From: Puyan Lotfi <puyan@puyan.org>
Date: Fri, 31 May 2019 06:02:38 +0000 (+0000)
Subject: [MIR-Canon] Skip the first N vreg names lazily.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=cbd1c64005d33de20f9fd4a5f85670f395dc34f7;p=llvm

[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



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@362195 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/MIRCanonicalizerPass.cpp b/lib/CodeGen/MIRCanonicalizerPass.cpp
index d36c0c89ba0..a4097232d7d 100644
--- a/lib/CodeGen/MIRCanonicalizerPass.cpp
+++ b/lib/CodeGen/MIRCanonicalizerPass.cpp
@@ -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);
diff --git a/test/CodeGen/MIR/AArch64/multiple-lhs-operands.mir b/test/CodeGen/MIR/AArch64/multiple-lhs-operands.mir
index 5f4bd9897d8..1437e975596 100644
--- a/test/CodeGen/MIR/AArch64/multiple-lhs-operands.mir
+++ b/test/CodeGen/MIR/AArch64/multiple-lhs-operands.mir
@@ -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()