llvmbot wrote:

<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-x86

Author: Paul Murphy (pmur)

<details>
<summary>Changes</summary>

I found out these attributes are only support on s390x when prototyping my Rust 
[rfc](https://github.com/rust-lang/rfcs/pull/3917) for expanded instrumented 
function support.

Also, is this the correct/preferred way to insert nop's on x86?

---
Full diff: https://github.com/llvm/llvm-project/pull/184641.diff


10 Files Affected:

- (modified) clang/lib/Driver/ToolChains/Clang.cpp (+4-2) 
- (modified) clang/test/CodeGen/mnop-mcount.c (+8) 
- (modified) clang/test/CodeGen/mrecord-mcount.c (+8) 
- (modified) clang/test/Driver/mcount.c (+1-3) 
- (modified) llvm/lib/Target/X86/X86ISelDAGToDAG.cpp (+11-3) 
- (modified) llvm/lib/Target/X86/X86MCInstLower.cpp (+18) 
- (added) llvm/test/CodeGen/X86/mnop-mcount-01.ll (+26) 
- (added) llvm/test/CodeGen/X86/mnop-mcount-02.ll (+10) 
- (added) llvm/test/CodeGen/X86/mrecord-mcount-01.ll (+32) 
- (added) llvm/test/CodeGen/X86/mrecord-mcount-02.ll (+10) 


``````````diff
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp 
b/clang/lib/Driver/ToolChains/Clang.cpp
index e860136aae5b3..2807be2c7edd0 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -6884,14 +6884,16 @@ void Clang::ConstructJob(Compilation &C, const 
JobAction &JA,
             << A->getAsString(Args) << TripleStr;
     }
     if (Arg *A = Args.getLastArg(options::OPT_mnop_mcount)) {
-      if (Arch == llvm::Triple::systemz)
+      if (Arch == llvm::Triple::systemz || (TC.getTriple().isX86_64() &&
+                                           TC.getTriple().isOSBinFormatELF()))
         A->render(Args, CmdArgs);
       else
         D.Diag(diag::err_drv_unsupported_opt_for_target)
             << A->getAsString(Args) << TripleStr;
     }
     if (Arg *A = Args.getLastArg(options::OPT_mrecord_mcount)) {
-      if (Arch == llvm::Triple::systemz)
+      if (Arch == llvm::Triple::systemz || (TC.getTriple().isX86_64() &&
+                                           TC.getTriple().isOSBinFormatELF()))
         A->render(Args, CmdArgs);
       else
         D.Diag(diag::err_drv_unsupported_opt_for_target)
diff --git a/clang/test/CodeGen/mnop-mcount.c b/clang/test/CodeGen/mnop-mcount.c
index ebb21cc560e37..31b4e995cff02 100644
--- a/clang/test/CodeGen/mnop-mcount.c
+++ b/clang/test/CodeGen/mnop-mcount.c
@@ -6,6 +6,14 @@
 // RUN:   %s 2>&1 | FileCheck -check-prefix=NOPG %s
 // RUN: %clang_cc1 -mnop-mcount -triple s390x-ibm-linux -emit-llvm -o - %s \
 // RUN:   2>&1 | FileCheck -check-prefix=NOPG %s
+// RUN: %clang_cc1 -pg -mfentry -mnop-mcount -triple x86_64-ibm-linux 
-emit-llvm \
+// RUN:   -o - %s 2>&1 | FileCheck  %s
+// RUN: not %clang_cc1 -pg -mnop-mcount -triple x86_64-ibm-linux -emit-llvm -o 
- \
+// RUN:   %s 2>&1 | FileCheck -check-prefix=NOMFENTRY %s
+// RUN: %clang_cc1 -mfentry -mnop-mcount -triple x86_64-ibm-linux -emit-llvm 
-o - \
+// RUN:   %s 2>&1 | FileCheck -check-prefix=NOPG %s
+// RUN: %clang_cc1 -mnop-mcount -triple x86_64-ibm-linux -emit-llvm -o - %s \
+// RUN:   2>&1 | FileCheck -check-prefix=NOPG %s
 
 int foo(void) {
   return 0;
diff --git a/clang/test/CodeGen/mrecord-mcount.c 
b/clang/test/CodeGen/mrecord-mcount.c
index 292a807073cef..832d4ee5e3e9f 100644
--- a/clang/test/CodeGen/mrecord-mcount.c
+++ b/clang/test/CodeGen/mrecord-mcount.c
@@ -6,6 +6,14 @@
 // RUN:   %s 2>&1 | FileCheck -check-prefix=NOPG %s
 // RUN: %clang_cc1 -mrecord-mcount -triple s390x-ibm-linux -emit-llvm -o - %s \
 // RUN:   2>&1 | FileCheck -check-prefix=NOPG %s
+// RUN: %clang_cc1 -pg -mfentry -mrecord-mcount -triple x86_64-ibm-linux 
-emit-llvm \
+// RUN:   -o - %s 2>&1 | FileCheck  %s
+// RUN: not %clang_cc1 -pg -mrecord-mcount -triple x86_64-ibm-linux -emit-llvm 
-o - \
+// RUN:   %s 2>&1 | FileCheck -check-prefix=NOMFENTRY %s
+// RUN: %clang_cc1 -mfentry -mrecord-mcount -triple x86_64-ibm-linux 
-emit-llvm -o - \
+// RUN:   %s 2>&1 | FileCheck -check-prefix=NOPG %s
+// RUN: %clang_cc1 -mrecord-mcount -triple x86_64-ibm-linux -emit-llvm -o - %s 
\
+// RUN:   2>&1 | FileCheck -check-prefix=NOPG %s
 
 int foo(void) {
   return 0;
diff --git a/clang/test/Driver/mcount.c b/clang/test/Driver/mcount.c
index 70f554745b9c3..72d48b3806fe7 100644
--- a/clang/test/Driver/mcount.c
+++ b/clang/test/Driver/mcount.c
@@ -1,12 +1,10 @@
 // RUN: %clang --target=s390x -c -### %s -mnop-mcount -mrecord-mcount 2>&1 | 
FileCheck %s
+// RUN: %clang --target=x86_64 -c -### %s -mnop-mcount -mrecord-mcount 2>&1 | 
FileCheck %s
 
 // CHECK: "-mnop-mcount"
 // CHECK: "-mrecord-mcount"
 
-// RUN: not %clang --target=x86_64 -c -### %s -mnop-mcount -mrecord-mcount 
2>&1 | FileCheck --check-prefix=ERR1 %s
 // RUN: not %clang --target=aarch64 -c -### %s -mnop-mcount -mrecord-mcount 
2>&1 | FileCheck --check-prefix=ERR2 %s
 
-// ERR1: error: unsupported option '-mnop-mcount' for target 'x86_64'
-// ERR1: error: unsupported option '-mrecord-mcount' for target 'x86_64'
 // ERR2: error: unsupported option '-mnop-mcount' for target 'aarch64'
 // ERR2: error: unsupported option '-mrecord-mcount' for target 'aarch64'
diff --git a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp 
b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
index 101ea3e231a5c..aa7efb8a05e1c 100644
--- a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -179,11 +179,19 @@ namespace {
     bool runOnMachineFunction(MachineFunction &MF) override {
       // Reset the subtarget each time through.
       Subtarget = &MF.getSubtarget<X86Subtarget>();
-      IndirectTlsSegRefs = MF.getFunction().hasFnAttribute(
-                             "indirect-tls-seg-refs");
+      const Function &F = MF.getFunction();
+
+      IndirectTlsSegRefs = F.hasFnAttribute("indirect-tls-seg-refs");
+
+      if (F.getFnAttribute("fentry-call").getValueAsString() != "true") {
+        if (F.hasFnAttribute("mnop-mcount"))
+          report_fatal_error("mnop-mcount only supported with fentry-call");
+        if (F.hasFnAttribute("mrecord-mcount"))
+          report_fatal_error("mrecord-mcount only supported with fentry-call");
+      }
 
       // OptFor[Min]Size are used in pattern predicates that isel is matching.
-      OptForMinSize = MF.getFunction().hasMinSize();
+      OptForMinSize = F.hasMinSize();
       return SelectionDAGISel::runOnMachineFunction(MF);
     }
 
diff --git a/llvm/lib/Target/X86/X86MCInstLower.cpp 
b/llvm/lib/Target/X86/X86MCInstLower.cpp
index 4ef4718e1b01c..8bbd40d973fab 100644
--- a/llvm/lib/Target/X86/X86MCInstLower.cpp
+++ b/llvm/lib/Target/X86/X86MCInstLower.cpp
@@ -26,6 +26,7 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringExtras.h"
+#include "llvm/BinaryFormat/ELF.h"
 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
 #include "llvm/CodeGen/MachineConstantPool.h"
 #include "llvm/CodeGen/MachineFunction.h"
@@ -44,6 +45,7 @@
 #include "llvm/MC/MCInst.h"
 #include "llvm/MC/MCInstBuilder.h"
 #include "llvm/MC/MCSection.h"
+#include "llvm/MC/MCSectionELF.h"
 #include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCSymbol.h"
 #include "llvm/MC/TargetRegistry.h"
@@ -885,6 +887,22 @@ void X86AsmPrinter::LowerFENTRY_CALL(const MachineInstr 
&MI,
                                      X86MCInstLower &MCIL) {
   bool Is64Bits = Subtarget->is64Bit();
   MCContext &Ctx = OutStreamer->getContext();
+
+  if (MF->getFunction().hasFnAttribute("mrecord-mcount")) {
+    MCSymbol *DotSym = OutContext.createTempSymbol();
+    OutStreamer->pushSection();
+    OutStreamer->switchSection(
+        Ctx.getELFSection("__mcount_loc", ELF::SHT_PROGBITS, ELF::SHF_ALLOC));
+    OutStreamer->emitSymbolValue(DotSym, Is64Bits ? 8 : 4);
+    OutStreamer->popSection();
+    OutStreamer->emitLabel(DotSym);
+  }
+
+  if (MF->getFunction().hasFnAttribute("mnop-mcount")) {
+    emitX86Nops(*OutStreamer, 5, Subtarget);
+    return;
+  }
+
   MCSymbol *fentry = Ctx.getOrCreateSymbol("__fentry__");
   const MCSymbolRefExpr *Op = MCSymbolRefExpr::create(fentry, Ctx);
 
diff --git a/llvm/test/CodeGen/X86/mnop-mcount-01.ll 
b/llvm/test/CodeGen/X86/mnop-mcount-01.ll
new file mode 100644
index 0000000000000..ddefa497659f3
--- /dev/null
+++ b/llvm/test/CodeGen/X86/mnop-mcount-01.ll
@@ -0,0 +1,26 @@
+; RUN: llc %s -mtriple=x86_64-linux-gnu -o - -verify-machineinstrs \
+; RUN:   | FileCheck %s
+
+define void @test1() #0 {
+entry:
+  ret void
+
+; CHECK-LABEL: @test1
+; CHECK: callq __fentry__
+; CHECK-NOT: nopl 8(%rax,%rax)
+; CHECK: retq
+}
+
+define void @test2() #1 {
+entry:
+  ret void
+
+; CHECK-LABEL: @test2
+; CHECK-NOT: callq __fentry__
+; CHECK: nopl 8(%rax,%rax)
+; CHECK: retq
+}
+
+attributes #0 = { "fentry-call"="true" }
+attributes #1 = { "fentry-call"="true" "mnop-mcount" }
+
diff --git a/llvm/test/CodeGen/X86/mnop-mcount-02.ll 
b/llvm/test/CodeGen/X86/mnop-mcount-02.ll
new file mode 100644
index 0000000000000..d576e0f289818
--- /dev/null
+++ b/llvm/test/CodeGen/X86/mnop-mcount-02.ll
@@ -0,0 +1,10 @@
+; RUN: not --crash llc %s -mtriple=x86_64-linux-gnu -o - 2>&1 | FileCheck %s
+;
+; CHECK: LLVM ERROR: mnop-mcount only supported with fentry-call
+
+define void @test1() #0 {
+entry:
+  ret void
+}
+
+attributes #0 = { "instrument-function-entry-inlined"="mcount" "mnop-mcount" }
diff --git a/llvm/test/CodeGen/X86/mrecord-mcount-01.ll 
b/llvm/test/CodeGen/X86/mrecord-mcount-01.ll
new file mode 100644
index 0000000000000..6202a652b8831
--- /dev/null
+++ b/llvm/test/CodeGen/X86/mrecord-mcount-01.ll
@@ -0,0 +1,32 @@
+; RUN: llc %s -mtriple=x86_64-linux-gnu -o - -verify-machineinstrs \
+; RUN:   | FileCheck %s
+
+define void @test1() #0 {
+entry:
+  ret void
+
+; CHECK-LABEL: test1:
+; CHECK: .section __mcount_loc,"a",@progbits
+; CHECK: .quad .Ltmp0
+; CHECK: .text
+; CHECK: .Ltmp0:
+; CHECK: callq __fentry__
+; CHECK: retq 
+}
+
+define void @test2() #1 {
+entry:
+  ret void
+
+; CHECK-LABEL: test2:
+; CHECK: .section __mcount_loc,"a",@progbits
+; CHECK: .quad .Ltmp1
+; CHECK: .text
+; CHECK: .Ltmp1:
+; CHECK: nopl 8(%rax,%rax)
+; CHECK-NOT: callq __fentry__
+; CHECK: retq
+}
+
+attributes #0 = { "fentry-call"="true" "mrecord-mcount" }
+attributes #1 = { "fentry-call"="true" "mnop-mcount" "mrecord-mcount" }
diff --git a/llvm/test/CodeGen/X86/mrecord-mcount-02.ll 
b/llvm/test/CodeGen/X86/mrecord-mcount-02.ll
new file mode 100644
index 0000000000000..a1f80f1840c41
--- /dev/null
+++ b/llvm/test/CodeGen/X86/mrecord-mcount-02.ll
@@ -0,0 +1,10 @@
+; RUN: not --crash llc %s -mtriple=x86_64-linux-gnu -o - 2>&1 | FileCheck %s
+;
+; CHECK: LLVM ERROR: mrecord-mcount only supported with fentry-call
+
+define void @test1() #0 {
+entry:
+  ret void
+}
+
+attributes #0 = { "instrument-function-entry-inlined"="mcount" 
"mrecord-mcount" }

``````````

</details>


https://github.com/llvm/llvm-project/pull/184641
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