diff --git a/internal/engine/wazevo/frontend/frontend_test.go b/internal/engine/wazevo/frontend/frontend_test.go index d1040a4a12..b982556d8b 100644 --- a/internal/engine/wazevo/frontend/frontend_test.go +++ b/internal/engine/wazevo/frontend/frontend_test.go @@ -1058,14 +1058,14 @@ blk1: () <-- (blk0) Call f1:sig1, exec_ctx, module_ctx v5:i64 = Load module_ctx, 0x8 v6:i64 = Uload32 module_ctx, 0x10 - Jump blk3, v2 + Jump blk3 blk2: () <-- (blk0) - Jump blk3, v2 + Jump blk3 -blk3: (v7:i32) <-- (blk1,blk2) +blk3: () <-- (blk1,blk2) v8:i64 = Iconst_64 0x4 - v9:i64 = UExtend v7, 32->64 + v9:i64 = UExtend v2, 32->64 v10:i64 = Uload32 module_ctx, 0x10 v11:i64 = Iadd v9, v8 v12:i32 = Icmp lt_u, v10, v11 @@ -2869,7 +2869,7 @@ blk0: (exec_ctx:i64, module_ctx:i64, v2:i32) blk1: () <-- (blk0) v11:i32 = Load v9, 0x10 - Jump blk3, v2 + Jump blk3 blk2: () <-- (blk0) v12:i32 = Load v9, 0x10 @@ -2880,18 +2880,13 @@ blk2: () <-- (blk0) ExitIfTrue v16, exec_ctx, memory_out_of_bounds v17:i32 = Load v9, 0x30 v18:i32 = Load v9, 0x25 - Jump blk3, v2 + Jump blk3 -blk3: (v19:i32) <-- (blk1,blk2) - v20:i64 = Iconst_64 0x19 - v21:i64 = UExtend v19, 32->64 - v22:i64 = Uload32 module_ctx, 0x10 - v23:i64 = Iadd v21, v20 - v24:i32 = Icmp lt_u, v22, v23 - ExitIfTrue v24, exec_ctx, memory_out_of_bounds - v25:i64 = Load module_ctx, 0x8 - v26:i64 = Iadd v25, v21 - v27:i32 = Load v26, 0x15 +blk3: () <-- (blk1,blk2) + v20:i64 = Load module_ctx, 0x8 + v21:i64 = UExtend v2, 32->64 + v22:i64 = Iadd v20, v21 + v23:i32 = Load v22, 0x15 Jump blk_ret `, }, diff --git a/internal/engine/wazevo/ssa/builder.go b/internal/engine/wazevo/ssa/builder.go index 316e626149..0b700c4b19 100644 --- a/internal/engine/wazevo/ssa/builder.go +++ b/internal/engine/wazevo/ssa/builder.go @@ -518,21 +518,42 @@ func (b *builder) findValue(typ Type, variable Variable, blk *basicBlock) Value // If this block has multiple predecessors, we have to gather the definitions, // and treat them as an argument to this block. // - // The first thing is to define a new parameter to this block which may or may not be redundant, but - // later we eliminate trivial params in an optimization pass. This must be done before finding the - // definitions in the predecessors so that we can break the cycle. - paramValue := blk.AddParam(b, typ) - b.DefineVariable(variable, paramValue, blk) - - // After the new param is added, we have to manipulate the original branching instructions - // in predecessors so that they would pass the definition of `variable` as the argument to - // the newly added PHI. + // But before that, we have to check if the possible definitions are the same Value. + tmpValue := b.allocateValue(typ) + // Break the cycle by defining the variable with the tmpValue. + b.DefineVariable(variable, tmpValue, blk) + // Check all the predecessors if they have the same definition. + uniqueValue := ValueInvalid for i := range blk.preds { - pred := &blk.preds[i] - value := b.findValue(typ, variable, pred.blk) - pred.branch.addArgumentBranchInst(b, value) + predValue := b.findValue(typ, variable, blk.preds[i].blk) + if uniqueValue == ValueInvalid { + uniqueValue = predValue + } else if uniqueValue != predValue { + uniqueValue = ValueInvalid + break + } + } + + if uniqueValue != ValueInvalid { + // If all the predecessors have the same definition, we can use that value. + b.DefineVariable(variable, uniqueValue, blk) + b.alias(tmpValue, uniqueValue) + return uniqueValue + } else { + // Otherwise, add the tmpValue to this block as a parameter which may or may not be redundant, but + // later we eliminate trivial params in an optimization pass. This must be done before finding the + // definitions in the predecessors so that we can break the cycle. + blk.addParamOn(tmpValue) + // After the new param is added, we have to manipulate the original branching instructions + // in predecessors so that they would pass the definition of `variable` as the argument to + // the newly added PHI. + for i := range blk.preds { + pred := &blk.preds[i] + value := b.findValue(typ, variable, pred.blk) + pred.branch.addArgumentBranchInst(b, value) + } + return tmpValue } - return paramValue } // Seal implements Builder.Seal.