[llvm] 09507b5 - [AArch64][SME] Disable NEON in streaming mode

[Cullen Rhodes via llvm-commits]

Author: Cullen Rhodes
Date: 2021-08-16T07:56:48Z
New Revision: 09507b53250dc266632c204558cb1c2b56e8ddea

URL: https://github.com/llvm/llvm-project/commit/09507b53250dc266632c204558cb1c2b56e8ddea
DIFF: https://github.com/llvm/llvm-project/commit/09507b53250dc266632c204558cb1c2b56e8ddea.diff

LOG: [AArch64][SME] Disable NEON in streaming mode

In streaming mode most of the NEON instruction set is illegal, disable
NEON when compiling with `+streaming-sve`, unless NEON is explictly
requested.

Subsequent patches will add support for the small subset of NEON
instructions that are legal in streaming mode.

Reviewed By: paulwalker-arm, david-arm

Differential Revision: https://reviews.llvm.org/D107902

Added: 
    llvm/test/MC/AArch64/SME/streaming-sve-feature.s

Modified: 
    llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCTargetDesc.cpp

Removed: 
    


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diff  --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCTargetDesc.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCTargetDesc.cpp
index 3c2df1621e118..987cabce6cc98 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCTargetDesc.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCTargetDesc.cpp
@@ -57,7 +57,16 @@ createAArch64MCSubtargetInfo(const Triple &TT, StringRef CPU, StringRef FS) {
       CPU = "apple-a12";
   }
 
-  return createAArch64MCSubtargetInfoImpl(TT, CPU, /*TuneCPU*/ CPU, FS);
+  // Most of the NEON instruction set isn't supported in streaming mode on SME
+  // targets, disable NEON unless explicitly requested.
+  bool RequestedNEON = FS.contains("neon");
+  bool RequestedStreamingSVE = FS.contains("streaming-sve");
+  MCSubtargetInfo *STI =
+      createAArch64MCSubtargetInfoImpl(TT, CPU, /*TuneCPU*/ CPU, FS);
+  if (RequestedStreamingSVE && !RequestedNEON &&
+      STI->hasFeature(AArch64::FeatureNEON))
+    STI->ToggleFeature(AArch64::FeatureNEON);
+  return STI;
 }
 
 void AArch64_MC::initLLVMToCVRegMapping(MCRegisterInfo *MRI) {

diff  --git a/llvm/test/MC/AArch64/SME/streaming-sve-feature.s b/llvm/test/MC/AArch64/SME/streaming-sve-feature.s
new file mode 100644
index 0000000000000..e35505ca39c58
--- /dev/null
+++ b/llvm/test/MC/AArch64/SME/streaming-sve-feature.s
@@ -0,0 +1,8 @@
+// RUN: llvm-mc -triple=aarch64 -mattr=+streaming-sve,+neon < %s 2>&1 | FileCheck %s
+// RUN: not llvm-mc -triple=aarch64 -mattr=+streaming-sve < %s 2>&1 | FileCheck %s --check-prefix=CHECK-ERROR
+
+// Verify NEON is disabled when targeting streaming mode, if it's not
+// explicitly requested.
+add v0.8b, v1.8b, v2.8b
+// CHECK: add v0.8b, v1.8b, v2.8b
+// CHECK-ERROR: error: instruction requires: neon