[Feature Request]: expose LLVM_TARGETS_TO_BUILD in third-party/llvm/Makefile so builder can override.

[hpcpony]

Summary of Feature

Description:
Would it be reasonable to change third-party/llvm/Makefile so that if a user has LLVM_TARGETS_TO_BUILD (or if you want to call it something else that's fine) defined then that is used as opposed to the current default ("host;X86;AArch64;NVPTX;AMDGPU"). If no environment value is defined then default to everything: . Typically I only need "host" or "host" + one of the GPUs and I don't really need to build everything else.

Is this issue currently blocking your progress?
no

[mppf]

Sounds like a good idea. @hpcpony I think this could be a relatively small change to third-party/llvm/Makefile. Would you be up for making a PR to do it?

[hpcpony]

Sorry, I've been away...

I don't know how to do all the github stuff, nor have resources to test on other than one system but here's the diff of what I do locally to third-party/llvm/Makefile that seems to be working for me:

4a5,8
> ifndef CHPL_LLVM_TARGETS_TO_BUILD
> export CHPL_LLVM_TARGETS_TO_BUILD="host;X86;AArch64;NVPTX;AMDGPU"
> endif
> 
106c110
< 	    -DLLVM_TARGETS_TO_BUILD="host;X86;AArch64;NVPTX;AMDGPU" \
---
> 	    -DLLVM_TARGETS_TO_BUILD=$(CHPL_LLVM_TARGETS_TO_BUILD) \

[jabraham17]

I found myself really wanting this improvement today and tried the diff. I made a small adjustment so that something like export CHPL_LLVM_TARGETS_TO_BUILD='host;NVPTX' gets properly quoted, but this was a nice time saver.

diff --git a/third-party/llvm/Makefile b/third-party/llvm/Makefile
index 5db91cbd182..0b982d1eb9e 100644
--- a/third-party/llvm/Makefile
+++ b/third-party/llvm/Makefile
@@ -12,6 +12,12 @@ else
   CHPL_LLVM_DEBUG := -DCMAKE_BUILD_TYPE=Release
 endif
 
+ifndef CHPL_LLVM_TARGETS_TO_BUILD
+  CHPL_LLVM_TARGETS_TO_BUILD := "host;X86;AArch64;NVPTX;AMDGPU"
+else
+  CHPL_LLVM_TARGETS_TO_BUILD := "$(CHPL_LLVM_TARGETS_TO_BUILD)"
+endif
+
 # activate LLVM asserts if it's from `make ASSERTS=1`
 # or if CHPL_LLVM_DEVELOPER is set
 CHPL_LLVM_ASSERTS := 0
@@ -105,7 +111,7 @@ llvm-config: FORCE
 	    -DCLANG_ENABLE_ARCMT=0 \
 	    -DCLANG_ANALYZER_ENABLE_Z3_SOLVER=0 \
 	    -DCLANG_ENABLE_STATIC_ANALYZER=0 \
-	    -DLLVM_TARGETS_TO_BUILD="host;X86;AArch64;NVPTX;AMDGPU" \
+	    -DLLVM_TARGETS_TO_BUILD=$(CHPL_LLVM_TARGETS_TO_BUILD) \
 	    -DLLVM_INSTALL_UTILS=ON \
 	    $(CHPL_LLVM_NO_TESTS) \
 	    $(CHPL_LLVM_ENABLE_PROJECTS) \

[bradcray]

@jabraham17 : As an advocate, would you be up for making a PR for this since @hpcpony seems (understandably) disinclined to go through the GitHub learning curve?

[jabraham17]

Yup, done in #26341