[Wasm GC] SimplifyLocals: Switch local.get to use a more refined type when possible (#5194)

(local.set $refined (cast (local.get $plain)))
..
.. (local.get $plain) .. ;; we can change this to read from $refined

By using the more refined type we may be able to eliminate casts later.

To do this, look at the fallthrough value (so we can look through a cast or a block
value - this is the reason for the small wasm2js improvements in tests), and also
extend the code that picks which local index to read to look at types (previously
we just ignored any pairs of locals with different types).

1 files changed, 18 insertions, 36 deletions

diff --git a/test/wasm2js/float_literals-modified.2asm.js.opt b/test/wasm2js/float_literals-modified.2asm.js.opt
index 1e69b6304..613e52a40 100644
--- a/test/wasm2js/float_literals-modified.2asm.js.opt
+++ b/test/wasm2js/float_literals-modified.2asm.js.opt
@@ -108,9 +108,8 @@ function asmFunc(imports) {
   $0_1 = wasm2js_scratch_load_i32(1) | 0;
   $1 = wasm2js_scratch_load_i32(0) | 0;
   i64toi32_i32$HIGH_BITS = $0_1;
-  $0_1 = $1;
   setTempRet0(i64toi32_i32$HIGH_BITS | 0);
-  return $0_1;
+  return $1;
  }
  
  function legalstub$32() {
@@ -119,9 +118,8 @@ function asmFunc(imports) {
   $0_1 = wasm2js_scratch_load_i32(1) | 0;
   $1 = wasm2js_scratch_load_i32(0) | 0;
   i64toi32_i32$HIGH_BITS = $0_1;
-  $0_1 = $1;
   setTempRet0(i64toi32_i32$HIGH_BITS | 0);
-  return $0_1;
+  return $1;
  }
  
  function legalstub$34() {
@@ -130,9 +128,8 @@ function asmFunc(imports) {
   $0_1 = wasm2js_scratch_load_i32(1) | 0;
   $1 = wasm2js_scratch_load_i32(0) | 0;
   i64toi32_i32$HIGH_BITS = $0_1;
-  $0_1 = $1;
   setTempRet0(i64toi32_i32$HIGH_BITS | 0);
-  return $0_1;
+  return $1;
  }
  
  function legalstub$35() {
@@ -141,9 +138,8 @@ function asmFunc(imports) {
   $0_1 = wasm2js_scratch_load_i32(1) | 0;
   $1 = wasm2js_scratch_load_i32(0) | 0;
   i64toi32_i32$HIGH_BITS = $0_1;
-  $0_1 = $1;
   setTempRet0(i64toi32_i32$HIGH_BITS | 0);
-  return $0_1;
+  return $1;
  }
  
  function legalstub$36() {
@@ -152,9 +148,8 @@ function asmFunc(imports) {
   $0_1 = wasm2js_scratch_load_i32(1) | 0;
   $1 = wasm2js_scratch_load_i32(0) | 0;
   i64toi32_i32$HIGH_BITS = $0_1;
-  $0_1 = $1;
   setTempRet0(i64toi32_i32$HIGH_BITS | 0);
-  return $0_1;
+  return $1;
  }
  
  function legalstub$37() {
@@ -163,9 +158,8 @@ function asmFunc(imports) {
   $0_1 = wasm2js_scratch_load_i32(1) | 0;
   $1 = wasm2js_scratch_load_i32(0) | 0;
   i64toi32_i32$HIGH_BITS = $0_1;
-  $0_1 = $1;
   setTempRet0(i64toi32_i32$HIGH_BITS | 0);
-  return $0_1;
+  return $1;
  }
  
  function legalstub$38() {
@@ -174,9 +168,8 @@ function asmFunc(imports) {
   $0_1 = wasm2js_scratch_load_i32(1) | 0;
   $1 = wasm2js_scratch_load_i32(0) | 0;
   i64toi32_i32$HIGH_BITS = $0_1;
-  $0_1 = $1;
   setTempRet0(i64toi32_i32$HIGH_BITS | 0);
-  return $0_1;
+  return $1;
  }
  
  function legalstub$39() {
@@ -185,9 +178,8 @@ function asmFunc(imports) {
   $0_1 = wasm2js_scratch_load_i32(1) | 0;
   $1 = wasm2js_scratch_load_i32(0) | 0;
   i64toi32_i32$HIGH_BITS = $0_1;
-  $0_1 = $1;
   setTempRet0(i64toi32_i32$HIGH_BITS | 0);
-  return $0_1;
+  return $1;
  }
  
  function legalstub$41() {
@@ -196,9 +188,8 @@ function asmFunc(imports) {
   $0_1 = wasm2js_scratch_load_i32(1) | 0;
   $1 = wasm2js_scratch_load_i32(0) | 0;
   i64toi32_i32$HIGH_BITS = $0_1;
-  $0_1 = $1;
   setTempRet0(i64toi32_i32$HIGH_BITS | 0);
-  return $0_1;
+  return $1;
  }
  
  function legalstub$42() {
@@ -207,9 +198,8 @@ function asmFunc(imports) {
   $0_1 = wasm2js_scratch_load_i32(1) | 0;
   $1 = wasm2js_scratch_load_i32(0) | 0;
   i64toi32_i32$HIGH_BITS = $0_1;
-  $0_1 = $1;
   setTempRet0(i64toi32_i32$HIGH_BITS | 0);
-  return $0_1;
+  return $1;
  }
  
  function legalstub$44() {
@@ -218,9 +208,8 @@ function asmFunc(imports) {
   $0_1 = wasm2js_scratch_load_i32(1) | 0;
   $1 = wasm2js_scratch_load_i32(0) | 0;
   i64toi32_i32$HIGH_BITS = $0_1;
-  $0_1 = $1;
   setTempRet0(i64toi32_i32$HIGH_BITS | 0);
-  return $0_1;
+  return $1;
  }
  
  function legalstub$45() {
@@ -229,9 +218,8 @@ function asmFunc(imports) {
   $0_1 = wasm2js_scratch_load_i32(1) | 0;
   $1 = wasm2js_scratch_load_i32(0) | 0;
   i64toi32_i32$HIGH_BITS = $0_1;
-  $0_1 = $1;
   setTempRet0(i64toi32_i32$HIGH_BITS | 0);
-  return $0_1;
+  return $1;
  }
  
  function legalstub$46() {
@@ -240,9 +228,8 @@ function asmFunc(imports) {
   $0_1 = wasm2js_scratch_load_i32(1) | 0;
   $1 = wasm2js_scratch_load_i32(0) | 0;
   i64toi32_i32$HIGH_BITS = $0_1;
-  $0_1 = $1;
   setTempRet0(i64toi32_i32$HIGH_BITS | 0);
-  return $0_1;
+  return $1;
  }
  
  function legalstub$47() {
@@ -251,9 +238,8 @@ function asmFunc(imports) {
   $0_1 = wasm2js_scratch_load_i32(1) | 0;
   $1 = wasm2js_scratch_load_i32(0) | 0;
   i64toi32_i32$HIGH_BITS = $0_1;
-  $0_1 = $1;
   setTempRet0(i64toi32_i32$HIGH_BITS | 0);
-  return $0_1;
+  return $1;
  }
  
  function legalstub$48() {
@@ -262,9 +248,8 @@ function asmFunc(imports) {
   $0_1 = wasm2js_scratch_load_i32(1) | 0;
   $1 = wasm2js_scratch_load_i32(0) | 0;
   i64toi32_i32$HIGH_BITS = $0_1;
-  $0_1 = $1;
   setTempRet0(i64toi32_i32$HIGH_BITS | 0);
-  return $0_1;
+  return $1;
  }
  
  function legalstub$49() {
@@ -273,9 +258,8 @@ function asmFunc(imports) {
   $0_1 = wasm2js_scratch_load_i32(1) | 0;
   $1 = wasm2js_scratch_load_i32(0) | 0;
   i64toi32_i32$HIGH_BITS = $0_1;
-  $0_1 = $1;
   setTempRet0(i64toi32_i32$HIGH_BITS | 0);
-  return $0_1;
+  return $1;
  }
  
  function legalstub$50() {
@@ -284,9 +268,8 @@ function asmFunc(imports) {
   $0_1 = wasm2js_scratch_load_i32(1) | 0;
   $1 = wasm2js_scratch_load_i32(0) | 0;
   i64toi32_i32$HIGH_BITS = $0_1;
-  $0_1 = $1;
   setTempRet0(i64toi32_i32$HIGH_BITS | 0);
-  return $0_1;
+  return $1;
  }
  
  function legalstub$59() {
@@ -295,9 +278,8 @@ function asmFunc(imports) {
   $0_1 = wasm2js_scratch_load_i32(1) | 0;
   $1 = wasm2js_scratch_load_i32(0) | 0;
   i64toi32_i32$HIGH_BITS = $0_1;
-  $0_1 = $1;
   setTempRet0(i64toi32_i32$HIGH_BITS | 0);
-  return $0_1;
+  return $1;
  }
  
  return {