[Codegen] Make sure kill flags are not incorrect from removed machine phi's
We need to clear the kill flags on both SingleValReg and OldReg, to ensure they remain
conservatively correct.
Differential Revision: https://reviews.llvm.org/D58114
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@353847 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/OptimizePHIs.cpp b/lib/CodeGen/OptimizePHIs.cpp
index fb2340b..c70b622 100644
--- a/lib/CodeGen/OptimizePHIs.cpp
+++ b/lib/CodeGen/OptimizePHIs.cpp
@@ -181,11 +181,12 @@
if (!MRI->constrainRegClass(SingleValReg, MRI->getRegClass(OldReg)))
continue;
- // for the case SingleValReg taken from copy instr
- MRI->clearKillFlags(SingleValReg);
-
MRI->replaceRegWith(OldReg, SingleValReg);
MI->eraseFromParent();
+
+ // The kill flags on OldReg and SingleValReg may no longer be correct.
+ MRI->clearKillFlags(SingleValReg);
+
++NumPHICycles;
Changed = true;
continue;
diff --git a/test/CodeGen/Thumb/opt-phis.mir b/test/CodeGen/Thumb/opt-phis.mir
new file mode 100644
index 0000000..e3d0a8b
--- /dev/null
+++ b/test/CodeGen/Thumb/opt-phis.mir
@@ -0,0 +1,38 @@
+# RUN: llc -mtriple thumbv6m-none-eabi -run-pass=opt-phis -verify-machineinstrs -o - %s | FileCheck %s
+--- |
+ target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+ target triple = "thumbv6m-arm-none-eabi"
+
+ define i32 @funca() { unreachable }
+
+...
+---
+name: funca
+tracksRegLiveness: true
+body: |
+ bb.0:
+ successors: %bb.2(0x40000000), %bb.3(0x40000000)
+
+ %0:tgpr, dead $cpsr = tMOVi8 255, 14, $noreg
+ %1:tgpr, dead $cpsr = tMOVi8 128, 14, $noreg
+ tCMPi8 %0, 0, 14, $noreg, implicit-def $cpsr
+ tBcc %bb.3, 1, $cpsr
+
+ bb.2:
+ successors: %bb.3(0x80000000)
+
+ bb.3:
+ successors: %bb.0(0x80000000)
+
+ %2:tgpr = PHI %0, %bb.2, %0, %bb.0
+ %3:tgpr, $cpsr = tSUBrr %1, killed %2, 14, $noreg
+ %4:tgpr, $cpsr = tADDrr killed %3, killed %0, 14, $noreg
+ tB %bb.0, 14, $noreg
+
+# Make sure the kill flags are not incorrect
+# CHECK-LABEL: name: funca
+# CHECK-NOT: PHI
+# CHECK: tSUBrr %1, %0
+# CHECK: tADDrr killed %3, %0
+
+...
