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Fix out-of-order stepping behavior in programs with hoisted constants.

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When the Constant Hoisting pass moves expensive constants into a
common block, it would assign a debug location equal to the last use
of that constant. While this is certainly intuitive, it places the
constant in an out-of-order location, according to the debug location
information. This produces out-of-order stepping when debugging
programs affected by this pass.

This patch creates in-order stepping behavior by merging the debug
locations for hoisted constants, and the new insertion point.

Patch by Matthew Voss!

Differential Revision: https://reviews.llvm.org/D38088

llvm-svn: 317827
This commit is contained in:
Paul Robinson 2017-11-09 20:01:31 +00:00
parent b41889c358
commit 4494c25a38
3 changed files with 102 additions and 1 deletions
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7
lib/Transforms/Scalar/ConstantHoisting.cpp
View File

@ -60,6 +60,7 @@
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/IR/DebugInfoMetadata.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
@ -716,6 +717,9 @@ bool ConstantHoistingPass::emitBaseConstants() {
IntegerType *Ty = ConstInfo.BaseConstant->getType();
Instruction *Base =
new BitCastInst(ConstInfo.BaseConstant, Ty, "const", IP);
Base->setDebugLoc(IP->getDebugLoc());
DEBUG(dbgs() << "Hoist constant (" << *ConstInfo.BaseConstant
<< ") to BB " << IP->getParent()->getName() << '\n'
<< *Base << '\n');
@ -734,6 +738,8 @@ bool ConstantHoistingPass::emitBaseConstants() {
emitBaseConstants(Base, RCI.Offset, U);
ReBasesNum++;
}
Base->setDebugLoc(DILocation::getMergedLocation(Base->getDebugLoc(), U.Inst->getDebugLoc()));
}
}
UsesNum = Uses;
@ -742,7 +748,6 @@ bool ConstantHoistingPass::emitBaseConstants() {
assert(!Base->use_empty() && "The use list is empty!?");
assert(isa<Instruction>(Base->user_back()) &&
"All uses should be instructions.");
Base->setDebugLoc(cast<Instruction>(Base->user_back())->getDebugLoc());
}
(void)UsesNum;
(void)ReBasesNum;

55
test/Transforms/ConstantHoisting/X86/dbg-dominatingblock.ll Normal file
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@ -0,0 +1,55 @@
; RUN: opt -S -consthoist < %s | FileCheck %s
; ModuleID = 'test-hoist-debug.cpp'
source_filename = "test-hoist-debug.cpp"
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
; Function Attrs: noinline nounwind optnone uwtable
define i32 @_Z3foov() !dbg !7 {
; CHECK: bitcast
; CHECK-NOT: !dbg !11
; CHECK: inttoptr
entry:
%a0 = inttoptr i64 4646526064 to i32*
%v0 = load i32, i32* %a0, align 16, !dbg !11
%c = alloca i32, align 4
store i32 1, i32* %c, align 4
%0 = load i32, i32* %c, align 4
%cmp = icmp eq i32 %0, 0
br i1 %cmp, label %if.then, label %if.else
if.then: ; preds = %entry
%a1 = inttoptr i64 4646526080 to i32*
%v1 = load i32, i32* %a1, align 16, !dbg !11
br label %return
if.else: ; preds = %entry
%a2 = inttoptr i64 4646526096 to i32*
%v2 = load i32, i32* %a2, align 16, !dbg !11
br label %return
return: ; preds = %if.else, %if.then
%vx = phi i32 [%v1, %if.then], [%v2, %if.else]
%r0 = add i32 %vx, %v0
ret i32 %r0
}
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!3, !4, !5}
!llvm.ident = !{!6}
!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 6.0.0 (trunk 313291)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
!1 = !DIFile(filename: "test-hoist-debug.cpp", directory: "/tmp")
!2 = !{}
!3 = !{i32 2, !"Dwarf Version", i32 4}
!4 = !{i32 2, !"Debug Info Version", i32 3}
!5 = !{i32 1, !"wchar_size", i32 4}
!6 = !{!"clang version 6.0.0 (trunk 313291)"}
!7 = distinct !DISubprogram(name: "foo", linkageName: "_Z3foov", 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 = !{!10}
!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!11 = !DILocation(line: 2, column: 3, scope: !7)
!12 = !DILocation(line: 3, column: 3, scope: !7)
!13 = !DILocation(line: 4, column: 3, scope: !7)

41
test/Transforms/ConstantHoisting/X86/dbg-samebasicblock.ll Normal file
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@ -0,0 +1,41 @@
; RUN: opt -S -consthoist < %s | FileCheck %s
; ModuleID = 'test-hoist-debug.cpp'
source_filename = "test-hoist-debug.cpp"
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
; Function Attrs: noinline nounwind optnone uwtable
define i32 @_Z3foov() !dbg !7 {
; CHECK: bitcast
; CHECK: !dbg !11
; CHECK: inttoptr
%a0 = inttoptr i64 4646526064 to i32*, !dbg !11
%v0 = load i32, i32* %a0, align 16, !dbg !11
%a1 = inttoptr i64 4646526080 to i32*
%v1 = load i32, i32* %a1, align 16, !dbg !11
%a2 = inttoptr i64 4646526096 to i32*
%v2 = load i32, i32* %a2, align 16, !dbg !11
%r0 = add i32 %v0, %v1
%r1 = add i32 %r0, %v2
ret i32 %r1
}
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!3, !4, !5}
!llvm.ident = !{!6}
!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 6.0.0 (trunk 313291)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
!1 = !DIFile(filename: "test-hoist-debug.cpp", directory: "/tmp")
!2 = !{}
!3 = !{i32 2, !"Dwarf Version", i32 4}
!4 = !{i32 2, !"Debug Info Version", i32 3}
!5 = !{i32 1, !"wchar_size", i32 4}
!6 = !{!"clang version 6.0.0 (trunk 313291)"}
!7 = distinct !DISubprogram(name: "foo", linkageName: "_Z3foov", 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 = !{!10}
!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!11 = !DILocation(line: 2, column: 3, scope: !7)