From 6a963f76cad7ecaf93c2f53359069ced354f340c Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault@amd.com>
Date: Fri, 21 Jul 2017 23:56:13 +0000
Subject: [PATCH] RA: Remove assert on empty live intervals

This is possible if there is an undef use when
splitting the vreg during spilling.

Fixes bug 33620.

llvm-svn: 308808
---
 llvm/lib/CodeGen/RegAllocBase.cpp             |  1 -
 .../AMDGPU/spill-empty-live-interval.mir      | 40 +++++++++++++++++++
 2 files changed, 40 insertions(+), 1 deletion(-)
 create mode 100644 llvm/test/CodeGen/AMDGPU/spill-empty-live-interval.mir

diff --git a/llvm/lib/CodeGen/RegAllocBase.cpp b/llvm/lib/CodeGen/RegAllocBase.cpp
index a7b7a9f8ab15..5a80bd95d6e4 100644
--- a/llvm/lib/CodeGen/RegAllocBase.cpp
+++ b/llvm/lib/CodeGen/RegAllocBase.cpp
@@ -144,7 +144,6 @@ void RegAllocBase::allocatePhysRegs() {
         continue;
       }
       DEBUG(dbgs() << "queuing new interval: " << *SplitVirtReg << "\n");
-      assert(!SplitVirtReg->empty() && "expecting non-empty interval");
       assert(TargetRegisterInfo::isVirtualRegister(SplitVirtReg->reg) &&
              "expect split value in virtual register");
       enqueue(SplitVirtReg);
diff --git a/llvm/test/CodeGen/AMDGPU/spill-empty-live-interval.mir b/llvm/test/CodeGen/AMDGPU/spill-empty-live-interval.mir
new file mode 100644
index 000000000000..68bd8c45dcb0
--- /dev/null
+++ b/llvm/test/CodeGen/AMDGPU/spill-empty-live-interval.mir
@@ -0,0 +1,40 @@
+# RUN: llc -mtriple=amdgcn-amd-amdhsa-opencl -verify-machineinstrs -stress-regalloc=1 -start-before=simple-register-coalescing -stop-after=greedy -o - %s | FileCheck %s
+# https://bugs.llvm.org/show_bug.cgi?id=33620
+
+---
+# This would assert due to the empty live interval created for %vreg9
+# on the last S_NOP with an undef subreg use.
+
+# CHECK-LABEL: name: expecting_non_empty_interval
+
+# CHECK: undef %7.sub1 = V_MAC_F32_e32 0, undef %1, undef %7.sub1, implicit %exec
+# CHECK-NEXT: SI_SPILL_V64_SAVE %7, %stack.0, %sgpr0_sgpr1_sgpr2_sgpr3, %sgpr5, 0, implicit %exec :: (store 8 into %stack.0, align 4)
+# CHECK-NEXT: undef %5.sub1 = V_MOV_B32_e32 1786773504, implicit %exec
+# CHECK-NEXT: dead %2 = V_MUL_F32_e32 0, %5.sub1, implicit %exec
+
+# CHECK: S_NOP 0, implicit %6.sub1
+# CHECK-NEXT: %8 = SI_SPILL_V64_RESTORE %stack.0, %sgpr0_sgpr1_sgpr2_sgpr3, %sgpr5, 0, implicit %exec :: (load 8 from %stack.0, align 4)
+# CHECK-NEXT: S_NOP 0, implicit %8.sub1
+# CHECK-NEXT: S_NOP 0, implicit undef %9.sub0
+
+name: expecting_non_empty_interval
+tracksRegLiveness: true
+registers:
+  - { id: 0, class: vreg_64, preferred-register: '' }
+  - { id: 1, class: vgpr_32, preferred-register: '' }
+  - { id: 2, class: vgpr_32, preferred-register: '' }
+  - { id: 3, class: vreg_64, preferred-register: '' }
+body:             |
+  bb.0:
+    successors: %bb.1
+    undef %0.sub1 = V_MAC_F32_e32 0, undef %1, undef %0.sub1, implicit %exec
+    undef %3.sub1 = V_MOV_B32_e32 1786773504, implicit %exec
+    dead %2 = V_MUL_F32_e32 0, %3.sub1, implicit %exec
+
+  bb.1:
+    S_NOP 0, implicit %3.sub1
+    S_NOP 0, implicit %0.sub1
+    S_NOP 0, implicit undef %0.sub0
+    S_ENDPGM
+
+...
-- 
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