[llvm] r302109 - [XRay] Create an Index of sleds per function
Dean Michael Berris via llvm-commits
llvm-commits at lists.llvm.org
Wed May 3 20:37:57 PDT 2017
Author: dberris
Date: Wed May 3 22:37:57 2017
New Revision: 302109
URL: http://llvm.org/viewvc/llvm-project?rev=302109&view=rev
Log:
[XRay] Create an Index of sleds per function
Summary:
This change adds a new section to the xray-instrumented binary that
stores an index into ranges of the instrumentation map, where sleds
associated with the same function can be accessed as an array. At
runtime, we can get access to this index by function ID offset allowing
for selective patching and unpatching by function ID.
Each entry in this new section (xray_fn_idx) will include two pointers
indicating the start and one past the end of the sleds associated with
the same function. These entries will be 16 bytes long on x86 and
aarch64. On arm, we align to 16 bytes anyway so the runtime has to take
that into consideration.
__{start,stop}_xray_fn_idx will be the symbols that the runtime will
look for when we implement the selective patching/unpatching by function
id APIs. Because XRay synthesizes the function id's in a monotonically
increasing manner at runtime now, implementations (and users) can use
this table to look up the sleds associated with a specific function.
This is useful in implementations that want to do things like:
- Implement coverage mode for functions by patching everything
pre-main, then as functions are encountered, the installed handler
can unpatch the function that's been encountered after recording
that it's been called.
- Do "learning mode", so that the implementation can figure out some
statistical information about function calls by function id for a
time being, and then determine which functions are worth
uninstrumenting at runtime.
- Do "selective instrumentation" where an implementation can
specifically instrument only certain function id's at runtime
(either based on some external data, or through some other
heuristics) instead of patching all the instrumented functions at
runtime.
Reviewers: dblaikie, echristo, chandlerc, javed.absar
Subscribers: pelikan, aemerson, kpw, llvm-commits, rengolin
Differential Revision: https://reviews.llvm.org/D32693
Modified:
llvm/trunk/include/llvm/CodeGen/AsmPrinter.h
llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
llvm/trunk/test/CodeGen/AArch64/xray-attribute-instrumentation.ll
llvm/trunk/test/CodeGen/AArch64/xray-tail-call-sled.ll
llvm/trunk/test/CodeGen/ARM/xray-armv6-attribute-instrumentation.ll
llvm/trunk/test/CodeGen/ARM/xray-armv7-attribute-instrumentation.ll
llvm/trunk/test/CodeGen/X86/xray-attribute-instrumentation.ll
llvm/trunk/test/CodeGen/X86/xray-tail-call-sled.ll
Modified: llvm/trunk/include/llvm/CodeGen/AsmPrinter.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/AsmPrinter.h?rev=302109&r1=302108&r2=302109&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/AsmPrinter.h (original)
+++ llvm/trunk/include/llvm/CodeGen/AsmPrinter.h Wed May 3 22:37:57 2017
@@ -242,7 +242,7 @@ public:
};
// All the sleds to be emitted.
- std::vector<XRayFunctionEntry> Sleds;
+ SmallVector<XRayFunctionEntry, 4> Sleds;
// Helper function to record a given XRay sled.
void recordSled(MCSymbol *Sled, const MachineInstr &MI, SledKind Kind);
Modified: llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp?rev=302109&r1=302108&r2=302109&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp (original)
+++ llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp Wed May 3 22:37:57 2017
@@ -2761,37 +2761,63 @@ void AsmPrinter::emitXRayTable() {
auto PrevSection = OutStreamer->getCurrentSectionOnly();
auto Fn = MF->getFunction();
- MCSection *Section = nullptr;
+ MCSection *InstMap = nullptr;
+ MCSection *FnSledIndex = nullptr;
if (MF->getSubtarget().getTargetTriple().isOSBinFormatELF()) {
if (Fn->hasComdat()) {
- Section = OutContext.getELFSection("xray_instr_map", ELF::SHT_PROGBITS,
+ InstMap = OutContext.getELFSection("xray_instr_map", ELF::SHT_PROGBITS,
ELF::SHF_ALLOC | ELF::SHF_GROUP, 0,
Fn->getComdat()->getName());
+ FnSledIndex = OutContext.getELFSection("xray_fn_idx", ELF::SHT_PROGBITS,
+ ELF::SHF_ALLOC | ELF::SHF_GROUP, 0,
+ Fn->getComdat()->getName());
} else {
- Section = OutContext.getELFSection("xray_instr_map", ELF::SHT_PROGBITS,
+ InstMap = OutContext.getELFSection("xray_instr_map", ELF::SHT_PROGBITS,
ELF::SHF_ALLOC);
+ FnSledIndex = OutContext.getELFSection("xray_fn_idx", ELF::SHT_PROGBITS,
+ ELF::SHF_ALLOC);
}
} else if (MF->getSubtarget().getTargetTriple().isOSBinFormatMachO()) {
- Section = OutContext.getMachOSection("__DATA", "xray_instr_map", 0,
+ InstMap = OutContext.getMachOSection("__DATA", "xray_instr_map", 0,
SectionKind::getReadOnlyWithRel());
+ FnSledIndex = OutContext.getMachOSection("__DATA", "xray_fn_idx", 0,
+ SectionKind::getReadOnlyWithRel());
} else {
llvm_unreachable("Unsupported target");
}
// Before we switch over, we force a reference to a label inside the
- // xray_instr_map section. Since this function is always called just
- // before the function's end, we assume that this is happening after
- // the last return instruction.
-
+ // xray_instr_map and xray_fn_idx sections. Since this function is always
+ // called just before the function's end, we assume that this is happening
+ // after the last return instruction. We also use the synthetic label in the
+ // xray_inster_map as a delimeter for the range of sleds for this function in
+ // the index.
auto WordSizeBytes = MAI->getCodePointerSize();
- MCSymbol *Tmp = OutContext.createTempSymbol("xray_synthetic_", true);
+ MCSymbol *SledsStart = OutContext.createTempSymbol("xray_synthetic_", true);
+ MCSymbol *IdxRef = OutContext.createTempSymbol("xray_fn_idx_synth_", true);
OutStreamer->EmitCodeAlignment(16);
- OutStreamer->EmitSymbolValue(Tmp, WordSizeBytes, false);
- OutStreamer->SwitchSection(Section);
- OutStreamer->EmitLabel(Tmp);
+ OutStreamer->EmitSymbolValue(SledsStart, WordSizeBytes, false);
+ OutStreamer->EmitSymbolValue(IdxRef, WordSizeBytes, false);
+
+ // Now we switch to the instrumentation map section. Because this is done
+ // per-function, we are able to create an index entry that will represent the
+ // range of sleds associated with a function.
+ OutStreamer->SwitchSection(InstMap);
+ OutStreamer->EmitLabel(SledsStart);
for (const auto &Sled : Sleds)
Sled.emit(WordSizeBytes, OutStreamer.get(), CurrentFnSym);
+ MCSymbol *SledsEnd = OutContext.createTempSymbol("xray_synthetic_end", true);
+ OutStreamer->EmitLabel(SledsEnd);
+ // We then emit a single entry in the index per function. We use the symbols
+ // that bound the instrumentation map as the range for a specific function.
+ // Each entry here will be 16-byte aligned, as we're writing down two
+ // pointers.
+ OutStreamer->SwitchSection(FnSledIndex);
+ OutStreamer->EmitCodeAlignment(16);
+ OutStreamer->EmitLabel(IdxRef);
+ OutStreamer->EmitSymbolValue(SledsStart, WordSizeBytes);
+ OutStreamer->EmitSymbolValue(SledsEnd, WordSizeBytes);
OutStreamer->SwitchSection(PrevSection);
Sleds.clear();
}
Modified: llvm/trunk/test/CodeGen/AArch64/xray-attribute-instrumentation.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AArch64/xray-attribute-instrumentation.ll?rev=302109&r1=302108&r2=302109&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/AArch64/xray-attribute-instrumentation.ll (original)
+++ llvm/trunk/test/CodeGen/AArch64/xray-attribute-instrumentation.ll Wed May 3 22:37:57 2017
@@ -26,6 +26,7 @@ define i32 @foo() nounwind noinline uwta
}
; CHECK: .p2align 4
; CHECK-NEXT: .xword .Lxray_synthetic_0
+; CHECK-NEXT: .xword .Lxray_fn_idx_synth_0
; CHECK-NEXT: .section xray_instr_map,{{.*}}
; CHECK-LABEL: Lxray_synthetic_0:
; CHECK: .xword .Lxray_sled_0
Modified: llvm/trunk/test/CodeGen/AArch64/xray-tail-call-sled.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AArch64/xray-tail-call-sled.ll?rev=302109&r1=302108&r2=302109&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/AArch64/xray-tail-call-sled.ll (original)
+++ llvm/trunk/test/CodeGen/AArch64/xray-tail-call-sled.ll Wed May 3 22:37:57 2017
@@ -29,10 +29,16 @@ define i32 @callee() nounwind noinline u
}
; CHECK: .p2align 4
; CHECK-NEXT: .xword .Lxray_synthetic_0
+; CHECK-NEXT: .xword .Lxray_fn_idx_synth_0
; CHECK-NEXT: .section xray_instr_map,{{.*}}
; CHECK-LABEL: Lxray_synthetic_0:
; CHECK: .xword .Lxray_sled_0
; CHECK: .xword .Lxray_sled_1
+; CHECK-LABEL: Lxray_synthetic_end0:
+; CHECK: .section xray_fn_idx,{{.*}}
+; CHECK-LABEL: Lxray_fn_idx_synth_0:
+; CHECK: .xword .Lxray_synthetic_0
+; CHECK-NEXT: .xword .Lxray_synthetic_end0
define i32 @caller() nounwind noinline uwtable "function-instrument"="xray-always" {
; CHECK: .p2align 2
@@ -63,7 +69,13 @@ define i32 @caller() nounwind noinline u
}
; CHECK: .p2align 4
; CHECK-NEXT: .xword .Lxray_synthetic_1
+; CHECK-NEXT: .xword .Lxray_fn_idx_synth_1
; CHECK-NEXT: .section xray_instr_map,{{.*}}
; CHECK-LABEL: Lxray_synthetic_1:
; CHECK: .xword .Lxray_sled_2
; CHECK: .xword .Lxray_sled_3
+; CHECK-LABEL: Lxray_synthetic_end1:
+; CHECK: .section xray_fn_idx,{{.*}}
+; CHECK-LABEL: Lxray_fn_idx_synth_1:
+; CHECK: .xword .Lxray_synthetic_1
+; CHECK-NEXT: .xword .Lxray_synthetic_end1
Modified: llvm/trunk/test/CodeGen/ARM/xray-armv6-attribute-instrumentation.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/ARM/xray-armv6-attribute-instrumentation.ll?rev=302109&r1=302108&r2=302109&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/ARM/xray-armv6-attribute-instrumentation.ll (original)
+++ llvm/trunk/test/CodeGen/ARM/xray-armv6-attribute-instrumentation.ll Wed May 3 22:37:57 2017
@@ -25,7 +25,13 @@ define i32 @foo() nounwind noinline uwta
}
; CHECK: .p2align 4
; CHECK-NEXT: .long {{.*}}Lxray_synthetic_0
+; CHECK-NEXT: .long {{.*}}Lxray_fn_idx_synth_0
; CHECK-NEXT: .section {{.*}}xray_instr_map{{.*}}
; CHECK-LABEL: Lxray_synthetic_0:
; CHECK: .long {{.*}}Lxray_sled_0
; CHECK: .long {{.*}}Lxray_sled_1
+; CHECK-LABEL: Lxray_synthetic_end0:
+; CHECK: .section {{.*}}xray_fn_idx{{.*}}
+; CHECK-LABEL: Lxray_fn_idx_synth_0:
+; CHECK: .long {{.*}}Lxray_synthetic_0
+; CHECK-NEXT: .long {{.*}}Lxray_synthetic_end0
Modified: llvm/trunk/test/CodeGen/ARM/xray-armv7-attribute-instrumentation.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/ARM/xray-armv7-attribute-instrumentation.ll?rev=302109&r1=302108&r2=302109&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/ARM/xray-armv7-attribute-instrumentation.ll (original)
+++ llvm/trunk/test/CodeGen/ARM/xray-armv7-attribute-instrumentation.ll Wed May 3 22:37:57 2017
@@ -25,7 +25,14 @@ define i32 @foo() nounwind noinline uwta
}
; CHECK: .p2align 4
; CHECK-NEXT: .long {{.*}}Lxray_synthetic_0
+; CHECK-NEXT: .long {{.*}}Lxray_fn_idx_synth_0
; CHECK-NEXT: .section {{.*}}xray_instr_map{{.*}}
; CHECK-LABEL: Lxray_synthetic_0:
; CHECK: .long {{.*}}Lxray_sled_0
; CHECK: .long {{.*}}Lxray_sled_1
+; CHECK-LABEL: Lxray_synthetic_end0:
+; CHECK: .section {{.*}}xray_fn_idx{{.*}}
+; CHECK-LABEL: Lxray_fn_idx_synth_0:
+; CHECK: .long {{.*}}xray_synthetic_0
+; CHECK-NEXT: .long {{.*}}xray_synthetic_end0
+
Modified: llvm/trunk/test/CodeGen/X86/xray-attribute-instrumentation.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/xray-attribute-instrumentation.ll?rev=302109&r1=302108&r2=302109&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/xray-attribute-instrumentation.ll (original)
+++ llvm/trunk/test/CodeGen/X86/xray-attribute-instrumentation.ll Wed May 3 22:37:57 2017
@@ -15,10 +15,17 @@ define i32 @foo() nounwind noinline uwta
}
; CHECK: .p2align 4, 0x90
; CHECK-NEXT: .quad {{.*}}xray_synthetic_0
+; CHECK-NEXT: .quad {{.*}}xray_fn_idx_synth_0
; CHECK-NEXT: .section {{.*}}xray_instr_map
; CHECK-LABEL: Lxray_synthetic_0:
; CHECK: .quad {{.*}}xray_sled_0
; CHECK: .quad {{.*}}xray_sled_1
+; CHECK-LABEL: Lxray_synthetic_end0:
+; CHECK: .section {{.*}}xray_fn_idx
+; CHECK-LABEL: Lxray_fn_idx_synth_0:
+; CHECK: .quad {{.*}}xray_synthetic_0
+; CHECK-NEXT: .quad {{.*}}xray_synthetic_end0
+
; We test multiple returns in a single function to make sure we're getting all
; of them with XRay instrumentation.
@@ -46,8 +53,14 @@ NotEqual:
}
; CHECK: .p2align 4, 0x90
; CHECK-NEXT: .quad {{.*}}xray_synthetic_1
+; CHECK-NEXT: .quad {{.*}}xray_fn_idx_synth_1
; CHECK-NEXT: .section {{.*}}xray_instr_map
; CHECK-LABEL: Lxray_synthetic_1:
; CHECK: .quad {{.*}}xray_sled_2
; CHECK: .quad {{.*}}xray_sled_3
; CHECK: .quad {{.*}}xray_sled_4
+; CHECK-LABEL: Lxray_synthetic_end1:
+; CHECK: .section {{.*}}xray_fn_idx
+; CHECK-LABEL: Lxray_fn_idx_synth_1:
+; CHECK: .quad {{.*}}xray_synthetic_1
+; CHECK-NEXT: .quad {{.*}}xray_synthetic_end1
Modified: llvm/trunk/test/CodeGen/X86/xray-tail-call-sled.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/xray-tail-call-sled.ll?rev=302109&r1=302108&r2=302109&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/xray-tail-call-sled.ll (original)
+++ llvm/trunk/test/CodeGen/X86/xray-tail-call-sled.ll Wed May 3 22:37:57 2017
@@ -14,11 +14,17 @@ define i32 @callee() nounwind noinline u
; CHECK-NEXT: nopw %cs:512(%rax,%rax)
}
; CHECK: .p2align 4, 0x90
-; CHECK-NEXT: .quad {{.*}}xray_synthetic_0
+; CHECK-NEXT: .quad {{.*}}xray_synthetic_0{{.*}}
+; CHECK-NEXT: .quad {{.*}}xray_fn_idx_synth_0{{.*}}
; CHECK-NEXT: .section {{.*}}xray_instr_map
; CHECK-LABEL: Lxray_synthetic_0:
; CHECK: .quad {{.*}}xray_sled_0
; CHECK: .quad {{.*}}xray_sled_1
+; CHECK-LABEL: Lxray_synthetic_end0:
+; CHECK-NEXT: .section {{.*}}xray_fn_idx
+; CHECK-LABEL: Lxray_fn_idx_synth_0:
+; CHECK: .quad {{.*}}xray_synthetic_0
+; CHECK-NEXT: .quad {{.*}}xray_synthetic_end0
define i32 @caller() nounwind noinline uwtable "function-instrument"="xray-always" {
; CHECK: .p2align 1, 0x90
@@ -36,7 +42,13 @@ define i32 @caller() nounwind noinline u
ret i32 %retval
}
; CHECK: .p2align 4, 0x90
-; CHECK-NEXT: .quad {{.*}}xray_synthetic_1
+; CHECK-NEXT: .quad {{.*}}xray_synthetic_1{{.*}}
+; CHECK-NEXT: .quad {{.*}}xray_fn_idx_synth_1{{.*}}
; CHECK-LABEL: Lxray_synthetic_1:
; CHECK: .quad {{.*}}xray_sled_2
; CHECK: .quad {{.*}}xray_sled_3
+; CHECK-LABEL: Lxray_synthetic_end1:
+; CHECK: .section {{.*}}xray_fn_idx
+; CHECK-LABEL: Lxray_fn_idx_synth_1:
+; CHECK: .quad {{.*}}xray_synthetic_1
+; CHECK: .quad {{.*}}xray_synthetic_end1
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