[NVVM][MLIR] Remove Pure trait from clock, clock64, globaltimer Ops #147608
+85
−42
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
|
@llvm/pr-subscribers-mlir-llvm @llvm/pr-subscribers-mlir Author: Pradeep Kumar (schwarzschild-radius) ChangesThis commit removes Pure trait from clock, clock64 and globaltimer Ops by creating NVVM_NCSpecialRegisterOp class to represent Ops which return non-constant values. This prevents CSE pass from optimizing away redundant uses of them Full diff: https://github.com/llvm/llvm-project/pull/147608.diff 2 Files Affected:
diff --git a/mlir/include/mlir/Dialect/LLVMIR/NVVMOps.td b/mlir/include/mlir/Dialect/LLVMIR/NVVMOps.td
index 6895e946b8a45..a0d23853a52dd 100644
--- a/mlir/include/mlir/Dialect/LLVMIR/NVVMOps.td
+++ b/mlir/include/mlir/Dialect/LLVMIR/NVVMOps.td
@@ -159,6 +159,13 @@ class NVVM_SpecialRegisterOp<string mnemonic, list<Trait> traits = []> :
let assemblyFormat = "attr-dict `:` type($res)";
}
+// NVVM_NCSpecialRegisterOp represents a non-constant special register
+class NVVM_NCSpecialRegisterOp<string mnemonic, list<Trait> traits = []> :
+ NVVM_IntrOp<mnemonic, traits, 1> {
+ let arguments = (ins);
+ let assemblyFormat = "attr-dict `:` type($res)";
+}
+
class NVVM_SpecialRangeableRegisterOp<string mnemonic, list<Trait> traits = []> :
NVVM_SpecialRegisterOp<mnemonic,
!listconcat(traits,
@@ -249,9 +256,9 @@ def NVVM_ClusterDim : NVVM_SpecialRangeableRegisterOp<"read.ptx.sreg.cluster.nct
//===----------------------------------------------------------------------===//
// Clock registers
-def NVVM_ClockOp : NVVM_SpecialRegisterOp<"read.ptx.sreg.clock">;
-def NVVM_Clock64Op : NVVM_SpecialRegisterOp<"read.ptx.sreg.clock64">;
-def NVVM_GlobalTimerOp : NVVM_SpecialRegisterOp<"read.ptx.sreg.globaltimer">;
+def NVVM_ClockOp : NVVM_NCSpecialRegisterOp<"read.ptx.sreg.clock">;
+def NVVM_Clock64Op : NVVM_NCSpecialRegisterOp<"read.ptx.sreg.clock64">;
+def NVVM_GlobalTimerOp : NVVM_NCSpecialRegisterOp<"read.ptx.sreg.globaltimer">;
//===----------------------------------------------------------------------===//
// envreg registers
diff --git a/mlir/test/Dialect/LLVMIR/cse-nvvm.mlir b/mlir/test/Dialect/LLVMIR/cse-nvvm.mlir
new file mode 100644
index 0000000000000..8d24c3846f178
--- /dev/null
+++ b/mlir/test/Dialect/LLVMIR/cse-nvvm.mlir
@@ -0,0 +1,37 @@
+// RUN: mlir-opt %s -cse -split-input-file -verify-diagnostics | FileCheck %s
+
+// CHECK-LABEL: @nvvm_special_regs_clock
+llvm.func @nvvm_special_regs_clock() -> !llvm.struct<(i32, i32)> {
+ %0 = llvm.mlir.zero: !llvm.struct<(i32, i32)>
+ // CHECK: {{.*}} = nvvm.read.ptx.sreg.clock
+ %1 = nvvm.read.ptx.sreg.clock : i32
+ // CHECK: {{.*}} = nvvm.read.ptx.sreg.clock
+ %2 = nvvm.read.ptx.sreg.clock : i32
+ %4 = llvm.insertvalue %1, %0[0]: !llvm.struct<(i32, i32)>
+ %5 = llvm.insertvalue %2, %4[1]: !llvm.struct<(i32, i32)>
+ llvm.return %5: !llvm.struct<(i32, i32)>
+}
+
+// CHECK-LABEL: @nvvm_special_regs_clock64
+llvm.func @nvvm_special_regs_clock64() -> !llvm.struct<(i64, i64)> {
+ %0 = llvm.mlir.zero: !llvm.struct<(i64, i64)>
+ // CHECK: {{.*}} = nvvm.read.ptx.sreg.clock64
+ %1 = nvvm.read.ptx.sreg.clock64 : i64
+ // CHECK: {{.*}} = nvvm.read.ptx.sreg.clock64
+ %2 = nvvm.read.ptx.sreg.clock64 : i64
+ %4 = llvm.insertvalue %1, %0[0]: !llvm.struct<(i64, i64)>
+ %5 = llvm.insertvalue %2, %4[1]: !llvm.struct<(i64, i64)>
+ llvm.return %5: !llvm.struct<(i64, i64)>
+}
+
+// CHECK-LABEL: @nvvm_special_regs_globaltimer
+llvm.func @nvvm_special_regs_globaltimer() -> !llvm.struct<(i64, i64)> {
+ %0 = llvm.mlir.zero: !llvm.struct<(i64, i64)>
+ // CHECK: {{.*}} = nvvm.read.ptx.sreg.globaltimer
+ %1 = nvvm.read.ptx.sreg.globaltimer : i64
+ // CHECK: {{.*}} = nvvm.read.ptx.sreg.globaltimer
+ %2 = nvvm.read.ptx.sreg.globaltimer : i64
+ %4 = llvm.insertvalue %1, %0[0]: !llvm.struct<(i64, i64)>
+ %5 = llvm.insertvalue %2, %4[1]: !llvm.struct<(i64, i64)>
+ llvm.return %5: !llvm.struct<(i64, i64)>
+}
|
grypp
reviewed
Jul 9, 2025
|
Thanks good catch! |
schwarzschild-radius
force-pushed
the
update_traits_for_clock_ops
branch
from
bd6b00c to
ef6165d
Compare
durga4github
approved these changes
Jul 10, 2025
schwarzschild-radius
force-pushed
the
update_traits_for_clock_ops
branch
2 times, most recently
from
ddab115 to
f49d36d
Compare
grypp
reviewed
Jul 11, 2025
Comment on lines
156
to
158
| // NVVM_PureSpecialRegisterOp represents special register ops that can | ||
| // speculated and does not touch memory. These operations are always | ||
| // legal to hoist or sink. |
There was a problem hiding this comment.
I don't think we need extra comment here. Pure is self-explanatory
There was a problem hiding this comment.
Got it. Reverted the comment
This commit removes Pure trait from clock, clock64 and globaltimer Ops by creating NVVM_NCSpecialRegisterOp class to represent Ops which return non-constant values. This prevents CSE pass from optimizing away redundant uses of them
schwarzschild-radius
force-pushed
the
update_traits_for_clock_ops
branch
from
f49d36d to
9c0d0f6
Compare
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This commit removes Pure trait from clock, clock64 and globaltimer Ops by creating NVVM_NCSpecialRegisterOp class to represent Ops which return non-constant values. This prevents CSE pass from optimizing away redundant uses of them