[CodeGen][TailDuplicator] Don't duplicate blocks with INLINEASM_BRllvmorg-11.0.0-rc6llvmorg-11.0.0

Tail duplication of a block with an INLINEASM_BR may result in a PHI
node on the indirect branch. This is okay, but it also introduces a copy
for that PHI node *after* the INLINEASM_BR, which is not okay.

See: https://github.com/ClangBuiltLinux/linux/issues/1125

Differential Revision: https://reviews.llvm.org/D88823

(cherry picked from commit d2c61d2bf9bd1efad49acba2f2751112522686aa)

2 files changed, 69 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/TailDuplicator.cpp b/llvm/lib/CodeGen/TailDuplicator.cpp
index bd554189f12b..f9773f74a7bd 100644
--- a/llvm/lib/CodeGen/TailDuplicator.cpp
+++ b/llvm/lib/CodeGen/TailDuplicator.cpp
@@ -627,6 +627,14 @@ bool TailDuplicator::shouldTailDuplicate(bool IsSimple,
     if (PreRegAlloc && MI.isCall())
       return false;
 
+    // TailDuplicator::appendCopies will erroneously place COPYs after
+    // INLINEASM_BR instructions after 4b0aa5724fea, which demonstrates the same
+    // bug that was fixed in f7a53d82c090.
+    // FIXME: Use findPHICopyInsertPoint() to find the correct insertion point
+    //        for the COPY when replacing PHIs.
+    if (MI.getOpcode() == TargetOpcode::INLINEASM_BR)
+      return false;
+
     if (MI.isBundle())
       InstrCount += MI.getBundleSize();
     else if (!MI.isPHI() && !MI.isMetaInstruction())
diff --git a/llvm/test/CodeGen/X86/tail-dup-asm-goto.ll b/llvm/test/CodeGen/X86/tail-dup-asm-goto.ll
new file mode 100644
index 000000000000..77aa3adf0fc6
--- /dev/null
+++ b/llvm/test/CodeGen/X86/tail-dup-asm-goto.ll
@@ -0,0 +1,61 @@
+; NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+; RUN: llc -mtriple=x86_64-linux -stop-after=early-tailduplication < %s | FileCheck %s
+
+; Ensure that we don't duplicate a block with an "INLINEASM_BR" instruction
+; during code gen.
+declare void @foo()
+
+define i8* @test1(i8** %arg1, i8* %arg2) {
+  ; CHECK-LABEL: name: test1
+  ; CHECK: bb.0.bb:
+  ; CHECK:   successors: %bb.1(0x50000000), %bb.2(0x30000000)
+  ; CHECK:   liveins: $rdi, $rsi
+  ; CHECK:   [[COPY:%[0-9]+]]:gr64 = COPY $rsi
+  ; CHECK:   [[COPY1:%[0-9]+]]:gr64 = COPY $rdi
+  ; CHECK:   [[MOV64rm:%[0-9]+]]:gr64 = MOV64rm [[COPY1]], 1, $noreg, 0, $noreg :: (load 8 from %ir.arg1)
+  ; CHECK:   [[SUB64rr:%[0-9]+]]:gr64 = SUB64rr [[MOV64rm]], [[COPY]], implicit-def $eflags
+  ; CHECK:   JCC_1 %bb.2, 4, implicit $eflags
+  ; CHECK:   JMP_1 %bb.1
+  ; CHECK: bb.1.bb100:
+  ; CHECK:   successors: %bb.3(0x80000000)
+  ; CHECK:   MOV64mi32 [[COPY1]], 1, $noreg, 0, $noreg, 0 :: (store 8 into %ir.arg1)
+  ; CHECK:   JMP_1 %bb.3
+  ; CHECK: bb.2.bb106:
+  ; CHECK:   successors: %bb.3(0x80000000)
+  ; CHECK:   ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+  ; CHECK:   CALL64pcrel32 @foo, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp
+  ; CHECK:   ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+  ; CHECK: bb.3.bb110:
+  ; CHECK:   successors: %bb.5(0x80000000), %bb.4(0x00000000)
+  ; CHECK:   [[PHI:%[0-9]+]]:gr64 = PHI [[COPY]], %bb.2, [[MOV64rm]], %bb.1
+  ; CHECK:   INLINEASM_BR &"#$0 $1 $2", 9 /* sideeffect mayload attdialect */, 13 /* imm */, 42, 13 /* imm */, 0, 13 /* imm */, blockaddress(@test1, %ir-block.bb17.i.i.i), 12 /* clobber */, implicit-def early-clobber $df, 12 /* clobber */, implicit-def early-clobber $fpsw, 12 /* clobber */, implicit-def early-clobber $eflags
+  ; CHECK:   JMP_1 %bb.5
+  ; CHECK: bb.4.bb17.i.i.i (address-taken):
+  ; CHECK:   successors: %bb.5(0x80000000)
+  ; CHECK: bb.5.kmem_cache_has_cpu_partial.exit:
+  ; CHECK:   $rax = COPY [[PHI]]
+  ; CHECK:   RET 0, $rax
+bb:
+  %i28.i = load i8*, i8** %arg1, align 8
+  %if = icmp ne i8* %i28.i, %arg2
+  br i1 %if, label %bb100, label %bb106
+
+bb100:                                            ; preds = %bb
+  store i8* null, i8** %arg1, align 8
+  br label %bb110
+
+bb106:                                            ; preds = %bb
+  call void @foo()
+  br label %bb110
+
+bb110:                                            ; preds = %bb106, %bb100
+  %i10.1 = phi i8* [ %arg2, %bb106 ], [ %i28.i, %bb100 ]
+  callbr void asm sideeffect "#$0 $1 $2", "i,i,X,~{dirflag},~{fpsr},~{flags}"(i32 42, i1 false, i8* blockaddress(@test1, %bb17.i.i.i))
+          to label %kmem_cache_has_cpu_partial.exit [label %bb17.i.i.i]
+
+bb17.i.i.i:                                       ; preds = %bb110
+  br label %kmem_cache_has_cpu_partial.exit
+
+kmem_cache_has_cpu_partial.exit:                  ; preds = %bb110
+  ret i8* %i10.1
+}