Add a really quick hack at a machine code sinking pass, enabled with --enable-sinking.

It is missing validity checks, so it is known broken.  However, it is powerful enough
to compile this contrived code:

void test1(int C, double A, double B, double *P) {
  double Tmp = A*A+B*B;
  *P = C ? Tmp : A;
}

into:

_test1:
	movsd	8(%esp), %xmm0
	cmpl	$0, 4(%esp)
	je	LBB1_2	# entry
LBB1_1:	# entry
	movsd	16(%esp), %xmm1
	mulsd	%xmm1, %xmm1
	mulsd	%xmm0, %xmm0
	addsd	%xmm1, %xmm0
LBB1_2:	# entry
	movl	24(%esp), %eax
	movsd	%xmm0, (%eax)
	ret

instead of:

_test1:
	movsd	16(%esp), %xmm0
	mulsd	%xmm0, %xmm0
	movsd	8(%esp), %xmm1
	movapd	%xmm1, %xmm2
	mulsd	%xmm2, %xmm2
	addsd	%xmm0, %xmm2
	cmpl	$0, 4(%esp)
	je	LBB1_2	# entry
LBB1_1:	# entry
	movapd	%xmm2, %xmm1
LBB1_2:	# entry
	movl	24(%esp), %eax
	movsd	%xmm1, (%eax)
	ret

woo.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45570 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 9 insertions, 0 deletions

diff --git a/lib/CodeGen/LLVMTargetMachine.cpp b/lib/CodeGen/LLVMTargetMachine.cpp
index 05284347f0..6a8e775e6b 100644
--- a/lib/CodeGen/LLVMTargetMachine.cpp
+++ b/lib/CodeGen/LLVMTargetMachine.cpp
@@ -29,6 +29,12 @@ static cl::opt<bool> PrintISelInput("print-isel-input", cl::Hidden,
 static cl::opt<bool> PrintEmittedAsm("print-emitted-asm", cl::Hidden,
     cl::desc("Dump emitter generated instructions as assembly"));
 
+// Hidden options to help debugging
+static cl::opt<bool>
+EnableSinking("enable-sinking", cl::init(false), cl::Hidden,
+              cl::desc("Perform sinking on machine code"));
+
+
 FileModel::Model
 LLVMTargetMachine::addPassesToEmitFile(FunctionPassManager &PM,
                                        std::ostream &Out,
@@ -68,6 +74,9 @@ LLVMTargetMachine::addPassesToEmitFile(FunctionPassManager &PM,
     PM.add(createMachineFunctionPrinterPass(cerr));
 
   PM.add(createMachineLICMPass());
+  
+  if (EnableSinking)
+    PM.add(createMachineSinkingPass());
 
   // Perform register allocation to convert to a concrete x86 representation
   PM.add(createRegisterAllocator());