0071-RISCV-Expose-options-to-enable-optimisation-of-compl.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Alex Bradbury <asb@lowrisc.org>
Subject: [RISCV] Expose options to enable optimisation of complex GEPs

Experimental, it seems both PPC and AArch64 have experimented with this. Seems
to have minimal effect on generated code in my current benchmark set.
---
 lib/Target/RISCV/LLVMBuild.txt          |  2 +-
 lib/Target/RISCV/RISCVTargetMachine.cpp | 20 ++++++++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/lib/Target/RISCV/LLVMBuild.txt b/lib/Target/RISCV/LLVMBuild.txt
index ab21565b0c2..840f3a47f22 100644
--- a/lib/Target/RISCV/LLVMBuild.txt
+++ b/lib/Target/RISCV/LLVMBuild.txt
@@ -31,5 +31,5 @@ type = Library
 name = RISCVCodeGen
 parent = RISCV
 required_libraries = AsmPrinter Core CodeGen MC RISCVAsmPrinter RISCVDesc
-  RISCVInfo SelectionDAG Support Target
+  RISCVInfo Scalar SelectionDAG Support Target
 add_to_library_groups = RISCV
diff --git a/lib/Target/RISCV/RISCVTargetMachine.cpp b/lib/Target/RISCV/RISCVTargetMachine.cpp
index 7cf90fa66e2..8b2adaeac3b 100644
--- a/lib/Target/RISCV/RISCVTargetMachine.cpp
+++ b/lib/Target/RISCV/RISCVTargetMachine.cpp
@@ -21,8 +21,15 @@
 #include "llvm/Support/FormattedStream.h"
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Target/TargetOptions.h"
+#include "llvm/Transforms/Scalar.h"
+
 using namespace llvm;
 
+static cl::opt<bool>
+EnableGEPOpt("riscv-gep-opt", cl::Hidden,
+             cl::desc("Enable optimizations on complex GEPs"),
+             cl::init(false));
+
 extern "C" void LLVMInitializeRISCVTarget() {
   RegisterTargetMachine<RISCVTargetMachine> X(getTheRISCV32Target());
   RegisterTargetMachine<RISCVTargetMachine> Y(getTheRISCV64Target());
@@ -87,6 +94,19 @@ TargetPassConfig *RISCVTargetMachine::createPassConfig(PassManagerBase &PM) {
 void RISCVPassConfig::addIRPasses() {
   addPass(createAtomicExpandPass());
 
+  if (TM->getOptLevel() == CodeGenOpt::Aggressive && EnableGEPOpt) {
+    // Call SeparateConstOffsetFromGEP pass to extract constants within indices
+    // and lower a GEP with multiple indices to either arithmetic operations or
+    // multiple GEPs with single index.
+    addPass(createSeparateConstOffsetFromGEPPass(TM, true));
+    // Call EarlyCSE pass to find and remove subexpressions in the lowered
+    // result.
+    addPass(createEarlyCSEPass());
+    // Do loop invariant code motion in case part of the lowered result is
+    // invariant.
+    addPass(createLICMPass());
+  }
+
   TargetPassConfig::addIRPasses();
 }
 
-- 
2.16.2