From 8ed22f27a4da1955d052c7963affd231381e55be Mon Sep 17 00:00:00 2001
From: Takeshi Yoneda <t.y.mathetake@gmail.com>
Date: Tue, 21 May 2024 15:39:11 +0900
Subject: [PATCH] ssa: simplifies basicBlock.params

Signed-off-by: Takeshi Yoneda <t.y.mathetake@gmail.com>
---
 internal/engine/wazevo/ssa/basic_block.go | 30 +++++++++--------------
 internal/engine/wazevo/ssa/builder.go     |  2 +-
 internal/engine/wazevo/ssa/pass.go        |  4 +--
 3 files changed, 14 insertions(+), 22 deletions(-)

diff --git a/internal/engine/wazevo/ssa/basic_block.go b/internal/engine/wazevo/ssa/basic_block.go
index 10b6b4b62b..0fc592a058 100644
--- a/internal/engine/wazevo/ssa/basic_block.go
+++ b/internal/engine/wazevo/ssa/basic_block.go
@@ -88,10 +88,12 @@ type (
 	basicBlock struct {
 		id                      BasicBlockID
 		rootInstr, currentInstr *Instruction
-		params                  []blockParam
-		predIter                int
-		preds                   []basicBlockPredecessorInfo
-		success                 []*basicBlock
+		// params are Values that represent parameters to a basicBlock.
+		// Each parameter can be considered as an output of PHI instruction in traditional SSA.
+		params   []Value
+		predIter int
+		preds    []basicBlockPredecessorInfo
+		success  []*basicBlock
 		// singlePred is the alias to preds[0] for fast lookup, and only set after Seal is called.
 		singlePred *basicBlock
 		// lastDefinitions maps Variable to its last definition in this block.
@@ -128,15 +130,6 @@ type (
 	// BasicBlockID is the unique ID of a basicBlock.
 	BasicBlockID uint32
 
-	// blockParam implements Value and represents a parameter to a basicBlock.
-	blockParam struct {
-		// value is the Value that corresponds to the parameter in this block,
-		// and can be considered as an output of PHI instruction in traditional SSA.
-		value Value
-		// typ is the type of the parameter.
-		typ Type
-	}
-
 	unknownValue struct {
 		// variable is the variable that this unknownValue represents.
 		variable Variable
@@ -190,13 +183,13 @@ func (bb *basicBlock) ReturnBlock() bool {
 // AddParam implements BasicBlock.AddParam.
 func (bb *basicBlock) AddParam(b Builder, typ Type) Value {
 	paramValue := b.allocateValue(typ)
-	bb.params = append(bb.params, blockParam{typ: typ, value: paramValue})
+	bb.params = append(bb.params, paramValue)
 	return paramValue
 }
 
 // addParamOn adds a parameter to this block whose value is already allocated.
-func (bb *basicBlock) addParamOn(typ Type, value Value) {
-	bb.params = append(bb.params, blockParam{typ: typ, value: value})
+func (bb *basicBlock) addParamOn(value Value) {
+	bb.params = append(bb.params, value)
 }
 
 // Params implements BasicBlock.Params.
@@ -206,8 +199,7 @@ func (bb *basicBlock) Params() int {
 
 // Param implements BasicBlock.Param.
 func (bb *basicBlock) Param(i int) Value {
-	p := &bb.params[i]
-	return p.value
+	return bb.params[i]
 }
 
 // Valid implements BasicBlock.Valid.
@@ -339,7 +331,7 @@ func (bb *basicBlock) addPred(blk BasicBlock, branch *Instruction) {
 func (bb *basicBlock) FormatHeader(b Builder) string {
 	ps := make([]string, len(bb.params))
 	for i, p := range bb.params {
-		ps[i] = p.value.formatWithType(b)
+		ps[i] = p.formatWithType(b)
 	}
 
 	if len(bb.preds) > 0 {
diff --git a/internal/engine/wazevo/ssa/builder.go b/internal/engine/wazevo/ssa/builder.go
index 1fc84d2eaf..f5414079e4 100644
--- a/internal/engine/wazevo/ssa/builder.go
+++ b/internal/engine/wazevo/ssa/builder.go
@@ -523,7 +523,7 @@ func (b *builder) Seal(raw BasicBlock) {
 	for _, v := range blk.unknownValues {
 		variable, phiValue := v.variable, v.value
 		typ := b.definedVariableType(variable)
-		blk.addParamOn(typ, phiValue)
+		blk.addParamOn(phiValue)
 		for i := range blk.preds {
 			pred := &blk.preds[i]
 			predValue := b.findValue(typ, variable, pred.blk)
diff --git a/internal/engine/wazevo/ssa/pass.go b/internal/engine/wazevo/ssa/pass.go
index a2e986cd15..0dfd132cf0 100644
--- a/internal/engine/wazevo/ssa/pass.go
+++ b/internal/engine/wazevo/ssa/pass.go
@@ -126,7 +126,7 @@ func passRedundantPhiEliminationOpt(b *builder) {
 			paramNum := len(blk.params)
 
 			for paramIndex := 0; paramIndex < paramNum; paramIndex++ {
-				phiValue := blk.params[paramIndex].value
+				phiValue := blk.params[paramIndex]
 				redundant := true
 
 				nonSelfReferencingValue := ValueInvalid
@@ -184,7 +184,7 @@ func passRedundantPhiEliminationOpt(b *builder) {
 
 			// Still need to have the definition of the value of the PHI (previously as the parameter).
 			for _, redundantParamIndex := range redundantParameterIndexes {
-				phiValue := blk.params[redundantParamIndex].value
+				phiValue := blk.params[redundantParamIndex]
 				onlyValue := b.redundantParameterIndexToValue[redundantParamIndex]
 				// Create an alias in this block from the only phi argument to the phi value.
 				b.alias(phiValue, onlyValue)