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, 23 insertions, 0 deletions

diff --git a/llvm/test/Bitcode/fcmp-fast.ll b/llvm/test/Bitcode/fcmp-fast.ll
new file mode 100644
index 00000000000..126e3652e3a
--- /dev/null
+++ b/llvm/test/Bitcode/fcmp-fast.ll
@@ -0,0 +1,23 @@
+; RUN: llvm-as < %s | llvm-dis > %t0
+; RUN: opt -S < %s > %t1
+; RUN: diff %t0 %t1
+; RUN: FileCheck < %t1 %s
+
+; Make sure flags on fcmp instructions are serialized/deserialized properly.
+
+define i1 @foo(float %a, float %b, double %c, double %d) {
+  ; CHECK:   %plain = fcmp ueq float %a, %b
+  %plain = fcmp ueq float %a, %b
+  ; CHECK:   %fast = fcmp fast olt float %a, %b
+  %fast = fcmp fast olt float %a, %b
+  ; CHECK:   %nsz = fcmp nsz uge float %a, %b
+  %nsz = fcmp nsz uge float %a, %b
+  ; CHECK:   %nnan = fcmp nnan nsz oge double %c, %d
+  %nnan = fcmp nnan nsz oge double %c, %d
+
+  %dce1 = or i1 %plain, %fast
+  %dce2 = or i1 %dce1, %nsz
+  %dce3 = or i1 %dce2, %nnan
+
+  ret i1 %dce3
+}