[clang] [Hexagon] Driver: Always use resource include directory (PR #186494)

[Alexey Karyakin via cfe-commits]

https://github.com/quic-akaryaki updated https://github.com/llvm/llvm-project/pull/186494

>From a6dc263d8b0ce2efdf56218d8333729d476ae3a0 Mon Sep 17 00:00:00 2001
From: Alexey Karyakin <akaryaki at qti.qualcomm.com>
Date: Fri, 13 Mar 2026 10:41:55 -0700
Subject: [PATCH] [Hexagon] Driver: Always use resource include dir

Before #185456, non-linux triples used the resource include directory
implicitly, by logic in preprocessor. #185456 disables that logic
for all Hexagon triples. To compensate, add the resource include
directory in the driver. This also makes the corresponding driver
logic less convoluted.

The order of inclusion is now uniform for all triples: resource
directory first and default or user-specified sysroot next.
---
 clang/lib/Driver/ToolChains/Hexagon.cpp   | 27 +++++++++--------------
 clang/test/Driver/hexagon-toolchain-elf.c | 15 +++++++++++++
 2 files changed, 25 insertions(+), 17 deletions(-)

diff --git a/clang/lib/Driver/ToolChains/Hexagon.cpp b/clang/lib/Driver/ToolChains/Hexagon.cpp
index 084f51721315c..4a3f1375543cc 100644
--- a/clang/lib/Driver/ToolChains/Hexagon.cpp
+++ b/clang/lib/Driver/ToolChains/Hexagon.cpp
@@ -706,21 +706,18 @@ void HexagonToolChain::AddClangSystemIncludeArgs(const ArgList &DriverArgs,
   if (DriverArgs.hasArg(options::OPT_nostdinc))
     return;
 
-  const bool IsELF = !getTriple().isMusl() && !getTriple().isOSLinux();
+  const Driver &D = getDriver();
+  const bool UseBuiltins = !DriverArgs.hasArg(options::OPT_nobuiltininc);
+  const bool HasSysRoot = !D.SysRoot.empty();
   const bool IsLinuxMusl = getTriple().isMusl() && getTriple().isOSLinux();
 
-  const Driver &D = getDriver();
-  SmallString<128> ResourceDirInclude(D.ResourceDir);
-  if (!IsELF) {
+  if (UseBuiltins) {
+    SmallString<128> ResourceDirInclude(D.ResourceDir);
     llvm::sys::path::append(ResourceDirInclude, "include");
-    if (!DriverArgs.hasArg(options::OPT_nobuiltininc) &&
-        (!IsLinuxMusl || DriverArgs.hasArg(options::OPT_nostdlibinc)))
-      addSystemInclude(DriverArgs, CC1Args, ResourceDirInclude);
+    addSystemInclude(DriverArgs, CC1Args, ResourceDirInclude);
   }
   if (DriverArgs.hasArg(options::OPT_nostdlibinc))
     return;
-
-  const bool HasSysRoot = !D.SysRoot.empty();
   if (HasSysRoot) {
     SmallString<128> P(D.SysRoot);
     if (IsLinuxMusl)
@@ -733,15 +730,11 @@ void HexagonToolChain::AddClangSystemIncludeArgs(const ArgList &DriverArgs,
     addSystemInclude(DriverArgs, CC1Args, P + "/usr/local/include");
     // TOOL_INCLUDE_DIR
     AddMultilibIncludeArgs(DriverArgs, CC1Args);
+  } else {
+    std::string TargetDir = getHexagonTargetDir(D.Dir, D.PrefixDirs);
+    addExternCSystemInclude(DriverArgs, CC1Args,
+                            TargetDir + "/hexagon/include");
   }
-
-  if (!DriverArgs.hasArg(options::OPT_nobuiltininc) && IsLinuxMusl)
-    addSystemInclude(DriverArgs, CC1Args, ResourceDirInclude);
-
-  if (HasSysRoot)
-    return;
-  std::string TargetDir = getHexagonTargetDir(D.Dir, D.PrefixDirs);
-  addExternCSystemInclude(DriverArgs, CC1Args, TargetDir + "/hexagon/include");
 }
 
 void HexagonToolChain::addLibCxxIncludePaths(
diff --git a/clang/test/Driver/hexagon-toolchain-elf.c b/clang/test/Driver/hexagon-toolchain-elf.c
index bff4819488453..a3aac15905d46 100644
--- a/clang/test/Driver/hexagon-toolchain-elf.c
+++ b/clang/test/Driver/hexagon-toolchain-elf.c
@@ -27,17 +27,32 @@
 // CHECK111: "-cc1"
 // CHECK111-NOT: "-internal-externc-isystem"
 
+// RUN: %clang -### --target=hexagon-unknown-elf \
+// RUN:   -ccc-install-dir %S/Inputs/hexagon_tree/Tools/bin \
+// RUN:   -resource-dir=%S/Inputs/resource_dir %s 2>&1 | FileCheck -check-prefix=CHECK-RESOURCE-DIR %s
+// CHECK-RESOURCE-DIR: InstalledDir: [[INSTALLED_DIR:.+]]
+// CHECK-RESOURCE-DIR: "-cc1"
+// CHECK-RESOURCE-DIR: "-resource-dir" "[[RESOURCE:[^"]+]]"
+// CHECK-RESOURCE-DIR: "-internal-isystem" "[[RESOURCE]]{{/|\\\\}}include"
+// CHECK-RESOURCE-DIR: "-internal-externc-isystem" "{{.*}}/Inputs/hexagon_tree/Tools/bin/../target/hexagon/include"
+
 // RUN: %clangxx -### --target=hexagon-unknown-elf \
 // RUN:   -ccc-install-dir %S/Inputs/hexagon_tree/Tools/bin \
 // RUN:   -nostdinc++ %s 2>&1 | FileCheck -check-prefix=CHECK112 %s
+// CHECK112: InstalledDir: [[INSTALLED_DIR:.+]]
 // CHECK112: "-cc1"
+// CHECK112: "-resource-dir" "[[RESOURCE:[^"]+]]"
+// CHECK112: "-internal-isystem" "[[RESOURCE]]{{/|\\\\}}include"
 // CHECK112-NOT: "-internal-isystem"
 // CHECK112-DAG: "-internal-externc-isystem" "{{.*}}/Inputs/hexagon_tree/Tools/bin/../target/hexagon/include"
 
 // RUN: %clangxx -### --target=hexagon-unknown-elf -fno-integrated-as    \
 // RUN:   -ccc-install-dir %S/Inputs/hexagon_tree/qc/bin \
 // RUN:   -nostdlibinc %s 2>&1 | FileCheck -check-prefix=CHECK113 %s
+// CHECK113: InstalledDir: [[INSTALLED_DIR:.+]]
 // CHECK113: "-cc1"
+// CHECK113: "-resource-dir" "[[RESOURCE:[^"]+]]"
+// CHECK113: "-internal-isystem" "[[RESOURCE]]{{/|\\\\}}include"
 // CHECK113-NOT: "-internal-isystem"
 // CHECK113-NOT: "-internal-externc-isystem"