e122a5 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblySubtarget.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblySubtarget.cpp
@@ -41,7 +41,8 @@ WebAssemblySubtarget::WebAssemblySubtarget(const Triple &TT,
                                            const std::string &FS,
                                            const TargetMachine &TM)
     : WebAssemblyGenSubtargetInfo(TT, CPU, FS), HasSIMD128(false),
-      HasAtomics(false), CPUString(CPU), TargetTriple(TT), FrameLowering(),
+      HasAtomics(false), HasNontrappingFPToInt(false), CPUString(CPU),
+      TargetTriple(TT), FrameLowering(),
       InstrInfo(initializeSubtargetDependencies(FS)), TSInfo(),
       TLInfo(TM, *this) {}