[libc-commits] [PATCH] D153388: [libc] Add basic utility support for timing functions on the GPU

[Joseph Huber via Phabricator via libc-commits]

jhuber6 updated this revision to Diff 533101.
jhuber6 added a comment.

Using `__has_builtin`


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D153388/new/

https://reviews.llvm.org/D153388

Files:
  libc/src/__support/GPU/amdgpu/utils.h
  libc/src/__support/GPU/generic/utils.h
  libc/src/__support/GPU/nvptx/utils.h


Index: libc/src/__support/GPU/nvptx/utils.h
===================================================================
--- libc/src/__support/GPU/nvptx/utils.h
+++ libc/src/__support/GPU/nvptx/utils.h
@@ -134,6 +134,20 @@
   __nvvm_bar_warp_sync(mask);
 }
 
+/// Returns the current value of the GPU's processor clock.
+LIBC_INLINE uint64_t clock() {
+  uint64_t timestamp;
+  asm volatile("mov.u64  %0, %%clock64;" : "=l"(timestamp));
+  return timestamp;
+}
+
+/// Returns a global fixed-frequency timer at nanosecond frequency.
+LIBC_INLINE uint64_t time() {
+  uint64_t nsecs;
+  asm volatile("mov.u64  %0, %%globaltimer;" : "=l"(nsecs));
+  return nsecs;
+}
+
 } // namespace gpu
 } // namespace __llvm_libc
 
Index: libc/src/__support/GPU/generic/utils.h
===================================================================
--- libc/src/__support/GPU/generic/utils.h
+++ libc/src/__support/GPU/generic/utils.h
@@ -67,6 +67,10 @@
 
 LIBC_INLINE void sync_lane(uint64_t) {}
 
+LIBC_INLINE uint64_t clock() { return 0; }
+
+LIBC_INLINE uint64_t time() { return 0; }
+
 } // namespace gpu
 } // namespace __llvm_libc
 
Index: libc/src/__support/GPU/amdgpu/utils.h
===================================================================
--- libc/src/__support/GPU/amdgpu/utils.h
+++ libc/src/__support/GPU/amdgpu/utils.h
@@ -144,6 +144,21 @@
   __builtin_amdgcn_wave_barrier();
 }
 
+/// Returns the current value of the GPU's processor clock.
+/// NOTE: The RDNA3 architecture replaced this with a 20-bit cycle counter.
+LIBC_INLINE uint64_t clock() { return __builtin_readcyclecounter(); }
+
+/// Returns a fixed-frequency timestamp. The actual frequency is dependent on
+/// the card and can only be queried via the driver.
+LIBC_INLINE uint64_t time() {
+  if constexpr (__has_builtin(__builtin_amdgcn_s_sendmsg_rtnl))
+    return __builtin_amdgcn_s_sendmsg_rtnl(0x83);
+  else if (__has_builtin(__builtin_amdgcn_s_memrealtime))
+    return __builtin_amdgcn_s_memrealtime();
+  else
+    return __builtin_amdgcn_s_memtime();
+}
+
 } // namespace gpu
 } // namespace __llvm_libc
 


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