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[clang] Add -ffinite-loops & -fno-finite-loops options.
This patch adds 2 new options to control when Clang adds `mustprogress`: 1. -ffinite-loops: assume all loops are finite; mustprogress is added to all loops, regardless of the selected language standard. 2. -fno-finite-loops: assume no loop is finite; mustprogress is not added to any loop or function. We could add mustprogress to functions without loops, but we would have to detect that in Clang, which is probably not worth it. Reviewed By: jdoerfert Differential Revision: https://reviews.llvm.org/D96419
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‎clang/include/clang/Basic/CodeGenOptions.def

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Original file line numberDiff line numberDiff line change
@@ -266,6 +266,9 @@ CODEGENOPT(VectorizeLoop , 1, 0) ///< Run loop vectorizer.
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CODEGENOPT(VectorizeSLP , 1, 0) ///< Run SLP vectorizer.
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CODEGENOPT(ProfileSampleAccurate, 1, 0) ///< Sample profile is accurate.
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269+
/// Treat loops as finite: language, always, never.
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ENUM_CODEGENOPT(FiniteLoops, FiniteLoopsKind, 2, FiniteLoopsKind::Language)
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/// Attempt to use register sized accesses to bit-fields in structures, when
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/// possible.
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CODEGENOPT(UseRegisterSizedBitfieldAccess , 1, 0)

‎clang/include/clang/Basic/CodeGenOptions.h

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@@ -140,6 +140,12 @@ class CodeGenOptions : public CodeGenOptionsBase {
140140
All, // Keep all frame pointers.
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};
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143+
enum FiniteLoopsKind {
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Language, // Not specified, use language standard.
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Always, // All loops are assumed to be finite.
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Never, // No loop is assumed to be finite.
147+
};
148+
143149
/// The code model to use (-mcmodel).
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std::string CodeModel;
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‎clang/include/clang/Driver/Options.td

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@@ -2469,6 +2469,11 @@ def fno_unroll_loops : Flag<["-"], "fno-unroll-loops">, Group<f_Group>,
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defm reroll_loops : BoolFOption<"reroll-loops",
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CodeGenOpts<"RerollLoops">, DefaultFalse,
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PosFlag<SetTrue, [CC1Option], "Turn on loop reroller">, NegFlag<SetFalse>>;
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def ffinite_loops: Flag<["-"], "ffinite-loops">, Group<f_Group>,
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HelpText<"Assume all loops are finite.">, Flags<[CC1Option]>;
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def fno_finite_loops: Flag<["-"], "fno-finite-loops">, Group<f_Group>,
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HelpText<"Do not assume that any loop is finite.">, Flags<[CC1Option]>;
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def ftrigraphs : Flag<["-"], "ftrigraphs">, Group<f_Group>,
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HelpText<"Process trigraph sequences">, Flags<[CC1Option]>;
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def fno_trigraphs : Flag<["-"], "fno-trigraphs">, Group<f_Group>,

‎clang/lib/CodeGen/CodeGenFunction.h

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Original file line numberDiff line numberDiff line change
@@ -507,12 +507,26 @@ class CodeGenFunction : public CodeGenTypeCache {
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/// True if the C++ Standard Requires Progress.
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bool CPlusPlusWithProgress() {
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if (CGM.getCodeGenOpts().getFiniteLoops() ==
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CodeGenOptions::FiniteLoopsKind::Never)
512+
return false;
513+
if (CGM.getCodeGenOpts().getFiniteLoops() ==
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CodeGenOptions::FiniteLoopsKind::Never)
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return false;
516+
510517
return getLangOpts().CPlusPlus11 || getLangOpts().CPlusPlus14 ||
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getLangOpts().CPlusPlus17 || getLangOpts().CPlusPlus20;
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}
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/// True if the C Standard Requires Progress.
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bool CWithProgress() {
523+
if (CGM.getCodeGenOpts().getFiniteLoops() ==
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CodeGenOptions::FiniteLoopsKind::Always)
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return true;
526+
if (CGM.getCodeGenOpts().getFiniteLoops() ==
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CodeGenOptions::FiniteLoopsKind::Never)
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return false;
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return getLangOpts().C11 || getLangOpts().C17 || getLangOpts().C2x;
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}
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‎clang/lib/Driver/ToolChains/Clang.cpp

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Original file line numberDiff line numberDiff line change
@@ -5640,6 +5640,9 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
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if (A->getOption().matches(options::OPT_freroll_loops))
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CmdArgs.push_back("-freroll-loops");
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Args.AddLastArg(CmdArgs, options::OPT_ffinite_loops,
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options::OPT_fno_finite_loops);
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Args.AddLastArg(CmdArgs, options::OPT_fwritable_strings);
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Args.AddLastArg(CmdArgs, options::OPT_funroll_loops,
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options::OPT_fno_unroll_loops);

‎clang/lib/Frontend/CompilerInvocation.cpp

Lines changed: 5 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1633,7 +1633,6 @@ bool CompilerInvocation::ParseCodeGenArgsImpl(CodeGenOptions &Opts,
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Opts.UnrollLoops =
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Args.hasFlag(OPT_funroll_loops, OPT_fno_unroll_loops,
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(Opts.OptimizationLevel > 1));
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Opts.BinutilsVersion =
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std::string(Args.getLastArgValue(OPT_fbinutils_version_EQ));
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@@ -1921,6 +1920,11 @@ bool CompilerInvocation::ParseCodeGenArgsImpl(CodeGenOptions &Opts,
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19221921
Opts.EmitVersionIdentMetadata = Args.hasFlag(OPT_Qy, OPT_Qn, true);
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1923+
if (Args.hasArg(options::OPT_ffinite_loops))
1924+
Opts.FiniteLoops = CodeGenOptions::FiniteLoopsKind::Always;
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else if (Args.hasArg(options::OPT_fno_finite_loops))
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Opts.FiniteLoops = CodeGenOptions::FiniteLoopsKind::Never;
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return Success && Diags.getNumErrors() == NumErrorsBefore;
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}
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‎clang/test/CodeGen/attr-mustprogress.c

Lines changed: 19 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -2,6 +2,9 @@
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// RUN: %clang_cc1 -std=c11 -triple=x86_64-unknown-linux-gnu -S -emit-llvm %s -o - | FileCheck --check-prefix=CHECK --check-prefix=C11 %s
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// RUN: %clang_cc1 -std=c18 -triple=x86_64-unknown-linux-gnu -S -emit-llvm %s -o - | FileCheck --check-prefix=CHECK --check-prefix=C11 %s
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// RUN: %clang_cc1 -std=c2x -triple=x86_64-unknown-linux-gnu -S -emit-llvm %s -o - | FileCheck --check-prefix=CHECK --check-prefix=C11 %s
5+
//
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// RUN: %clang_cc1 -std=c11 -ffinite-loops -triple=x86_64-unknown-linux-gnu -S -emit-llvm %s -o - | FileCheck --check-prefix=CHECK --check-prefix=FINITE %s
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// RUN: %clang_cc1 -std=c11 -fno-finite-loops -triple=x86_64-unknown-linux-gnu -S -emit-llvm %s -o - | FileCheck --check-prefix=CHECK --check-prefix=C99 %s
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69
int a = 0;
710
int b = 0;
@@ -13,7 +16,7 @@ int b = 0;
1316
// CHECK-NEXT: entry:
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// CHECK-NEXT: br label %for.cond
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// CHECK: for.cond:
16-
// CHECK-NOT: br {{.*}}!llvm.loop
19+
// CHECK-NOT: br {{.*}}!llvm.loop
1720
//
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void f0() {
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for (; ;) ;
@@ -45,8 +48,9 @@ void f1() {
4548
// CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[TMP0]], [[TMP1]]
4649
// CHECK-NEXT: br i1 [[CMP]], label %for.body, label %for.end
4750
// CHECK: for.body:
48-
// C99-NOT: br {{.*}} !llvm.loop
49-
// C11: br label %for.cond, !llvm.loop [[LOOP1:!.*]]
51+
// C99-NOT: br {{.*}} !llvm.loop
52+
// C11: br label %for.cond, !llvm.loop [[LOOP1:!.*]]
53+
// FINITE: br label %for.cond, !llvm.loop [[LOOP1:!.*]]
5054
// CHECK: for.end:
5155
// CHECK-NEXT: ret void
5256
//
@@ -73,6 +77,7 @@ void f2() {
7377
// CHECK: for.body2:
7478
// C99-NOT: br {{.*}}, !llvm.loop
7579
// C11: br label %for.cond1, !llvm.loop [[LOOP2:!.*]]
80+
// FINITE: br label %for.cond1, !llvm.loop [[LOOP2:!.*]]
7681
// CHECK: for.end3:
7782
// CHECK-NEXT: ret void
7883
//
@@ -88,7 +93,8 @@ void F() {
8893
// CHECK-NEXT: entry:
8994
// CHECK-NEXT: br label %while.body
9095
// CHECK: while.body:
91-
// CHECK-NOT: br {{.*}}, !llvm.loop
96+
// CHECK-NOT: br {{.*}}, !llvm.loop
97+
//
9298
void w1() {
9399
while (1) {
94100
}
@@ -104,8 +110,9 @@ void w1() {
104110
// CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[TMP0]], [[TMP1]]
105111
// CHECK-NEXT: br i1 [[CMP]], label %while.body, label %while.end
106112
// CHECK: while.body:
107-
// C11: br label %while.cond, [[LOOP5:!llvm.loop !.*]]
108113
// C99-NOT: br {{.*}}, !llvm.loop
114+
// C11: br label %while.cond, !llvm.loop [[LOOP3:!.*]]
115+
// FINITE: br label %while.cond, !llvm.loop [[LOOP3:!.*]]
109116
// CHECK: while.end:
110117
// CHECK-NEXT: ret void
111118
//
@@ -125,7 +132,8 @@ void w2() {
125132
// CHECK-NEXT: br i1 [[CMP]], label %while.body, label %while.end
126133
// CHECK: while.body:
127134
// C99-NOT: br {{.*}} !llvm.loop
128-
// C11: br label %while.cond, !llvm.loop [[LOOP3:!.*]]
135+
// C11: br label %while.cond, !llvm.loop [[LOOP4:!.*]]
136+
// FINITE: br label %while.cond, !llvm.loop [[LOOP4:!.*]]
129137
// CHECK: while.end:
130138
// CHECK-NEXT: br label %while.body2
131139
// CHECK: while.body2:
@@ -165,7 +173,8 @@ void d1() {
165173
// CHECK-NEXT: [[TMP1:%.*]] = load i32, i32* @b, align 4
166174
// CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[TMP0]], [[TMP1]]
167175
// C99-NOT: br {{.*}}, !llvm.loop
168-
// C11: br i1 [[CMP]], label %do.body, label %do.end, !llvm.loop [[LOOP4:!.*]]
176+
// C11: br i1 [[CMP]], label %do.body, label %do.end, !llvm.loop [[LOOP5:!.*]]
177+
// FINITE: br i1 [[CMP]], label %do.body, label %do.end, !llvm.loop [[LOOP5:!.*]]
169178
// CHECK: do.end:
170179
// CHECK-NEXT: ret void
171180
//
@@ -191,7 +200,8 @@ void d2() {
191200
// CHECK-NEXT: [[TMP1:%.*]] = load i32, i32* @b, align 4
192201
// CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[TMP0]], [[TMP1]]
193202
// C99-NOT: br {{.*}}, !llvm.loop
194-
// C11: br i1 [[CMP]], label %do.body1, label %do.end3, !llvm.loop [[LOOP5:!.*]]
203+
// C11: br i1 [[CMP]], label %do.body1, label %do.end3, !llvm.loop [[LOOP6:!.*]]
204+
// FINITE: br i1 [[CMP]], label %do.body1, label %do.end3, !llvm.loop [[LOOP6:!.*]]
195205
// CHECK: do.end3:
196206
// CHECK-NEXT: ret void
197207
//
@@ -208,3 +218,4 @@ void D() {
208218
// C11: [[LOOP3]] = distinct !{[[LOOP3]], [[MP]]}
209219
// C11: [[LOOP4]] = distinct !{[[LOOP4]], [[MP]]}
210220
// C11: [[LOOP5]] = distinct !{[[LOOP5]], [[MP]]}
221+
// C11: [[LOOP6]] = distinct !{[[LOOP6]], [[MP]]}

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