[PowerPC] Use the MachineCombiner to reassociate fadd/fmul

This is a direct port of the code from the X86 backend (r239486/r240361), which
uses the MachineCombiner to reassociate (floating-point) adds/muls to increase
ILP, to the PowerPC backend. The rationale is the same.

There is a lot of copy-and-paste here between the X86 code and the PowerPC
code, and we should extract at least some of this into CodeGen somewhere.
However, I don't want to do that until this code is enhanced to handle FMAs as
well. After that, we'll be in a better position to extract the common parts.

llvm-svn: 242279

1 files changed, 9 insertions, 0 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCTargetMachine.cpp b/llvm/lib/Target/PowerPC/PPCTargetMachine.cpp
index 1daf244..b602edb 100644
--- a/llvm/lib/Target/PowerPC/PPCTargetMachine.cpp
+++ b/llvm/lib/Target/PowerPC/PPCTargetMachine.cpp
@@ -57,6 +57,11 @@ EnableExtraTOCRegDeps("enable-ppc-extra-toc-reg-deps",
                       cl::desc("Add extra TOC register dependencies"),
                       cl::init(true), cl::Hidden);
 
+static cl::opt<bool>
+EnableMachineCombinerPass("ppc-machine-combiner",
+                          cl::desc("Enable the machine combiner pass"),
+                          cl::init(true), cl::Hidden);
+
 extern "C" void LLVMInitializePowerPCTarget() {
   // Register the targets
   RegisterTargetMachine<PPC32TargetMachine> A(ThePPC32Target);
@@ -316,6 +321,10 @@ bool PPCPassConfig::addPreISel() {
 
 bool PPCPassConfig::addILPOpts() {
   addPass(&EarlyIfConverterID);
+
+  if (EnableMachineCombinerPass)
+    addPass(&MachineCombinerID);
+
   return true;
 }