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

[Daniel Hoekwater via Phabricator via llvm-commits]

dhoekwater updated this revision to Diff 554472.
dhoekwater added a comment.

Place cheap checks before expensive ones per reviewer feedback


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D158647/new/

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
@@ -602,6 +602,33 @@
   ret i32 %4
 }
 
+define void @foo20(i1 zeroext %0) !prof !14 !section_prefix !15 {
+;; Check that blocks containing or targeted by asm goto aren't split.
+; MFS-DEFAULTS-LABEL:        foo20
+; MFS-DEFAULTS-AARCH64-NOT:  foo20.cold:
+; MFS-DEFAULTS-X86:          .section        .text.split.foo20
+; MFS-DEFAULTS-X86:          foo20.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
@@ -8408,6 +8408,14 @@
 
 bool AArch64InstrInfo::isMBBSafeToSplitToCold(
     const MachineBasicBlock &MBB) const {
+  // Asm Goto blocks can contain conditional branches to goto labels, which can
+  // get moved out of range of the branch instruction.
+  auto isAsmGoto = [](const MachineInstr &MI) {
+    return MI.getOpcode() == AArch64::INLINEASM_BR;
+  };
+  if (llvm::any_of(MBB, isAsmGoto) || MBB.isInlineAsmBrIndirectTarget())
+    return false;
+
   // Because jump tables are label-relative instead of table-relative, they all
   // must be in the same section or relocation fixup handling will fail.
 


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