[llvm] 9b98692 - [AMDGPU] Run LowerLDS at the end of the fullLTO pipeline (#75333)

[via llvm-commits]

Author: Pierre van Houtryve
Date: 2024-03-18T09:09:43+01:00
New Revision: 9b98692eedb78aa106539c36ba02944f32cae1ff

URL: https://github.com/llvm/llvm-project/commit/9b98692eedb78aa106539c36ba02944f32cae1ff
DIFF: https://github.com/llvm/llvm-project/commit/9b98692eedb78aa106539c36ba02944f32cae1ff.diff

LOG: [AMDGPU] Run LowerLDS at the end of the fullLTO pipeline (#75333)

This change allows us to use `--lto-partitions` in some cases (not at
all guaranteed it works perfectly), as LDS is lowered before the module
is split for parallel codegen.

We must run LowerLDS before splitting modules as it needs to see all
callers of functions with LDS to properly lower them.

Added: 
    llvm/test/CodeGen/AMDGPU/lto-lower-module-lds.ll

Modified: 
    llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp b/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp
index 2b457fe519d96c..c96625092a76c8 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp
@@ -793,6 +793,15 @@ void AMDGPUTargetMachine::registerPassBuilderCallbacks(
 
         PM.addPass(createCGSCCToFunctionPassAdaptor(std::move(FPM)));
       });
+
+  PB.registerFullLinkTimeOptimizationLastEPCallback(
+      [this](ModulePassManager &PM, OptimizationLevel Level) {
+        // We want to support the -lto-partitions=N option as "best effort".
+        // For that, we need to lower LDS earlier in the pipeline before the
+        // module is partitioned for codegen.
+        if (EnableLowerModuleLDS)
+          PM.addPass(AMDGPULowerModuleLDSPass(*this));
+      });
 }
 
 int64_t AMDGPUTargetMachine::getNullPointerValue(unsigned AddrSpace) {

diff  --git a/llvm/test/CodeGen/AMDGPU/lto-lower-module-lds.ll b/llvm/test/CodeGen/AMDGPU/lto-lower-module-lds.ll
new file mode 100644
index 00000000000000..b813b8047bf24c
--- /dev/null
+++ b/llvm/test/CodeGen/AMDGPU/lto-lower-module-lds.ll
@@ -0,0 +1,47 @@
+
+; Default O0
+; RUN: opt -mtriple=amdgcn-- -mcpu=gfx1030 %s -o %t.bc
+; RUN: llvm-lto2 run -O0 -cg-opt-level 0 %t.bc -o %t.s -r %t.bc,test,px -debug-pass-manager -debug-pass=Structure 2>&1 | FileCheck %s
+
+; Unified O0
+; RUN: opt -unified-lto -thinlto-split-lto-unit -thinlto-bc -mtriple=amdgcn-- -mcpu=gfx1030 %s -o %t.bc
+; RUN: llvm-lto2 run -unified-lto=full -O0 -cg-opt-level 0 %t.bc -o %t.s -r %t.bc,test,px -debug-pass-manager -debug-pass=Structure 2>&1 | FileCheck %s
+
+; Default O1
+; RUN: opt -mtriple=amdgcn-- -mcpu=gfx1030 %s -o %t.bc
+; RUN: llvm-lto2 run -O1 -cg-opt-level 1 %t.bc -o %t.s -r %t.bc,test,px -debug-pass-manager -debug-pass=Structure 2>&1 | FileCheck %s
+
+; Unified O1
+; RUN: opt -unified-lto -thinlto-split-lto-unit -thinlto-bc -mtriple=amdgcn-- -mcpu=gfx1030 %s -o %t.bc
+; RUN: llvm-lto2 run -unified-lto=full -O1 -cg-opt-level 1 %t.bc -o %t.s -r %t.bc,test,px -debug-pass-manager -debug-pass=Structure 2>&1 | FileCheck %s
+
+; Default O2
+; RUN: opt -mtriple=amdgcn-- -mcpu=gfx1030 %s -o %t.bc
+; RUN: llvm-lto2 run -O2 -cg-opt-level 2 %t.bc -o %t.s -r %t.bc,test,px -debug-pass-manager -debug-pass=Structure 2>&1 | FileCheck %s
+
+; Unified O2
+; RUN: opt -unified-lto -thinlto-split-lto-unit -thinlto-bc -mtriple=amdgcn-- -mcpu=gfx1030 %s -o %t.bc
+; RUN: llvm-lto2 run -unified-lto=full -O2 -cg-opt-level 2 %t.bc -o %t.s -r %t.bc,test,px -debug-pass-manager -debug-pass=Structure 2>&1 | FileCheck %s
+
+; Default O3
+; RUN: opt -mtriple=amdgcn-- -mcpu=gfx1030 %s -o %t.bc
+; RUN: llvm-lto2 run -O3 -cg-opt-level 3 %t.bc -o %t.s -r %t.bc,test,px -debug-pass-manager -debug-pass=Structure 2>&1 | FileCheck %s
+
+; Unified O3
+; RUN: opt -unified-lto -thinlto-split-lto-unit -thinlto-bc -mtriple=amdgcn-- -mcpu=gfx1030 %s -o %t.bc
+; RUN: llvm-lto2 run -unified-lto=full -O3 -cg-opt-level 3 %t.bc -o %t.s -r %t.bc,test,px -debug-pass-manager -debug-pass=Structure 2>&1 | FileCheck %s
+
+; First print will be from the New PM during the full LTO pipeline.
+; Second print will be from the legacy PM during the CG pipeline.
+
+; CHECK: Running pass: AMDGPULowerModuleLDSPass on [module]
+; CHECK: ModulePass Manager
+; CHECK:   Lower uses of LDS variables from non-kernel functions
+
+ at lds = internal unnamed_addr addrspace(3) global i32 undef, align 4
+
+define amdgpu_kernel void @test() {
+entry:
+  store i32 1, ptr addrspace(3) @lds
+  ret void
+}