[Hexagon] Remove fp-contract=fast setting for at O3

[bcahoon]

Summary

Change Hexagon so that the setting for fp-contract is the default setting. This makes Hexagon consistent with all the other targets.

clang/lib/Driver/ToolChains/Hexagon.cpp

unsigned HexagonToolChain::getOptimizationLevel(
   if (S.getAsInteger(10, OptLevel))
     return 0;
   return OptLevel;
 }
 
 void HexagonToolChain::addClangTargetOptions(const ArgList &DriverArgs,
                                              ArgStringList &CC1Args,
                                              Action::OffloadKind) const {
-  if (!DriverArgs.hasArg(options::OPT_ffp_contract)) {
-    unsigned OptLevel = getOptimizationLevel(DriverArgs);
-    if (OptLevel >= 3)
-      CC1Args.push_back("-ffp-contract=fast");
-  }
   if (DriverArgs.hasArg(options::OPT_ffixed_r19)) {
     CC1Args.push_back("-target-feature");
     CC1Args.push_back("+reserved-r19");
   }
   if (isAutoHVXEnabled(DriverArgs)) {
     CC1Args.push_back("-mllvm");
     CC1Args.push_back("-hexagon-autohvx");
   }

clang/test/Driver/hexagon-toolchain-elf.c

 // CHECK025: "-cc1" {{.*}} "-target-cpu" "hexagonv65"
 // CHECK025: hexagon-link{{.*}}/Inputs/hexagon_tree/Tools/bin/../target/hexagon/lib/v65/crt0
 
 // RUN: %clang -### -target hexagon-unknown-elf \
 // RUN:   -ccc-install-dir %S/Inputs/hexagon_tree/Tools/bin \
 // RUN:   -O3 \
 // RUN:   %s 2>&1 \
 // RUN:   | FileCheck -check-prefix=CHECK026 %s
-// CHECK026: "-ffp-contract=fast"
+// CHECK026-NOT: "-ffp-contract=fast"
 // CHECK026: hexagon-link
 
 // RUN: %clang -### -target hexagon-unknown-elf \
 // RUN:   -ccc-install-dir %S/Inputs/hexagon_tree/Tools/bin \
 // RUN:   -O3 -ffp-contract=off \
 // RUN:   %s 2>&1 \
 // RUN:   | FileCheck -check-prefix=CHECK027 %s
 // CHECK027-NOT: "-ffp-contract=fast"