From 36ec1bc6c023811235d9f5fb664feff09bc7b4f7 Mon Sep 17 00:00:00 2001
From: FICTURE7 <FICTURE7@gmail.com>
Date: Sat, 12 Sep 2020 19:32:53 +0400
Subject: Relax block ordering constraints (#1535)

* Relax block ordering constraints

Before `block.Next` had to follow `block.ListNext`, now it does not.
Instead `CodeGenerator` will now emit the necessary jump instructions
to ensure control flow.

This makes control flow and block order modifications easier. It also
eliminates some simple cases of redundant branches.

* Set PPTC version
---
 ARMeilleure/CodeGen/X86/CodeGenerator.cs | 25 ++++++++++++++++++-------
 1 file changed, 18 insertions(+), 7 deletions(-)

(limited to 'ARMeilleure/CodeGen/X86/CodeGenerator.cs')

diff --git a/ARMeilleure/CodeGen/X86/CodeGenerator.cs b/ARMeilleure/CodeGen/X86/CodeGenerator.cs
index f2d4c462..a51f4a13 100644
--- a/ARMeilleure/CodeGen/X86/CodeGenerator.cs
+++ b/ARMeilleure/CodeGen/X86/CodeGenerator.cs
@@ -32,7 +32,6 @@ namespace ARMeilleure.CodeGen.X86
             Add(Instruction.BitwiseExclusiveOr,      GenerateBitwiseExclusiveOr);
             Add(Instruction.BitwiseNot,              GenerateBitwiseNot);
             Add(Instruction.BitwiseOr,               GenerateBitwiseOr);
-            Add(Instruction.Branch,                  GenerateBranch);
             Add(Instruction.BranchIf,                GenerateBranchIf);
             Add(Instruction.ByteSwap,                GenerateByteSwap);
             Add(Instruction.Call,                    GenerateCall);
@@ -168,6 +167,23 @@ namespace ARMeilleure.CodeGen.X86
                             GenerateOperation(context, operation);
                         }
                     }
+
+                    if (block.SuccessorCount == 0)
+                    {
+                        // The only blocks which can have 0 successors are exit blocks.
+                        Debug.Assert(block.Operations.Last is Operation operation &&
+                                     (operation.Instruction == Instruction.Tailcall ||
+                                      operation.Instruction == Instruction.Return));
+                    }
+                    else
+                    {
+                        BasicBlock succ = block.GetSuccessor(0);
+
+                        if (succ != block.ListNext)
+                        {
+                            context.JumpTo(succ);
+                        }
+                    }
                 }
 
                 Logger.EndPass(PassName.CodeGeneration);
@@ -512,11 +528,6 @@ namespace ARMeilleure.CodeGen.X86
             context.Assembler.Or(dest, src2, dest.Type);
         }
 
-        private static void GenerateBranch(CodeGenContext context, Operation operation)
-        {
-            context.JumpTo(context.CurrBlock.Branch);
-        }
-
         private static void GenerateBranchIf(CodeGenContext context, Operation operation)
         {
             Operand comp = operation.GetSource(2);
@@ -527,7 +538,7 @@ namespace ARMeilleure.CodeGen.X86
 
             GenerateCompareCommon(context, operation);
 
-            context.JumpTo(cond, context.CurrBlock.Branch);
+            context.JumpTo(cond, context.CurrBlock.GetSuccessor(1));
         }
 
         private static void GenerateByteSwap(CodeGenContext context, Operation operation)
-- 
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