[clang] [CIR] Implement codegen for inline assembly without input and output operands (PR #153546)

[Bruno Cardoso Lopes via cfe-commits]

================
@@ -0,0 +1,136 @@
+//===--- CIRGenAsm.cpp - Inline Assembly Support for CIR CodeGen ---------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains code to emit inline assembly.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Basic/DiagnosticSema.h"
+#include "llvm/ADT/StringExtras.h"
+
+#include "CIRGenFunction.h"
+#include "TargetInfo.h"
+#include "clang/CIR/MissingFeatures.h"
+
+using namespace clang;
+using namespace clang::CIRGen;
+using namespace cir;
+
+static AsmFlavor inferFlavor(const CIRGenModule &cgm, const AsmStmt &s) {
+  AsmFlavor gnuAsmFlavor =
+      cgm.getCodeGenOpts().getInlineAsmDialect() == CodeGenOptions::IAD_ATT
+          ? AsmFlavor::x86_att
+          : AsmFlavor::x86_intel;
+
+  return isa<MSAsmStmt>(&s) ? AsmFlavor::x86_intel : gnuAsmFlavor;
+}
+
+static void collectClobbers(const CIRGenFunction &cgf, const AsmStmt &s,
+                            std::string &constraints, bool &hasUnwindClobber,
+                            bool &readOnly, bool readNone) {
+
+  hasUnwindClobber = false;
+  const CIRGenModule &cgm = cgf.getCIRGenModule();
+
+  // Clobbers
+  for (unsigned i = 0, e = s.getNumClobbers(); i != e; i++) {
+    std::string clobberStr = s.getClobber(i);
+    StringRef clobber{clobberStr};
+    if (clobber == "memory")
+      readOnly = readNone = false;
+    else if (clobber == "unwind") {
+      hasUnwindClobber = true;
+      continue;
+    } else if (clobber != "cc") {
+      clobber = cgf.getTarget().getNormalizedGCCRegisterName(clobber);
+      if (cgm.getCodeGenOpts().StackClashProtector &&
+          cgf.getTarget().isSPRegName(clobber)) {
+        cgm.getDiags().Report(s.getAsmLoc(),
+                              diag::warn_stack_clash_protection_inline_asm);
+      }
+    }
+
+    if (isa<MSAsmStmt>(&s)) {
+      if (clobber == "eax" || clobber == "edx") {
+        if (constraints.find("=&A") != std::string::npos)
+          continue;
+        std::string::size_type position1 =
+            constraints.find("={" + clobber.str() + "}");
+        if (position1 != std::string::npos) {
+          constraints.insert(position1 + 1, "&");
+          continue;
+        }
+        std::string::size_type position2 = constraints.find("=A");
+        if (position2 != std::string::npos) {
+          constraints.insert(position2 + 1, "&");
+          continue;
+        }
+      }
+    }
+    if (!constraints.empty())
+      constraints += ',';
+
+    constraints += "~{";
+    constraints += clobber;
+    constraints += '}';
+  }
+
+  // Add machine specific clobbers
+  std::string_view machineClobbers = cgf.getTarget().getClobbers();
+  if (!machineClobbers.empty()) {
+    if (!constraints.empty())
+      constraints += ',';
+    constraints += machineClobbers;
+  }
+}
+
+mlir::LogicalResult CIRGenFunction::emitAsmStmt(const AsmStmt &s) {
+  // Assemble the final asm string.
+  std::string asmString = s.generateAsmString(getContext());
+
+  std::string constraints;
+
+  // An inline asm can be marked readonly if it meets the following conditions:
+  //  - it doesn't have any sideeffects
+  //  - it doesn't clobber memory
+  //  - it doesn't return a value by-reference
+  // It can be marked readnone if it doesn't have any input memory constraints
+  // in addition to meeting the conditions listed above.
+  bool readOnly = true, readNone = true;
+
+  if (s.getNumInputs() != 0 || s.getNumOutputs() != 0) {
+    assert(!cir::MissingFeatures::asmInputOperands());
+    assert(!cir::MissingFeatures::asmOutputOperands());
+    cgm.errorNYI(s.getAsmLoc(), "asm with operands");
+  }
+
+  bool hasUnwindClobber = false;
+  collectClobbers(*this, s, constraints, hasUnwindClobber, readOnly, readNone);
+
+  llvm::SmallVector<mlir::ValueRange, 8> operands;
+  mlir::Type resultType;
+
+  bool hasSideEffect = s.isVolatile() || s.getNumOutputs() == 0;
+
+  cir::InlineAsmOp ia = builder.create<cir::InlineAsmOp>(
+      getLoc(s.getAsmLoc()), resultType, operands, asmString, constraints,
+      hasSideEffect, inferFlavor(cgm, s), mlir::ArrayAttr());
+
+  if (false /*IsGCCAsmGoto*/) {
----------------
bcardosolopes wrote:

Please add `bool isGCCAsmGoto = false;` closer to the function entry and then update the if statement to use it.

https://github.com/llvm/llvm-project/pull/153546