[PATCH] D127294: [AARCH64 folding] Do not fold any copy with NZCV

[Serguei Katkov via Phabricator via llvm-commits]

skatkov created this revision.
skatkov added reviewers: MatzeB, qcolombet, gberry.
Herald added subscribers: hiraditya, kristof.beyls.
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There is no instruction to fold NZCV, so, just do not do it.

Without the fix the added test case crashes with an assert
"Mismatched register size in non subreg COPY"


https://reviews.llvm.org/D127294

Files:
  llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
  llvm/test/CodeGen/AArch64/spill-fold.mir


Index: llvm/test/CodeGen/AArch64/spill-fold.mir
===================================================================
--- llvm/test/CodeGen/AArch64/spill-fold.mir
+++ llvm/test/CodeGen/AArch64/spill-fold.mir
@@ -5,6 +5,7 @@
   define i64 @test_subreg_spill_fold3() { ret i64 0 }
   define i64 @test_subreg_fill_fold() { ret i64 0 }
   define double @test_subreg_fill_fold2() { ret double 0.0 }
+  define i64 @test_nzcv_spill_fold() { ret i64 0 }
 ...
 ---
 # CHECK-LABEL: name: test_subreg_spill_fold
@@ -80,3 +81,18 @@
     $d0 = COPY %1
     RET_ReallyLR implicit $d0
 ...
+---
+# CHECK-LABEL: name: test_nzcv_spill_fold
+# Ensure that nzcv COPY cannot be folded.
+name:            test_nzcv_spill_fold
+registers:
+  - { id: 0, class: gpr64 }
+body:             |
+  bb.0:
+    ; CHECK: %1:gpr64 = COPY $nzcv
+    ; CHECK: STRXui %1, %stack.0, 0 :: (store (s64) into %stack.0)
+    %0 = COPY $nzcv
+    INLINEASM &nop, 1, 12, implicit-def dead $x0, 12, implicit-def dead $x1, 12, implicit-def dead $x2, 12, implicit-def dead $x3, 12, implicit-def dead $x4, 12, implicit-def dead $x5, 12, implicit-def dead $x6, 12, implicit-def dead $x7, 12, implicit-def dead $x8, 12, implicit-def dead $x9, 12, implicit-def dead $x10, 12, implicit-def dead $x11, 12, implicit-def dead $x12, 12, implicit-def dead $x13, 12, implicit-def dead $x14, 12, implicit-def dead $x15, 12, implicit-def dead $x16, 12, implicit-def dead $x17, 12, implicit-def dead $x18, 12, implicit-def dead $x19, 12, implicit-def dead $x20, 12, implicit-def dead $x21, 12, implicit-def dead $x22, 12, implicit-def dead $x23, 12, implicit-def dead $x24, 12, implicit-def dead $x25, 12, implicit-def dead $x26, 12, implicit-def dead $x27, 12, implicit-def dead $x28, 12, implicit-def dead $fp, 12, implicit-def dead $lr, 12, implicit-def $sp
+    $x0 = COPY %0
+    RET_ReallyLR implicit $x0
+...
Index: llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
===================================================================
--- llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
+++ llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
@@ -4402,6 +4402,9 @@
       MF.getRegInfo().constrainRegClass(SrcReg, &AArch64::GPR64RegClass);
       return nullptr;
     }
+    // Nothing can folded with copy from/to NZCV.
+    if (SrcReg == AArch64::NZCV || DstReg == AArch64::NZCV)
+      return nullptr;
   }
 
   // Handle the case where a copy is being spilled or filled but the source


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