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[BDCE] Salvage debug info from dying insts 

This results in 15 additional unique source variables in a stage2 build
of FileCheck (at '-Os -g'), with a negligible increase in the size of
the .debug_loc section.

llvm-svn: 325660
This commit is contained in:
Vedant Kumar 2018-02-21 01:55:33 +00:00
parent 9fbf64139e
commit 56492f9177
2 changed files with 13 additions and 0 deletions
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2
llvm/lib/Transforms/Scalar/BDCE.cpp
View File

@ -26,6 +26,7 @@
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/Local.h"
using namespace llvm;
#define DEBUG_TYPE "bdce"
@ -114,6 +115,7 @@ static bool bitTrackingDCE(Function &F, DemandedBits &DB) {
if (!DB.isInstructionDead(&I))
continue;
salvageDebugInfo(I);
Worklist.push_back(&I);
I.dropAllReferences();
Changed = true;

11
llvm/test/Transforms/BDCE/basic.ll
View File

@ -1,5 +1,6 @@
; RUN: opt -S -bdce -instsimplify < %s | FileCheck %s
; RUN: opt -S -instsimplify < %s | FileCheck %s -check-prefix=CHECK-IO
; RUN: opt -S -debugify -bdce < %s | FileCheck %s -check-prefix=DEBUGIFY
target datalayout = "E-m:e-i64:64-n32:64"
target triple = "powerpc64-unknown-linux-gnu"
@ -381,6 +382,16 @@ entry:
; CHECK: ret i16
}
; DEBUGIFY-LABEL: @tar9
define signext i16 @tar9(i32 signext %x) #0 {
entry:
%call = tail call signext i32 @foo(i32 signext 5) #0
%and = and i32 %call, 33554432
; DEBUGIFY: call void @llvm.dbg.value(metadata i32 %call, metadata {{.*}}, metadata !DIExpression(DW_OP_constu, 33554432, DW_OP_and, DW_OP_stack_value))
%cast = trunc i32 %call to i16
ret i16 %cast
}
attributes #0 = { nounwind readnone }
attributes #1 = { nounwind }