[llvm-branch-commits] [clang] 84b9e44 - [CIR] Add Function Argument Demotion support (#170915)
via llvm-branch-commits
llvm-branch-commits at lists.llvm.org
Tue Dec 9 15:51:25 PST 2025
Author: adams381
Date: 2025-12-09T15:09:25-08:00
New Revision: 84b9e444454a06ddf01f568164e3d5c8d956707d
URL: https://github.com/llvm/llvm-project/commit/84b9e444454a06ddf01f568164e3d5c8d956707d
DIFF: https://github.com/llvm/llvm-project/commit/84b9e444454a06ddf01f568164e3d5c8d956707d.diff
LOG: [CIR] Add Function Argument Demotion support (#170915)
This PR migrates the Function Argument Demotion feature from the
incubator repository to upstream. The feature handles K&R-style function
parameters that are promoted (e.g., short->int, float->double) and
demotes them back to their declared types.
## Changes
- Add emitArgumentDemotion helper function for type demotion
- Create emitFunctionProlog function to handle function prologue setup
(addresses existing TODO to move parameter handling logic)
- Move parameter handling logic into emitFunctionProlog
- Add test case kr-func-promote.c to verify the feature
Tested: All CIR tests pass (320/321, 99.69%). The one unsupported test
is an expected failure.
Added:
clang/test/CIR/CodeGen/kr-func-promote.c
Modified:
clang/lib/CIR/CodeGen/CIRGenFunction.cpp
clang/lib/CIR/CodeGen/CIRGenFunction.h
Removed:
################################################################################
diff --git a/clang/lib/CIR/CodeGen/CIRGenFunction.cpp b/clang/lib/CIR/CodeGen/CIRGenFunction.cpp
index 492cbb69fabb3..6b2e60a551198 100644
--- a/clang/lib/CIR/CodeGen/CIRGenFunction.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenFunction.cpp
@@ -16,6 +16,7 @@
#include "CIRGenCall.h"
#include "CIRGenValue.h"
#include "mlir/IR/Location.h"
+#include "clang/AST/Attr.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/GlobalDecl.h"
#include "clang/CIR/MissingFeatures.h"
@@ -422,28 +423,35 @@ cir::TryOp CIRGenFunction::LexicalScope::getClosestTryParent() {
return nullptr;
}
-void CIRGenFunction::startFunction(GlobalDecl gd, QualType returnType,
- cir::FuncOp fn, cir::FuncType funcType,
- FunctionArgList args, SourceLocation loc,
- SourceLocation startLoc) {
- assert(!curFn &&
- "CIRGenFunction can only be used for one function at a time");
+/// An argument came in as a promoted argument; demote it back to its
+/// declared type.
+static mlir::Value emitArgumentDemotion(CIRGenFunction &cgf, const VarDecl *var,
+ mlir::Value value) {
+ mlir::Type ty = cgf.convertType(var->getType());
- curFn = fn;
+ // This can happen with promotions that actually don't change the
+ // underlying type, like the enum promotions.
+ if (value.getType() == ty)
+ return value;
- const Decl *d = gd.getDecl();
+ assert((mlir::isa<cir::IntType>(ty) || cir::isAnyFloatingPointType(ty)) &&
+ "unexpected promotion type");
- didCallStackSave = false;
- curCodeDecl = d;
- const auto *fd = dyn_cast_or_null<FunctionDecl>(d);
- curFuncDecl = d->getNonClosureContext();
+ if (mlir::isa<cir::IntType>(ty))
+ return cgf.getBuilder().CIRBaseBuilderTy::createIntCast(value, ty);
- prologueCleanupDepth = ehStack.stable_begin();
+ return cgf.getBuilder().createFloatingCast(value, ty);
+}
- mlir::Block *entryBB = &fn.getBlocks().front();
- builder.setInsertionPointToStart(entryBB);
+void CIRGenFunction::emitFunctionProlog(const FunctionArgList &args,
+ mlir::Block *entryBB,
+ const FunctionDecl *fd,
+ SourceLocation bodyBeginLoc) {
+ // Naked functions don't have prologues.
+ if (fd && fd->hasAttr<NakedAttr>()) {
+ cgm.errorNYI(bodyBeginLoc, "naked function decl");
+ }
- // TODO(cir): this should live in `emitFunctionProlog
// Declare all the function arguments in the symbol table.
for (const auto nameValue : llvm::zip(args, entryBB->getArguments())) {
const VarDecl *paramVar = std::get<0>(nameValue);
@@ -466,20 +474,64 @@ void CIRGenFunction::startFunction(GlobalDecl gd, QualType returnType,
cast<ParmVarDecl>(paramVar)->isKNRPromoted();
assert(!cir::MissingFeatures::constructABIArgDirectExtend());
if (isPromoted)
- cgm.errorNYI(fd->getSourceRange(), "Function argument demotion");
+ paramVal = emitArgumentDemotion(*this, paramVar, paramVal);
// Location of the store to the param storage tracked as beginning of
// the function body.
- mlir::Location fnBodyBegin = getLoc(fd->getBody()->getBeginLoc());
+ mlir::Location fnBodyBegin = getLoc(bodyBeginLoc);
builder.CIRBaseBuilderTy::createStore(fnBodyBegin, paramVal, addrVal);
}
assert(builder.getInsertionBlock() && "Should be valid");
+}
+
+void CIRGenFunction::startFunction(GlobalDecl gd, QualType returnType,
+ cir::FuncOp fn, cir::FuncType funcType,
+ FunctionArgList args, SourceLocation loc,
+ SourceLocation startLoc) {
+ assert(!curFn &&
+ "CIRGenFunction can only be used for one function at a time");
+
+ curFn = fn;
+
+ const Decl *d = gd.getDecl();
+
+ didCallStackSave = false;
+ curCodeDecl = d;
+ const auto *fd = dyn_cast_or_null<FunctionDecl>(d);
+ curFuncDecl = d->getNonClosureContext();
+
+ prologueCleanupDepth = ehStack.stable_begin();
+
+ mlir::Block *entryBB = &fn.getBlocks().front();
+ builder.setInsertionPointToStart(entryBB);
+
+ // Determine the function body begin location for the prolog.
+ // If fd is null or has no body, use startLoc as fallback.
+ SourceLocation bodyBeginLoc = startLoc;
+ if (fd) {
+ if (Stmt *body = fd->getBody())
+ bodyBeginLoc = body->getBeginLoc();
+ else
+ bodyBeginLoc = fd->getLocation();
+ }
+
+ emitFunctionProlog(args, entryBB, fd, bodyBeginLoc);
// When the current function is not void, create an address to store the
// result value.
- if (!returnType->isVoidType())
- emitAndUpdateRetAlloca(returnType, getLoc(fd->getBody()->getEndLoc()),
+ if (!returnType->isVoidType()) {
+ // Determine the function body end location.
+ // If fd is null or has no body, use loc as fallback.
+ SourceLocation bodyEndLoc = loc;
+ if (fd) {
+ if (Stmt *body = fd->getBody())
+ bodyEndLoc = body->getEndLoc();
+ else
+ bodyEndLoc = fd->getLocation();
+ }
+ emitAndUpdateRetAlloca(returnType, getLoc(bodyEndLoc),
getContext().getTypeAlignInChars(returnType));
+ }
if (isa_and_nonnull<CXXMethodDecl>(d) &&
cast<CXXMethodDecl>(d)->isInstance()) {
diff --git a/clang/lib/CIR/CodeGen/CIRGenFunction.h b/clang/lib/CIR/CodeGen/CIRGenFunction.h
index 0df812bcfb94e..15322ee72a1b0 100644
--- a/clang/lib/CIR/CodeGen/CIRGenFunction.h
+++ b/clang/lib/CIR/CodeGen/CIRGenFunction.h
@@ -954,6 +954,11 @@ class CIRGenFunction : public CIRGenTypeCache {
clang::QualType buildFunctionArgList(clang::GlobalDecl gd,
FunctionArgList &args);
+ /// Emit the function prologue: declare function arguments in the symbol
+ /// table.
+ void emitFunctionProlog(const FunctionArgList &args, mlir::Block *entryBB,
+ const FunctionDecl *fd, SourceLocation bodyBeginLoc);
+
/// Emit code for the start of a function.
/// \param loc The location to be associated with the function.
/// \param startLoc The location of the function body.
diff --git a/clang/test/CIR/CodeGen/kr-func-promote.c b/clang/test/CIR/CodeGen/kr-func-promote.c
new file mode 100644
index 0000000000000..5fed068a30398
--- /dev/null
+++ b/clang/test/CIR/CodeGen/kr-func-promote.c
@@ -0,0 +1,42 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -std=c89 -fclangir -emit-cir %s -o %t.cir
+// RUN: FileCheck --input-file=%t.cir %s -check-prefix=CIR
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -std=c89 -fclangir -emit-llvm %s -o %t-cir.ll
+// RUN: FileCheck --input-file=%t-cir.ll %s -check-prefix=LLVM
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -std=c89 -emit-llvm %s -o %t.ll
+// RUN: FileCheck --input-file=%t.ll %s -check-prefix=OGCG
+
+// CIR: cir.func {{.*}}@foo(%arg0: !s32i
+// CIR: %0 = cir.alloca !s16i, !cir.ptr<!s16i>, ["x", init]
+// CIR: %1 = cir.cast integral %arg0 : !s32i -> !s16i
+// CIR: cir.store %1, %0 : !s16i, !cir.ptr<!s16i>
+// expected-warning at +1 {{a function definition without a prototype is deprecated}}
+void foo(x) short x; {}
+
+// LLVM: define{{.*}} void @foo(i32 %0)
+// LLVM: %[[X_PTR:.*]] = alloca i16, i64 1, align 2
+// LLVM: %[[X:.*]] = trunc i32 %0 to i16
+// LLVM: store i16 %[[X]], ptr %[[X_PTR]], align 2
+
+// OGCG: define{{.*}} void @foo(i32 noundef %0)
+// OGCG: entry:
+// OGCG: %[[X_PTR:.*]] = alloca i16, align 2
+// OGCG: %[[X:.*]] = trunc i32 %0 to i16
+// OGCG: store i16 %[[X]], ptr %[[X_PTR]], align 2
+
+// CIR: cir.func{{.*}}no_proto dso_local @bar(%arg0: !cir.double
+// CIR: %0 = cir.alloca !cir.float, !cir.ptr<!cir.float>, ["f", init]
+// CIR: %1 = cir.cast floating %arg0 : !cir.double -> !cir.float
+// CIR: cir.store %1, %0 : !cir.float, !cir.ptr<!cir.float>
+// expected-warning at +1 {{a function definition without a prototype is deprecated}}
+void bar(f) float f; {}
+
+// LLVM: define{{.*}} void @bar(double %0)
+// LLVM: %[[F_PTR:.*]] = alloca float, i64 1, align 4
+// LLVM: %[[F:.*]] = fptrunc double %0 to float
+// LLVM: store float %[[F]], ptr %[[F_PTR]], align 4
+
+// OGCG: define{{.*}} void @bar(double noundef %0)
+// OGCG: entry:
+// OGCG: %[[F_PTR:.*]] = alloca float, align 4
+// OGCG: %[[F:.*]] = fptrunc double %0 to float
+// OGCG: store float %[[F]], ptr %[[F_PTR]], align 4
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