[llvm] r362195 - [MIR-Canon] Skip the first N vreg names lazily.

[Puyan Lotfi via llvm-commits]

Author: zer0
Date: Thu May 30 23:02:38 2019
New Revision: 362195

URL: http://llvm.org/viewvc/llvm-project?rev=362195&view=rev
Log:
[MIR-Canon] Skip the first N vreg names lazily.

This consolidates the vreg skip code into one function (SkipVRegs()).
SkipVRegs() now knows if it should skip as if it is the first initialization or
subsequent skips.

The first skip is also done the first time createVirtualRegister is called by
the cursor instead of by the cursor's constructor. This prevents verifier
errors on machine functions that have no vregs (where the verifier will
complain that there are vregs when the function uses none).

Differential Revision: https://reviews.llvm.org/D62717


Modified:
    llvm/trunk/lib/CodeGen/MIRCanonicalizerPass.cpp
    llvm/trunk/test/CodeGen/MIR/AArch64/multiple-lhs-operands.mir

Modified: llvm/trunk/lib/CodeGen/MIRCanonicalizerPass.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MIRCanonicalizerPass.cpp?rev=362195&r1=362194&r2=362195&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MIRCanonicalizerPass.cpp (original)
+++ llvm/trunk/lib/CodeGen/MIRCanonicalizerPass.cpp Thu May 30 23:02:38 2019
@@ -483,18 +483,14 @@ class NamedVRegCursor {
   unsigned virtualVRegNumber;
 
 public:
-  NamedVRegCursor(MachineRegisterInfo &MRI) : MRI(MRI) {
-    unsigned VRegGapIndex = 0;
-    const unsigned VR_GAP = (++VRegGapIndex * 1000);
-
-    unsigned I = MRI.createIncompleteVirtualRegister();
-    const unsigned E = (((I + VR_GAP) / VR_GAP) + 1) * VR_GAP;
-
-    virtualVRegNumber = E;
-  }
+  NamedVRegCursor(MachineRegisterInfo &MRI) : MRI(MRI), virtualVRegNumber(0) {}
 
   void SkipVRegs() {
     unsigned VRegGapIndex = 1;
+    if (!virtualVRegNumber) {
+      VRegGapIndex = 0;
+      virtualVRegNumber = MRI.createIncompleteVirtualRegister();
+    }
     const unsigned VR_GAP = (++VRegGapIndex * 1000);
 
     unsigned I = virtualVRegNumber;
@@ -511,6 +507,8 @@ public:
   }
 
   unsigned createVirtualRegister(unsigned VReg) {
+    if (!virtualVRegNumber)
+      SkipVRegs();
     std::string S;
     raw_string_ostream OS(S);
     OS << "namedVReg" << (virtualVRegNumber & ~0x80000000);

Modified: llvm/trunk/test/CodeGen/MIR/AArch64/multiple-lhs-operands.mir
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/MIR/AArch64/multiple-lhs-operands.mir?rev=362195&r1=362194&r2=362195&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/MIR/AArch64/multiple-lhs-operands.mir (original)
+++ llvm/trunk/test/CodeGen/MIR/AArch64/multiple-lhs-operands.mir Thu May 30 23:02:38 2019
@@ -2,6 +2,9 @@
 # This test ensures that the MIR parser can parse multiple register machine
 # operands before '='.
 
+# This tests that a MIR file with no vregs does not get altered by mir-canon.
+# RUN: llc -mtriple=aarch64 -o - -run-pass mir-canonicalizer -verify-machineinstrs %s
+
 --- |
 
   declare void @foo()