LiveRangeCalc: Fix reporting of invalid vreg usage in liveness calculation

Machine programs need a definition of each vreg before reaching a use
(the definition may come from an IMPLICIT_DEF instruction). This class
of errors is not detected by the MachineVerifier because of efficiency
concerns. LiveRangeCalc used to report these problems, make it do that
again (followup to r279625).

Also use report_fatal_error() instead of llvm_unreachable() as the error
reporting is only present in asserts build anyway.

llvm-svn: 281914

2 files changed, 34 insertions, 3 deletions

diff --git a/llvm/lib/CodeGen/LiveRangeCalc.cpp b/llvm/lib/CodeGen/LiveRangeCalc.cpp
index 281cf1fb5a8..9f6262bd9a9 100644
--- a/llvm/lib/CodeGen/LiveRangeCalc.cpp
+++ b/llvm/lib/CodeGen/LiveRangeCalc.cpp
@@ -361,14 +361,14 @@ bool LiveRangeCalc::findReachingDefs(LiveRange &LR, MachineBasicBlock &UseMBB,
     MachineBasicBlock *MBB = MF->getBlockNumbered(WorkList[i]);
 
 #ifndef NDEBUG
-    if (Undefs.size() > 0 && MBB->pred_empty()) {
+    if (MBB->pred_empty()) {
       MBB->getParent()->verify();
       errs() << "Use of " << PrintReg(PhysReg)
              << " does not have a corresponding definition on every path:\n";
       const MachineInstr *MI = Indexes->getInstructionFromIndex(Use);
       if (MI != nullptr)
         errs() << Use << " " << *MI;
-      llvm_unreachable("Use not jointly dominated by defs.");
+      report_fatal_error("Use not jointly dominated by defs.");
     }
 
     if (TargetRegisterInfo::isPhysicalRegister(PhysReg) &&
@@ -378,7 +378,7 @@ bool LiveRangeCalc::findReachingDefs(LiveRange &LR, MachineBasicBlock &UseMBB,
       errs() << "The register " << PrintReg(PhysReg, TRI)
              << " needs to be live in to BB#" << MBB->getNumber()
              << ", but is missing from the live-in list.\n";
-      llvm_unreachable("Invalid global physical register");
+      report_fatal_error("Invalid global physical register");
     }
 #endif
     FoundUndef |= MBB->pred_empty();
diff --git a/llvm/test/CodeGen/X86/invalid-liveness.mir b/llvm/test/CodeGen/X86/invalid-liveness.mir
new file mode 100644
index 00000000000..ca862472ba8
--- /dev/null
+++ b/llvm/test/CodeGen/X86/invalid-liveness.mir
@@ -0,0 +1,31 @@
+# RUN: not llc -march=x86 -run-pass liveintervals -o - %s 2>&1 | FileCheck %s
+# REQUIRES: asserts
+
+--- |
+  define void @func() { ret void }
+...
+---
+# Liveness calculation should detect that we do not have a definition for vreg0
+# on all paths; In this example a def for vreg0 is missing when jumping from
+# bb.0 to bb.3.
+#
+# CHECK: Use of %vreg0 does not have a corresponding definition on every path
+# CHECK: ERROR: Use not jointly dominated by defs.
+name: func
+registers:
+  - { id: 0, class: gr32 }
+body: |
+  bb.0:
+    successors: %bb.2, %bb.3
+    JG_1 %bb.2, implicit %eflags
+    JMP_1 %bb.3
+
+  bb.2:
+    successors: %bb.3
+    %0 = IMPLICIT_DEF
+    JMP_1 %bb.3
+
+  bb.3:
+    %eax = COPY %0
+    RETQ %eax
+...