From e67d50d5a6290ec9968344ee5712ebf62847fea8 Mon Sep 17 00:00:00 2001
From: Max Graey <maxgraey@gmail.com>
Date: Tue, 20 Jul 2021 22:28:07 +0300
Subject: [Optimize Instructions] Simplify sign extentions (#4004)

requiring sign-extension:
```
i64(x) << 56 >> 56   ==>   i64.extend8_s(x)
i64(x) << 48 >> 48   ==>   i64.extend16_s(x)
i64(x) << 32 >> 32   ==>   i64.extend32_s(x)
i64.extend_i32_s(i32.wrap_i64(x))   ==>   i64.extend32_s(x)
```
general:
```
i32.wrap_i64(i64.extend_i32_s(x))   ==>   x
i32.wrap_i64(i64.extend_i32_u(x))   ==>   x
```
---
 src/passes/OptimizeInstructions.cpp | 51 +++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

(limited to 'src')

diff --git a/src/passes/OptimizeInstructions.cpp b/src/passes/OptimizeInstructions.cpp
index 106bfea19..59b1130d1 100644
--- a/src/passes/OptimizeInstructions.cpp
+++ b/src/passes/OptimizeInstructions.cpp
@@ -405,6 +405,31 @@ struct OptimizeInstructions
           }
         }
       }
+      {
+        if (getModule()->features.hasSignExt()) {
+          Const *c1, *c2;
+          Expression* x;
+          // i64(x) << 56 >> 56   ==>   i64.extend8_s(x)
+          // i64(x) << 48 >> 48   ==>   i64.extend16_s(x)
+          // i64(x) << 32 >> 32   ==>   i64.extend32_s(x)
+          if (matches(curr,
+                      binary(ShrSInt64,
+                             binary(ShlInt64, any(&x), i64(&c1)),
+                             i64(&c2))) &&
+              Bits::getEffectiveShifts(c1) == Bits::getEffectiveShifts(c2)) {
+            switch (64 - Bits::getEffectiveShifts(c1)) {
+              case 8:
+                return replaceCurrent(builder.makeUnary(ExtendS8Int64, x));
+              case 16:
+                return replaceCurrent(builder.makeUnary(ExtendS16Int64, x));
+              case 32:
+                return replaceCurrent(builder.makeUnary(ExtendS32Int64, x));
+              default:
+                break;
+            }
+          }
+        }
+      }
       {
         // unsigned(x) >= 0   =>   i32(1)
         Const* c;
@@ -791,6 +816,18 @@ struct OptimizeInstructions
           return replaceCurrent(curr);
         }
       }
+      {
+        // i32.wrap_i64(i64.extend_i32_s(x))  =>  x
+        // i32.wrap_i64(i64.extend_i32_u(x))  =>  x
+        Unary* inner;
+        Expression* x;
+        if (matches(curr,
+                    unary(WrapInt64, unary(&inner, ExtendSInt32, any(&x)))) ||
+            matches(curr,
+                    unary(WrapInt64, unary(&inner, ExtendUInt32, any(&x))))) {
+          return replaceCurrent(x);
+        }
+      }
       {
         // i32.eqz(i32.wrap_i64(x))  =>  i64.eqz(x)
         //   where maxBits(x) <= 32
@@ -803,6 +840,20 @@ struct OptimizeInstructions
           return replaceCurrent(inner);
         }
       }
+      {
+        Unary* inner;
+        Expression* x;
+        if (getModule()->features.hasSignExt()) {
+          // i64.extend_i32_s(i32.wrap_i64(x))  =>  i64.extend32_s(x)
+          if (matches(curr,
+                      unary(ExtendSInt32, unary(&inner, WrapInt64, any(&x))))) {
+            inner->op = ExtendS32Int64;
+            inner->type = Type::i64;
+            inner->value = x;
+            return replaceCurrent(inner);
+          }
+        }
+      }
     }
 
     if (curr->op == EqZInt32) {
-- 
cgit v1.2.3