The only useful loop unrolling flag to give realistically is

'-fno-unroll-loops'. The option to the backend is even called
'DisableUnrollLoops'. This is precisely the form that Clang *didn't*
support. We didn't recognize the flag, we didn't pass it to the CC1
layer, and even if we did we wouldn't use it. Clang only inspected the
positive form of the flag, and only did so to enable loop unrolling when
the optimization level wasn't high enough. This only occurs for an
optimization level that even has a chance of running the loop unroller
when optimizing for size.

This commit wires up the 'no' variant, and switches the code to actually
follow the standard flag pattern of using the last flag and allowing
a flag in either direction to override the default.

I think this is still wrong. I don't know why we disable the loop
unroller entirely *from Clang* when optimizing for size, as the loop
unrolling pass *already has special logic* for the case where the
function is attributed as optimized for size! We should really be
trusting that. Maybe in a follow-up patch, I don't really want to change
behavior here.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@187969 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/clang/Driver/Options.td b/include/clang/Driver/Options.td
index 21f0417b35f49ad51e8d77e8a16eb75e2eb585cb..4598265aeb396818d33bcb118a7c193729f6b67c 100644 (file)
--- a/include/clang/Driver/Options.td
+++ b/include/clang/Driver/Options.td
@@ -791,6 +791,8 @@ def ftrap_function_EQ : Joined<["-"], "ftrap-function=">, Group<f_Group>, Flags<
 def funit_at_a_time : Flag<["-"], "funit-at-a-time">, Group<f_Group>;
 def funroll_loops : Flag<["-"], "funroll-loops">, Group<f_Group>,
   HelpText<"Turn on loop unroller">, Flags<[CC1Option]>;
+def fno_unroll_loops : Flag<["-"], "fno-unroll-loops">, Group<f_Group>,
+  HelpText<"Turn off loop unroller">, Flags<[CC1Option]>;
 def funsigned_bitfields : Flag<["-"], "funsigned-bitfields">, Group<f_Group>;
 def funsigned_char : Flag<["-"], "funsigned-char">, Group<f_Group>;
 def funwind_tables : Flag<["-"], "funwind-tables">, Group<f_Group>;

diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index e4acadbb510145dd25a2afd7c6c0d6724687ff15..ebfc3175f0fe7ce7b80f103c42aa50521228b969 100644 (file)
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -2977,7 +2977,8 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
       CmdArgs.push_back("-fwrapv");
   }
   Args.AddLastArg(CmdArgs, options::OPT_fwritable_strings);
-  Args.AddLastArg(CmdArgs, options::OPT_funroll_loops);
+  Args.AddLastArg(CmdArgs, options::OPT_funroll_loops,
+                  options::OPT_fno_unroll_loops);
 
   Args.AddLastArg(CmdArgs, options::OPT_pthread);
 

diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index a4c93fa5b502de5ad438de9001413310cf3df426..f88c124f08cb65ab0f3165a4a5ab8e767a3b0862 100644 (file)
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -351,8 +351,9 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
   Opts.OptimizeSize = getOptimizationLevelSize(Args);
   Opts.SimplifyLibCalls = !(Args.hasArg(OPT_fno_builtin) ||
                             Args.hasArg(OPT_ffreestanding));
-  Opts.UnrollLoops = Args.hasArg(OPT_funroll_loops) ||
-                     (Opts.OptimizationLevel > 1 && !Opts.OptimizeSize);
+  Opts.UnrollLoops =
+      Args.hasFlag(OPT_funroll_loops, OPT_fno_unroll_loops,
+                   (Opts.OptimizationLevel > 1 && !Opts.OptimizeSize));
 
   Opts.Autolink = !Args.hasArg(OPT_fno_autolink);
   Opts.AsmVerbose = Args.hasArg(OPT_masm_verbose);

diff --git a/test/Driver/clang_f_opts.c b/test/Driver/clang_f_opts.c
index 41d0b5e63db4aead68a0eda05671f9013b959987..87843d3b22f67b27c9e62adac12fc3f2b4acc194 100644 (file)
--- a/test/Driver/clang_f_opts.c
+++ b/test/Driver/clang_f_opts.c
@@ -37,6 +37,13 @@
 // FP-CONTRACT-FAST-CHECK: -ffp-contract=fast
 // FP-CONTRACT-OFF-CHECK: -ffp-contract=off
 
+// RUN: %clang -### -S -funroll-loops %s 2>&1 | FileCheck -check-prefix=CHECK-UNROLL-LOOPS %s
+// RUN: %clang -### -S -fno-unroll-loops %s 2>&1 | FileCheck -check-prefix=CHECK-NO-UNROLL-LOOPS %s
+// RUN: %clang -### -S -fno-unroll-loops -funroll-loops %s 2>&1 | FileCheck -check-prefix=CHECK-UNROLL-LOOPS %s
+// RUN: %clang -### -S -funroll-loops -fno-unroll-loops %s 2>&1 | FileCheck -check-prefix=CHECK-NO-UNROLL-LOOPS %s
+// CHECK-UNROLL-LOOPS: "-funroll-loops"
+// CHECK-NO-UNROLL-LOOPS: "-fno-unroll-loops"
+
 // RUN: %clang -### -S -fvectorize %s 2>&1 | FileCheck -check-prefix=CHECK-VECTORIZE %s
 // RUN: %clang -### -S -fno-vectorize -fvectorize %s 2>&1 | FileCheck -check-prefix=CHECK-VECTORIZE %s
 // RUN: %clang -### -S -fno-vectorize %s 2>&1 | FileCheck -check-prefix=CHECK-NO-VECTORIZE %s