From f2348301ea59bfd1fa96cbe684780dfc36a1a69d Mon Sep 17 00:00:00 2001
From: Ben Vanik <ben.vanik@gmail.com>
Date: Sun, 15 Dec 2013 14:40:18 -0800
Subject: [PATCH] More aggressive constant propagation pass.

---
 .../passes/constant_propagation_pass.cc       | 108 ++++++++++++++++++
 src/alloy/hir/instr.cc                        |  10 +-
 src/alloy/hir/instr.h                         |   1 +
 3 files changed, 118 insertions(+), 1 deletion(-)

diff --git a/src/alloy/compiler/passes/constant_propagation_pass.cc b/src/alloy/compiler/passes/constant_propagation_pass.cc
index 2ddbce90f..2f49c41ad 100644
--- a/src/alloy/compiler/passes/constant_propagation_pass.cc
+++ b/src/alloy/compiler/passes/constant_propagation_pass.cc
@@ -48,6 +48,72 @@ int ConstantPropagationPass::Run(FunctionBuilder* builder) {
     while (i) {
       Value* v = i->dest;
       switch (i->opcode->num) {
+      case OPCODE_DEBUG_BREAK_TRUE:
+        if (i->src1.value->IsConstant()) {
+          if (i->src1.value->IsConstantTrue()) {
+            i->Replace(&OPCODE_DEBUG_BREAK_info, i->flags);
+          } else {
+            i->Remove();
+          }
+        }
+        break;
+
+      case OPCODE_TRAP_TRUE:
+        if (i->src1.value->IsConstant()) {
+          if (i->src1.value->IsConstantTrue()) {
+            i->Replace(&OPCODE_TRAP_info, i->flags);
+          } else {
+            i->Remove();
+          }
+        }
+        break;
+
+      case OPCODE_CALL_TRUE:
+        if (i->src1.value->IsConstant()) {
+          if (i->src1.value->IsConstantTrue()) {
+            auto symbol_info = i->src2.symbol_info;
+            i->Replace(&OPCODE_CALL_info, i->flags);
+            i->src1.symbol_info = symbol_info;
+          } else {
+            i->Remove();
+          }
+        }
+        break;
+      case OPCODE_CALL_INDIRECT_TRUE:
+        if (i->src1.value->IsConstant()) {
+          if (i->src1.value->IsConstantTrue()) {
+            auto value = i->src2.value;
+            i->Replace(&OPCODE_CALL_INDIRECT_info, i->flags);
+            i->set_src1(value);
+          } else {
+            i->Remove();
+          }
+        }
+        break;
+
+      case OPCODE_BRANCH_TRUE:
+        if (i->src1.value->IsConstant()) {
+          if (i->src1.value->IsConstantTrue()) {
+            auto label = i->src2.label;
+            i->Replace(&OPCODE_BRANCH_info, i->flags);
+            i->src1.label = label;
+          } else {
+            i->Remove();
+          }
+        }
+        break;
+      case OPCODE_BRANCH_FALSE:
+        if (i->src1.value->IsConstant()) {
+          if (i->src1.value->IsConstantFalse()) {
+            auto label = i->src2.label;
+            i->Replace(&OPCODE_BRANCH_info, i->flags);
+            i->src1.label = label;
+          } else {
+            i->Remove();
+          }
+        }
+        break;
+
       case OPCODE_CAST:
         if (i->src1.value->IsConstant()) {
           TypeName target_type = v->type;
@@ -81,6 +147,39 @@ int ConstantPropagationPass::Run(FunctionBuilder* builder) {
         }
         break;
 
+      case OPCODE_SELECT:
+        if (i->src1.value->IsConstant()) {
+          if (i->src1.value->IsConstantTrue()) {
+            v->set_from(i->src2.value);
+          } else {
+            v->set_from(i->src3.value);
+          }
+          i->Remove();
+        }
+        break;
+      case OPCODE_IS_TRUE:
+        if (i->src1.value->IsConstant()) {
+          if (i->src1.value->IsConstantTrue()) {
+            v->set_constant((int8_t)1);
+          } else {
+            v->set_constant((int8_t)0);
+          }
+          i->Remove();
+        }
+        break;
+      case OPCODE_IS_FALSE:
+        if (i->src1.value->IsConstant()) {
+          if (i->src1.value->IsConstantFalse()) {
+            v->set_constant((int8_t)1);
+          } else {
+            v->set_constant((int8_t)0);
+          }
+          i->Remove();
+        }
+        break;
+
+      // TODO(benvanik): compares
+
       case OPCODE_ADD:
         if (i->src1.value->IsConstant() && i->src2.value->IsConstant()) {
           v->set_from(i->src1.value);
@@ -183,6 +282,7 @@ int ConstantPropagationPass::Run(FunctionBuilder* builder) {
           i->Remove();
         }
         break;
+      // TODO(benvanik): VECTOR_SHL
       case OPCODE_SHR:
         if (i->src1.value->IsConstant() && i->src2.value->IsConstant()) {
           v->set_from(i->src1.value);
@@ -197,6 +297,7 @@ int ConstantPropagationPass::Run(FunctionBuilder* builder) {
           i->Remove();
         }
         break;
+      // TODO(benvanik): ROTATE_LEFT
       case OPCODE_BYTE_SWAP:
         if (i->src1.value->IsConstant()) {
           v->set_from(i->src1.value);
@@ -204,6 +305,13 @@ int ConstantPropagationPass::Run(FunctionBuilder* builder) {
           i->Remove();
         }
         break;
+      // TODO(benvanik): INSERT/EXTRACT
+      // TODO(benvanik): SPLAT/PERMUTE/SWIZZLE
+      case OPCODE_SPLAT:
+        if (i->src1.value->IsConstant()) {
+          // Quite a few of these, from building vec128s.
+        }
+        break;
       }
       i = i->next;
     }
diff --git a/src/alloy/hir/instr.cc b/src/alloy/hir/instr.cc
index 0cc38464c..b800a24dd 100644
--- a/src/alloy/hir/instr.cc
+++ b/src/alloy/hir/instr.cc
@@ -48,7 +48,10 @@ void Instr::set_src3(Value* value) {
   src3_use = value ? value->AddUse(block->arena, this) : NULL;
 }
 
-void Instr::Remove() {
+void Instr::Replace(const OpcodeInfo* opcode, uint16_t flags) {
+  this->opcode = opcode;
+  this->flags = flags;
+
   if (dest) {
     dest->def = NULL;
   }
@@ -64,6 +67,11 @@ void Instr::Remove() {
     src3.value->RemoveUse(src3_use);
     src3_use = NULL;
   }
+}
+
+void Instr::Remove() {
+  // Remove all srcs/dest.
+  Replace(&OPCODE_NOP_info, 0);
 
   if (prev) {
     prev->next = next;
diff --git a/src/alloy/hir/instr.h b/src/alloy/hir/instr.h
index 517232cc5..764c62ef8 100644
--- a/src/alloy/hir/instr.h
+++ b/src/alloy/hir/instr.h
@@ -54,6 +54,7 @@ public:
   void set_src2(Value* value);
   void set_src3(Value* value);
 
+  void Replace(const OpcodeInfo* opcode, uint16_t flags);
   void Remove();
 };