[X86] Remove EFLAGS from live-in lists in X86FlagsCopyLowering.

When EFLAGS is no longer live into a basic block, remove it from the live-in
list.

Fixes https://bugs.llvm.org/show_bug.cgi?id=44462.

Review: Craig Topper

Differential Revision: https://reviews.llvm.org/D71375

2 files changed, 95 insertions, 0 deletions

diff --git a/llvm/lib/Target/X86/X86FlagsCopyLowering.cpp b/llvm/lib/Target/X86/X86FlagsCopyLowering.cpp
index 0915a1532df..b1d2de29c89 100644
--- a/llvm/lib/Target/X86/X86FlagsCopyLowering.cpp
+++ b/llvm/lib/Target/X86/X86FlagsCopyLowering.cpp
@@ -702,6 +702,9 @@ bool X86FlagsCopyLoweringPass::runOnMachineFunction(MachineFunction &MF) {
           }
 
           Blocks.push_back(SuccMBB);
+
+          // After this, EFLAGS will be recreated before each use.
+          SuccMBB->removeLiveIn(X86::EFLAGS);
         }
     } while (!Blocks.empty());
 
diff --git a/llvm/test/CodeGen/X86/copy-eflags-liveinlists.mir b/llvm/test/CodeGen/X86/copy-eflags-liveinlists.mir
new file mode 100644
index 00000000000..54454fe0017
--- /dev/null
+++ b/llvm/test/CodeGen/X86/copy-eflags-liveinlists.mir
@@ -0,0 +1,92 @@
+# RUN: llc -mtriple=i686-unknown-unknown -run-pass=x86-flags-copy-lowering \
+# RUN:  -print-after=x86-flags-copy-lowering %s -o - | FileCheck %s
+#
+# Check that $eflags is removed from live-in lists of successor blocks.
+#
+# CHECK-NOT: liveins: $eflags
+
+--- |
+  define void @fun(i16 %arg, i64 %arg1, i8 %arg2, i8* %arg3, i32 %arg4) { ret void}
+...
+---
+name:            fun
+alignment:       16
+tracksRegLiveness: true
+registers:
+  - { id: 0, class: gr16 }
+  - { id: 1, class: gr16 }
+  - { id: 2, class: gr16 }
+  - { id: 3, class: gr32 }
+  - { id: 4, class: gr32 }
+  - { id: 5, class: gr8 }
+  - { id: 6, class: gr32 }
+  - { id: 7, class: gr32 }
+  - { id: 8, class: gr32 }
+  - { id: 9, class: gr32 }
+  - { id: 10, class: gr32 }
+  - { id: 11, class: gr32 }
+  - { id: 12, class: gr32 }
+  - { id: 13, class: gr8 }
+  - { id: 14, class: gr32 }
+  - { id: 15, class: gr32 }
+  - { id: 16, class: gr32_abcd }
+  - { id: 17, class: gr8 }
+  - { id: 18, class: gr8 }
+  - { id: 19, class: gr32 }
+  - { id: 20, class: gr32 }
+frameInfo:
+  maxAlignment:    4
+fixedStack:
+  - { id: 0, offset: 20, size: 4, alignment: 4, isImmutable: true }
+  - { id: 1, offset: 16, size: 4, alignment: 4, isImmutable: true }
+  - { id: 2, offset: 12, size: 1, alignment: 4, isImmutable: true }
+  - { id: 3, offset: 8, size: 4, alignment: 4, isImmutable: true }
+  - { id: 4, offset: 4, size: 4, alignment: 4, isImmutable: true }
+  - { id: 5, size: 2, alignment: 4, isImmutable: true }
+machineFunctionInfo: {}
+body:             |
+  bb.0:
+    %4:gr32 = MOV32rm %fixed-stack.3, 1, $noreg, 0, $noreg :: (load 4 from %fixed-stack.3)
+    %3:gr32 = MOV32rm %fixed-stack.4, 1, $noreg, 0, $noreg :: (load 4 from %fixed-stack.4)
+    %7:gr32 = MOV32rm %fixed-stack.0, 1, $noreg, 0, $noreg :: (load 4 from %fixed-stack.0)
+    %6:gr32 = MOV32rm %fixed-stack.1, 1, $noreg, 0, $noreg :: (load 4 from %fixed-stack.1)
+    %5:gr8 = MOV8rm %fixed-stack.2, 1, $noreg, 0, $noreg :: (load 1 from %fixed-stack.2, align 4)
+    %9:gr32 = IMPLICIT_DEF
+    %11:gr32 = IMPLICIT_DEF
+  
+  bb.1:
+    successors: %bb.2, %bb.3
+  
+    CMP32rr %3, %9, implicit-def $eflags
+    %10:gr32 = SBB32rr %4, %11, implicit-def $eflags, implicit $eflags
+    %12:gr32 = COPY $eflags
+    %13:gr8 = SETCCr 12, implicit $eflags
+    %14:gr32 = MOVZX32rr8 killed %13
+    %15:gr32 = NEG32r %14, implicit-def dead $eflags
+    %16:gr32_abcd = MOV32r0 implicit-def dead $eflags
+    $eflags = COPY %12
+    %17:gr8 = COPY %16.sub_8bit
+    JCC_1 %bb.3, 12, implicit $eflags
+  
+  bb.2:
+    liveins: $eflags
+  
+  
+  bb.3:
+    successors: %bb.4, %bb.5
+    liveins: $eflags
+  
+    %18:gr8 = PHI %5, %bb.2, %17, %bb.1
+    MOV8mr %6, 1, $noreg, 0, $noreg, killed %18 :: (volatile store 1 into %ir.arg3)
+    JCC_1 %bb.5, 12, implicit $eflags
+  
+  bb.4:
+  
+  bb.5:
+    %19:gr32 = PHI %16, %bb.4, %15, %bb.3
+    $eax = COPY %7
+    CDQ implicit-def $eax, implicit-def $edx, implicit $eax
+    IDIV32r killed %19, implicit-def dead $eax, implicit-def $edx, implicit-def dead $eflags, implicit $eax, implicit $edx
+    JMP_1 %bb.1
+
+...