[clang] [Hexagon] Add LTO options to Hexagon driver link args (PR #191336)

[Brian Cain via cfe-commits]

https://github.com/androm3da created https://github.com/llvm/llvm-project/pull/191336

The Hexagon driver's constructHexagonLinkArgs() was not calling addLTOOptions(). This meant that LTO plugin options weren't forwarded to the linker.

This caused a crash when using ThinLTO with -fenable-matrix on llvm-test-suite/SingleSource/UnitTests/matrix-types-spec.cpp: LowerMatrixIntrinsicsPass did not run in the LTO backend because -enable-matrix was not forwarded via -plugin-opt.

Add the addLTOOptions() call to both the musl and bare-metal code paths in constructHexagonLinkArgs().

>From a5ba34e1dfba03961d73480dda89c18b3cce77b0 Mon Sep 17 00:00:00 2001
From: Brian Cain <brian.cain at oss.qualcomm.com>
Date: Thu, 9 Apr 2026 20:54:08 -0700
Subject: [PATCH] [Hexagon] Add LTO options to Hexagon driver link args

The Hexagon driver's constructHexagonLinkArgs() was not calling
addLTOOptions(). This meant that LTO plugin options weren't forwarded
to the linker.

This caused a crash when using ThinLTO with -fenable-matrix on
llvm-test-suite/SingleSource/UnitTests/matrix-types-spec.cpp:
LowerMatrixIntrinsicsPass did not run in the LTO backend because
-enable-matrix was not forwarded via -plugin-opt.

Add the addLTOOptions() call to both the musl and bare-metal code
paths in constructHexagonLinkArgs().
---
 clang/lib/Driver/ToolChains/Hexagon.cpp     |  8 ++++++++
 clang/test/Driver/hexagon-toolchain-elf.c   | 12 ++++++++++++
 clang/test/Driver/hexagon-toolchain-linux.c | 13 +++++++++++++
 3 files changed, 33 insertions(+)

diff --git a/clang/lib/Driver/ToolChains/Hexagon.cpp b/clang/lib/Driver/ToolChains/Hexagon.cpp
index e5c90089f8cf0..801682eef57d3 100644
--- a/clang/lib/Driver/ToolChains/Hexagon.cpp
+++ b/clang/lib/Driver/ToolChains/Hexagon.cpp
@@ -358,6 +358,10 @@ constructHexagonLinkArgs(Compilation &C, const JobAction &JA,
                               options::OPT_t, options::OPT_u_Group});
     AddLinkerInputs(HTC, Inputs, Args, CmdArgs, JA);
 
+    if (D.isUsingLTO())
+      addLTOOptions(HTC, Args, CmdArgs, Output, Inputs,
+                    D.getLTOMode() == LTOK_Thin);
+
     ToolChain::UnwindLibType UNW = HTC.GetUnwindLibType(Args);
 
     if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nodefaultlibs)) {
@@ -438,6 +442,10 @@ constructHexagonLinkArgs(Compilation &C, const JobAction &JA,
 
   AddLinkerInputs(HTC, Inputs, Args, CmdArgs, JA);
 
+  if (D.isUsingLTO())
+    addLTOOptions(HTC, Args, CmdArgs, Output, Inputs,
+                  D.getLTOMode() == LTOK_Thin);
+
   //----------------------------------------------------------------------------
   // Libraries
   //----------------------------------------------------------------------------
diff --git a/clang/test/Driver/hexagon-toolchain-elf.c b/clang/test/Driver/hexagon-toolchain-elf.c
index f2634559f75ea..16cfddedc12ca 100644
--- a/clang/test/Driver/hexagon-toolchain-elf.c
+++ b/clang/test/Driver/hexagon-toolchain-elf.c
@@ -598,3 +598,15 @@
 // RUN:   -ccc-install-dir %S/Inputs/hexagon_tree/Tools/bin \
 // RUN:   -mcpu=hexagonv60 %s 2>&1 | FileCheck -check-prefix=CHECK384 %s
 // CHECK384:          "-fno-use-init-array"
+// -----------------------------------------------------------------------------
+// ThinLTO passes LTO options to the linker
+// -----------------------------------------------------------------------------
+// RUN: touch %t.o
+// RUN: %clang -### --target=hexagon-unknown-elf \
+// RUN:   -ccc-install-dir %S/Inputs/hexagon_tree/Tools/bin \
+// RUN:   -mcpu=hexagonv60 \
+// RUN:   -fuse-ld=lld \
+// RUN:   -flto=thin -fenable-matrix \
+// RUN:   %t.o 2>&1 | FileCheck -check-prefix=CHECK-LTO %s
+// CHECK-LTO: "-plugin-opt=thinlto"
+// CHECK-LTO: "-plugin-opt=-enable-matrix"
diff --git a/clang/test/Driver/hexagon-toolchain-linux.c b/clang/test/Driver/hexagon-toolchain-linux.c
index c1a59c1fc99b5..05d8b53ec1aad 100644
--- a/clang/test/Driver/hexagon-toolchain-linux.c
+++ b/clang/test/Driver/hexagon-toolchain-linux.c
@@ -213,3 +213,16 @@
 // RUN:   --sysroot=%S/Inputs/basic_linux_libcxx_tree %s 2>&1 | FileCheck -check-prefix=CHECK-NOSAN %s
 // CHECK-NOSAN-NOT: "-L{{.*}}{{/|\\\\}}msan"
 // CHECK-NOSAN-NOT: "-L{{.*}}{{/|\\\\}}asan"
+// -----------------------------------------------------------------------------
+// ThinLTO passes LTO options to the linker
+// -----------------------------------------------------------------------------
+// RUN: touch %t.o
+// RUN: %clang -### --target=hexagon-unknown-linux-musl \
+// RUN:   -ccc-install-dir %S/Inputs/hexagon_tree/Tools/bin \
+// RUN:   -mcpu=hexagonv60 \
+// RUN:   -fuse-ld=lld \
+// RUN:   -flto=thin -fenable-matrix \
+// RUN:   --sysroot=%S/Inputs/basic_linux_libcxx_tree %t.o 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-LTO %s
+// CHECK-LTO: "-plugin-opt=thinlto"
+// CHECK-LTO: "-plugin-opt=-enable-matrix"