[llvm] dbf9b93 - [AArch64][SME] Disable tail-call optimization for __arm_locally_streaming functions. (#65258)

[via llvm-commits]

Author: sdesmalen-arm
Date: 2023-09-04T15:11:22+01:00
New Revision: dbf9b93f25d60cdad11aa624d6b58f6ee6c5075f

URL: https://github.com/llvm/llvm-project/commit/dbf9b93f25d60cdad11aa624d6b58f6ee6c5075f
DIFF: https://github.com/llvm/llvm-project/commit/dbf9b93f25d60cdad11aa624d6b58f6ee6c5075f.diff

LOG: [AArch64][SME] Disable tail-call optimization for __arm_locally_streaming functions. (#65258)

When calling a function which requires no streaming-mode change from an
__arm_locally_streaming function, LLVM would otherwise emit:

  // function prologue
  smstart
  b streaming_compatible_function   // tail call
  // never an smstop

Added: 
    

Modified: 
    llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
    llvm/test/CodeGen/AArch64/sme-streaming-body.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index 4c54dcea693668..16fe5bc2786318 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -6980,7 +6980,8 @@ bool AArch64TargetLowering::isEligibleForTailCallOptimization(
   SMEAttrs CallerAttrs(MF.getFunction());
   auto CalleeAttrs = CLI.CB ? SMEAttrs(*CLI.CB) : SMEAttrs(SMEAttrs::Normal);
   if (CallerAttrs.requiresSMChange(CalleeAttrs) ||
-      CallerAttrs.requiresLazySave(CalleeAttrs))
+      CallerAttrs.requiresLazySave(CalleeAttrs) ||
+      CallerAttrs.hasStreamingBody())
     return false;
 
   // Functions using the C or Fast calling convention that have an SVE signature

diff  --git a/llvm/test/CodeGen/AArch64/sme-streaming-body.ll b/llvm/test/CodeGen/AArch64/sme-streaming-body.ll
index 74dd66fedceb77..a92a815e93bea4 100644
--- a/llvm/test/CodeGen/AArch64/sme-streaming-body.ll
+++ b/llvm/test/CodeGen/AArch64/sme-streaming-body.ll
@@ -308,3 +308,24 @@ for.cond.cleanup:
   ret float %add
 
 }
+
+define void @disable_tailcallopt() "aarch64_pstate_sm_body" nounwind {
+; CHECK-LABEL: disable_tailcallopt:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    stp d15, d14, [sp, #-80]! // 16-byte Folded Spill
+; CHECK-NEXT:    stp d13, d12, [sp, #16] // 16-byte Folded Spill
+; CHECK-NEXT:    stp d11, d10, [sp, #32] // 16-byte Folded Spill
+; CHECK-NEXT:    stp d9, d8, [sp, #48] // 16-byte Folded Spill
+; CHECK-NEXT:    str x30, [sp, #64] // 8-byte Folded Spill
+; CHECK-NEXT:    smstart sm
+; CHECK-NEXT:    bl streaming_compatible_callee
+; CHECK-NEXT:    smstop sm
+; CHECK-NEXT:    ldp d9, d8, [sp, #48] // 16-byte Folded Reload
+; CHECK-NEXT:    ldr x30, [sp, #64] // 8-byte Folded Reload
+; CHECK-NEXT:    ldp d11, d10, [sp, #32] // 16-byte Folded Reload
+; CHECK-NEXT:    ldp d13, d12, [sp, #16] // 16-byte Folded Reload
+; CHECK-NEXT:    ldp d15, d14, [sp], #80 // 16-byte Folded Reload
+; CHECK-NEXT:    ret
+  tail call void @streaming_compatible_callee();
+  ret void;
+}