[llvm] [LTO] Reset DiscardValueNames in optimize(). (PR #78705)

[Florian Hahn via llvm-commits]

https://github.com/fhahn created https://github.com/llvm/llvm-project/pull/78705

libLTO parses options late, so at the moment the option is ignored. To fix that, 
re-set it in optimize(), as at this point the options have been parsed. When 
LTOCodeGenerator's constructor executes, the options haven't been passed 
by the linker to libLTO yet.

Note that we keep the value name of `%add = add..` because when the module
 is imported, DiscardValueNames is still set to false (the default when building 
with assertions).

I tried to improve this in libLTO, but I am not sure if there's a suitable callback when all options have been set.

>From bcbc97d0cd9b258d8ab246016484fb93cec32ed4 Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Fri, 5 Jan 2024 22:01:21 +0000
Subject: [PATCH] [LTO] Reset DiscardValueNames in optimize().

libLTO parses options late, so re-set them in optimize(). When
LTOCodeGenerator's constructor executes, the options haven't been passed
by the linker to libLTO yet.

Note that we keep the value name of `%add = add..` because when the
module is imported, DiscardValueNames is still set to false (the default
when building wiht assertions).

I tried to improve this in libLTO, but I am not sure if there's a
suitable callback when all options have been set.
---
 llvm/lib/LTO/LTOCodeGenerator.cpp          | 3 +++
 llvm/test/tools/lto/discard-value-names.ll | 3 +--
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/LTO/LTOCodeGenerator.cpp b/llvm/lib/LTO/LTOCodeGenerator.cpp
index 52d8fff14be9ce..727ab7b0db41a6 100644
--- a/llvm/lib/LTO/LTOCodeGenerator.cpp
+++ b/llvm/lib/LTO/LTOCodeGenerator.cpp
@@ -582,6 +582,9 @@ bool LTOCodeGenerator::optimize() {
   if (!this->determineTarget())
     return false;
 
+  // libLTO parses options late, so re-set them here.
+  Context.setDiscardValueNames(LTODiscardValueNames);
+
   auto DiagFileOrErr = lto::setupLLVMOptimizationRemarks(
       Context, RemarksFilename, RemarksPasses, RemarksFormat,
       RemarksWithHotness, RemarksHotnessThreshold);
diff --git a/llvm/test/tools/lto/discard-value-names.ll b/llvm/test/tools/lto/discard-value-names.ll
index 723b0701ae22ce..04d25eaf6067c5 100644
--- a/llvm/test/tools/lto/discard-value-names.ll
+++ b/llvm/test/tools/lto/discard-value-names.ll
@@ -7,11 +7,10 @@
 
 ; The test requires asserts, as it depends on the default value for
 ; -lto-discard-value-names at the moment.
-; FIXME: -lto-discard-value-names is ignored at the moment.
 
 ; REQUIRES: asserts
 
-; DISCARD: %cmp.i = icmp
+; DISCARD: %{{[0-9]+}} = icmp
 ; DISCARD: %add = add i32
 
 ; KEEP: %cmp.i = icmp