Propagate the target to clang-cl when it's used to preprocess C. (#4627)

Author: just-harry

driver/cpreprocessor.cpp

@@ -4,9 +4,12 @@
 #include "driver/cl_options.h"
 #include "driver/timetrace.h"
 #include "driver/tool.h"
+#include "gen/irstate.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/Program.h"
+#include "llvm/MC/MCSubtargetInfo.h"
+#include "llvm/Target/TargetMachine.h"
 
 namespace {
 const char *getPathToImportc_h(const Loc &loc) {
@@ -119,6 +122,27 @@ FileName runCPreprocessor(FileName csrcfile, const Loc &loc,
       args.push_back("/PD");              // print all macro definitions
       args.push_back("/Zc:preprocessor"); // use the new conforming preprocessor
     } else {
+      // propagate the target to the preprocessor
+      args.push_back("-target");
+      args.push_back(triple.getTriple());
+
+#if LDC_LLVM_VER >= 1800 // getAllProcessorFeatures was introduced in this version
+      // propagate all enabled/disabled features to the preprocessor
+      const auto &subTarget = gTargetMachine->getMCSubtargetInfo();
+      const auto &featureBits = subTarget->getFeatureBits();
+      llvm::SmallString<64> featureString;
+      for (const auto &feature : subTarget->getAllProcessorFeatures()) {
+        args.push_back("-Xclang");
+        args.push_back("-target-feature");
+        args.push_back("-Xclang");
+
+        featureString += featureBits.test(feature.Value) ? '+' : '-';
+        featureString += feature.Key;
+        args.push_back(featureString.str().str());
+        featureString.clear();
+      }
+#endif
+
       // print macro definitions (clang-cl doesn't support /PD - use clang's
       // -dD)
       args.push_back("-Xclang");

tests/driver/clang-cl-target-forwarding.d

@@ -0,0 +1,17 @@
+// On Windows, either clang-cl or cl is used to preprocess C.
+// If clang-cl is used, LDC's target triple and any target features should be
+// passed to clang-cl.
+
+// REQUIRES: Windows && target_X86 && target_AArch64
+
+// RUN: %ldc -mtriple=x86_64-pc-windows-msvc -mcpu=znver1 -v -c %S/inputs/preprocessable.c | FileCheck %s -check-prefix=znver1
+// RUN: %ldc -mtriple=x86_64-pc-windows-msvc -mcpu=znver1 -mattr -sse4a -v -c %S/inputs/preprocessable.c | FileCheck %s -check-prefix=znver1-sans-sse4a
+// RUN: %ldc -mtriple=x86_64-pc-windows-msvc -mcpu=znver2 -v -c %S/inputs/preprocessable.c | FileCheck %s -check-prefix=znver2
+// RUN: %ldc -mtriple=aarch64-pc-windows-msvc -mcpu=apple-a10 -v -c %S/inputs/preprocessable.c | FileCheck %s -check-prefix=apple-a10
+// RUN: %ldc -mtriple=aarch64-pc-windows-msvc -mcpu=apple-a11 -v -c %S/inputs/preprocessable.c | FileCheck %s -check-prefix=apple-a11
+
+// znver1: {{\\cl\.exe[[:space:]]|\\clang-cl\.exe[[:space:]].*-target[[:space:]]+x86_64-pc-windows-msvc.*-Xclang[[:space:]]+-target-feature[[:space:]]+-Xclang[[:space:]]+\-clwb.*-Xclang[[:space:]]+-target-feature[[:space:]]+-Xclang[[:space:]]+\+sse4a}}
+// znver1-sans-sse4a: {{\\cl\.exe[[:space:]]|\\clang-cl\.exe[[:space:]].*-target[[:space:]]+x86_64-pc-windows-msvc.*-Xclang[[:space:]]+-target-feature[[:space:]]+-Xclang[[:space:]]+\-clwb.*-Xclang[[:space:]]+-target-feature[[:space:]]+-Xclang[[:space:]]+\-sse4a}}
+// znver2: {{\\cl\.exe[[:space:]]|\\clang-cl\.exe[[:space:]].*-target[[:space:]]+x86_64-pc-windows-msvc.*-Xclang[[:space:]]+-target-feature[[:space:]]+-Xclang[[:space:]]+\+clwb}}
+// apple-a10: {{\\cl\.exe[[:space:]]|\\clang-cl\.exe[[:space:]].*-target[[:space:]]+aarch64-pc-windows-msvc.*-Xclang[[:space:]]+-target-feature[[:space:]]+-Xclang[[:space:]]+\+apple-a10.*-Xclang[[:space:]]+-target-feature[[:space:]]+-Xclang[[:space:]]+\-apple-a11}}
+// apple-a11: {{\\cl\.exe[[:space:]]|\\clang-cl\.exe[[:space:]].*-target[[:space:]]+aarch64-pc-windows-msvc.*-Xclang[[:space:]]+-target-feature[[:space:]]+-Xclang[[:space:]]+\-apple-a10.*-Xclang[[:space:]]+-target-feature[[:space:]]+-Xclang[[:space:]]+\+apple-a11}}