[PATCH] D158647: [CodeGen][AArch64] Don't split inline asm goto blocks or their targets

[Daniel Hoekwater via Phabricator via llvm-commits]

dhoekwater created this revision.
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Machine function splitting + branch relaxation currently don't properly
handle inline asm goto blocks that conditional branch to cold goto
labels. While such inline asm is technically invalid, machine
function splitting is the only thing that exposes it as such.

Since machine function splitting doesn't help too much in these
circumstances anyway, disable it for asm goto blocks and their targets.

Depends on D157124 <https://reviews.llvm.org/D157124>


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D158647

Files:
  llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
  llvm/test/CodeGen/Generic/machine-function-splitter.ll


Index: llvm/test/CodeGen/Generic/machine-function-splitter.ll
===================================================================
--- llvm/test/CodeGen/Generic/machine-function-splitter.ll
+++ llvm/test/CodeGen/Generic/machine-function-splitter.ll
@@ -514,6 +514,33 @@
   ret i32 %4
 }
 
+define void @foo17(i1 zeroext %0) !prof !14 !section_prefix !15 {
+;; Check that blocks containing or targeted by asm goto aren't split.
+; MFS-DEFAULTS-LABEL:        foo17
+; MFS-DEFAULTS-AARCH64-NOT:  foo17.cold:
+; MFS-DEFAULTS-X86:          .section        .text.split.foo17
+; MFS-DEFAULTS-X86:          foo17.cold:
+; MFS-DEFAULTS-X86-DAG:      # %cold_asm
+; MFS-DEFAULTS-X86-DAG:      # %cold_asm_target
+
+  br i1 %0, label %hot, label %cold_asm, !prof !17
+
+hot:
+  %2 = call i32 @bar()
+  ret void
+
+cold_asm:
+    callbr void asm sideeffect "nop", "!i"() #3
+          to label %asm.fallthrough [label %cold_asm_target]
+
+asm.fallthrough:
+    br label %cold_asm_target
+
+cold_asm_target:
+  %3 = call i32 @baz()
+  ret void
+}
+
 declare i32 @bar()
 declare i32 @baz()
 declare i32 @bam()
Index: llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
===================================================================
--- llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
+++ llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
@@ -8418,7 +8418,16 @@
            llvm::any_of(MJTI->getJumpTables(), isInJumpTable);
   };
 
-  return !containsJumpTableLookup(MBB) && !isJumpTableTarget(MBB);
+  if (containsJumpTableLookup(MBB) || isJumpTableTarget(MBB))
+    return false;
+
+  auto isAsmGoto = [](const MachineInstr &MI) {
+    return MI.getOpcode() == AArch64::INLINEASM_BR;
+  };
+  if (llvm::any_of(MBB, isAsmGoto) || MBB.isInlineAsmBrIndirectTarget())
+    return false;
+
+  return true;
 }
 
 std::optional<ParamLoadedValue>


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