AMDGPU: enable 128-bit for local addr space under an option

Author: Samuel Pitoiset

ds_read_b128 and ds_write_b128 have been recently enabled
under the amdgpu-ds128 option because the performance benefit
is unclear.

Though, using 128-bit loads/stores for the local address space
appears to introduce regressions in tessellation shaders. Not
sure what is broken, but as ds_read_b128/ds_write_b128 are not
enabled by default, just introduce a global option and enable
128-bit only if requested (until it's fixed/used correctly).

v2: - fix regressions in merge-stores.ll and multiple_tails.ll

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105464
llvm-svn: 329764

1 files changed, 3 insertions, 2 deletions

diff --git a/llvm/lib/Target/AMDGPU/AMDGPUSubtarget.h b/llvm/lib/Target/AMDGPU/AMDGPUSubtarget.h
index e3455d34324..cd080263c5a 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUSubtarget.h
+++ b/llvm/lib/Target/AMDGPU/AMDGPUSubtarget.h
@@ -133,6 +133,7 @@ protected:
   bool EnableLoadStoreOpt;
   bool EnableUnsafeDSOffsetFolding;
   bool EnableSIScheduler;
+  bool EnableDS128;
   bool DumpCode;
 
   // Subtarget statically properties set by tablegen
@@ -412,8 +413,8 @@ public:
 
   /// \returns If target supports ds_read/write_b128 and user enables generation
   /// of ds_read/write_b128.
-  bool useDS128(bool UserEnable) const {
-    return CIInsts && UserEnable;
+  bool useDS128() const {
+    return CIInsts && EnableDS128;
   }
 
   /// \returns If MUBUF instructions always perform range checking, even for