[llvm] [libc] Only enable `LLVM_FULL_BUILD_MODE` by default for GPU targets (PR #84664)

[Joseph Huber via llvm-commits]

https://github.com/jhuber6 created https://github.com/llvm/llvm-project/pull/84664

Summary:
Currently we have a conditional that turns the full build on by default
if it is a default target. This used to work fine when the GPU was the
only target that was ever present. However, we've recently changed to
allow building multiple of these at the same time. That means we should
have the ability to build overlay mode in the CPU mode and full build in
the GPU mode. This patch makes some simple adjustments to pass the
arguments per-triple. This slightly extends the existing `-DRUNTIMES_`
argument support to also transform any extra CMake inputs rather than
just the passed CMake variables.


>From 8c24add0b7fed68d7f3f864baffa96285e53f7ea Mon Sep 17 00:00:00 2001
From: Joseph Huber <huberjn at outlook.com>
Date: Sat, 9 Mar 2024 20:13:17 -0600
Subject: [PATCH] [libc] Only enable `LLVM_FULL_BUILD_MODE` by default for GPU
 targets

Summary:
Currently we have a conditional that turns the full build on by default
if it is a default target. This used to work fine when the GPU was the
only target that was ever present. However, we've recently changed to
allow building multiple of these at the same time. That means we should
have the ability to build overlay mode in the CPU mode and full build in
the GPU mode. This patch makes some simple adjustments to pass the
arguments per-triple. This slightly extends the existing `-DRUNTIMES_`
argument support to also transform any extra CMake inputs rather than
just the passed CMake variables.
---
 llvm/runtimes/CMakeLists.txt | 42 +++++++++++++++++++++++++-----------
 1 file changed, 29 insertions(+), 13 deletions(-)

diff --git a/llvm/runtimes/CMakeLists.txt b/llvm/runtimes/CMakeLists.txt
index 9b5e758b6ede57..3f3c482adccd37 100644
--- a/llvm/runtimes/CMakeLists.txt
+++ b/llvm/runtimes/CMakeLists.txt
@@ -358,6 +358,14 @@ function(runtime_register_target name)
         endif()
       endif()
     endforeach()
+    foreach(variable_name ${${name}_extra_args})
+      string(FIND "${variable_name}" "-DRUNTIMES_${extra_name}_" out)
+      if("${out}" EQUAL 0)
+        string(REPLACE "-DRUNTIMES_${extra_name}_" "" new_name ${variable_name})
+        string(REPLACE ";" "|" new_value "${new_name}")
+        list(APPEND ${name}_extra_args "-D${new_value}")
+      endif()
+    endforeach()
   endforeach()
 
   set_enable_per_target_runtime_dir()
@@ -438,21 +446,29 @@ if(runtimes)
     if(NOT hdrgen_exe)
       message(FATAL_ERROR "libc-hdrgen executable missing")
     endif()
-    set(libc_cmake_args "-DLIBC_HDRGEN_EXE=${hdrgen_exe}"
-                        "-DLLVM_LIBC_FULL_BUILD=ON")
+    list(APPEND libc_cmake_args "-DLIBC_HDRGEN_EXE=${hdrgen_exe}")
     list(APPEND extra_deps ${hdrgen_deps})
-    if(LLVM_LIBC_GPU_BUILD)
-      list(APPEND libc_cmake_args "-DLLVM_LIBC_GPU_BUILD=ON")
-      # The `libc` project may require '-DCUDAToolkit_ROOT' in GPU mode.
-      if(CUDAToolkit_ROOT)
-        list(APPEND libc_cmake_args "-DCUDAToolkit_ROOT=${CUDAToolkit_ROOT}")
-      endif()
-      foreach(dep clang-offload-packager nvptx-arch amdgpu-arch)
-        if(TARGET ${dep})
-          list(APPEND extra_deps ${dep})
-        endif()
-      endforeach()
+  endif()
+  if(LLVM_LIBC_GPU_BUILD)
+    list(APPEND libc_cmake_args "-DLLVM_LIBC_GPU_BUILD=ON")
+    if("libc" IN_LIST RUNTIMES_amdgcn-amd-amdhsa_LLVM_ENABLE_RUNTIMES)
+      list(APPEND libc_cmake_args "-DRUNTIMES_amdgcn-amd-amdhsa_LLVM_LIBC_FULL_BUILD=ON")
     endif()
+    if("libc" IN_LIST RUNTIMES_nvptx64-nvidia-cuda_LLVM_ENABLE_RUNTIMES)
+      list(APPEND libc_cmake_args "-DRUNTIMES_nvptx64-nvidia-cuda_LLVM_LIBC_FULL_BUILD=ON")
+    endif()
+    # The `libc` project may require '-DCUDAToolkit_ROOT' in GPU mode.
+    if(CUDAToolkit_ROOT)
+      list(APPEND libc_cmake_args "-DCUDAToolkit_ROOT=${CUDAToolkit_ROOT}")
+    endif()
+    foreach(dep clang-offload-packager nvptx-arch amdgpu-arch)
+      if(TARGET ${dep})
+        list(APPEND extra_deps ${dep})
+      endif()
+    endforeach()
+  endif()
+  if(LLVM_LIBC_FULL_BUILD)
+    list(APPEND libc_cmake_args "-DLLVM_LIBC_FULL_BUILD=ON")
   endif()
   if(NOT LLVM_RUNTIME_TARGETS)
     runtime_default_target(