Treat BasicBlock with only dbg calls as an empty BasicBlock

Treat BasicBlock with only dbg calls as an empty BasicBlock

Author: matborzyszkowski

IGC/Compiler/CISACodeGen/BlockCoalescing.cpp

@@ -55,10 +55,11 @@ namespace IGC
         for (uint i = 0; i < patternMatch->m_numBlocks; i++)
         {
             SBasicBlock& block = patternMatch->m_blocks[i];
+
             // An empty block would have only one pattern matching the branch instruction
-            if (block.m_dags.size() == 1)
+            if (block.bb->sizeWithoutDebug() == 1)
             {
-                if (BranchInst * br = dyn_cast<BranchInst>(block.m_dags[0].m_root))
+                if (BranchInst * br = dyn_cast<BranchInst>(&block.bb->back()))
                 {
                     if (br->isUnconditional())
                     {

IGC/Compiler/tests/DebugInfo/EmitVISAPass/bb_with_dbg_calls.ll

@@ -0,0 +1,121 @@
+;=========================== begin_copyright_notice ============================
+;
+; Copyright (C) 2025 Intel Corporation
+;
+; SPDX-License-Identifier: MIT
+;
+;============================ end_copyright_notice =============================
+
+; The test checks if the BB with only dbg calls is treated as empty BB and
+; the compiler doesn't emit this BB in visaasm.
+
+; For provided .ll file we can skip BB with only LOC information, e.g.:
+
+; .function "_main_0"
+; _main_0:
+;     FILE "/test.cl"
+;     LOC 3
+;     mov (M1_NM, 1) Trunc(0,0)<1> 0x0:ud
+;     lsc_load.slm (M1_NM, 1)  V0032:d32t  flat[Trunc]:a32
+;     mov (M1_NM, 1) bTrunc(0,0)<1> b(0,0)<0;1,0>
+;     lsc_load.slm (M1_NM, 1)  V0033:d32t  flat[bTrunc]:a32
+;     add (M1_NM, 1) add_(0,0)<1> V0032(0,0)<0;1,0> V0033(0,0)<0;1,0>
+;
+; _test_001_bb0:                  -----> We don't need emit _test_001_bb0 basic block,
+;     LOC 0                       -----> because this BB is empty (has only dbg calls
+;     LOC 3                       -----> and br instruction in .ll file)
+;
+; _test_002_exit:
+;     mov (M1_NM, 1) resultTrunc(0,0)<1> result(0,0)<0;1,0>
+;     lsc_store.slm (M1_NM, 1)  flat[resultTrunc]:a32  add_:d32t
+;     LOC 4
+;     ret (M1, 1)
+
+
+; REQUIRES: llvm-14-plus, regkeys
+
+; RUN: igc_opt --opaque-pointers -platformdg2 -igc-emit-visa %s -regkey DumpVISAASMToConsole | FileCheck %s
+
+define spir_kernel void @test(i32 addrspace(3)* align 4 %a, i32 addrspace(3)* align 4 %b, i32 addrspace(3)* align 4 %result, <8 x i32> %r0, <3 x i32> %globalOffset) #0 !dbg !473 {
+entry:
+  call void @llvm.dbg.value(metadata i32 addrspace(3)* %b, metadata !480, metadata !DIExpression()), !dbg !483
+  call void @llvm.dbg.value(metadata i32 addrspace(3)* %result, metadata !481, metadata !DIExpression()), !dbg !483
+  %0 = load i32, i32 addrspace(3)* null, align 4294967296, !dbg !484
+  %1 = load i32, i32 addrspace(3)* %b, align 4, !dbg !485
+  %add = add nsw i32 %0, %1, !dbg !486, !spirv.Decorations !487
+  br label %bb0
+bb0:
+  call void @llvm.dbg.value(metadata i32 addrspace(3)* %b, metadata !480, metadata !DIExpression()), !dbg !483
+  call void @llvm.dbg.value(metadata i32 addrspace(3)* %result, metadata !481, metadata !DIExpression()), !dbg !483
+  br label %exit
+exit:
+  store i32 %add, i32 addrspace(3)* %result, align 4, !dbg !489
+  ret void, !dbg !490, !stats.blockFrequency.digits !491, !stats.blockFrequency.scale !492
+}
+
+; CHECK: .function "[[FUNC:[^ ]+]]"
+; CHECK: [[FUNC]]:
+; CHECK:    FILE "/test.cl"
+; CHECK:    LOC 3
+; CHECK:    mov (M1_NM, 1) Trunc(0,0)<1> 0x0:ud
+; CHECK:    lsc_load.slm (M1_NM, 1)  V0032:d32t  flat[Trunc]:a32
+; CHECK:    mov (M1_NM, 1) bTrunc(0,0)<1> b(0,0)<0;1,0>
+; CHECK:    lsc_load.slm (M1_NM, 1)  V0033:d32t  flat[bTrunc]:a32
+; CHECK:    add (M1_NM, 1) add_(0,0)<1> V0032(0,0)<0;1,0> V0033(0,0)<0;1,0>
+; CHECK: [[BB_EXIT:[^ ]+]]
+; CHECK:    mov (M1_NM, 1) resultTrunc(0,0)<1> result(0,0)<0;1,0>
+; CHECK:    lsc_store.slm (M1_NM, 1)  flat[resultTrunc]:a32  add_:d32t
+; CHECK:    LOC 4
+; CHECK:    ret (M1, 1)
+
+declare void @llvm.dbg.value(metadata, metadata, metadata) #1
+
+!llvm.module.flags = !{!0, !1, !2}
+!llvm.dbg.cu = !{!3}
+!spirv.MemoryModel = !{!5}
+!spirv.Source = !{!6}
+!spirv.Generator = !{!7}
+!igc.functions = !{!8}
+!IGCMetadata = !{!14}
+!opencl.ocl.version = !{!471, !471}
+!opencl.spir.version = !{!471, !471}
+!llvm.ident = !{!472, !472}
+!printf.strings = !{}
+!0 = !{i32 7, !"Dwarf Version", i32 4}
+!1 = !{i32 2, !"Debug Info Version", i32 3}
+!2 = !{i32 1, !"wchar_size", i32 4}
+!3 = distinct !DICompileUnit(language: DW_LANG_OpenCL, file: !4, producer: "clang version 15.0.0", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
+!4 = !DIFile(filename: "test.cl", directory: "/")
+!5 = !{i32 2, i32 2}
+!6 = !{i32 3, i32 102000}
+!7 = !{i16 6, i16 14}
+!8 = !{void (i32 addrspace(3)*, i32 addrspace(3)*, i32 addrspace(3)*, <8 x i32>, <3 x i32>)* @test, !9}
+!9 = !{!10, !11}
+!10 = !{!"function_type", i32 0}
+!11 = !{!"implicit_arg_desc", !12, !13}
+!12 = !{i32 0}
+!13 = !{i32 2}
+!14 = !{!"ModuleMD", !15}
+!15 = !{!"isPrecise", i1 false}
+!471 = !{i32 2, i32 0}
+!472 = !{!"clang version 15.0.0"}
+!473 = distinct !DISubprogram(name: "test", scope: null, file: !4, line: 1, type: !474, scopeLine: 2, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !3, templateParams: !482, retainedNodes: !478)
+!474 = !DISubroutineType(types: !475)
+!475 = !{null, !476, !476, !476}
+!476 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !477, size: 64, dwarfAddressSpace: 3)
+!477 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!478 = !{!479, !480, !481}
+!479 = !DILocalVariable(name: "a", arg: 1, scope: !473, file: !4, line: 1, type: !476)
+!480 = !DILocalVariable(name: "b", arg: 2, scope: !473, file: !4, line: 1, type: !476)
+!481 = !DILocalVariable(name: "result", arg: 3, scope: !473, file: !4, line: 1, type: !476)
+!482 = !{}
+!483 = !DILocation(line: 0, scope: !473)
+!484 = !DILocation(line: 3, column: 17, scope: !473)
+!485 = !DILocation(line: 3, column: 24, scope: !473)
+!486 = !DILocation(line: 3, column: 22, scope: !473)
+!487 = !{!488}
+!488 = !{i32 4469}
+!489 = !DILocation(line: 3, column: 15, scope: !473)
+!490 = !DILocation(line: 4, column: 1, scope: !473)
+!491 = !{!"80"}
+!492 = !{!"-3"}