[llvm] Opt-in flag for X86DiscriminateMemOps

Summary:
Currently, if an instruction with a memory operand has no debug information,
X86DiscriminateMemOps will generate one based on the first line of the
enclosing function, or the last seen debug info.

This may cause confusion in certain debugging scenarios. The long term
approach would be to use the line number '0' in such cases, however, that
brings in challenges: the base discriminator value range is limited
(4096 values).

For the short term, adding an opt-in flag for this feature.

See bug 40319 (https://bugs.llvm.org/show_bug.cgi?id=40319)

Reviewers: dblaikie, jmorse, gbedwell

Reviewed By: dblaikie

Subscribers: aprantl, eraman, hiraditya

Differential Revision: https://reviews.llvm.org/D57257

llvm-svn: 352246

diff --git a/llvm/lib/Target/X86/X86DiscriminateMemOps.cpp b/llvm/lib/Target/X86/X86DiscriminateMemOps.cpp
index a76f9c8..f6bd580 100644 (file)
--- a/llvm/lib/Target/X86/X86DiscriminateMemOps.cpp
+++ b/llvm/lib/Target/X86/X86DiscriminateMemOps.cpp
@@ -26,6 +26,14 @@ using namespace llvm;
 
 #define DEBUG_TYPE "x86-discriminate-memops"
 
+static cl::opt<bool> EnableDiscriminateMemops(
+    DEBUG_TYPE, cl::init(false),
+    cl::desc("Generate unique debug info for each instruction with a memory "
+             "operand. Should be enabled for profile-drived cache prefetching, "
+             "both in the build of the binary being profiled, as well as in "
+             "the build of the binary consuming the profile."),
+    cl::Hidden);
+
 namespace {
 
 using Location = std::pair<StringRef, unsigned>;
@@ -66,6 +74,9 @@ char X86DiscriminateMemOps::ID = 0;
 X86DiscriminateMemOps::X86DiscriminateMemOps() : MachineFunctionPass(ID) {}
 
 bool X86DiscriminateMemOps::runOnMachineFunction(MachineFunction &MF) {
+  if (!EnableDiscriminateMemops)
+    return false;
+
   DISubprogram *FDI = MF.getFunction().getSubprogram();
   if (!FDI || !FDI->getUnit()->getDebugInfoForProfiling())
     return false;

diff --git a/llvm/lib/Target/X86/X86InsertPrefetch.cpp b/llvm/lib/Target/X86/X86InsertPrefetch.cpp
index f898cde..02ae737 100644 (file)
--- a/llvm/lib/Target/X86/X86InsertPrefetch.cpp
+++ b/llvm/lib/Target/X86/X86InsertPrefetch.cpp
@@ -33,7 +33,8 @@ using namespace sampleprof;
 
 static cl::opt<std::string>
     PrefetchHintsFile("prefetch-hints-file",
-                      cl::desc("Path to the prefetch hints profile."),
+                      cl::desc("Path to the prefetch hints profile. See also "
+                               "-x86-discriminate-memops"),
                       cl::Hidden);
 namespace {
 

diff --git a/llvm/test/CodeGen/X86/discriminate-mem-ops.ll b/llvm/test/CodeGen/X86/discriminate-mem-ops.ll
index b77a91f..a30dc22 100644 (file)
--- a/llvm/test/CodeGen/X86/discriminate-mem-ops.ll
+++ b/llvm/test/CodeGen/X86/discriminate-mem-ops.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s | FileCheck %s
+; RUN: llc -x86-discriminate-memops  < %s | FileCheck %s
 ;
 ; original source, compiled with -O3 -gmlt -fdebug-info-for-profiling:
 ; int sum(int* arr, int pos1, int pos2) {

diff --git a/llvm/test/CodeGen/X86/insert-prefetch-inline.ll b/llvm/test/CodeGen/X86/insert-prefetch-inline.ll
index 5f8373f..62c02fa 100644 (file)
--- a/llvm/test/CodeGen/X86/insert-prefetch-inline.ll
+++ b/llvm/test/CodeGen/X86/insert-prefetch-inline.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s -prefetch-hints-file=%S/insert-prefetch-inline.afdo | FileCheck %s
+; RUN: llc < %s -x86-discriminate-memops -prefetch-hints-file=%S/insert-prefetch-inline.afdo | FileCheck %s
 ;
 ; Verify we can insert prefetch instructions in code belonging to inlined
 ; functions.

diff --git a/llvm/test/CodeGen/X86/insert-prefetch-invalid-instr.ll b/llvm/test/CodeGen/X86/insert-prefetch-invalid-instr.ll
index 004fb56..d0c4ac3 100644 (file)
--- a/llvm/test/CodeGen/X86/insert-prefetch-invalid-instr.ll
+++ b/llvm/test/CodeGen/X86/insert-prefetch-invalid-instr.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s -prefetch-hints-file=%S/insert-prefetch-invalid-instr.afdo | FileCheck %s
+; RUN: llc < %s -x86-discriminate-memops -prefetch-hints-file=%S/insert-prefetch-invalid-instr.afdo | FileCheck %s
 ; ModuleID = 'prefetch.cc'
 source_filename = "prefetch.cc"
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"

diff --git a/llvm/test/CodeGen/X86/insert-prefetch.ll b/llvm/test/CodeGen/X86/insert-prefetch.ll
index 9e77772..fe0fd98 100644 (file)
--- a/llvm/test/CodeGen/X86/insert-prefetch.ll
+++ b/llvm/test/CodeGen/X86/insert-prefetch.ll
@@ -1,5 +1,5 @@
-; RUN: llc < %s -prefetch-hints-file=%S/insert-prefetch.afdo | FileCheck %s
-; RUN: llc < %s -prefetch-hints-file=%S/insert-prefetch-other.afdo | FileCheck %s -check-prefix=OTHERS
+; RUN: llc < %s -x86-discriminate-memops -prefetch-hints-file=%S/insert-prefetch.afdo | FileCheck %s
+; RUN: llc < %s -x86-discriminate-memops -prefetch-hints-file=%S/insert-prefetch-other.afdo | FileCheck %s -check-prefix=OTHERS
 ;
 ; original source, compiled with -O3 -gmlt -fdebug-info-for-profiling:
 ; int sum(int* arr, int pos1, int pos2) {