Teach isGuarantdToTransferExecToSuccessor about debug info intrinsics

Calls to `@llvm.dbg.*` can be assumed to terminate.

llvm-svn: 272180

2 files changed, 81 insertions, 3 deletions

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index d735448f1dd..323fe83bff6 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -3448,10 +3448,13 @@ bool llvm::isGuaranteedToTransferExecutionToSuccessor(const Instruction *I) {
   // atomic operations are guaranteed to terminate on most platforms
   // and most functions terminate.
 
+  // Calls can throw and thus not terminate, and invokes may not terminate and
+  // could throw to non-successor (see bug 24185 for details).
+  if (isa<CallInst>(I) || isa<InvokeInst>(I))
+    // However, llvm.dbg intrinsics are safe, since they're no-ops.
+    return isa<DbgInfoIntrinsic>(I);
+
   return !I->isAtomic() &&       // atomics may never succeed on some platforms
-         !isa<CallInst>(I) &&    // could throw and might not terminate
-         !isa<InvokeInst>(I) &&  // might not terminate and could throw to
-                                 //   non-successor (see bug 24185 for details).
          !isa<ResumeInst>(I) &&  // has no successors
          !isa<ReturnInst>(I);    // has no successors
 }
diff --git a/llvm/test/Analysis/ScalarEvolution/flags-from-poison-dbg.ll b/llvm/test/Analysis/ScalarEvolution/flags-from-poison-dbg.ll
new file mode 100644
index 00000000000..30b83578137
--- /dev/null
+++ b/llvm/test/Analysis/ScalarEvolution/flags-from-poison-dbg.ll
@@ -0,0 +1,75 @@
+; RUN: opt -analyze -scalar-evolution < %s | FileCheck %s
+
+; Make sure poison value tracking works in the presence of @llvm.dbg
+; intrinsics.  Unfortunately, I was not able to reduce this file
+; further while still keeping the debug info well formed.
+
+define void @foo(i32 %n, i32* %arr) !dbg !7 {
+; CHECK-LABEL: Classifying expressions for: @foo
+entry:
+  %cmp1 = icmp slt i32 0, %n, !dbg !12
+  br i1 %cmp1, label %for.body.lr.ph, label %for.end, !dbg !15
+
+for.body.lr.ph:                                   ; preds = %entry
+  br label %for.body, !dbg !15
+
+for.body:                                         ; preds = %for.inc, %for.body.lr.ph
+  %i.02 = phi i32 [ 0, %for.body.lr.ph ], [ %inc, %for.inc ]
+  %add = add nsw i32 %i.02, 50, !dbg !16
+  call void @llvm.dbg.value(metadata i32 %add, i64 0, metadata !18, metadata !19), !dbg !20
+  %idxprom = sext i32 %add to i64, !dbg !21
+
+; CHECK:  %idxprom = sext i32 %add to i64
+; CHECK-NEXT:  -->  {50,+,1}<nuw><nsw><%for.body>
+
+  %arrayidx = getelementptr inbounds i32, i32* %arr, i64 %idxprom, !dbg !21
+  store i32 100, i32* %arrayidx, align 4, !dbg !22
+  br label %for.inc, !dbg !23
+
+for.inc:                                          ; preds = %for.body
+  %inc = add nsw i32 %i.02, 1, !dbg !24
+  %cmp = icmp slt i32 %inc, %n, !dbg !12
+  br i1 %cmp, label %for.body, label %for.cond.for.end_crit_edge, !dbg !15, !llvm.loop !25
+
+for.cond.for.end_crit_edge:                       ; preds = %for.inc
+  br label %for.end, !dbg !15
+
+for.end:                                          ; preds = %for.cond.for.end_crit_edge, %entry
+  ret void, !dbg !27
+}
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.value(metadata, i64, metadata, metadata)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 3.9.0  (llvm/trunk 271857)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "x.c", directory: "/Users/sanjoy/Code/clang/build/debug+asserts-x86")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 2}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"PIC Level", i32 2}
+!6 = !{!"clang version 3.9.0  (llvm/trunk 271857)"}
+!7 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 1, type: !8, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!8 = !DISubroutineType(types: !9)
+!9 = !{null, !10, !11}
+!10 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+!11 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !10, size: 64, align: 64)
+!12 = !DILocation(line: 2, column: 24, scope: !13)
+!13 = distinct !DILexicalBlock(scope: !14, file: !1, line: 2, column: 6)
+!14 = distinct !DILexicalBlock(scope: !7, file: !1, line: 2, column: 6)
+!15 = !DILocation(line: 2, column: 6, scope: !14)
+!16 = !DILocation(line: 3, column: 14, scope: !17)
+!17 = distinct !DILexicalBlock(scope: !13, file: !1, line: 2, column: 34)
+!18 = !DILocalVariable(name: "k", scope: !17, file: !1, line: 3, type: !10)
+!19 = !DIExpression()
+!20 = !DILocation(line: 3, column: 8, scope: !17)
+!21 = !DILocation(line: 4, column: 4, scope: !17)
+!22 = !DILocation(line: 4, column: 11, scope: !17)
+!23 = !DILocation(line: 5, column: 6, scope: !17)
+!24 = !DILocation(line: 2, column: 30, scope: !13)
+!25 = distinct !{!25, !26}
+!26 = !DILocation(line: 2, column: 6, scope: !7)
+!27 = !DILocation(line: 6, column: 1, scope: !7)