[clang] [Clang] Generate the GEP instead of adding AST nodes (PR #73730)
Bill Wendling via cfe-commits
cfe-commits at lists.llvm.org
Tue Nov 28 17:20:02 PST 2023
https://github.com/bwendling created https://github.com/llvm/llvm-project/pull/73730
This is an alternative to https://github.com/llvm/llvm-project/pull/73465. It generates the GEP directly. It's not tested well, but it might be a nicer solution rather than adding AST nodes.
PTAL
>From 3e500c2a7c6b7895ebe292a1ed50e04409ba149c Mon Sep 17 00:00:00 2001
From: Bill Wendling <morbo at google.com>
Date: Tue, 28 Nov 2023 17:17:54 -0800
Subject: [PATCH] [Clang] Generate the GEP instead of adding AST nodes
---
clang/lib/CodeGen/CGBuiltin.cpp | 3 +-
clang/lib/CodeGen/CGExpr.cpp | 99 +++++++++++++++++++----------
clang/lib/CodeGen/CodeGenFunction.h | 4 +-
3 files changed, 70 insertions(+), 36 deletions(-)
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index c83ea966fdeadc6..487bd14244e531c 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -916,8 +916,7 @@ CodeGenFunction::emitFlexibleArrayMemberSize(const Expr *E, unsigned Type,
// Build a load of the counted_by field.
bool IsSigned = CountedByFD->getType()->isSignedIntegerType();
- const Expr *CountedByExpr = BuildCountedByFieldExpr(Base, CountedByFD);
- Value *CountedByInst = EmitAnyExprToTemp(CountedByExpr).getScalarVal();
+ Value *CountedByInst = BuildCountedByFieldExpr(Base, CountedByFD);
llvm::Type *CountedByTy = CountedByInst->getType();
// Build a load of the index and subtract it from the count.
diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index 9fe8f1d7da780c8..b77d9d8904dfc2d 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -26,6 +26,7 @@
#include "clang/AST/Attr.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/NSAPI.h"
+#include "clang/AST/StmtVisitor.h"
#include "clang/Basic/Builtins.h"
#include "clang/Basic/CodeGenOptions.h"
#include "clang/Basic/SourceManager.h"
@@ -940,8 +941,7 @@ static llvm::Value *getArrayIndexingBound(CodeGenFunction &CGF,
if (const ValueDecl *VD = CGF.FindCountedByField(Base)) {
IndexedType = Base->getType();
- const Expr *E = CGF.BuildCountedByFieldExpr(Base, VD);
- return CGF.EmitAnyExprToTemp(E).getScalarVal();
+ return CGF.BuildCountedByFieldExpr(Base, VD);
}
}
@@ -956,42 +956,77 @@ static llvm::Value *getArrayIndexingBound(CodeGenFunction &CGF,
return nullptr;
}
-const Expr *
+namespace {
+
+struct MemberExprBaseVisitor
+ : public StmtVisitor<MemberExprBaseVisitor, Expr *> {
+ MemberExprBaseVisitor() = default;
+
+ //===--------------------------------------------------------------------===//
+ // Visitor Methods
+ //===--------------------------------------------------------------------===//
+
+ Expr *Visit(Expr *E) {
+ return StmtVisitor<MemberExprBaseVisitor, Expr *>::Visit(E);
+ }
+
+ Expr *VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
+ return Visit(E->getBase());
+ }
+ Expr *VisitCastExpr(CastExpr *E) {
+ return Visit(E->getSubExpr());
+ }
+ Expr *VisitDeclRefExpr(DeclRefExpr *E) {
+ return E;
+ }
+ Expr *VisitMemberExpr(MemberExpr *E) {
+ return Visit(E->getBase());
+ }
+ Expr *VisitParenExpr(ParenExpr *E) {
+ return Visit(E->getSubExpr());
+ }
+ Expr *VisitUnaryOperator(UnaryOperator *E) {
+ return Visit(E->getSubExpr());
+ }
+};
+
+} // end anonymous namespace
+
+llvm::Value *
CodeGenFunction::BuildCountedByFieldExpr(const Expr *Base,
const ValueDecl *CountedByVD) {
// Find the outer struct expr (i.e. p in p->a.b.c.d).
- Expr *CountedByExpr = const_cast<Expr *>(Base)->IgnoreParenImpCasts();
-
- // Work our way up the expression until we reach the DeclRefExpr.
- while (!isa<DeclRefExpr>(CountedByExpr))
- if (const auto *ME = dyn_cast<MemberExpr>(CountedByExpr))
- CountedByExpr = ME->getBase()->IgnoreParenImpCasts();
-
- // Add back an implicit cast to create the required pr-value.
- CountedByExpr = ImplicitCastExpr::Create(
- getContext(), CountedByExpr->getType(), CK_LValueToRValue, CountedByExpr,
- nullptr, VK_PRValue, FPOptionsOverride());
-
- if (const auto *IFD = dyn_cast<IndirectFieldDecl>(CountedByVD)) {
- // The counted_by field is inside an anonymous struct / union. The
- // IndirectFieldDecl has the correct order of FieldDecls to build this
- // easily. (Yay!)
- for (NamedDecl *ND : IFD->chain()) {
- auto *VD = cast<ValueDecl>(ND);
- CountedByExpr =
- MemberExpr::CreateImplicit(getContext(), CountedByExpr,
- CountedByExpr->getType()->isPointerType(),
- VD, VD->getType(), VK_LValue, OK_Ordinary);
+ Expr *CountedByExpr = MemberExprBaseVisitor().Visit(const_cast<Expr *>(Base));
+
+ llvm::Value *Res =
+ CountedByExpr->getType()->isPointerType()
+ ? EmitPointerWithAlignment(CountedByExpr).getPointer()
+ : EmitDeclRefLValue(cast<DeclRefExpr>(CountedByExpr)).getPointer(*this);
+
+ auto *Zero = llvm::ConstantInt::get(Int32Ty, 0);
+ SmallVector<llvm::Value *, 4> Indices{Zero};
+ if (const auto *FD = dyn_cast<FieldDecl>(CountedByVD)) {
+ Indices.emplace_back(llvm::ConstantInt::get(Int32Ty, FD->getFieldIndex()));
+ } else if (const auto *I = dyn_cast<IndirectFieldDecl>(CountedByVD)) {
+ for (auto *ND : I->chain()) {
+ if (auto *FD = dyn_cast<FieldDecl>(ND)) {
+ Indices.emplace_back(llvm::ConstantInt::get(Int32Ty, FD->getFieldIndex()));
+ }
}
- } else {
- CountedByExpr = MemberExpr::CreateImplicit(
- getContext(), const_cast<Expr *>(CountedByExpr),
- CountedByExpr->getType()->isPointerType(),
- const_cast<ValueDecl *>(CountedByVD), CountedByVD->getType(), VK_LValue,
- OK_Ordinary);
}
- return CountedByExpr;
+ const DeclContext *DC = CountedByVD->getLexicalDeclContext();
+ const auto *CountedByRD = cast<RecordDecl>(DC);
+
+ llvm::Type *Ty = CGM.getTypes().ConvertType(QualType(CountedByRD->getTypeForDecl(), 0));
+ Res = Builder.CreateGEP(Ty, Res, Indices, "bork");
+
+ QualType CountedByTy(CountedByVD->getType());
+ TypeInfo TI = getContext().getTypeInfo(CountedByTy);
+ Ty = CGM.getTypes().ConvertType(CountedByTy);
+ Address Addr(Res, Ty, CharUnits::fromQuantity(TI.Align / getContext().getCharWidth()));
+
+ return Builder.CreateLoad(Addr, Res, "fork");
}
const ValueDecl *
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 618e78809db408b..e3137eb65dbad23 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -3032,8 +3032,8 @@ class CodeGenFunction : public CodeGenTypeCache {
const ValueDecl *FindCountedByField(const Expr *Base);
/// Build an expression accessing the "counted_by" field.
- const Expr *BuildCountedByFieldExpr(const Expr *Base,
- const ValueDecl *CountedByVD);
+ llvm::Value *BuildCountedByFieldExpr(const Expr *Base,
+ const ValueDecl *CountedByVD);
llvm::Value *EmitScalarPrePostIncDec(const UnaryOperator *E, LValue LV,
bool isInc, bool isPre);
More information about the cfe-commits
mailing list