From cbd1a9443bda7791d606825766ec264550df5ccf Mon Sep 17 00:00:00 2001
From: inglorion <voodoo@inglorion.net>
Date: Tue, 13 Jul 2010 21:13:15 +0200
Subject: [PATCH] Made top-level blocks in i386 and AMD64 set EBP/RBP, so
 BP-relative addressing can be used inside the block.

---
 lib/voodoo/generators/amd64_nasm_generator.rb | 16 ++++------------
 lib/voodoo/generators/i386_nasm_generator.rb  | 16 ++++------------
 lib/voodoo/generators/nasm_generator.rb       | 23 ++++++++++++++++++++++-
 3 files changed, 30 insertions(+), 25 deletions(-)

diff --git a/lib/voodoo/generators/amd64_nasm_generator.rb b/lib/voodoo/generators/amd64_nasm_generator.rb
index 86d30ac..00044fd 100644
--- a/lib/voodoo/generators/amd64_nasm_generator.rb
+++ b/lib/voodoo/generators/amd64_nasm_generator.rb
@@ -76,6 +76,10 @@ module Voodoo
       @CX = 'rcx'
       # Data index
       @DX = 'rdx'
+      # Base pointer
+      @BP = 'rbp'
+      # Stack pointer
+      @SP = 'rsp'
       super params
     end
 
@@ -206,18 +210,6 @@ module Voodoo
       end
     end
 
-    # Ends the current block.
-    def end_block
-      emit "; end block\n"
-
-      # De-allocate block's variables
-      nvars = @environment.locals - @environment.parent.locals
-      emit "add rsp, #{nvars * @WORDSIZE}\n" unless nvars == 0
-
-      # Restore old value of @environment
-      @environment = @environment.parent
-    end
-
     #
     # == Loading Values
     #
diff --git a/lib/voodoo/generators/i386_nasm_generator.rb b/lib/voodoo/generators/i386_nasm_generator.rb
index ee9ddd8..b0e7e92 100644
--- a/lib/voodoo/generators/i386_nasm_generator.rb
+++ b/lib/voodoo/generators/i386_nasm_generator.rb
@@ -56,6 +56,10 @@ module Voodoo
       @CX = 'ecx'
       # Data index
       @DX = 'edx'
+      # Base pointer
+      @BP = 'ebp'
+      # Stack pointer
+      @SP = 'esp'
       super params
     end
 
@@ -70,18 +74,6 @@ module Voodoo
       end
     end
 
-    # Ends the current block.
-    def end_block
-      emit "; end block\n"
-
-      # De-allocate block's variables
-      nvars = @environment.locals - @environment.parent.locals
-      emit "add esp, #{nvars * @WORDSIZE}\n" unless nvars == 0
-
-      # Restore old value of @environment
-      @environment = @environment.parent
-    end
-
     # Emit function prologue.
     def emit_function_prologue formals = []
       emit "push ebp\nmov ebp, esp\n"
diff --git a/lib/voodoo/generators/nasm_generator.rb b/lib/voodoo/generators/nasm_generator.rb
index e1ddbf6..f600fb2 100644
--- a/lib/voodoo/generators/nasm_generator.rb
+++ b/lib/voodoo/generators/nasm_generator.rb
@@ -21,7 +21,7 @@ module Voodoo
   # - @SCRATCH_REG
   # - @WORD_NAME
   # - @WORDSIZE
-  # - @AX, @BX, @CX, and @DX
+  # - @AX, @BX, @CX, @DX, @BP, and @SP
   class NasmGenerator < CommonCodeGenerator
     def initialize params = {}
       super params
@@ -178,10 +178,31 @@ module Voodoo
     # Begins a new block.
     def begin_block
       emit "; begin block\n"
+      # If entering a block at top level,
+      # Save @BP, then set @BP to @SP
+      if @environment == @top_level
+        emit "push #{@BP}\n"
+        emit "mov #{@BP}, #{@SP}\n"
+      end
       environment = Environment.new @environment
       @environment = environment
     end
 
+    # Ends the current block.
+    def end_block
+      emit "; end block\n"
+
+      # De-allocate block's variables
+      nvars = @environment.locals - @environment.parent.locals
+      emit "add #{@SP}, #{nvars * @WORDSIZE}\n" unless nvars == 0
+
+      # Restore old value of @environment
+      @environment = @environment.parent
+
+      # If returning to top level, restore old @BP
+      emit "pop #{@BP}\n" if @environment == @top_level
+    end
+
     #
     # == Conditionals
     #
-- 
2.11.4.GIT