[llvm] 874fbe2 - [MachineSink] Clear kill flags on operands outside loop

[Carl Ritson via llvm-commits]

Author: Carl Ritson
Date: 2022-06-24T14:02:48+09:00
New Revision: 874fbe2cbbe6f548858d0c8e804eb66ca477697c

URL: https://github.com/llvm/llvm-project/commit/874fbe2cbbe6f548858d0c8e804eb66ca477697c
DIFF: https://github.com/llvm/llvm-project/commit/874fbe2cbbe6f548858d0c8e804eb66ca477697c.diff

LOG: [MachineSink] Clear kill flags on operands outside loop

If an instruction is sunk into a loop then any kill flags on
operands declared outside the loop must be cleared as these
will be live for all loop iterations.

Fixes #46827

Reviewed By: MatzeB

Differential Revision: https://reviews.llvm.org/D126754

Added: 
    llvm/test/CodeGen/SystemZ/machinelicm-sunk-kill-flags.mir

Modified: 
    llvm/lib/CodeGen/MachineSink.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/CodeGen/MachineSink.cpp b/llvm/lib/CodeGen/MachineSink.cpp
index 3f2330b925774..006ba9273dfbe 100644
--- a/llvm/lib/CodeGen/MachineSink.cpp
+++ b/llvm/lib/CodeGen/MachineSink.cpp
@@ -1289,6 +1289,12 @@ bool MachineSinking::SinkIntoCycle(MachineCycle *Cycle, MachineInstr &I) {
   SinkBlock->splice(SinkBlock->SkipPHIsAndLabels(SinkBlock->begin()), Preheader,
                     I);
 
+  // Conservatively clear any kill flags on uses of sunk instruction
+  for (MachineOperand &MO : I.operands()) {
+    if (MO.isReg() && MO.readsReg())
+      RegsToClearKillFlags.insert(MO.getReg());
+  }
+
   // The instruction is moved from its basic block, so do not retain the
   // debug information.
   assert(!I.isDebugInstr() && "Should not sink debug inst");

diff  --git a/llvm/test/CodeGen/SystemZ/machinelicm-sunk-kill-flags.mir b/llvm/test/CodeGen/SystemZ/machinelicm-sunk-kill-flags.mir
new file mode 100644
index 0000000000000..43c286a830b42
--- /dev/null
+++ b/llvm/test/CodeGen/SystemZ/machinelicm-sunk-kill-flags.mir
@@ -0,0 +1,75 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple=s390x-linux-gnu -sink-insts-to-avoid-spills -verify-machineinstrs -run-pass=machine-sink -o - %s | FileCheck %s
+
+# Test kill flags are cleared after sinking operations into cycle during MachineLICM.
+
+--- |
+  target datalayout = "E-m:e-i1:8:16-i8:8:16-i64:64-f128:64-a:8:16-n32:64"
+  target triple = "s390x-unknown-linux-gnu"
+
+  %0 = type <{ i32, [3 x i8] }>
+
+  @b = external dso_local global [1 x %0], align 2
+
+  define dso_local void @c() local_unnamed_addr {
+    ret void
+  }
+
+...
+---
+name:            c
+tracksRegLiveness: true
+body:             |
+  ; CHECK-LABEL: name: c
+  ; CHECK: bb.0:
+  ; CHECK-NEXT:   successors: %bb.1(0x80000000)
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   [[LARL:%[0-9]+]]:addr64bit = LARL @b
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.1:
+  ; CHECK-NEXT:   successors: %bb.1(0x80000000)
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   [[LA:%[0-9]+]]:gr64bit = LA [[LARL]], 49, $noreg
+  ; CHECK-NEXT:   [[LGHI:%[0-9]+]]:gr64bit = LGHI 7
+  ; CHECK-NEXT:   [[DEF:%[0-9]+]]:gr64bit = IMPLICIT_DEF
+  ; CHECK-NEXT:   [[DEF1:%[0-9]+]]:gr64bit = IMPLICIT_DEF
+  ; CHECK-NEXT:   ADJCALLSTACKDOWN 0, 0
+  ; CHECK-NEXT:   $r2d = COPY [[DEF]]
+  ; CHECK-NEXT:   $r3d = COPY [[LA]]
+  ; CHECK-NEXT:   $r4d = COPY [[LGHI]]
+  ; CHECK-NEXT:   CallBRASL &memcpy, $r2d, $r3d, $r4d, csr_systemz_elf, implicit-def dead $r14d, implicit-def dead $cc, implicit $fpc, implicit-def $r2d
+  ; CHECK-NEXT:   ADJCALLSTACKUP 0, 0
+  ; CHECK-NEXT:   ADJCALLSTACKDOWN 0, 0
+  ; CHECK-NEXT:   $r2d = COPY [[DEF1]]
+  ; CHECK-NEXT:   $r3d = COPY [[LA]]
+  ; CHECK-NEXT:   $r4d = COPY [[LGHI]]
+  ; CHECK-NEXT:   CallBRASL &memcpy, $r2d, $r3d, $r4d, csr_systemz_elf, implicit-def dead $r14d, implicit-def dead $cc, implicit $fpc, implicit-def $r2d
+  ; CHECK-NEXT:   ADJCALLSTACKUP 0, 0
+  ; CHECK-NEXT:   J %bb.1
+  bb.0:
+    successors: %bb.1(0x80000000)
+
+    %1:addr64bit = LARL @b
+    %0:gr64bit = LA killed %1, 49, $noreg
+    %2:gr64bit = LGHI 7
+    %3:gr64bit = IMPLICIT_DEF
+    %5:gr64bit = IMPLICIT_DEF
+
+  bb.1:
+    successors: %bb.1(0x80000000)
+
+    ADJCALLSTACKDOWN 0, 0
+    $r2d = COPY %3
+    $r3d = COPY %0
+    $r4d = COPY %2
+    CallBRASL &memcpy, $r2d, $r3d, $r4d, csr_systemz_elf, implicit-def dead $r14d, implicit-def dead $cc, implicit $fpc, implicit-def $r2d
+    ADJCALLSTACKUP 0, 0
+    ADJCALLSTACKDOWN 0, 0
+    $r2d = COPY %5
+    $r3d = COPY %0
+    $r4d = COPY %2
+    CallBRASL &memcpy, $r2d, $r3d, $r4d, csr_systemz_elf, implicit-def dead $r14d, implicit-def dead $cc, implicit $fpc, implicit-def $r2d
+    ADJCALLSTACKUP 0, 0
+    J %bb.1
+
+...