[llvm] r285212 - Reapply: "Remove debug location from common tail when tail-merging"
Robert Lougher via llvm-commits
llvm-commits at lists.llvm.org
Wed Oct 26 10:01:47 PDT 2016
Author: rlougher
Date: Wed Oct 26 12:01:47 2016
New Revision: 285212
URL: http://llvm.org/viewvc/llvm-project?rev=285212&view=rev
Log:
Reapply: "Remove debug location from common tail when tail-merging"
This reapplies revision 285093. Original commit message:
The branch folding pass tail merges blocks into a common-tail. However, the
tail retains the debug information from one of the original inputs to the
merge (chosen randomly). This is a problem for sampled-based PGO, as hits
on the common-tail will be attributed to whichever block was chosen,
irrespective of which path was actually taken to the common-tail.
This patch fixes the issue by nulling the debug location for the common-tail.
Differential Revision: https://reviews.llvm.org/D25742
Added:
llvm/trunk/test/DebugInfo/X86/tail-merge.ll
Modified:
llvm/trunk/lib/CodeGen/BranchFolding.cpp
llvm/trunk/test/DebugInfo/COFF/local-variables.ll
Modified: llvm/trunk/lib/CodeGen/BranchFolding.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/BranchFolding.cpp?rev=285212&r1=285211&r2=285212&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/BranchFolding.cpp (original)
+++ llvm/trunk/lib/CodeGen/BranchFolding.cpp Wed Oct 26 12:01:47 2016
@@ -720,8 +720,6 @@ bool BranchFolder::CreateCommonTailOnlyB
SameTails[commonTailIndex].getTailStartPos();
MachineBasicBlock *MBB = SameTails[commonTailIndex].getBlock();
- // If the common tail includes any debug info we will take it pretty
- // randomly from one of the inputs. Might be better to remove it?
DEBUG(dbgs() << "\nSplitting BB#" << MBB->getNumber() << ", size "
<< maxCommonTailLength);
@@ -898,6 +896,11 @@ bool BranchFolder::TryTailMergeBlocks(Ma
// Recompute common tail MBB's edge weights and block frequency.
setCommonTailEdgeWeights(*MBB);
+ // Remove the original debug location from the common tail.
+ for (auto &MI : *MBB)
+ if (!MI.isDebugValue())
+ MI.setDebugLoc(DebugLoc());
+
// MBB is common tail. Adjust all other BB's to jump to this one.
// Traversal must be forwards so erases work.
DEBUG(dbgs() << "\nUsing common tail in BB#" << MBB->getNumber()
Modified: llvm/trunk/test/DebugInfo/COFF/local-variables.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/COFF/local-variables.ll?rev=285212&r1=285211&r2=285212&view=diff
==============================================================================
--- llvm/trunk/test/DebugInfo/COFF/local-variables.ll (original)
+++ llvm/trunk/test/DebugInfo/COFF/local-variables.ll Wed Oct 26 12:01:47 2016
@@ -63,11 +63,9 @@
; ASM: .cv_loc 2 1 5 3 # t.cpp:5:3
; ASM: callq capture
; ASM: leaq 36(%rsp), %rcx
-; ASM: [[inline_site2_end:\.Ltmp.*]]:
+; ASM: [[else_end:\.Ltmp.*]]:
; ASM: .LBB0_3: # %if.end
-; ASM: .cv_loc 0 1 15 5 # t.cpp:15:5
; ASM: callq capture
-; ASM: [[else_end:\.Ltmp.*]]:
; ASM: .cv_loc 0 1 17 1 # t.cpp:17:1
; ASM: nop
; ASM: addq $56, %rsp
@@ -101,7 +99,7 @@
; ASM: .long 116 # TypeIndex
; ASM: .short 0 # Flags
; ASM: .asciz "v"
-; ASM: .cv_def_range [[inline_site2]] [[inline_site2_end]], "E\021O\001\000\0000\000\000\000"
+; ASM: .cv_def_range [[inline_site2]] [[else_end]], "E\021O\001\000\0000\000\000\000"
; ASM: .short 4430 # Record kind: S_INLINESITE_END
; OBJ: Subsection [
@@ -159,7 +157,7 @@
; OBJ: LocalVariableAddrRange {
; OBJ: OffsetStart: .text+0x2D
; OBJ: ISectStart: 0x0
-; OBJ: Range: 0x24
+; OBJ: Range: 0x1F
; OBJ: }
; OBJ: }
; OBJ: InlineSite {
@@ -200,7 +198,7 @@
; OBJ: ChangeLineOffset: 1
; OBJ: ChangeCodeOffset: 0x35
; OBJ: ChangeCodeOffsetAndLineOffset: {CodeOffset: 0xD, LineOffset: 1}
-; OBJ: ChangeCodeLength: 0xA
+; OBJ: ChangeCodeLength: 0xF
; OBJ: ]
; OBJ: }
; OBJ: Local {
Added: llvm/trunk/test/DebugInfo/X86/tail-merge.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/tail-merge.ll?rev=285212&view=auto
==============================================================================
--- llvm/trunk/test/DebugInfo/X86/tail-merge.ll (added)
+++ llvm/trunk/test/DebugInfo/X86/tail-merge.ll Wed Oct 26 12:01:47 2016
@@ -0,0 +1,76 @@
+; RUN: llc %s -mtriple=x86_64-unknown-unknown -use-unknown-locations=true -o - | FileCheck %s
+
+; Generated with "clang -gline-tables-only -c -emit-llvm -o - | opt -sroa -S"
+; from source:
+;
+; extern int foo(int);
+; extern int bar(int);
+;
+; int test(int a, int b) {
+; if(b)
+; a += foo(a);
+; else
+; a += bar(a);
+; return a;
+; }
+
+; When tail-merging the debug location of the common tail should be removed.
+
+; CHECK-LABEL: test:
+; CHECK: movl %edi, [[REG:%.*]]
+; CHECK: testl %esi, %esi
+; CHECK: je [[ELSE:.LBB[0-9]+_[0-9]+]]
+; CHECK: .loc 1 6 10
+; CHECK: callq foo
+; CHECK: jmp [[TAIL:.LBB[0-9]+_[0-9]+]]
+; CHECK: [[ELSE]]:
+; CHECK: .loc 1 8 10
+; CHECK: callq bar
+; CHECK: [[TAIL]]:
+; CHECK: .loc 1 0 0
+; CHECK: addl [[REG]], %eax
+; CHECK: .loc 1 9 3
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define i32 @test(i32 %a, i32 %b) !dbg !6 {
+entry:
+ %tobool = icmp ne i32 %b, 0, !dbg !8
+ br i1 %tobool, label %if.then, label %if.else, !dbg !8
+
+if.then: ; preds = %entry
+ %call = call i32 @foo(i32 %a), !dbg !9
+ %add = add nsw i32 %a, %call, !dbg !10
+ br label %if.end, !dbg !11
+
+if.else: ; preds = %entry
+ %call1 = call i32 @bar(i32 %a), !dbg !12
+ %add2 = add nsw i32 %a, %call1, !dbg !13
+ br label %if.end
+
+if.end: ; preds = %if.else, %if.then
+ %a.addr.0 = phi i32 [ %add, %if.then ], [ %add2, %if.else ]
+ ret i32 %a.addr.0, !dbg !14
+}
+
+declare i32 @foo(i32)
+declare i32 @bar(i32)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "", isOptimized: false, runtimeVersion: 0, emissionKind: LineTablesOnly, enums: !2)
+!1 = !DIFile(filename: "test.c", directory: "")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!6 = distinct !DISubprogram(name: "test", scope: !1, file: !1, line: 4, type: !7, isLocal: false, isDefinition: true, scopeLine: 4, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!7 = !DISubroutineType(types: !2)
+!8 = !DILocation(line: 5, column: 6, scope: !6)
+!9 = !DILocation(line: 6, column: 10, scope: !6)
+!10 = !DILocation(line: 6, column: 7, scope: !6)
+!11 = !DILocation(line: 6, column: 5, scope: !6)
+!12 = !DILocation(line: 8, column: 10, scope: !6)
+!13 = !DILocation(line: 8, column: 7, scope: !6)
+!14 = !DILocation(line: 9, column: 3, scope: !6)
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