[llvm] f034c98 - [PowerPC] mark dead def for ctr be clobber.

[Chen Zheng via llvm-commits]

Author: Chen Zheng
Date: 2022-11-18T06:55:42Z
New Revision: f034c98af000f9b1d260bee036ecf653062e1e90

URL: https://github.com/llvm/llvm-project/commit/f034c98af000f9b1d260bee036ecf653062e1e90
DIFF: https://github.com/llvm/llvm-project/commit/f034c98af000f9b1d260bee036ecf653062e1e90.diff

LOG: [PowerPC] mark dead def for ctr be clobber.

TLS pseudo ADDIStlsgdHA will have such def. This dead def should
also prevent PPC from generating CTR loops.

Added: 
    

Modified: 
    llvm/lib/Target/PowerPC/PPCCTRLoops.cpp
    llvm/test/CodeGen/PowerPC/ctrloops64.mir

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/PowerPC/PPCCTRLoops.cpp b/llvm/lib/Target/PowerPC/PPCCTRLoops.cpp
index 87d62f1619bc3..6de366c2bb664 100644
--- a/llvm/lib/Target/PowerPC/PPCCTRLoops.cpp
+++ b/llvm/lib/Target/PowerPC/PPCCTRLoops.cpp
@@ -114,14 +114,10 @@ bool PPCCTRLoops::isCTRClobber(MachineInstr *MI, bool CheckReads) const {
     // CTR defination inside the callee of a call instruction will not impact
     // the defination of MTCTRloop, so we can use definesRegister() for the
     // check, no need to check the regmask.
-    return (MI->definesRegister(PPC::CTR) &&
-            !MI->registerDefIsDead(PPC::CTR)) ||
-           (MI->definesRegister(PPC::CTR8) &&
-            !MI->registerDefIsDead(PPC::CTR8));
+    return MI->definesRegister(PPC::CTR) || MI->definesRegister(PPC::CTR8);
   }
 
-  if ((MI->modifiesRegister(PPC::CTR) && !MI->registerDefIsDead(PPC::CTR)) ||
-      (MI->modifiesRegister(PPC::CTR8) && !MI->registerDefIsDead(PPC::CTR8)))
+  if (MI->modifiesRegister(PPC::CTR) || MI->modifiesRegister(PPC::CTR8))
     return true;
 
   if (MI->getDesc().isCall())

diff  --git a/llvm/test/CodeGen/PowerPC/ctrloops64.mir b/llvm/test/CodeGen/PowerPC/ctrloops64.mir
index 8e50c555195b1..de37e6accd40e 100644
--- a/llvm/test/CodeGen/PowerPC/ctrloops64.mir
+++ b/llvm/test/CodeGen/PowerPC/ctrloops64.mir
@@ -345,3 +345,30 @@ body:             |
 
     BLR8 implicit $lr8, implicit $rm
 ...
+---
+name:            test_fail_dead_def_in_preheader
+# CHECK: test_fail_dead_def_in_preheader
+tracksRegLiveness: true
+body:             |
+  bb.0.entry:
+
+    %0:g8rc = LI8 2048
+    %1:g8rc = LI8 1024
+    MTCTR8loop killed %0:g8rc, implicit-def dead $ctr8
+    MTCTR8 killed %1:g8rc, implicit-def dead $ctr8
+    ; CHECK-NOT: MTCTR8loop
+    ; CHECK-NOT: BDNZ8
+    ; CHECK: ADDI8
+    ; CHECK: CMPLDI
+    ; CHECK: BC
+
+  bb.1:
+
+    %2:crbitrc = DecreaseCTR8loop 1, implicit-def dead $ctr8, implicit $ctr8
+    BC killed %2:crbitrc, %bb.1
+    B %bb.2
+
+  bb.2:
+
+    BLR8 implicit $lr8, implicit $rm
+...