[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 fb2340b722190f77919f4e1cfdc492a962dac93a..c70b62252139e7ccc8474bd801f12d58235422f5 100644 (file)
--- a/lib/CodeGen/OptimizePHIs.cpp
+++ b/lib/CodeGen/OptimizePHIs.cpp
@@ -181,11 +181,12 @@ bool OptimizePHIs::OptimizeBB(MachineBasicBlock &MBB) {
       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 (file)
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
+
+...