[utils] InlineFunction: fix for debug info affecting optimizations

Summary:
Debug info affects output from "opt -inline", InlineFunction could
not handle the llvm.dbg.value when it exist between alloca
instructions.

Problem was that the first alloca in a sequence of allocas was
handled differently from the subsequence alloca instructions. Now
all static alloca instructions are treated the same (being removed
if the have no uses). So it does not matter if there are dbg
instructions (or any other instructions) in between.

Fix the issue: https://bugs.llvm.org/show_bug.cgi?id=43291k

Patch by: yechunliang (Chris Ye)

Reviewers: bjope, jmorse, vsk, probinson, jdoerfert, mtrofin, aprantl, fhahn

Reviewed By: bjope

Subscribers: uabelho, ormris, aprantl, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D68633

1 files changed, 71 insertions, 0 deletions

diff --git a/llvm/test/Transforms/Inline/inline-skip-use-empty-alloca.ll b/llvm/test/Transforms/Inline/inline-skip-use-empty-alloca.ll
new file mode 100644
index 00000000000..48545f10cb3
--- /dev/null
+++ b/llvm/test/Transforms/Inline/inline-skip-use-empty-alloca.ll
@@ -0,0 +1,71 @@
+; RUN: opt < %s -S -inline | FileCheck %s
+; RUN: opt < %s -S -strip-debug -inline | FileCheck %s
+
+; https://bugs.llvm.org/show_bug.cgi?id=43291
+; The purpose of this test is to check if there is use_empty in the inner loop when scanning
+; blocks of allocas, if the alloca is use_empty, skip it when allocas inlining.
+
+define void @foo(i16 %k) !dbg !6 {
+  call void @llvm.dbg.value(metadata i16 %k, metadata !14, metadata !DIExpression()), !dbg !15
+  %alloca_a = alloca i32
+  call void @llvm.dbg.value(metadata i16 %k, metadata !14, metadata !DIExpression()), !dbg !15
+  %alloca_b = alloca [3 x i32]
+  call void @llvm.dbg.value(metadata i16 %k, metadata !14, metadata !DIExpression()), !dbg !15
+  %alloca_c = alloca i32
+  call void @llvm.dbg.value(metadata i16 %k, metadata !14, metadata !DIExpression()), !dbg !15
+  %alloca_a..1 = bitcast i32* %alloca_a to i8**, !dbg !16
+  %alloca_c..1 = bitcast i32* %alloca_c to i8**, !dbg !16
+  %_tmp23 = icmp ne i16 %k, 0
+  br i1 %_tmp23, label %bb1, label %bb2
+
+bb1:                                              ; preds = %0
+  %_tmp28 = getelementptr [3 x i32], [3 x i32]* %alloca_b, i16 0, i64 0
+  store i32 0, i32* %_tmp28
+  br label %bb2
+
+bb2:                                              ; preds = %bb1, %0
+  ret void
+}
+
+define i16 @bar() !dbg !17 {
+  ; CHECK-LABEL: bar
+  ; CHECK: %alloca_a.i = alloca i32
+  ; CHECK-NOT: %alloca_b.i = alloca [3 x i32]
+  ; CHECK: %alloca_c.i = alloca i32
+  call void @foo(i16 0), !dbg !20
+  br label %bb1
+
+bb1:                                              ; preds = %0
+  ret i16 0
+}
+
+; Function Attrs: nounwind readnone speculatable willreturn
+declare void @llvm.dbg.value(metadata, metadata, metadata) #0
+
+attributes #0 = { nounwind readnone speculatable willreturn }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4}
+!llvm.ident = !{!5}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "Foo", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !2, globals: !2)
+!1 = !DIFile(filename: "foo2.c", directory: "/tmp")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{!"Foo"}
+!6 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 17, type: !7, scopeLine: 17, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !2)
+!7 = !DISubroutineType(types: !8)
+!8 = !{!9, !13}
+!9 = !DIDerivedType(tag: DW_TAG_typedef, name: "int64_t", file: !10, line: 76, baseType: !11)
+!10 = !DIFile(filename: "stdint.h", directory: "/tmp")
+!11 = !DIDerivedType(tag: DW_TAG_typedef, name: "__i64_t", file: !1, baseType: !12)
+!12 = !DIBasicType(name: "signed long long", size: 64, encoding: DW_ATE_signed)
+!13 = !DIBasicType(name: "int", size: 16, encoding: DW_ATE_signed)
+!14 = !DILocalVariable(name: "k", arg: 1, scope: !6, file: !1, line: 17, type: !13)
+!15 = !DILocation(line: 0, scope: !6)
+!16 = !DILocation(line: 19, column: 3, scope: !6)
+!17 = distinct !DISubprogram(name: "g", scope: !1, file: !1, line: 8, type: !18, scopeLine: 8, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !2)
+!18 = !DISubroutineType(types: !19)
+!19 = !{!13}
+!20 = !DILocation(line: 8, column: 7, scope: !17)