[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, 0 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblySubtarget.h b/llvm/lib/Target/WebAssembly/WebAssemblySubtarget.h
index 8ca04543d5e..a6bf0b6d54f 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblySubtarget.h
+++ b/llvm/lib/Target/WebAssembly/WebAssemblySubtarget.h
@@ -31,6 +31,7 @@ namespace llvm {
 class WebAssemblySubtarget final : public WebAssemblyGenSubtargetInfo {
   bool HasSIMD128;
   bool HasAtomics;
+  bool HasNontrappingFPToInt;
 
   /// String name of used CPU.
   std::string CPUString;
@@ -76,6 +77,7 @@ public:
   bool hasAddr64() const { return TargetTriple.isArch64Bit(); }
   bool hasSIMD128() const { return HasSIMD128; }
   bool hasAtomics() const { return HasAtomics; }
+  bool hasNontrappingFPToInt() const { return HasNontrappingFPToInt; }
 
   /// Parses features string setting specified subtarget options. Definition of
   /// function is auto generated by tblgen.