[PATCH] D27913: [XRay] Fix assertion failure on empty machine basic blocks (PR 31424)
Dean Michael Berris via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Mon Dec 19 00:24:14 PST 2016
dberris updated this revision to Diff 81922.
dberris marked 4 inline comments as done.
dberris added a comment.
- Do not instrument empty functions
- Add test for an empty function
https://reviews.llvm.org/D27913
Files:
lib/CodeGen/XRayInstrumentation.cpp
test/CodeGen/X86/xray-empty-firstmbb.mir
test/CodeGen/X86/xray-empty-function.mir
Index: test/CodeGen/X86/xray-empty-function.mir
===================================================================
--- /dev/null
+++ test/CodeGen/X86/xray-empty-function.mir
@@ -0,0 +1,13 @@
+# RUN: llc -run-pass xray-instrumentation -mtriple=x86_64-unknown-linux-gnu -o - %s | FileCheck %s
+#
+# Make sure we can handle empty functions.
+---
+name: empty
+tracksRegLiveness: true
+liveins:
+ - { reg: '%edi'}
+body: |
+ bb.0:
+ ; CHECK-NOT: PATCHABLE_FUNCTION_ENTER
+...
+
Index: test/CodeGen/X86/xray-empty-firstmbb.mir
===================================================================
--- /dev/null
+++ test/CodeGen/X86/xray-empty-firstmbb.mir
@@ -0,0 +1,23 @@
+# RUN: llc -run-pass xray-instrumentation -mtriple=x86_64-unknown-linux-gnu -o - %s | FileCheck %s
+#
+# Make sure we can handle empty first basic blocks.
+
+--- |
+
+ define i32 @foo() noinline uwtable "xray-instruction-threshold"="1" {
+ entry:
+ unreachable
+ }
+
+...
+
+---
+name: foo
+tracksRegLiveness: true
+liveins:
+ - { reg: '%edi'}
+body: |
+ bb.0.entry:
+ liveins: %edi
+ ; CHECK-NOT: PATCHABLE_FUNCTION_ENTER
+...
Index: lib/CodeGen/XRayInstrumentation.cpp
===================================================================
--- lib/CodeGen/XRayInstrumentation.cpp
+++ lib/CodeGen/XRayInstrumentation.cpp
@@ -129,7 +129,16 @@
return false; // Function is too small.
}
- auto &FirstMBB = *MF.begin();
+ // We look for the first non-empty MachineBasicBlock, so that we can insert
+ // the function instrumentation in the appropriate place.
+ auto MBI =
+ std::find_if(MF.begin(), MF.end(),
+ [&](const MachineBasicBlock &MBB) { return !MBB.empty(); });
+ if (MBI == MF.end())
+ return false; // The function is empty.
+
+ auto *TII = MF.getSubtarget().getInstrInfo();
+ auto &FirstMBB = *MBI;
auto &FirstMI = *FirstMBB.begin();
if (!MF.getSubtarget().isXRaySupported()) {
@@ -142,7 +151,6 @@
// First, insert an PATCHABLE_FUNCTION_ENTER as the first instruction of the
// MachineFunction.
- auto *TII = MF.getSubtarget().getInstrInfo();
BuildMI(FirstMBB, FirstMI, FirstMI.getDebugLoc(),
TII->get(TargetOpcode::PATCHABLE_FUNCTION_ENTER));
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