From 50587974b5d309131138aa1e75f8dbeecde473e9 Mon Sep 17 00:00:00 2001
From: Ben Vanik <ben.vanik@gmail.com>
Date: Tue, 14 Jan 2014 00:39:31 -0800
Subject: [PATCH] Not sure why I thought I could do this.

---
 .../compiler/passes/simplification_pass.cc    | 30 +------------------
 .../compiler/passes/simplification_pass.h     |  1 -
 2 files changed, 1 insertion(+), 30 deletions(-)

diff --git a/src/alloy/compiler/passes/simplification_pass.cc b/src/alloy/compiler/passes/simplification_pass.cc
index 41c766505..14cea8681 100644
--- a/src/alloy/compiler/passes/simplification_pass.cc
+++ b/src/alloy/compiler/passes/simplification_pass.cc
@@ -31,13 +31,7 @@ int SimplificationPass::Run(HIRBuilder* builder) {
 void SimplificationPass::EliminateConversions(HIRBuilder* builder) {
   // First, we check for truncates/extensions that can be skipped.
   // This generates some assignments which then the second step will clean up.
-  // Only zero extend truncates can be skipped:
-  //   v1.i32 = truncate v0.i64
-  //   v2.i64 = zero_extend v1.i32
-  // becomes:
-  //   v1.i32 = truncate v0.i64 (may be dead code removed later)
-  //   v2.i64 = v0.i64
-  // But both zero/sign extends can be skipped:
+  // Both zero/sign extends can be skipped:
   //   v1.i64 = zero/sign_extend v0.i32
   //   v2.i32 = truncate v1.i64
   // becomes:
@@ -53,9 +47,6 @@ void SimplificationPass::EliminateConversions(HIRBuilder* builder) {
       if (i->opcode == &OPCODE_TRUNCATE_info) {
         // Matches zero/sign_extend + truncate.
         CheckTruncate(i);
-      } else if (i->opcode == &OPCODE_ZERO_EXTEND_info) {
-        // Matches truncate + zero_extend.
-        CheckZeroExtend(i);
       } else if (i->opcode == &OPCODE_BYTE_SWAP_info) {
         // Matches byte swap + byte swap.
         // This is pretty rare within the same basic block, but is in the
@@ -96,25 +87,6 @@ void SimplificationPass::CheckTruncate(Instr* i) {
   }
 }
 
-void SimplificationPass::CheckZeroExtend(Instr* i) {
-  // Walk backward up src's chain looking for a truncate. We may have
-  // assigns, so skip those.
-  auto src = i->src1.value;
-  Instr* def = src->def;
-  while (def && def->opcode == &OPCODE_ASSIGN_info) {
-    // Skip asignments.
-    def = def->src1.value->def;
-  }
-  if (def && def->opcode == &OPCODE_TRUNCATE_info) {
-    // Value comes from a truncate.
-    if (def->src1.value->type == i->dest->type) {
-      // Types match, use original by turning this into an assign.
-      i->Replace(&OPCODE_ASSIGN_info, 0);
-      i->set_src1(def->src1.value);
-    }
-  }
-}
-
 void SimplificationPass::CheckByteSwap(Instr* i) {
   // Walk backward up src's chain looking for a byte swap. We may have
   // assigns, so skip those.
diff --git a/src/alloy/compiler/passes/simplification_pass.h b/src/alloy/compiler/passes/simplification_pass.h
index b4dbe3b02..19e1023fb 100644
--- a/src/alloy/compiler/passes/simplification_pass.h
+++ b/src/alloy/compiler/passes/simplification_pass.h
@@ -28,7 +28,6 @@ public:
 private:
   void EliminateConversions(hir::HIRBuilder* builder);
   void CheckTruncate(hir::Instr* i);
-  void CheckZeroExtend(hir::Instr* i);
   void CheckByteSwap(hir::Instr* i);
 
   void SimplifyAssignments(hir::HIRBuilder* builder);