[llvm] 6d97ca6 - [AMDGPU] Increase detection range for s_mov, v_cmpx transformation.

[Thomas Symalla via llvm-commits]

Author: Thomas Symalla
Date: 2022-04-08T12:47:24+02:00
New Revision: 6d97ca690c4d9f59226d06e30233e247a3308e9b

URL: https://github.com/llvm/llvm-project/commit/6d97ca690c4d9f59226d06e30233e247a3308e9b
DIFF: https://github.com/llvm/llvm-project/commit/6d97ca690c4d9f59226d06e30233e247a3308e9b.diff

LOG: [AMDGPU] Increase detection range for s_mov, v_cmpx transformation.

We found that it might be beneficial to have the SIOptimizeExecMasking
pass detect more cases where v_cmp, s_and_saveexec patterns can be
transformed to s_mov, v_cmpx patterns. Currently, the search range
for finding a fitting v_cmp instruction is 5, however, this is doubled
to 10 here.

Reviewed By: foad

Differential Revision: https://reviews.llvm.org/D123367

Added: 
    

Modified: 
    llvm/lib/Target/AMDGPU/SIOptimizeExecMasking.cpp
    llvm/test/CodeGen/AMDGPU/vcmp-saveexec-to-vcmpx.mir

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/AMDGPU/SIOptimizeExecMasking.cpp b/llvm/lib/Target/AMDGPU/SIOptimizeExecMasking.cpp
index 4c6189229812d..36f9ab6fbdb5f 100644
--- a/llvm/lib/Target/AMDGPU/SIOptimizeExecMasking.cpp
+++ b/llvm/lib/Target/AMDGPU/SIOptimizeExecMasking.cpp
@@ -302,12 +302,15 @@ static MachineInstr *
 findInstrBackwards(MachineInstr &Origin,
                    std::function<bool(MachineInstr *)> Pred,
                    ArrayRef<MCRegister> NonModifiableRegs,
-                   const SIRegisterInfo *TRI, unsigned MaxInstructions = 5) {
+                   const SIRegisterInfo *TRI, unsigned MaxInstructions = 20) {
   MachineBasicBlock::reverse_iterator A = Origin.getReverseIterator(),
                                       E = Origin.getParent()->rend();
   unsigned CurrentIteration = 0;
 
   for (++A; CurrentIteration < MaxInstructions && A != E; ++A) {
+    if (A->isDebugInstr())
+      continue;
+    
     if (Pred(&*A))
       return &*A;
 
@@ -315,7 +318,7 @@ findInstrBackwards(MachineInstr &Origin,
       if (A->modifiesRegister(Reg, TRI))
         return nullptr;
     }
-
+    
     ++CurrentIteration;
   }
 

diff  --git a/llvm/test/CodeGen/AMDGPU/vcmp-saveexec-to-vcmpx.mir b/llvm/test/CodeGen/AMDGPU/vcmp-saveexec-to-vcmpx.mir
index fceca41f49339..7407cdf526d0c 100644
--- a/llvm/test/CodeGen/AMDGPU/vcmp-saveexec-to-vcmpx.mir
+++ b/llvm/test/CodeGen/AMDGPU/vcmp-saveexec-to-vcmpx.mir
@@ -1,6 +1,5 @@
 # RUN: llc -march=amdgcn -mcpu=gfx1010 -mattr=-wavefrontsize32,+wavefrontsize64 -run-pass=si-optimize-exec-masking -verify-machineinstrs %s -o - | FileCheck --check-prefixes=GCN,GFX1010 %s
 # RUN: llc -march=amdgcn -mcpu=gfx1030 -mattr=-wavefrontsize32,+wavefrontsize64 -run-pass=si-optimize-exec-masking -verify-machineinstrs %s -o - | FileCheck --check-prefixes=GCN,GFX1030 %s
-
 ---
 
 # After the Optimize exec masking (post-RA) pass, there's a change of having v_cmpx instructions
@@ -62,3 +61,29 @@ body: |
     $sgpr2_sgpr3 = COPY $exec, implicit-def $exec
     $sgpr2_sgpr3 = S_AND_B64 killed renamable $sgpr2_sgpr3, killed renamable $sgpr0_sgpr1, implicit-def dead $scc
     $exec = S_MOV_B64_term killed renamable $sgpr2_sgpr3
+...
+
+---
+
+# Check if the sequence will be optimized even with more than 5 (unrelated) instructions inbetween the v_cmp and s_and_saveexec.
+
+# GCN-LABEL: name: vcmp_saveexec_to_mov_vcmpx_check_many_instrs
+# GFX1010: V_CMP_LT_F32_e64
+# GFX1010: S_AND_SAVEEXEC_B64
+# GFX1030: S_MOV_B64
+# GFX1030: V_CMPX_LT_F32_nosdst_e64 0, 953267991, 2
+name: vcmp_saveexec_to_mov_vcmpx_check_many_instrs
+tracksRegLiveness: true
+body: |
+  bb.0:
+    liveins: $vgpr0, $sgpr2, $vgpr1
+    renamable $sgpr0_sgpr1 = V_CMP_LT_F32_e64 0, 953267991, 2, $vgpr0, 0, implicit $mode, implicit $exec
+    $vgpr1 = V_WRITELANE_B32 0, $sgpr2, $vgpr1
+    $vgpr1 = V_WRITELANE_B32 0, $sgpr2, $vgpr1
+    $vgpr1 = V_WRITELANE_B32 0, $sgpr2, $vgpr1
+    $vgpr1 = V_WRITELANE_B32 0, $sgpr2, $vgpr1
+    $vgpr1 = V_WRITELANE_B32 0, $sgpr2, $vgpr1
+    $vgpr1 = V_WRITELANE_B32 0, $sgpr2, $vgpr1
+    $sgpr2_sgpr3 = COPY $exec, implicit-def $exec
+    $sgpr2_sgpr3 = S_AND_B64 killed renamable $sgpr2_sgpr3, killed renamable $sgpr0_sgpr1, implicit-def dead $scc
+    $exec = S_MOV_B64_term killed renamable $sgpr2_sgpr3