From: Mikael Holmen <mikael.holmen@ericsson.com>
Date: Wed, 4 Oct 2017 06:39:22 +0000 (+0000)
Subject: Revert r314879 "[UnreachableBlockElim] Use COPY if PHI input is undef"
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=66848ca5f7c1082cf2ae7f8e3f6ee55323d27714;p=llvm

Revert r314879 "[UnreachableBlockElim] Use COPY if PHI input is undef"

Build-bots broke on the new testcase. I'll investigate and fix.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@314880 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/UnreachableBlockElim.cpp b/lib/CodeGen/UnreachableBlockElim.cpp
index bdd25f29aea..407fd9b162e 100644
--- a/lib/CodeGen/UnreachableBlockElim.cpp
+++ b/lib/CodeGen/UnreachableBlockElim.cpp
@@ -207,12 +207,11 @@ bool UnreachableMachineBlockElim::runOnMachineFunction(MachineFunction &F) {
           MachineRegisterInfo &MRI = F.getRegInfo();
           unsigned InputSub = Input.getSubReg();
           if (InputSub == 0 &&
-              MRI.constrainRegClass(InputReg, MRI.getRegClass(OutputReg)) &&
-              !Input.isUndef()) {
+              MRI.constrainRegClass(InputReg, MRI.getRegClass(OutputReg))) {
             MRI.replaceRegWith(OutputReg, InputReg);
           } else {
             // The input register to the PHI has a subregister or it can't be
-            // constrained to the proper register class or it is undef:
+            // constrained to the proper register class:
             // insert a COPY instead of simply replacing the output
             // with the input.
             const TargetInstrInfo *TII = F.getSubtarget().getInstrInfo();
diff --git a/test/CodeGen/MIR/X86/unreachable-mbb-undef-phi.mir b/test/CodeGen/MIR/X86/unreachable-mbb-undef-phi.mir
deleted file mode 100644
index 1abfb19d638..00000000000
--- a/test/CodeGen/MIR/X86/unreachable-mbb-undef-phi.mir
+++ /dev/null
@@ -1,38 +0,0 @@
-# RUN: llc %s -o - -run-pass=processimpdefs -run-pass=unreachable-mbb-elimination | FileCheck %s
----
-name:            f
-tracksRegLiveness: true
-registers:
-  - { id: 0, class: gr32, preferred-register: '' }
-  - { id: 1, class: gr32, preferred-register: '' }
-  - { id: 2, class: gr32, preferred-register: '' }
-body:             |
-  bb.0:
-    %0 = IMPLICIT_DEF
-    JMP_1 %bb.1
-
-  bb.1:
-    %1 = PHI %0, %bb.0, %2, %bb.2
-    %2 = ADD32ri8 killed %1, 1, implicit-def %eflags
-    JMP_1 %bb.3
-
-  bb.2:
-    JMP_1 %bb.1
-
-  bb.3:
-...
-
-# bb2 above is dead and should be removed and the PHI should be replaced with a
-# COPY from an undef value since the bb0 value in the PHI is undef.
-
-# CHECK:  bb.0:
-# CHECK:    successors: %bb.1
-# CHECK:    JMP_1 %bb.1
-
-# CHECK:  bb.1:
-# CHECK:    successors: %bb.2
-# CHECK:    [[TMP1:%[0-9]+]] = COPY undef %{{[0-9]+}}
-# CHECK:    %{{[0-9]+}} = ADD32ri8 killed [[TMP1]], 1
-# CHECK:    JMP_1 %bb.2
-
-# CHECK:  bb.2: