[PATCH] D150221: Add option -fkeep-static-variables to emit all static variables

[Zheng Qian via Phabricator via cfe-commits]

qianzhen created this revision.
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qianzhen requested review of this revision.
Herald added subscribers: cfe-commits, MaskRay.
Herald added a project: clang.

This patch adds a new option -fkeep-static-variables to emit all static 
variables if required. This could be useful in cases where the presence of all 
static variables as symbols in the object file are required.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D150221

Files:
  clang/include/clang/Basic/CodeGenOptions.def
  clang/include/clang/Driver/Options.td
  clang/lib/CodeGen/CodeGenModule.cpp
  clang/lib/Driver/ToolChains/Clang.cpp
  clang/test/CodeGen/keep-static-variables.cpp


Index: clang/test/CodeGen/keep-static-variables.cpp
===================================================================
--- /dev/null
+++ clang/test/CodeGen/keep-static-variables.cpp
@@ -0,0 +1,23 @@
+// RUN: %clang_cc1 -fkeep-static-variables -emit-llvm %s -o - -triple=x86_64-unknown-linux-gnu | FileCheck %s --check-prefixes=CHECK,CHECK-ELF
+// RUN: %clang_cc1 -fkeep-static-variables -emit-llvm %s -o - -triple=powerpc64-ibm-aix-xcoff | FileCheck %s --check-prefixes=CHECK,CHECK-NON-ELF
+
+// CHECK: @_ZL2g1 = internal global i32 0, align 4
+// CHECK: @_ZL2g2 = internal global i32 1, align 4
+// CHECK: @_ZL2g3 = internal global i32 0, align 4
+// CHECK: @_ZL2g4 = internal global i32 2, align 4
+// CHECK-ELF: @llvm.compiler.used = appending global [4 x ptr] [ptr @_ZL2g1, ptr @_ZL2g2, ptr @_ZL2g3, ptr @_ZL2g4], section "llvm.metadata"
+// CHECK-NON-ELF: @llvm.used = appending global [4 x ptr] [ptr @_ZL2g1, ptr @_ZL2g2, ptr @_ZL2g3, ptr @_ZL2g4], section "llvm.metadata"
+
+static int g1;
+static int g2 = 1;
+static int g3;
+static int g4 = 2;
+
+int test1() {
+  g1 = 3;
+  return g1;
+}
+
+int test2() {
+  return g2;
+}
Index: clang/lib/Driver/ToolChains/Clang.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Clang.cpp
+++ clang/lib/Driver/ToolChains/Clang.cpp
@@ -7294,6 +7294,8 @@
 
   Args.addOptInFlag(CmdArgs, options::OPT_fkeep_static_consts,
                     options::OPT_fno_keep_static_consts);
+  Args.addOptInFlag(CmdArgs, options::OPT_fkeep_static_variables,
+                    options::OPT_fno_keep_static_variables);
   Args.addOptInFlag(CmdArgs, options::OPT_fcomplete_member_pointers,
                     options::OPT_fno_complete_member_pointers);
   Args.addOptOutFlag(CmdArgs, options::OPT_fcxx_static_destructors,
Index: clang/lib/CodeGen/CodeGenModule.cpp
===================================================================
--- clang/lib/CodeGen/CodeGenModule.cpp
+++ clang/lib/CodeGen/CodeGenModule.cpp
@@ -2198,11 +2198,15 @@
   if (D && D->hasAttr<UsedAttr>())
     addUsedOrCompilerUsedGlobal(GV);
 
-  if (CodeGenOpts.KeepStaticConsts && D && isa<VarDecl>(D)) {
+  if ((CodeGenOpts.KeepStaticConsts || CodeGenOpts.KeepStaticVariables) && D &&
+      isa<VarDecl>(D)) {
     const auto *VD = cast<VarDecl>(D);
-    if (VD->getType().isConstQualified() &&
-        VD->getStorageDuration() == SD_Static)
-      addUsedOrCompilerUsedGlobal(GV);
+    if (VD->getStorageDuration() == SD_Static) {
+      if (CodeGenOpts.KeepStaticVariables)
+        addUsedOrCompilerUsedGlobal(GV);
+      else if (CodeGenOpts.KeepStaticConsts && VD->getType().isConstQualified())
+        addUsedOrCompilerUsedGlobal(GV);
+    }
   }
 }
 
@@ -3084,11 +3088,14 @@
   if (LangOpts.EmitAllDecls)
     return true;
 
-  if (CodeGenOpts.KeepStaticConsts) {
+  if (CodeGenOpts.KeepStaticConsts || CodeGenOpts.KeepStaticVariables) {
     const auto *VD = dyn_cast<VarDecl>(Global);
-    if (VD && VD->getType().isConstQualified() &&
-        VD->getStorageDuration() == SD_Static)
-      return true;
+    if (VD && VD->getStorageDuration() == SD_Static) {
+      if (CodeGenOpts.KeepStaticVariables)
+        return true;
+      else if (CodeGenOpts.KeepStaticConsts && VD->getType().isConstQualified())
+        return true;
+    }
   }
 
   return getContext().DeclMustBeEmitted(Global);
Index: clang/include/clang/Driver/Options.td
===================================================================
--- clang/include/clang/Driver/Options.td
+++ clang/include/clang/Driver/Options.td
@@ -1697,6 +1697,10 @@
   CodeGenOpts<"KeepStaticConsts">, DefaultFalse,
   PosFlag<SetTrue, [CC1Option], "Keep">, NegFlag<SetFalse, [], "Don't keep">,
   BothFlags<[NoXarchOption], " static const variables if unused">>;
+defm keep_static_variables : BoolFOption<"keep-static-variables",
+  CodeGenOpts<"KeepStaticVariables">, DefaultFalse,
+  PosFlag<SetTrue, [CC1Option], "Keep">, NegFlag<SetFalse, [], "Don't keep">,
+  BothFlags<[NoXarchOption], " static variables if unused">>;
 defm fixed_point : BoolFOption<"fixed-point",
   LangOpts<"FixedPoint">, DefaultFalse,
   PosFlag<SetTrue, [CC1Option], "Enable">, NegFlag<SetFalse, [], "Disable">,
Index: clang/include/clang/Basic/CodeGenOptions.def
===================================================================
--- clang/include/clang/Basic/CodeGenOptions.def
+++ clang/include/clang/Basic/CodeGenOptions.def
@@ -472,6 +472,9 @@
 /// Whether to emit unused static constants.
 CODEGENOPT(KeepStaticConsts, 1, 0)
 
+/// Whether to emit all static variables.
+CODEGENOPT(KeepStaticVariables, 1, 0)
+
 /// Whether to follow the AAPCS enforcing at least one read before storing to a volatile bitfield
 CODEGENOPT(ForceAAPCSBitfieldLoad, 1, 0)
 

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