AMDGPU/SI: Add new target attribute InitialPSInputAddr

Summary:
This allows Mesa to pass initial SPI_PS_INPUT_ADDR to LLVM.
The register assigns VGPR locations to PS inputs, while the ENA register
determines whether or not they are loaded.

Mesa needs to set some inputs as not-movable, so that a pixel shader prolog
binary appended at the beginning can assume where some inputs are.

v2: Make PSInputAddr private, because there is never enough silly getters
    and setters for people to read.

Reviewers: tstellarAMD, arsenm

Subscribers: arsenm

Differential Revision: http://reviews.llvm.org/D16030

llvm-svn: 257591

1 files changed, 14 insertions, 7 deletions

diff --git a/llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp b/llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp
index add415e215c..3b4c235c0dc 100644
--- a/llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp
@@ -106,20 +106,27 @@ bool isReadOnlySegment(const GlobalValue *GV) {
   return GV->getType()->getAddressSpace() == AMDGPUAS::CONSTANT_ADDRESS;
 }
 
-static const char ShaderTypeAttribute[] = "ShaderType";
-
-unsigned getShaderType(const Function &F) {
-  Attribute A = F.getFnAttribute(ShaderTypeAttribute);
-  unsigned ShaderType = ShaderType::COMPUTE;
+static unsigned getIntegerAttribute(const Function &F, const char *Name,
+                                    unsigned Default) {
+  Attribute A = F.getFnAttribute(Name);
+  unsigned Result = Default;
 
   if (A.isStringAttribute()) {
     StringRef Str = A.getValueAsString();
-    if (Str.getAsInteger(0, ShaderType)) {
+    if (Str.getAsInteger(0, Result)) {
       LLVMContext &Ctx = F.getContext();
       Ctx.emitError("can't parse shader type");
     }
   }
-  return ShaderType;
+  return Result;
+}
+
+unsigned getShaderType(const Function &F) {
+  return getIntegerAttribute(F, "ShaderType", ShaderType::COMPUTE);
+}
+
+unsigned getInitialPSInputAddr(const Function &F) {
+  return getIntegerAttribute(F, "InitialPSInputAddr", 0);
 }
 
 bool isSI(const MCSubtargetInfo &STI) {