[llvm] 05d79e3 - [AMDGPU] Divergence-driven instruction selection for bitreverse

[Jay Foad via llvm-commits]

Author: Jay Foad
Date: 2022-02-24T20:21:59Z
New Revision: 05d79e3562e85c3d011760959e65232e8f36b949

URL: https://github.com/llvm/llvm-project/commit/05d79e3562e85c3d011760959e65232e8f36b949
DIFF: https://github.com/llvm/llvm-project/commit/05d79e3562e85c3d011760959e65232e8f36b949.diff

LOG: [AMDGPU] Divergence-driven instruction selection for bitreverse

Differential Revision: https://reviews.llvm.org/D119702

Added: 
    llvm/test/CodeGen/AMDGPU/divergence-driven-bitreverse.ll

Modified: 
    llvm/lib/Target/AMDGPU/SIInstructions.td
    llvm/lib/Target/AMDGPU/SOPInstructions.td
    llvm/lib/Target/AMDGPU/VOP1Instructions.td

Removed: 
    


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diff  --git a/llvm/lib/Target/AMDGPU/SIInstructions.td b/llvm/lib/Target/AMDGPU/SIInstructions.td
index 6e6b44fbad7a..81bfcb72d12a 100644
--- a/llvm/lib/Target/AMDGPU/SIInstructions.td
+++ b/llvm/lib/Target/AMDGPU/SIInstructions.td
@@ -2431,6 +2431,11 @@ def : GCNPat <
 
 }
 
+def : GCNPat<
+  (i64 (DivergentUnaryFrag<bitreverse> i64:$a)),
+  (REG_SEQUENCE VReg_64,
+   (V_BFREV_B32_e64 (i32 (EXTRACT_SUBREG VReg_64:$a, sub1))), sub0,
+   (V_BFREV_B32_e64 (i32 (EXTRACT_SUBREG VReg_64:$a, sub0))), sub1)>;
 
 // Prefer selecting to max when legal, but using mul is always valid.
 let AddedComplexity = -5 in {

diff  --git a/llvm/lib/Target/AMDGPU/SOPInstructions.td b/llvm/lib/Target/AMDGPU/SOPInstructions.td
index c69b79e524de..73106af35c94 100644
--- a/llvm/lib/Target/AMDGPU/SOPInstructions.td
+++ b/llvm/lib/Target/AMDGPU/SOPInstructions.td
@@ -235,10 +235,10 @@ def : GCNPat <
 
 let isReMaterializable = 1, isAsCheapAsAMove = 1 in {
 def S_BREV_B32 : SOP1_32 <"s_brev_b32",
-  [(set i32:$sdst, (bitreverse i32:$src0))]
+  [(set i32:$sdst, (UniformUnaryFrag<bitreverse> i32:$src0))]
 >;
 def S_BREV_B64 : SOP1_64 <"s_brev_b64",
-  [(set i64:$sdst, (bitreverse i64:$src0))]
+  [(set i64:$sdst, (UniformUnaryFrag<bitreverse> i64:$src0))]
 >;
 } // End isReMaterializable = 1, isAsCheapAsAMove = 1
 

diff  --git a/llvm/lib/Target/AMDGPU/VOP1Instructions.td b/llvm/lib/Target/AMDGPU/VOP1Instructions.td
index 48548d8b6722..0ba6139d4e3d 100644
--- a/llvm/lib/Target/AMDGPU/VOP1Instructions.td
+++ b/llvm/lib/Target/AMDGPU/VOP1Instructions.td
@@ -282,7 +282,7 @@ defm V_COS_F32 : VOP1Inst <"v_cos_f32", VOP_F32_F32, AMDGPUcos>;
 } // End TRANS = 1, SchedRW = [WriteTrans32]
 
 defm V_NOT_B32 : VOP1Inst <"v_not_b32", VOP_I32_I32>;
-defm V_BFREV_B32 : VOP1Inst <"v_bfrev_b32", VOP_I32_I32, bitreverse>;
+defm V_BFREV_B32 : VOP1Inst <"v_bfrev_b32", VOP_I32_I32, DivergentUnaryFrag<bitreverse>>;
 defm V_FFBH_U32 : VOP1Inst <"v_ffbh_u32", VOP_I32_I32, AMDGPUffbh_u32>;
 defm V_FFBL_B32 : VOP1Inst <"v_ffbl_b32", VOP_I32_I32, AMDGPUffbl_b32>;
 defm V_FFBH_I32 : VOP1Inst <"v_ffbh_i32", VOP_I32_I32, AMDGPUffbh_i32>;

diff  --git a/llvm/test/CodeGen/AMDGPU/divergence-driven-bitreverse.ll b/llvm/test/CodeGen/AMDGPU/divergence-driven-bitreverse.ll
new file mode 100644
index 000000000000..bd87162264e4
--- /dev/null
+++ b/llvm/test/CodeGen/AMDGPU/divergence-driven-bitreverse.ll
@@ -0,0 +1,43 @@
+; RUN: llc -march=amdgcn -stop-after=amdgpu-isel < %s | FileCheck -check-prefix=GCN %s
+
+; GCN-FUNC: uniform_bitreverse_i32
+; GCN: S_BREV_B32
+define amdgpu_kernel void @uniform_bitreverse_i32(i32 %val, i32 addrspace(1)* %out) {
+  %res = call i32 @llvm.bitreverse.i32(i32 %val)
+  store i32 %res, i32 addrspace(1)* %out
+  ret void
+}
+
+; GCN-FUNC: divergent_bitreverse_i32
+; GCN: V_BFREV_B32
+define amdgpu_kernel void @divergent_bitreverse_i32(i32 %val, i32 addrspace(1)* %out) {
+  %tid = call i32 @llvm.amdgcn.workitem.id.x()
+  %divergent = add i32 %val, %tid
+  %res = call i32 @llvm.bitreverse.i32(i32 %divergent)
+  store i32 %res, i32 addrspace(1)* %out
+  ret void
+}
+
+; GCN-FUNC: uniform_bitreverse_i64
+; GCN: S_BREV_B64
+define amdgpu_kernel void @uniform_bitreverse_i64(i64 %val, i64 addrspace(1)* %out) {
+  %res = call i64 @llvm.bitreverse.i64(i64 %val)
+  store i64 %res, i64 addrspace(1)* %out
+  ret void
+}
+
+; GCN-FUNC: divergent_bitreverse_i64
+; GCN: V_BFREV_B32
+; GCN: V_BFREV_B32
+define amdgpu_kernel void @divergent_bitreverse_i64(i64 %val, i64 addrspace(1)* %out) {
+  %tid = call i32 @llvm.amdgcn.workitem.id.x()
+  %ext = zext i32 %tid to i64
+  %divergent = add i64 %val, %ext
+  %res = call i64 @llvm.bitreverse.i64(i64 %divergent)
+  store i64 %res, i64 addrspace(1)* %out
+  ret void
+}
+
+declare i32 @llvm.amdgcn.workitem.id.x()
+declare i32 @llvm.bitreverse.i32(i32)
+declare i64 @llvm.bitreverse.i64(i64)