[AMDGPU] Run always inliner early in opt

We can mark functions to always inline early in the opt. Since we do not have
call support this early inlining creates opportunities for inter-procedural
optimizations which would not occur otherwise.

Differential Revision: https://reviews.llvm.org/D31016

llvm-svn: 297958

llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp

@@ -244,6 +244,7 @@ void AMDGPUTargetMachine::adjustPassManager(PassManagerBuilder &Builder) {
         }));
         PM.add(createGlobalDCEPass());
       }
+      PM.add(createAMDGPUAlwaysInlinePass());
   });
 }
 

llvm/test/CodeGen/AMDGPU/early-inline.ll

@@ -0,0 +1,21 @@
+; RUN: opt -mtriple=amdgcn-- -O1 -S -inline-threshold=1 %s | FileCheck %s
+
+define i32 @callee(i32 %x) {
+entry:
+  %mul1 = mul i32 %x, %x
+  %mul2 = mul i32 %mul1, %x
+  %mul3 = mul i32 %mul1, %mul2
+  %mul4 = mul i32 %mul3, %mul2
+  %mul5 = mul i32 %mul4, %mul3
+  ret i32 %mul5
+}
+
+; CHECK-LABEL: @caller
+; CHECK: mul i32
+; CHECK-NOT: call i32
+
+define i32 @caller(i32 %x) {
+entry:
+  %res = call i32 @callee(i32 %x)
+  ret i32 %res
+}