[clang][Driver] recognize -ffp-contract=fast-honor-pragmas

-ffp-contract=fast-honor-pragmas is a valid option recognized
by clang -cc1 but it is missed by clang driver.

Reviewed by: Matt Arsenault

Differential Revision: https://reviews.llvm.org/D145648

Author: yxsamliu

clang/lib/Driver/ToolChains/Clang.cpp

@@ -2955,7 +2955,8 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
         // -ffp-model=precise sets PreciseFPModel to on and Val to
         // "precise". FPContract is set.
         ;
-      } else if (Val.equals("fast") || Val.equals("on") || Val.equals("off")) {
+      } else if (Val.equals("fast") || Val.equals("on") || Val.equals("off") ||
+                 Val.equals("fast-honor-pragmas")) {
         FPContract = Val;
         LastSeenFfpContractOption = Val;
       } else

clang/test/Driver/fp-contract.c

@@ -21,6 +21,10 @@
 // RUN: %clang -### -ffast-math -ffp-contract=fast -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-FPC-FAST %s
 
+// RUN: %clang -### -ffast-math -ffp-contract=fast-honor-pragmas -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-FPC-FAST-HONOR %s
+// CHECK-FPC-FAST-HONOR:     "-ffp-contract=fast-honor-pragmas"
+
 // RUN: %clang -### -ffp-contract=fast -ffast-math -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-FPC-FAST %s
 // RUN: %clang -### -ffp-contract=on -ffast-math -c %s 2>&1 \