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Optimize away calls to empty functions (#6626)

This commit is contained in:
Geza Lore 2025-11-02 22:11:02 +01:00 committed by GitHub
parent 611ffbe04e
commit d066504bb9
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GPG Key ID: B5690EEEBB952194
3 changed files with 38 additions and 2 deletions
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5
src/V3AstNodeOther.h
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@ -598,7 +598,10 @@ public:
bool recursive() const { return m_recursive; } bool recursive() const { return m_recursive; }
void cost(int cost) { m_cost = cost; } void cost(int cost) { m_cost = cost; }
// Special methods // Special methods
bool emptyBody() const { return !keepIfEmpty() && !argsp() && !varsp() && !stmtsp(); } bool emptyBody() const {
return !keepIfEmpty() && !argsp() && !varsp() && !stmtsp() && !isVirtual()
&& !dpiImportPrototype();
}
}; };
class AstCLocalScope final : public AstNode { class AstCLocalScope final : public AstNode {
// Pack statements into an unnamed scope when generating C++ // Pack statements into an unnamed scope when generating C++

17
src/V3Const.cpp
View File

@ -3669,10 +3669,25 @@ class ConstVisitor final : public VNVisitor {
void visit(AstStmtExpr* nodep) override { void visit(AstStmtExpr* nodep) override {
iterateChildren(nodep); iterateChildren(nodep);
if (!nodep->exprp() || VN_IS(nodep->exprp(), Const)) { // Malformed due to child being deleted, remove here
if (!nodep->exprp()) {
VL_DO_DANGLING(pushDeletep(nodep->unlinkFrBack()), nodep); VL_DO_DANGLING(pushDeletep(nodep->unlinkFrBack()), nodep);
return; return;
} }
// Remove if expression is trivially pure
if (VN_IS(nodep->exprp(), Const) || VN_IS(nodep->exprp(), VarRef)) {
VL_DO_DANGLING(pushDeletep(nodep->unlinkFrBack()), nodep);
return;
}
// Remove calls to empty functions
if (AstCCall* const callp = VN_CAST(nodep->exprp(), CCall)) {
AstCFunc* const funcp = callp->funcp();
if (!callp->argsp() && funcp->emptyBody()) {
VL_DO_DANGLING(pushDeletep(nodep->unlinkFrBack()), nodep);
return;
}
}
// TODO if there's an ExprStmt underneath just keep lower statements // TODO if there's an ExprStmt underneath just keep lower statements
// (No current test case needs this) // (No current test case needs this)
// TODO if non-pure, can remove. First need to clean up that many expressions used // TODO if non-pure, can remove. First need to clean up that many expressions used

18
test_regress/t/t_timing_debug2.out
View File

@ -205,6 +205,7 @@
-V{t#,#} Awaiting time 101: Process waiting at t/t_timing_class.v:274 -V{t#,#} Awaiting time 101: Process waiting at t/t_timing_class.v:274
-V{t#,#} Resuming delayed processes -V{t#,#} Resuming delayed processes
-V{t#,#} Resuming: Process waiting at t/t_timing_class.v:173 -V{t#,#} Resuming: Process waiting at t/t_timing_class.v:173
-V{t#,#}+ Vt_timing_debug2_t__03a__03aDelay10::__VnoInFunc_do_sth_else
-V{t#,#}+ Vt_timing_debug2_t__03a__03aDelay20::__VnoInFunc_do_delay -V{t#,#}+ Vt_timing_debug2_t__03a__03aDelay20::__VnoInFunc_do_delay
-V{t#,#} Resuming: Process waiting at t/t_timing_class.v:247 -V{t#,#} Resuming: Process waiting at t/t_timing_class.v:247
-V{t#,#} Process forked at t/t_timing_class.v:246 finished -V{t#,#} Process forked at t/t_timing_class.v:246 finished
@ -568,6 +569,7 @@
-V{t#,#} Resuming: Process waiting at t/t_timing_class.v:257 -V{t#,#} Resuming: Process waiting at t/t_timing_class.v:257
-V{t#,#}+ Vt_timing_debug2_t__03a__03aForkDelayClass::__VnoInFunc_do_delay -V{t#,#}+ Vt_timing_debug2_t__03a__03aForkDelayClass::__VnoInFunc_do_delay
-V{t#,#} Resuming: Process waiting at t/t_timing_class.v:174 -V{t#,#} Resuming: Process waiting at t/t_timing_class.v:174
-V{t#,#}+ Vt_timing_debug2_t__03a__03aDelay20::__VnoInFunc_do_sth_else
-V{t#,#}+ Vt_timing_debug2_t__03a__03aDelay40::__VnoInFunc_do_delay -V{t#,#}+ Vt_timing_debug2_t__03a__03aDelay40::__VnoInFunc_do_delay
-V{t#,#} Resuming: Process waiting at t/t_timing_class.v:131 -V{t#,#} Resuming: Process waiting at t/t_timing_class.v:131
-V{t#,#}+ Vt_timing_debug2_t__03a__03aClkClass::__VnoInFunc_flip -V{t#,#}+ Vt_timing_debug2_t__03a__03aClkClass::__VnoInFunc_flip
@ -1202,7 +1204,9 @@
-V{t#,#} Process forked at t/t_timing_class.v:250 finished -V{t#,#} Process forked at t/t_timing_class.v:250 finished
-V{t#,#} Resuming: Process waiting at t/t_timing_class.v:245 -V{t#,#} Resuming: Process waiting at t/t_timing_class.v:245
-V{t#,#} Resuming: Process waiting at t/t_timing_class.v:175 -V{t#,#} Resuming: Process waiting at t/t_timing_class.v:175
-V{t#,#}+ Vt_timing_debug2_t__03a__03aDelay40::__VnoInFunc_do_sth_else
-V{t#,#}+ Vt_timing_debug2_t__03a__03aNoDelay::__VnoInFunc_do_delay -V{t#,#}+ Vt_timing_debug2_t__03a__03aNoDelay::__VnoInFunc_do_delay
-V{t#,#}+ Vt_timing_debug2_t__03a__03aNoDelay::__VnoInFunc_do_sth_else
-V{t#,#}+ Vt_timing_debug2_t___eval_initial__TOP__t__Vtiming__6____Vfork_1__0 -V{t#,#}+ Vt_timing_debug2_t___eval_initial__TOP__t__Vtiming__6____Vfork_1__0
-V{t#,#}+ Vt_timing_debug2_t__03a__03aAssignDelayClass::__VnoInFunc_do_assign -V{t#,#}+ Vt_timing_debug2_t__03a__03aAssignDelayClass::__VnoInFunc_do_assign
-V{t#,#} Resuming: Process waiting at t/t_timing_class.v:76 -V{t#,#} Resuming: Process waiting at t/t_timing_class.v:76
@ -1543,3 +1547,17 @@
-V{t#,#}+ Vt_timing_debug2___024root___trigger_anySet__act -V{t#,#}+ Vt_timing_debug2___024root___trigger_anySet__act
-V{t#,#}End-of-eval cleanup -V{t#,#}End-of-eval cleanup
-V{t#,#}+ Vt_timing_debug2___024root___eval_final -V{t#,#}+ Vt_timing_debug2___024root___eval_final
-V{t#,#}+ Vt_timing_debug2_t__03a__03aDelay40::~
-V{t#,#}+ Vt_timing_debug2_t__03a__03aDelayClass::~
-V{t#,#}+ Vt_timing_debug2_t__03a__03aDelay20::~
-V{t#,#}+ Vt_timing_debug2_t__03a__03aDelayClass::~
-V{t#,#}+ Vt_timing_debug2_t__03a__03aDelay10::~
-V{t#,#}+ Vt_timing_debug2_t__03a__03aDelayClass::~
-V{t#,#}+ Vt_timing_debug2_t__03a__03aNoDelay::~
-V{t#,#}+ Vt_timing_debug2_t__03a__03aDelayClass::~
-V{t#,#}+ Vt_timing_debug2_t__03a__03aLocalWaitClass::~
-V{t#,#}+ Vt_timing_debug2___024unit__03a__03aBaseClass::~
-V{t#,#}+ Vt_timing_debug2_t__03a__03aWaitClass::~
-V{t#,#}+ Vt_timing_debug2___024unit__03a__03aBaseClass::~
-V{t#,#}+ Vt_timing_debug2_t__03a__03aEventClass::~
-V{t#,#}+ Vt_timing_debug2___024unit__03a__03aBaseClass::~