[llvm] [clang] [AMDGPU] Improve selection of ballot.i64 intrinsic in wave32 mode. (PR #71556)

[Valery Pykhtin via cfe-commits]

https://github.com/vpykhtin updated https://github.com/llvm/llvm-project/pull/71556

>From b6204d32554f082821da100043bf872b62f1740b Mon Sep 17 00:00:00 2001
From: Valery Pykhtin <valery.pykhtin at gmail.com>
Date: Mon, 20 Nov 2023 15:22:16 +0100
Subject: [PATCH] add instcombine rule

---
 clang/test/CodeGenOpenCL/builtins-amdgcn-wave32.cl  |  8 ++------
 llvm/lib/Target/AMDGPU/AMDGPUISelDAGToDAG.cpp       |  2 +-
 .../Target/AMDGPU/AMDGPUInstCombineIntrinsic.cpp    | 13 +++++++++++++
 .../InstCombine/AMDGPU/amdgcn-intrinsics.ll         |  6 ++++--
 4 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/clang/test/CodeGenOpenCL/builtins-amdgcn-wave32.cl b/clang/test/CodeGenOpenCL/builtins-amdgcn-wave32.cl
index 43553131f63c5..a0e27ce22fe7d 100644
--- a/clang/test/CodeGenOpenCL/builtins-amdgcn-wave32.cl
+++ b/clang/test/CodeGenOpenCL/builtins-amdgcn-wave32.cl
@@ -24,13 +24,11 @@ void test_ballot_wave32_target_attr(global uint* out, int a, int b)
 }
 
 // CHECK-LABEL: @test_read_exec(
-// CHECK: call i64 @llvm.amdgcn.ballot.i64(i1 true)
+// CHECK: call i32 @llvm.amdgcn.ballot.i32(i1 true)
 void test_read_exec(global uint* out) {
   *out = __builtin_amdgcn_read_exec();
 }
 
-// CHECK: declare i64 @llvm.amdgcn.ballot.i64(i1) #[[$NOUNWIND_READONLY:[0-9]+]]
-
 // CHECK-LABEL: @test_read_exec_lo(
 // CHECK: call i32 @llvm.amdgcn.ballot.i32(i1 true)
 void test_read_exec_lo(global uint* out) {
@@ -38,9 +36,7 @@ void test_read_exec_lo(global uint* out) {
 }
 
 // CHECK-LABEL: @test_read_exec_hi(
-// CHECK: call i64 @llvm.amdgcn.ballot.i64(i1 true)
-// CHECK: lshr i64 [[A:%.*]], 32
-// CHECK: trunc i64 [[B:%.*]] to i32
+// CHECK: store i32 0, ptr addrspace(1) %out
 void test_read_exec_hi(global uint* out) {
   *out = __builtin_amdgcn_read_exec_hi();
 }
diff --git a/llvm/lib/Target/AMDGPU/AMDGPUISelDAGToDAG.cpp b/llvm/lib/Target/AMDGPU/AMDGPUISelDAGToDAG.cpp
index a6d1da94b8907..f71f257ae8184 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUISelDAGToDAG.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUISelDAGToDAG.cpp
@@ -2371,7 +2371,7 @@ void AMDGPUDAGToDAGISel::SelectBRCOND(SDNode *N) {
     auto CC = cast<CondCodeSDNode>(Cond->getOperand(2))->get();
     if ((CC == ISD::SETEQ || CC == ISD::SETNE) &&
         isNullConstant(Cond->getOperand(1)) &&
-        // TODO: make condition below an assert after fixing ballot bitwidth.
+        // We may encounter ballot.i64 in wave32 mode on -O0.
         VCMP.getValueType().getSizeInBits() == ST->getWavefrontSize()) {
       // %VCMP = i(WaveSize) AMDGPUISD::SETCC ...
       // %C = i1 ISD::SETCC %VCMP, 0, setne/seteq
diff --git a/llvm/lib/Target/AMDGPU/AMDGPUInstCombineIntrinsic.cpp b/llvm/lib/Target/AMDGPU/AMDGPUInstCombineIntrinsic.cpp
index 5296415ab4c36..11022d01bbbf4 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUInstCombineIntrinsic.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUInstCombineIntrinsic.cpp
@@ -961,6 +961,19 @@ GCNTTIImpl::instCombineIntrinsic(InstCombiner &IC, IntrinsicInst &II) const {
         return IC.replaceInstUsesWith(II, Constant::getNullValue(II.getType()));
       }
     }
+    if (ST->isWave32() && II.getType()->getIntegerBitWidth() == 64) {
+      // %b64 = call i64 ballot.i64(...)
+      // =>
+      // %b32 = call i32 ballot.i32(...)
+      // %b64 = zext i32 %b32 to i64
+      Value *Call = IC.Builder.CreateZExtOrBitCast(
+          IC.Builder.CreateIntrinsic(Intrinsic::amdgcn_ballot,
+                                     {IC.Builder.getInt32Ty()},
+                                     {II.getArgOperand(0)}),
+          II.getType());
+      Call->takeName(&II);
+      return IC.replaceInstUsesWith(II, Call);
+    }
     break;
   }
   case Intrinsic::amdgcn_wqm_vote: {
diff --git a/llvm/test/Transforms/InstCombine/AMDGPU/amdgcn-intrinsics.ll b/llvm/test/Transforms/InstCombine/AMDGPU/amdgcn-intrinsics.ll
index 804283cc20cd6..94c32e3cbe99f 100644
--- a/llvm/test/Transforms/InstCombine/AMDGPU/amdgcn-intrinsics.ll
+++ b/llvm/test/Transforms/InstCombine/AMDGPU/amdgcn-intrinsics.ll
@@ -2599,7 +2599,8 @@ declare i32 @llvm.amdgcn.ballot.i32(i1) nounwind readnone convergent
 
 define i64 @ballot_nocombine_64(i1 %i) {
 ; CHECK-LABEL: @ballot_nocombine_64(
-; CHECK-NEXT:    [[B:%.*]] = call i64 @llvm.amdgcn.ballot.i64(i1 [[I:%.*]])
+; CHECK-NEXT:    [[TMP1:%.*]] = call i32 @llvm.amdgcn.ballot.i32(i1 [[I:%.*]])
+; CHECK-NEXT:    [[B:%.*]] = zext i32 [[TMP1]] to i64
 ; CHECK-NEXT:    ret i64 [[B]]
 ;
   %b = call i64 @llvm.amdgcn.ballot.i64(i1 %i)
@@ -2616,7 +2617,8 @@ define i64 @ballot_zero_64() {
 
 define i64 @ballot_one_64() {
 ; CHECK-LABEL: @ballot_one_64(
-; CHECK-NEXT:    [[B:%.*]] = call i64 @llvm.amdgcn.ballot.i64(i1 true)
+; CHECK-NEXT:    [[TMP1:%.*]] = call i32 @llvm.amdgcn.ballot.i32(i1 true)
+; CHECK-NEXT:    [[B:%.*]] = zext i32 [[TMP1]] to i64
 ; CHECK-NEXT:    ret i64 [[B]]
 ;
   %b = call i64 @llvm.amdgcn.ballot.i64(i1 1)