<div dir="ltr">This results in a new gcc warning:<div><br></div>[ 633s] /home/abuild/rpmbuild/BUILD/llvm/tools/clang/lib/AST/ExprConstant.cpp: In function '{anonymous}::EvalStmtResult EvaluateSwitch(clang::APValue&, {anonymous}::EvalInfo&, const clang::SwitchStmt*)': [ 633s] /home/abuild/rpmbuild/BUILD/llvm/tools/clang/lib/AST/ExprConstant.cpp:2876:1: warning: control reaches end of non-void function [-Wreturn-type]
</div><div class="gmail_extra"><br><br><div class="gmail_quote">On Sun, May 12, 2013 at 7:32 PM, Richard Smith <span dir="ltr"><<a href="mailto:richard-llvm@metafoo.co.uk" target="_blank">richard-llvm@metafoo.co.uk</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Author: rsmith<br>
Date: Sun May 12 12:32:42 2013<br>
New Revision: 181671<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=181671&view=rev" target="_blank">http://llvm.org/viewvc/llvm-project?rev=181671&view=rev</a><br>
Log:<br>
C++1y: support for 'switch' statements in constexpr functions. This is somewhat<br>
inefficient; we perform a linear scan of switch labels to find the one matching<br>
the condition, and then walk the body looking for that label. Both parts should<br>
be straightforward to optimize.<br>
<br>
Modified:<br>
cfe/trunk/include/clang/AST/Stmt.h<br>
cfe/trunk/lib/AST/ExprConstant.cpp<br>
cfe/trunk/test/SemaCXX/constant-expression-cxx1y.cpp<br>
<br>
Modified: cfe/trunk/include/clang/AST/Stmt.h<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/AST/Stmt.h?rev=181671&r1=181670&r2=181671&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/AST/Stmt.h?rev=181671&r1=181670&r2=181671&view=diff</a><br>
==============================================================================<br>
--- cfe/trunk/include/clang/AST/Stmt.h (original)<br>
+++ cfe/trunk/include/clang/AST/Stmt.h Sun May 12 12:32:42 2013<br>
@@ -967,9 +967,6 @@ public:<br>
SwitchCase *getSwitchCaseList() { return FirstCase; }<br>
<br>
/// \brief Set the case list for this switch statement.<br>
- ///<br>
- /// The caller is responsible for incrementing the retain counts on<br>
- /// all of the SwitchCase statements in this list.<br>
void setSwitchCaseList(SwitchCase *SC) { FirstCase = SC; }<br>
<br>
SourceLocation getSwitchLoc() const { return SwitchLoc; }<br>
<br>
Modified: cfe/trunk/lib/AST/ExprConstant.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/ExprConstant.cpp?rev=181671&r1=181670&r2=181671&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/ExprConstant.cpp?rev=181671&r1=181670&r2=181671&view=diff</a><br>
==============================================================================<br>
--- cfe/trunk/lib/AST/ExprConstant.cpp (original)<br>
+++ cfe/trunk/lib/AST/ExprConstant.cpp Sun May 12 12:32:42 2013<br>
@@ -2769,7 +2769,9 @@ enum EvalStmtResult {<br>
/// Hit a 'continue' statement.<br>
ESR_Continue,<br>
/// Hit a 'break' statement.<br>
- ESR_Break<br>
+ ESR_Break,<br>
+ /// Still scanning for 'case' or 'default' statement.<br>
+ ESR_CaseNotFound<br>
};<br>
}<br>
<br>
@@ -2803,12 +2805,13 @@ static bool EvaluateCond(EvalInfo &Info,<br>
}<br>
<br>
static EvalStmtResult EvaluateStmt(APValue &Result, EvalInfo &Info,<br>
- const Stmt *S);<br>
+ const Stmt *S, const SwitchCase *SC = 0);<br>
<br>
/// Evaluate the body of a loop, and translate the result as appropriate.<br>
static EvalStmtResult EvaluateLoopBody(APValue &Result, EvalInfo &Info,<br>
- const Stmt *Body) {<br>
- switch (EvalStmtResult ESR = EvaluateStmt(Result, Info, Body)) {<br>
+ const Stmt *Body,<br>
+ const SwitchCase *Case = 0) {<br>
+ switch (EvalStmtResult ESR = EvaluateStmt(Result, Info, Body, Case)) {<br>
case ESR_Break:<br>
return ESR_Succeeded;<br>
case ESR_Succeeded:<br>
@@ -2816,17 +2819,128 @@ static EvalStmtResult EvaluateLoopBody(A<br>
return ESR_Continue;<br>
case ESR_Failed:<br>
case ESR_Returned:<br>
+ case ESR_CaseNotFound:<br>
return ESR;<br>
}<br>
llvm_unreachable("Invalid EvalStmtResult!");<br>
}<br>
<br>
+/// Evaluate a switch statement.<br>
+static EvalStmtResult EvaluateSwitch(APValue &Result, EvalInfo &Info,<br>
+ const SwitchStmt *SS) {<br>
+ // Evaluate the switch condition.<br>
+ if (SS->getConditionVariable() &&<br>
+ !EvaluateDecl(Info, SS->getConditionVariable()))<br>
+ return ESR_Failed;<br>
+ APSInt Value;<br>
+ if (!EvaluateInteger(SS->getCond(), Value, Info))<br>
+ return ESR_Failed;<br>
+<br>
+ // Find the switch case corresponding to the value of the condition.<br>
+ // FIXME: Cache this lookup.<br>
+ const SwitchCase *Found = 0;<br>
+ for (const SwitchCase *SC = SS->getSwitchCaseList(); SC;<br>
+ SC = SC->getNextSwitchCase()) {<br>
+ if (isa<DefaultStmt>(SC)) {<br>
+ Found = SC;<br>
+ continue;<br>
+ }<br>
+<br>
+ const CaseStmt *CS = cast<CaseStmt>(SC);<br>
+ APSInt LHS = CS->getLHS()->EvaluateKnownConstInt(Info.Ctx);<br>
+ APSInt RHS = CS->getRHS() ? CS->getRHS()->EvaluateKnownConstInt(Info.Ctx)<br>
+ : LHS;<br>
+ if (LHS <= Value && Value <= RHS) {<br>
+ Found = SC;<br>
+ break;<br>
+ }<br>
+ }<br>
+<br>
+ if (!Found)<br>
+ return ESR_Succeeded;<br>
+<br>
+ // Search the switch body for the switch case and evaluate it from there.<br>
+ switch (EvalStmtResult ESR = EvaluateStmt(Result, Info, SS->getBody(), Found)) {<br>
+ case ESR_Break:<br>
+ return ESR_Succeeded;<br>
+ case ESR_Succeeded:<br>
+ case ESR_Continue:<br>
+ case ESR_Failed:<br>
+ case ESR_Returned:<br>
+ return ESR;<br>
+ case ESR_CaseNotFound:<br>
+ Found->dump();<br>
+ SS->getBody()->dump();<br>
+ llvm_unreachable("couldn't find switch case");<br>
+ }<br>
+}<br>
+<br>
// Evaluate a statement.<br>
static EvalStmtResult EvaluateStmt(APValue &Result, EvalInfo &Info,<br>
- const Stmt *S) {<br>
+ const Stmt *S, const SwitchCase *Case) {<br>
if (!Info.nextStep(S))<br>
return ESR_Failed;<br>
<br>
+ // If we're hunting down a 'case' or 'default' label, recurse through<br>
+ // substatements until we hit the label.<br>
+ if (Case) {<br>
+ // FIXME: We don't start the lifetime of objects whose initialization we<br>
+ // jump over. However, such objects must be of class type with a trivial<br>
+ // default constructor that initialize all subobjects, so must be empty,<br>
+ // so this almost never matters.<br>
+ switch (S->getStmtClass()) {<br>
+ case Stmt::CompoundStmtClass:<br>
+ // FIXME: Precompute which substatement of a compound statement we<br>
+ // would jump to, and go straight there rather than performing a<br>
+ // linear scan each time.<br>
+ case Stmt::LabelStmtClass:<br>
+ case Stmt::AttributedStmtClass:<br>
+ case Stmt::DoStmtClass:<br>
+ break;<br>
+<br>
+ case Stmt::CaseStmtClass:<br>
+ case Stmt::DefaultStmtClass:<br>
+ if (Case == S)<br>
+ Case = 0;<br>
+ break;<br>
+<br>
+ case Stmt::IfStmtClass: {<br>
+ // FIXME: Precompute which side of an 'if' we would jump to, and go<br>
+ // straight there rather than scanning both sides.<br>
+ const IfStmt *IS = cast<IfStmt>(S);<br>
+ EvalStmtResult ESR = EvaluateStmt(Result, Info, IS->getThen(), Case);<br>
+ if (ESR != ESR_CaseNotFound || !IS->getElse())<br>
+ return ESR;<br>
+ return EvaluateStmt(Result, Info, IS->getElse(), Case);<br>
+ }<br>
+<br>
+ case Stmt::WhileStmtClass: {<br>
+ EvalStmtResult ESR =<br>
+ EvaluateLoopBody(Result, Info, cast<WhileStmt>(S)->getBody(), Case);<br>
+ if (ESR != ESR_Continue)<br>
+ return ESR;<br>
+ break;<br>
+ }<br>
+<br>
+ case Stmt::ForStmtClass: {<br>
+ const ForStmt *FS = cast<ForStmt>(S);<br>
+ EvalStmtResult ESR =<br>
+ EvaluateLoopBody(Result, Info, FS->getBody(), Case);<br>
+ if (ESR != ESR_Continue)<br>
+ return ESR;<br>
+ if (FS->getInc() && !EvaluateIgnoredValue(Info, FS->getInc()))<br>
+ return ESR_Failed;<br>
+ break;<br>
+ }<br>
+<br>
+ case Stmt::DeclStmtClass:<br>
+ // FIXME: If the variable has initialization that can't be jumped over,<br>
+ // bail out of any immediately-surrounding compound-statement too.<br>
+ default:<br>
+ return ESR_CaseNotFound;<br>
+ }<br>
+ }<br>
+<br>
// FIXME: Mark all temporaries in the current frame as destroyed at<br>
// the end of each full-expression.<br>
switch (S->getStmtClass()) {<br>
@@ -2865,11 +2979,13 @@ static EvalStmtResult EvaluateStmt(APVal<br>
const CompoundStmt *CS = cast<CompoundStmt>(S);<br>
for (CompoundStmt::const_body_iterator BI = CS->body_begin(),<br>
BE = CS->body_end(); BI != BE; ++BI) {<br>
- EvalStmtResult ESR = EvaluateStmt(Result, Info, *BI);<br>
- if (ESR != ESR_Succeeded)<br>
+ EvalStmtResult ESR = EvaluateStmt(Result, Info, *BI, Case);<br>
+ if (ESR == ESR_Succeeded)<br>
+ Case = 0;<br>
+ else if (ESR != ESR_CaseNotFound)<br>
return ESR;<br>
}<br>
- return ESR_Succeeded;<br>
+ return Case ? ESR_CaseNotFound : ESR_Succeeded;<br>
}<br>
<br>
case Stmt::IfStmtClass: {<br>
@@ -2909,9 +3025,10 @@ static EvalStmtResult EvaluateStmt(APVal<br>
const DoStmt *DS = cast<DoStmt>(S);<br>
bool Continue;<br>
do {<br>
- EvalStmtResult ESR = EvaluateLoopBody(Result, Info, DS->getBody());<br>
+ EvalStmtResult ESR = EvaluateLoopBody(Result, Info, DS->getBody(), Case);<br>
if (ESR != ESR_Continue)<br>
return ESR;<br>
+ Case = 0;<br>
<br>
if (!EvaluateAsBooleanCondition(DS->getCond(), Continue, Info))<br>
return ESR_Failed;<br>
@@ -2983,11 +3100,27 @@ static EvalStmtResult EvaluateStmt(APVal<br>
return ESR_Succeeded;<br>
}<br>
<br>
+ case Stmt::SwitchStmtClass:<br>
+ return EvaluateSwitch(Result, Info, cast<SwitchStmt>(S));<br>
+<br>
case Stmt::ContinueStmtClass:<br>
return ESR_Continue;<br>
<br>
case Stmt::BreakStmtClass:<br>
return ESR_Break;<br>
+<br>
+ case Stmt::LabelStmtClass:<br>
+ return EvaluateStmt(Result, Info, cast<LabelStmt>(S)->getSubStmt(), Case);<br>
+<br>
+ case Stmt::AttributedStmtClass:<br>
+ // As a general principle, C++11 attributes can be ignored without<br>
+ // any semantic impact.<br>
+ return EvaluateStmt(Result, Info, cast<AttributedStmt>(S)->getSubStmt(),<br>
+ Case);<br>
+<br>
+ case Stmt::CaseStmtClass:<br>
+ case Stmt::DefaultStmtClass:<br>
+ return EvaluateStmt(Result, Info, cast<SwitchCase>(S)->getSubStmt(), Case);<br>
}<br>
}<br>
<br>
<br>
Modified: cfe/trunk/test/SemaCXX/constant-expression-cxx1y.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/constant-expression-cxx1y.cpp?rev=181671&r1=181670&r2=181671&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/constant-expression-cxx1y.cpp?rev=181671&r1=181670&r2=181671&view=diff</a><br>
==============================================================================<br>
--- cfe/trunk/test/SemaCXX/constant-expression-cxx1y.cpp (original)<br>
+++ cfe/trunk/test/SemaCXX/constant-expression-cxx1y.cpp Sun May 12 12:32:42 2013<br>
@@ -593,3 +593,117 @@ namespace assignment_op {<br>
}<br>
static_assert(testC(), "");<br>
}<br>
+<br>
+namespace switch_stmt {<br>
+ constexpr int f(char k) {<br>
+ bool b = false;<br>
+ int z = 6;<br>
+ switch (k) {<br>
+ return -1;<br>
+ case 0:<br>
+ if (false) {<br>
+ case 1:<br>
+ z = 1;<br>
+ for (; b;) {<br>
+ return 5;<br>
+ while (0)<br>
+ case 2: return 2;<br>
+ case 7: z = 7;<br>
+ do case 6: {<br>
+ return z;<br>
+ if (false)<br>
+ case 3: return 3;<br>
+ case 4: z = 4;<br>
+ } while (1);<br>
+ case 5: b = true;<br>
+ case 9: z = 9;<br>
+ }<br>
+ return z;<br>
+ } else if (false) case 8: z = 8;<br>
+ else if (false) {<br>
+ case 10:<br>
+ z = -10;<br>
+ break;<br>
+ }<br>
+ else z = 0;<br>
+ return z;<br>
+ default:<br>
+ return -1;<br>
+ }<br>
+ return -z;<br>
+ }<br>
+ static_assert(f(0) == 0, "");<br>
+ static_assert(f(1) == 1, "");<br>
+ static_assert(f(2) == 2, "");<br>
+ static_assert(f(3) == 3, "");<br>
+ static_assert(f(4) == 4, "");<br>
+ static_assert(f(5) == 5, "");<br>
+ static_assert(f(6) == 6, "");<br>
+ static_assert(f(7) == 7, "");<br>
+ static_assert(f(8) == 8, "");<br>
+ static_assert(f(9) == 9, "");<br>
+ static_assert(f(10) == 10, "");<br>
+<br>
+ // Check that we can continue an outer loop from within a switch.<br>
+ constexpr bool contin() {<br>
+ for (int n = 0; n != 10; ++n) {<br>
+ switch (n) {<br>
+ case 0:<br>
+ ++n;<br>
+ continue;<br>
+ case 1:<br>
+ return false;<br>
+ case 2:<br>
+ return true;<br>
+ }<br>
+ }<br>
+ return false;<br>
+ }<br>
+ static_assert(contin(), "");<br>
+<br>
+ constexpr bool switch_into_for() {<br>
+ int n = 0;<br>
+ switch (n) {<br>
+ for (; n == 1; ++n) {<br>
+ return n == 1;<br>
+ case 0: ;<br>
+ }<br>
+ }<br>
+ return false;<br>
+ }<br>
+ static_assert(switch_into_for(), "");<br>
+<br>
+ constexpr void duff_copy(char *a, const char *b, int n) {<br>
+ switch ((n - 1) % 8 + 1) {<br>
+ for ( ; n; n = (n - 1) & ~7) {<br>
+ case 8: a[n-8] = b[n-8];<br>
+ case 7: a[n-7] = b[n-7];<br>
+ case 6: a[n-6] = b[n-6];<br>
+ case 5: a[n-5] = b[n-5];<br>
+ case 4: a[n-4] = b[n-4];<br>
+ case 3: a[n-3] = b[n-3];<br>
+ case 2: a[n-2] = b[n-2];<br>
+ case 1: a[n-1] = b[n-1];<br>
+ }<br>
+ case 0: ;<br>
+ }<br>
+ }<br>
+<br>
+ constexpr bool test_copy(const char *str, int n) {<br>
+ char buffer[16] = {};<br>
+ duff_copy(buffer, str, n);<br>
+ for (int i = 0; i != sizeof(buffer); ++i)<br>
+ if (buffer[i] != (i < n ? str[i] : 0))<br>
+ return false;<br>
+ return true;<br>
+ }<br>
+ static_assert(test_copy("foo", 0), "");<br>
+ static_assert(test_copy("foo", 1), "");<br>
+ static_assert(test_copy("foo", 2), "");<br>
+ static_assert(test_copy("hello world", 0), "");<br>
+ static_assert(test_copy("hello world", 7), "");<br>
+ static_assert(test_copy("hello world", 8), "");<br>
+ static_assert(test_copy("hello world", 9), "");<br>
+ static_assert(test_copy("hello world", 10), "");<br>
+ static_assert(test_copy("hello world", 10), "");<br>
+}<br>
<br>
<br>
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</blockquote></div><br></div>