[clang] 1d62be2 - [clang][xray] Add -fxray-ignore-loops option

[Shoaib Meenai via cfe-commits]

Author: Ian Levesque
Date: 2020-01-17T13:32:24-08:00
New Revision: 1d62be244108547558c6d42ddcf2e4a7f3c6dd03

URL: https://github.com/llvm/llvm-project/commit/1d62be244108547558c6d42ddcf2e4a7f3c6dd03
DIFF: https://github.com/llvm/llvm-project/commit/1d62be244108547558c6d42ddcf2e4a7f3c6dd03.diff

LOG: [clang][xray] Add -fxray-ignore-loops option

XRay allows tuning by minimum function size, but also always instruments
functions with loops in them. If the minimum function size is set to a
large value the loop instrumention ends up causing most functions to be
instrumented anyway. This adds a new flag, -fxray-ignore-loops, to disable
the loop detection logic.

Differential Revision: https://reviews.llvm.org/D72873

Added: 
    clang/test/CodeGen/xray-ignore-loops.cpp

Modified: 
    clang/include/clang/Basic/CodeGenOptions.def
    clang/include/clang/Driver/Options.td
    clang/lib/CodeGen/CodeGenFunction.cpp
    clang/lib/Frontend/CompilerInvocation.cpp

Removed: 
    


################################################################################
diff  --git a/clang/include/clang/Basic/CodeGenOptions.def b/clang/include/clang/Basic/CodeGenOptions.def
index 50fc1836282f..9f4f83635673 100644
--- a/clang/include/clang/Basic/CodeGenOptions.def
+++ b/clang/include/clang/Basic/CodeGenOptions.def
@@ -106,6 +106,10 @@ CODEGENOPT(XRayAlwaysEmitCustomEvents , 1, 0)
 ///< Set when -fxray-always-emit-typedevents is enabled.
 CODEGENOPT(XRayAlwaysEmitTypedEvents , 1, 0)
 
+///< Set when -fxray-ignore-loops is enabled.
+CODEGENOPT(XRayIgnoreLoops , 1, 0)
+
+
 ///< Set the minimum number of instructions in a function to determine selective
 ///< XRay instrumentation.
 VALUE_CODEGENOPT(XRayInstructionThreshold , 32, 200)

diff  --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index abfa767afea8..ad829efe43da 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -1292,6 +1292,13 @@ def fxray_always_emit_typedevents : Flag<["-"], "fxray-always-emit-typedevents">
 def fnoxray_always_emit_typedevents : Flag<["-"], "fno-xray-always-emit-typedevents">, Group<f_Group>,
   Flags<[CC1Option]>;
 
+def fxray_ignore_loops : Flag<["-"], "fxray-ignore-loops">, Group<f_Group>,
+  Flags<[CC1Option]>,
+  HelpText<"Don't instrument functions with loops unless they also meet the minimum function size">;
+def fno_xray_ignore_loops : Flag<["-"], "fno-xray-ignore-loops">, Group<f_Group>,
+  Flags<[CC1Option]>;
+
+
 def fxray_link_deps : Flag<["-"], "fxray-link-deps">, Group<f_Group>,
   Flags<[CC1Option]>,
   HelpText<"Tells clang to add the link dependencies for XRay.">;

diff  --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 2bf94f697e01..75f5c0e545d1 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -818,6 +818,9 @@ void CodeGenFunction::StartFunction(GlobalDecl GD, QualType RetTy,
         Fn->addFnAttr(
             "xray-instruction-threshold",
             llvm::itostr(CGM.getCodeGenOpts().XRayInstructionThreshold));
+      if (CGM.getCodeGenOpts().XRayIgnoreLoops) {
+        Fn->addFnAttr("xray-ignore-loops");
+      }
     }
 
     if (const auto *Attr = D->getAttr<PatchableFunctionEntryAttr>()) {

diff  --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index e1e59565083b..3671e084b1ca 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1091,6 +1091,8 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
       Args.hasArg(OPT_fxray_always_emit_typedevents);
   Opts.XRayInstructionThreshold =
       getLastArgIntValue(Args, OPT_fxray_instruction_threshold_EQ, 200, Diags);
+  Opts.XRayIgnoreLoops =
+      Args.hasArg(OPT_fxray_ignore_loops, OPT_fno_xray_ignore_loops, false);
 
   auto XRayInstrBundles =
       Args.getAllArgValues(OPT_fxray_instrumentation_bundle);

diff  --git a/clang/test/CodeGen/xray-ignore-loops.cpp b/clang/test/CodeGen/xray-ignore-loops.cpp
new file mode 100644
index 000000000000..17ea2afbeece
--- /dev/null
+++ b/clang/test/CodeGen/xray-ignore-loops.cpp
@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 -fxray-instrument -fxray-ignore-loops -x c++ -std=c++11 -emit-llvm -o - %s -triple x86_64-unknown-linux-gnu | FileCheck %s
+
+int foo() {
+  return 1;
+}
+
+// CHECK: define i32 @_Z3foov() #[[ATTRS:[0-9]+]] {
+// CHECK-DAG: attributes #[[ATTRS]] = {{.*}} "xray-ignore-loops" {{.*}}