<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Aug 20, 2015 at 11:23 AM, Adrian Prantl via llvm-commits <span dir="ltr"><<a href="mailto:llvm-commits@lists.llvm.org" target="_blank">llvm-commits@lists.llvm.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Author: adrian<br>
Date: Thu Aug 20 13:23:56 2015<br>
New Revision: 245588<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=245588&view=rev" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project?rev=245588&view=rev</a><br>
Log:<br>
Fix a debug location handling bug in GVN.<br>
Caught by the famous "DebugLoc describes the currect SubProgram" assertion.<br></blockquote><div><br></div><div>Huzzah! \o/ ;) (sorry, I know they're a pain to track down, but it's a great way to find debug info quality bugs that would produce really shitty debug info if it weren't for this assertion)</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">When GVN is removing a nonlocal load it updates the debug location of the<br>
SSA value it replaced the load with with the one of the load.</blockquote><div><br>I guess I'm not quite following here (knowing next to nothing about GVN) - could you explain this in more detail? What transformation is GVN performing on a call?<br> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> In the<br>
testcase this actually overwrites a valid debug location with an empty one.<br>
<br>
In reality GVN has to make an arbitrary choice between two equally valid<br>
debug locations. This patch changes to behavior to only update the<br>
location if the value doesn't already have a debug location.<br>
<br>
Added:<br>
llvm/trunk/test/DebugInfo/gvn.ll<br>
Modified:<br>
llvm/trunk/lib/Transforms/Scalar/GVN.cpp<br>
<br>
Modified: llvm/trunk/lib/Transforms/Scalar/GVN.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/GVN.cpp?rev=245588&r1=245587&r2=245588&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/GVN.cpp?rev=245588&r1=245587&r2=245588&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/lib/Transforms/Scalar/GVN.cpp (original)<br>
+++ llvm/trunk/lib/Transforms/Scalar/GVN.cpp Thu Aug 20 13:23:56 2015<br>
@@ -1744,7 +1744,8 @@ bool GVN::processNonLocalLoad(LoadInst *<br>
if (isa<PHINode>(V))<br>
V->takeName(LI);<br>
if (Instruction *I = dyn_cast<Instruction>(V))<br>
- I->setDebugLoc(LI->getDebugLoc());<br>
+ if (LI->getDebugLoc())<br>
+ I->setDebugLoc(LI->getDebugLoc());<br>
if (V->getType()->getScalarType()->isPointerTy())<br>
MD->invalidateCachedPointerInfo(V);<br>
markInstructionForDeletion(LI);<br>
<br>
Added: llvm/trunk/test/DebugInfo/gvn.ll<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/gvn.ll?rev=245588&view=auto" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/gvn.ll?rev=245588&view=auto</a><br>
==============================================================================<br>
--- llvm/trunk/test/DebugInfo/gvn.ll (added)<br>
+++ llvm/trunk/test/DebugInfo/gvn.ll Thu Aug 20 13:23:56 2015<br>
@@ -0,0 +1,135 @@<br>
+; RUN: opt < %s -O2 -gvn -S | FileCheck %s<br>
+;<br>
+; Produced at -O2 from:<br></blockquote><div><br>Do you have the original reproduction -cc1 line, by chance? I'd be curious to see if this test case can be simplified a bit further to make the interesting part(s) more obvious.<br> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
+; struct context {<br>
+; int cur_pid<br>
+; };<br>
+; int a, b, c, f, d;<br>
+; int pid_for_task(int);<br>
+; sample(struct context *p1)<br>
+; {<br>
+; if (c)<br>
+; b = a;<br>
+; if (a && p1->cur_pid)<br>
+; sample_internal();<br>
+; }<br>
+; callback() {<br>
+; f = pid_for_task(d);<br>
+; sample(&f);<br>
+; }<br>
+<br>
+target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"<br>
+target triple = "arm64-apple-ios"<br>
+<br>
+%struct.context = type { i32 }<br>
+<br>
+@c = common global i32 0, align 4<br>
+@a = common global i32 0, align 4<br>
+@b = common global i32 0, align 4<br>
+@d = common global i32 0, align 4<br>
+@f = common global i32 0, align 4<br>
+<br>
+; Function Attrs: nounwind<br>
+declare i32 @sample_internal(...)<br>
+<br>
+; Function Attrs: nounwind<br>
+define i32 @callback() #0 {<br>
+entry:<br>
+ %0 = load i32, i32* @d, align 4, !dbg !37<br>
+<br>
+ ; Verify that the call still has a debug location after GVN.<br>
+ ; CHECK: %call = tail call i32 @pid_for_task(i32 %0) #{{[0-9]}}, !dbg<br>
+ %call = tail call i32 @pid_for_task(i32 %0) #3, !dbg !37<br>
+<br>
+ store i32 %call, i32* @f, align 4, !dbg !37<br>
+ tail call void @llvm.dbg.value(metadata %struct.context* bitcast (i32* @f to %struct.context*), i64 0, metadata !25, metadata !26) #3, !dbg !38<br>
+ %1 = load i32, i32* @c, align 4, !dbg !40<br>
+ %tobool.i = icmp eq i32 %1, 0, !dbg !40<br>
+ %.pr.i = load i32, i32* @a, align 4, !dbg !41<br>
+ br i1 %tobool.i, label %if.end.i, label %if.then.i, !dbg !42<br>
+<br>
+if.then.i: ; preds = %entry<br>
+ store i32 %.pr.i, i32* @b, align 4, !dbg !43<br>
+ br label %if.end.i, !dbg !43<br>
+<br>
+if.end.i: ; preds = %if.then.i, %entry<br>
+ %tobool1.i = icmp eq i32 %.pr.i, 0, !dbg !41<br>
+<br>
+ ; This instruction has no debug location -- in this<br>
+ ; particular case it was removed by a bug in SimplifyCFG.<br>
+ %2 = load i32, i32* @f, align 4<br>
+<br>
+ ; GVN is supposed to replace the load of @f with a direct reference to %call.<br>
+ ; CHECK: %tobool2.i = icmp eq i32 %call, 0, !dbg<br>
+ %tobool2.i = icmp eq i32 %2, 0, !dbg !41<br>
+<br>
+ %or.cond = or i1 %tobool1.i, %tobool2.i, !dbg !41<br>
+ br i1 %or.cond, label %sample.exit, label %if.then.3.i, !dbg !41<br>
+<br>
+if.then.3.i: ; preds = %if.end.i<br>
+ %call.i = tail call i32 bitcast (i32 (...)* @sample_internal to i32 ()*)() #3, !dbg !44<br>
+ br label %sample.exit, !dbg !44<br>
+<br>
+sample.exit: ; preds = %if.end.i, %if.then.3.i<br>
+ ret i32 undef, !dbg !45<br>
+}<br>
+<br>
+declare i32 @pid_for_task(i32) #1<br>
+<br>
+; Function Attrs: nounwind readnone<br>
+declare void @llvm.dbg.value(metadata, i64, metadata, metadata) #2<br>
+<br>
+attributes #0 = { nounwind }<br>
+attributes #2 = { nounwind readnone }<br>
+attributes #3 = { nounwind }<br>
+<br>
+!<a href="http://llvm.dbg.cu" rel="noreferrer" target="_blank">llvm.dbg.cu</a> = !{!0}<br>
+!llvm.module.flags = !{!22, !23}<br>
+!llvm.ident = !{!24}<br>
+<br>
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 3.8.0 (trunk 244473) (llvm/trunk 244644)", isOptimized: false, runtimeVersion: 0, emissionKind: 1, enums: !2, subprograms: !3, globals: !16)<br>
+!1 = !DIFile(filename: "test.c", directory: "/")<br>
+!2 = !{}<br>
+!3 = !{!4, !13}<br>
+!4 = !DISubprogram(name: "sample", scope: !5, file: !5, line: 6, type: !6, isLocal: false, isDefinition: true, scopeLine: 7, flags: DIFlagPrototyped, isOptimized: false, variables: !2)<br>
+!5 = !DIFile(filename: "test.i", directory: "/")<br>
+!6 = !DISubroutineType(types: !7)<br>
+!7 = !{!8, !9}<br>
+!8 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)<br>
+!9 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !10, size: 64, align: 64)<br>
+!10 = !DICompositeType(tag: DW_TAG_structure_type, name: "context", file: !5, line: 1, size: 32, align: 32, elements: !11)<br>
+!11 = !{!12}<br>
+!12 = !DIDerivedType(tag: DW_TAG_member, name: "cur_pid", scope: !10, file: !5, line: 2, baseType: !8, size: 32, align: 32)<br>
+!13 = !DISubprogram(name: "callback", scope: !5, file: !5, line: 13, type: !14, isLocal: false, isDefinition: true, scopeLine: 13, isOptimized: false, function: i32 ()* @callback, variables: !2)<br>
+!14 = !DISubroutineType(types: !15)<br>
+!15 = !{!8}<br>
+!16 = !{!17, !18, !19, !20, !21}<br>
+!17 = !DIGlobalVariable(name: "a", scope: !0, file: !5, line: 4, type: !8, isLocal: false, isDefinition: true, variable: i32* @a)<br>
+!18 = !DIGlobalVariable(name: "b", scope: !0, file: !5, line: 4, type: !8, isLocal: false, isDefinition: true, variable: i32* @b)<br>
+!19 = !DIGlobalVariable(name: "c", scope: !0, file: !5, line: 4, type: !8, isLocal: false, isDefinition: true, variable: i32* @c)<br>
+!20 = !DIGlobalVariable(name: "f", scope: !0, file: !5, line: 4, type: !8, isLocal: false, isDefinition: true, variable: i32* @f)<br>
+!21 = !DIGlobalVariable(name: "d", scope: !0, file: !5, line: 4, type: !8, isLocal: false, isDefinition: true, variable: i32* @d)<br>
+!22 = !{i32 2, !"Dwarf Version", i32 2}<br>
+!23 = !{i32 2, !"Debug Info Version", i32 3}<br>
+!24 = !{!"clang version 3.8.0 (trunk 244473) (llvm/trunk 244644)"}<br>
+!25 = !DILocalVariable(name: "p1", arg: 1, scope: !4, file: !5, line: 6, type: !9)<br>
+!26 = !DIExpression()<br>
+!27 = !DILocation(line: 6, scope: !4)<br>
+!28 = !DILocation(line: 8, scope: !29)<br>
+!29 = distinct !DILexicalBlock(scope: !4, file: !5, line: 8)<br>
+!30 = !DILocation(line: 10, scope: !31)<br>
+!31 = distinct !DILexicalBlock(scope: !4, file: !5, line: 10)<br>
+!32 = !DILocation(line: 8, scope: !4)<br>
+!33 = !DILocation(line: 9, scope: !29)<br>
+!34 = !DILocation(line: 10, scope: !4)<br>
+!35 = !DILocation(line: 11, scope: !31)<br>
+!36 = !DILocation(line: 12, scope: !4)<br>
+!37 = !DILocation(line: 14, scope: !13)<br>
+!38 = !DILocation(line: 6, scope: !4, inlinedAt: !39)<br>
+!39 = distinct !DILocation(line: 15, scope: !13)<br>
+!40 = !DILocation(line: 8, scope: !29, inlinedAt: !39)<br>
+!41 = !DILocation(line: 10, scope: !31, inlinedAt: !39)<br>
+!42 = !DILocation(line: 8, scope: !4, inlinedAt: !39)<br>
+!43 = !DILocation(line: 9, scope: !29, inlinedAt: !39)<br>
+!44 = !DILocation(line: 11, scope: !31, inlinedAt: !39)<br>
+!45 = !DILocation(line: 16, scope: !13)<br>
<br>
<br>
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</blockquote></div><br></div></div>