AMDGPU: Increase default stack alignment

8 and 16-byte values are common, so increase the default
alignment to avoid realigning the stack in most functions.

llvm-svn: 328821

1 files changed, 6 insertions, 1 deletions

diff --git a/llvm/lib/Target/AMDGPU/AMDGPUSubtarget.h b/llvm/lib/Target/AMDGPU/AMDGPUSubtarget.h
index 6312bb02feb..a7e52cb16c9 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUSubtarget.h
+++ b/llvm/lib/Target/AMDGPU/AMDGPUSubtarget.h
@@ -550,8 +550,13 @@ public:
   // Scratch is allocated in 256 dword per wave blocks for the entire
   // wavefront. When viewed from the perspecive of an arbitrary workitem, this
   // is 4-byte aligned.
+  //
+  // Only 4-byte alignment is really needed to access anything. Transformations
+  // on the pointer value itself may rely on the alignment / known low bits of
+  // the pointer. Set this to something above the minimum to avoid needing
+  // dynamic realignment in common cases.
   unsigned getStackAlignment() const {
-    return 4;
+    return 16;
   }
 
   bool enableMachineScheduler() const override {