<div dir="ltr">Hi Florian,<div><br></div><div>In our testing using the clang/utils/check_cfc tool we spotted a case where after this commit we're seeing a new codegen difference depending on whether or not -g is specified.  I've put the details in PR31319 ( <a href="https://llvm.org/bugs/show_bug.cgi?id=31319">https://llvm.org/bugs/show_bug.cgi?id=31319</a> ).</div><div><br></div><div>Thanks,</div><div><br></div><div>-Greg Bedwell</div><div>SN Systems Ltd - Sony Interactive Entertainment</div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On 6 December 2016 at 10:24, Florian Hahn 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: fhahn<br>
Date: Tue Dec  6 04:24:55 2016<br>
New Revision: 288794<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=288794&view=rev" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-<wbr>project?rev=288794&view=rev</a><br>
Log:<br>
[framelowering] Improve tracking of first CS pop instruction.<br>
<br>
<br>
Summary: This patch makes sure FirstCSPop and MBBI never point to DBG_VALUE instructions, which affected the code generated.<br>
<br>
Reviewers: mkuper, aprantl, MatzeB<br>
<br>
Subscribers: llvm-commits<br>
<br>
Differential Revision: <a href="https://reviews.llvm.org/D27343" rel="noreferrer" target="_blank">https://reviews.llvm.org/<wbr>D27343</a><br>
<br>
Added:<br>
    llvm/trunk/test/CodeGen/X86/<wbr>frame-lowering-debug-<wbr>intrinsic.ll<br>
Modified:<br>
    llvm/trunk/lib/Target/X86/<wbr>X86FrameLowering.cpp<br>
<br>
Modified: llvm/trunk/lib/Target/X86/<wbr>X86FrameLowering.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86FrameLowering.cpp?rev=288794&r1=288793&r2=288794&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-<wbr>project/llvm/trunk/lib/Target/<wbr>X86/X86FrameLowering.cpp?rev=<wbr>288794&r1=288793&r2=288794&<wbr>view=diff</a><br>
==============================<wbr>==============================<wbr>==================<br>
--- llvm/trunk/lib/Target/X86/<wbr>X86FrameLowering.cpp (original)<br>
+++ llvm/trunk/lib/Target/X86/<wbr>X86FrameLowering.cpp Tue Dec  6 04:24:55 2016<br>
@@ -1550,19 +1550,22 @@ void X86FrameLowering::<wbr>emitEpilogue(Mach<br>
   }<br>
   uint64_t SEHStackAllocAmt = NumBytes;<br>
<br>
+  MachineBasicBlock::iterator FirstCSPop = MBBI;<br>
   // Skip the callee-saved pop instructions.<br>
   while (MBBI != MBB.begin()) {<br>
     MachineBasicBlock::iterator PI = std::prev(MBBI);<br>
     unsigned Opc = PI->getOpcode();<br>
<br>
-    if ((Opc != X86::POP32r || !PI->getFlag(MachineInstr::<wbr>FrameDestroy)) &&<br>
-        (Opc != X86::POP64r || !PI->getFlag(MachineInstr::<wbr>FrameDestroy)) &&<br>
-        Opc != X86::DBG_VALUE && !PI->isTerminator())<br>
-      break;<br>
+    if (Opc != X86::DBG_VALUE && !PI->isTerminator()) {<br>
+      if ((Opc != X86::POP32r || !PI->getFlag(MachineInstr::<wbr>FrameDestroy)) &&<br>
+          (Opc != X86::POP64r || !PI->getFlag(MachineInstr::<wbr>FrameDestroy)))<br>
+        break;<br>
+      FirstCSPop = PI;<br>
+    }<br>
<br>
     --MBBI;<br>
   }<br>
-  MachineBasicBlock::iterator FirstCSPop = MBBI;<br>
+  MBBI = FirstCSPop;<br>
<br>
   if (TargetMBB) {<br>
     // Fill EAX/RAX with the address of the target block.<br>
<br>
Added: llvm/trunk/test/CodeGen/X86/<wbr>frame-lowering-debug-<wbr>intrinsic.ll<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/frame-lowering-debug-intrinsic.ll?rev=288794&view=auto" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-<wbr>project/llvm/trunk/test/<wbr>CodeGen/X86/frame-lowering-<wbr>debug-intrinsic.ll?rev=288794&<wbr>view=auto</a><br>
==============================<wbr>==============================<wbr>==================<br>
--- llvm/trunk/test/CodeGen/X86/<wbr>frame-lowering-debug-<wbr>intrinsic.ll (added)<br>
+++ llvm/trunk/test/CodeGen/X86/<wbr>frame-lowering-debug-<wbr>intrinsic.ll Tue Dec  6 04:24:55 2016<br>
@@ -0,0 +1,41 @@<br>
+; Test ensuring debug intrinsics do not affect generated function prologue.<br>
+;<br>
+; RUN: llc -O1 -mtriple=x86_64-unknown-<wbr>unknown -o - %s | FileCheck %s<br>
+<br>
+<br>
+define i64 @noDebug(i64 %a) {<br>
+  %call = call i64 @fn(i64 %a, i64 0)<br>
+  ret i64 %call<br>
+}<br>
+<br>
+; CHECK-LABEL: noDebug<br>
+; CHECK: popq %rcx<br>
+; CHECK: ret<br>
+<br>
+<br>
+define i64 @withDebug(i64 %a) !dbg !4 {<br>
+  %call = call i64 @fn(i64 %a, i64 0)<br>
+  tail call void @llvm.dbg.value(metadata i64 %call, i64 0, metadata !5, metadata !6), !dbg !7<br>
+  ret i64 %call<br>
+}<br>
+<br>
+; CHECK-LABEL: withDebug<br>
+; CHECK: popq %rcx<br>
+; CHECK: ret<br>
+<br>
+<br>
+declare i64 @fn(i64, i64)<br>
+<br>
+declare void @llvm.dbg.value(metadata, i64, metadata, metadata)<br>
+<br>
+!<a href="http://llvm.dbg.cu" rel="noreferrer" target="_blank">llvm.dbg.cu</a> = !{!0}<br>
+!llvm.module.flags = !{!2,!3}<br>
+<br>
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 4.0.0")<br>
+!1 = !DIFile(filename: "test.c", directory: "/")<br>
+!2 = !{i32 2, !"Dwarf Version", i32 4}<br>
+!3 = !{i32 2, !"Debug Info Version", i32 3}<br>
+!4 = distinct !DISubprogram(name: "withDebug", unit: !0)<br>
+!5 = !DILocalVariable(name: "w", scope: !4)<br>
+!6 = !DIExpression()<br>
+!7 = !DILocation(line: 210, column: 12, scope: !4)<br>
<br>
<br>
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</blockquote></div><br></div>