Add support for fast-math flags to the FCmp instruction.

FCmp behaves a lot like a floating-point binary operator in many ways,
and can benefit from fast-math information. Flags such as nsz and nnan
can affect if this fcmp (in combination with a select) can be treated
as a fminnum/fmaxnum operation.

This adds backwards-compatible bitcode support, IR parsing and writing,
LangRef changes and IRBuilder changes. I'll need to audit InstSimplify
and InstCombine in a followup to find places where flags should be
copied.

llvm-svn: 241901

1 files changed, 11 insertions, 2 deletions

diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index 91a88bc91fd..aa96d60ca0d 100644
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -4534,8 +4534,17 @@ int LLParser::ParseInstruction(Instruction *&Inst, BasicBlock *BB,
   case lltok::kw_and:
   case lltok::kw_or:
   case lltok::kw_xor:    return ParseLogical(Inst, PFS, KeywordVal);
-  case lltok::kw_icmp:
-  case lltok::kw_fcmp:   return ParseCompare(Inst, PFS, KeywordVal);
+  case lltok::kw_icmp:   return ParseCompare(Inst, PFS, KeywordVal);
+  case lltok::kw_fcmp: {
+    FastMathFlags FMF = EatFastMathFlagsIfPresent();
+    int Res = ParseCompare(Inst, PFS, KeywordVal);
+    if (Res != 0)
+      return Res;
+    if (FMF.any())
+      Inst->setFastMathFlags(FMF);
+    return 0;
+  }
+
   // Casts.
   case lltok::kw_trunc:
   case lltok::kw_zext: